Next Article in Journal
ESG and the Cost of Debt: Role of Media Coverage
Previous Article in Journal
How Does Foreign Direct Investment Impact the Sustainable Development? Empirical Evidence from China’s Coastal Areas
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Sustainability
Volume 16
Issue 12
10.3390/su16124992
sustainability-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Impact of Drip Irrigation with Recycled Wastewater on Aromatic Compound Composition in Capia Pepper (Capsicum annum L.)

by
Havva Eylem Polat
1,*,
Ozan Zambi
2,
Yalçın Güçer
3 and
Alper Serdar Anli
1
1
Agricultural Structures and Irrigation Department, Faculty of Agriculture, Ankara University, Ankara 06110, Türkiye
2
Division of Horticulture, Kalecik Vocational School, Ankara University, Ankara 06780, Türkiye
3
Beypazarı Vocational School, Ankara University, Ankara 06730, Türkiye
*
Author to whom correspondence should be addressed.
Sustainability 2024, 16(12), 4992; https://doi.org/10.3390/su16124992
Submission received: 29 April 2024 / Revised: 6 June 2024 / Accepted: 7 June 2024 / Published: 11 June 2024
(This article belongs to the Special Issue Contaminants in Irrigation Water Impacting the Safety of Fresh Produce)
Browse Figures
Versions Notes

Abstract

:
In recent years, treating and reusing polluted water for agricultural irrigation has become essential to ensuring water and food sustainability. In addition to the factors affecting human health in vegetables and fruits irrigated with treated wastewater, factors affecting consumer preferences, such as flavor and phenolic compounds, should also be examined. This study investigates the effect of treated wastewater irrigation on the aromatic compounds and phenolic composition of capia pepper, which holds a significant position and is extensively used in various food products in the food industry. Drip irrigation with treated and untreated wastewater from the Kalecik Wastewater Treatment Plant was applied to two pepper varieties in the Kalecik district of Ankara, Türkiye. This research found that wastewater irrigation impacted certain aroma components, including para-dichlorobenzene, alpha-cubebene, hexanoate, alpha-farnesene, limonene, isoamyl butyrate, squalene, and alpha-copaene, which contribute to the distinct aroma and fragrance of capia peppers. Total phenolic content, pH, and soluble solids were found to be high in peppers irrigated with wastewater, and it was observed that these parameters increased as the treatment levels of the wastewater decreased. The highest results were obtained in capia peppers irrigated with wastewater. Results indicate that heavy metal levels in peppers align with permissible limits, confirming the usability of both water sources. In the face of global water scarcity and the challenge of feeding an ever-growing population, studies like this offer valuable insights into sustainable and well-informed agricultural practices.

1. Introduction

Pepper belongs to the Solanaceae family and is considered one of the oldest food additives in human nutrition. It is also the world’s most produced and consumed vegetable [1]. Historical records indicate that Christopher Columbus named a fruit he brought from the New World ‘red pepper’ [2]. Peppers contain aroma compounds like alcohol, aldehyde, and ester [3,4]. Phenolic compounds positively affect human health and significantly influence food quality factors such as color, taste, and aroma in vegetables [5].
Pepper culture largely depends on environmental conditions [6] since pepper requires constant water and nutrients throughout the growing season [7]. Peppers grow best in soils rich in organic matter and have a light texture, such as silty sandy or silty loamy soils. The soil should have good water-holding capacity, be deep, well-drained, and have a pH ranging from 5.6 to 6.8. Maintaining the soil moisture level around 60% to 70% is important. The optimal temperature range for growing peppers is 18–26 °C [8,9]. Peppers have a fibrous root structure, which makes them sensitive to drought, so it is important to avoid excessive irrigation during cultivation [10].
The Food and Agriculture Organization (FAO) reported that the global fresh vegetable production reaches 1.1 billion tonnes. Turkey ranks fourth in the world with a vegetable production of 38.1 million tons. The production of peppers is increasing worldwide, with Turkey being the second largest producer at 3,091,295 tons, following China [11]. The Turkish Statistical Institute [12] reports that capia pepper makes up 46.8% of total pepper production, with a total of 1,445,275 tons. Capia pepper has many uses in the food industry, including in paste, canned goods, pickles, ketchup, roasted products, pepper juice, ready-made soups, and the food-drying sector [13].
The global population is predicted to reach between 9 and 11 billion by 2050 [14]. This rapid increase in population highlights the need for more effective and planned utilization of limited clean water resources. Studies indicate a six-fold increase in global water demand over the past 100 years [15]. Therefore, sustainable management of water resources has become a crucial issue, particularly in the agricultural sector. Water is an essential part of agriculture, and the rising demand for food, driven by population growth, increases the need for water for farming activities. However, the depletion and contamination of water sources threaten agriculture’s sustainability [16]. Treating polluted water for agricultural use is a significant strategy to efficiently utilize water resources and mitigate the environmental impacts of agriculture. According to Koç et al. [17], research predicts that Turkey will experience the most significant effects of climate change on water usage by 2070 compared to France, Spain, Italy, Greece, and Ukraine.
Pepper cultivation is often limited by water resources in warm and semi-arid regions; thus, optimum water management is required for pepper irrigation in these regions [18]. Water and nitrogen are critical factors determining pepper yield and quality [19].
Another study reported a decrease in capia pepper yield in response to increased levels of soil water stress [20]. Water stress leads to a significant reduction in nitrogen absorption by pepper plants [21]. Studies have been conducted on pepper and other vegetables where high-frequency drip irrigation and fertigation improved yields [22,23,24,25].
Over-watering can lead to diseases such as root rot in peppers and cause essential plant nutrients to leach away from the root zone. In pepper cultivation, it is important to use frequent, small-scale irrigation [26,27]. Insufficient soil moisture during the flowering period can cause flower drop, resulting in a reduction in fruit quantity, and during the fruit-setting period, it can cause shape deformities [28]. Protecting and increasing soil moisture has been frequently researched worldwide [29].
In addition to alternative irrigation strategies, different soil improvement practices have become compulsory to save irrigation water and fertilizer [30]. The advantages of using wastewater extend beyond its application as irrigation water. Its components, such as nitrogen and phosphorus, can reduce the fertilizer requirement in agriculture. However, using untreated wastewater for agricultural purposes carries certain risks. Some substances present in wastewater can adversely affect the environment and plant health.
Reclaimed water irrigation, while posing risks related to salinity and heavy metals, can be effectively managed through appropriate irrigation and agricultural practices. Reclaimed water contains a variety of fecal indicators and environmental pathogens, making reducing and controlling microbial contamination crucial [31,32,33,34]. Before utilizing wastewater for irrigation, it is essential to conduct thorough suitability analyses and implement them carefully. If wastewater is to be used for irrigation, drip irrigation systems are preferable over sprinkler irrigation methods. This is because the latter increases contact between plants and wastewater, which can harm both plants and humans in the environment. Considering this, we employed drip irrigation in our research. Wastewater may contain heavy metals and salts. Therefore, regular soil analyses in irrigated areas are necessary to prevent adverse effects on the soil. In addition, water analyses should be conducted to mitigate potential harm caused by wastewater [35]. Controlled application of wastewater, known to have various benefits, can minimize associated risks when used in irrigation [36]. A study confirmed that the levels of heavy metals in pepper and eggplant irrigated with effluent from a treatment plant were within permissible limits. This indicates that treated and untreated water sources can be used safely [37].
Reclaimed water typically contains higher concentrations of nutrients and microorganisms than tap water, which not only improves soil fertility and crop productivity but also increases the risk of pathogenic microorganism contamination. These results provide insights into the impacts of irrigation water quality on the complex compositions of endophytic microbial communities of peppers. Irrigation practices, such as mixing reclaimed water with conventional water sources and surface or subsurface drip irrigation, may alleviate the ecological risks of agricultural irrigation [38].
It is important to emphasize the necessity of determining the microbiological load content of wastewater and treated wastewater before utilization in vegetable cultivation. The consumption of vegetables whose roots, leaves, and fruits were irrigated with wastewater or treated wastewater may result in the transmission of bacteria such as E. coli, Salmonella, total coliform and Listeria monocytogenes to humans, which may subsequently lead to the development of health complications. Consequently, it is imperative to conduct microbial load analyses on vegetables irrigated with wastewater and treated wastewater [39].
According to Hamilton et al. [40], supplying water to raw vegetables through subsurface, furrow, or drip irrigation systems can effectively reduce the risks associated with production, post-harvest washing, disinfection, and food preparation.
Around three quarters of the world’s clean water resources are used in agriculture. Climate change is decreasing water resources and quality while increasing water demand. Therefore, it is crucial to implement appropriate strategies for reusing wastewater, particularly urban wastewater, to ensure the sustainability of water resources [41].
With the increasing consumption of freshwater resources, surface water pollution, water scarcity, and environmental degradation, the availability and utilization of unconventional water sources have begun to attract considerable attention. Reclaimed water has been widely used as an alternative water source for agricultural irrigation. However, exposure to reclaimed water may cause potential health hazards via skin contact, inhalation, or ingestion during conventional farming practices [42]. Although there are scientific studies on the effects of wastewater irrigation on human, soil, and plant health, there are very few studies on the differences that may occur in the aroma and phenolic compounds of fruits and vegetables irrigated with wastewater, which are important factors in consumer preferences.
The absence of comprehensive studies examining the effects of wastewater irrigation on heavy metals, aromatic compounds, and chemical properties in peppers underscores the significance of our research. Furthermore, our objective is to ascertain the potential impact of heavy metals in wastewater on capia peppers, a fruit vegetable, and determine whether their levels are within permissible limits. This study aims to investigate the effect of using wastewater as irrigation water, especially on the aromatic compounds in capia pepper, which is known for its rich aroma components and used in a wide variety of food products.

2. Materials and Methods

  • Location and design of experiment
The research conducted in 2023 in the Kalecik District of Ankara investigated the impact of wastewater on aromatic compounds in two different pepper varieties. Soil analysis was performed at the Ankara University Soil Science and Plant Nutrition Department Laboratory. Soil analysis results showed that the soil structure was clayey, slightly alkaline, non-saline, moderately rich in organic matter, and had a high lime content (Table 1).
The experiment employed irrigation water from the Kalecik Wastewater Treatment Plant, which has a daily capacity of 2500 m3. Table 2 presents the analysis results.
Table 3 shows that the amount of Cd, Pb, Ni, Co, and Mn in the wastewater used in our study is below the limit values for use as irrigation water according to the Permissible limits by the Food and Agriculture Organization [43].
  • Plant and water materials
The research utilized two varieties of capia pepper, Capsicum annuum L. cv. Capia cvs. Amfora and cvs. Yalova Yaglik. The pepper seedlings were planted with a row spacing of 35 cm and 35 cm between rows. The experiment had three replications in a randomized complete block design, considering edge effects. Fifteen plants were grown in each replication, and three different irrigation waters were applied:
  • Primary treated wastewater (physical treatment) (WW1).
  • Secondary treated wastewater (physical + biological treatment) (WW2) obtained from the Ankara Kalecik Wastewater Treatment Plant.
  • Tap water (MW).
The research was conducted in a region influenced by a continental climate. Hot and dry conditions characterize summers, while winters are cold and rainy, resulting in a high demand for water during the summer months. The prevailing wind direction in Ankara and its surroundings is northeast, with an average annual wind speed of 2.1 m/s. Ankara has a semi-arid climate, which is classified as BSk according to Köppen’s climate classification. The yearly average temperature is below 18.0 °C, and summer aridity is observed [44]. Ankara is classified as semi-arid (Ds2b3) according to Thornthwaite’s climate classification and experiences severe summers with water deficits. It also belongs to the first-degree mesothermal category and partially resembles marine climate.
Due to the increasing water demand, farmers must effectively manage and monitor the irrigation process. Conventional irrigation methods can cause over-irrigation and increase groundwater pollution by leaching chemicals and nutrients from the crop’s root zone. Additionally, these methods can lead to faster depletion of freshwater resources [45]. However, drip irrigation, a more efficient method of irrigation in terms of unit water use, reduces water loss through leaching and evaporation compared to other irrigation methods [46,47]. Drip irrigation enhances fertilization effectiveness and distributes nutrients more efficiently to the soil and plant root zones. It also reduces plant stress, shortens growth periods, and improves crop quality by providing a homogeneous yield [48]. Drip irrigation is a method used to regulate irrigation, aiming to optimize water usage, reduce energy consumption, and enhance crop quality. In the experimental area, drip irrigation was chosen as the primary method because of its efficiency and effectiveness.
Irrigation practices are influenced by several factors such as crop type, evapotranspiration, growth stage, climate, effective rainfall, and soil moisture. However, weather significantly determines crop water requirements, and agronomists often use weather station data to adjust irrigation schedules, thereby improving irrigation water use efficiency [49]. This underscores the importance of accurate and timely weather data in effective irrigation scheduling, a practice that is crucial for successful capia pepper cultivation.
Irrigation scheduling for the Kalecik region was planned based on climate data from the nearest meteorological station, the Esenboğa Station (Table 4). Irrigation activities were carried out from May to September, with 14 applications. The net irrigation water requirement of 521.84 mm was met throughout the growing period. The quantities of irrigation water used are illustrated in Figure 1. The irrigation water amounts required and the timing and intervals of irrigation were calculated using the CROPWAT 8.0 program. In addition, soil moisture content and plant phenological observations were monitored during irrigation applications.
  • Plant analysis
In our research, in addition to investigating the effect of wastewater applications on the quantity of aromatic compounds, we also examined their impact on water-soluble dry matter, titratable acidity, pH, and total phenolic content. For aromatic compound composition analyses, the Solid-phase micro-extraction (SPME) method was employed: 5 g of a homogenized pepper sample was taken and placed in 20 ml vials, the lids were closed, and the sample was mixed in the vortex for 2 s. The fiber (2 cm, DVB/CAR/PDMS, Supelco, Bellefonte, PA, USA), previously conditioned at 200 °C for 20 min GC-MS, was attached to the vial at 55 °C for 30 min. At the end of the period, the fiber was injected into GC-MS automatically, and analyses were performed.
Aroma analysis was performed using Shimadzu, model AOC-6000 GC-MS. The device used a Restek RTX-5MS (30 m × 0.25 mm × 0.25 μm) column. The method applied by Lau et al. (2018) was changed depending on the nesting of the peaks [50]. The following parameters were used for the analysis: injection temperature: 250 °C, pressure: 90.0 kPa, column flow rate: 1.61 mL/min, column temperature 1: 40 °C, standby time: 3 min, rate of increase: 4 °C/min, column temperature 2:240 °C, holding time at final temperature: 5 min, total flow 20.7 mL/min, partition ratio: 1/10. The C7–C30 alkane series was injected into the device using the determined method, and the RI calculation was performed. Peaks were defined in the FFNSC (natural and synthetic flavor and fragrance components) library to determine the peaks. The volatile aroma components in capia pepper samples were determined by similarity of 90% and above from the library. They were defined in terms of the percentage of the areas of the identified peaks in the total area.
Heavy metal analyses (Cd, Pb, Mn, Ni, Co) were performed using the Inductively Coupled Plasma–Optical Emission Spectrometry (ICP-OES) method.
The titratable acidity in homogenized samples was determined through titration and monitored using a pH meter. To achieve this, a specific amount of the sample underwent titration using a 0.1 N standardized NaOH solution, guided by a pH meter until reaching a pH of 8.1. The titration acidity was calculated using tartaric acid as ‘g/100 mL’ [51].
A total of 5 grams of pepper samples were ground and homogenized for pH measurement by mixing with 50 mL of distilled water. The pH of the resulting mixture was measured using a pH meter calibrated with buffer solutions in the range of 4.0 to 7.0 [52]. The Folin–Ciocalteu method was employed to quantify the total phenolic compound content in the samples. This analytical approach is based on reducing phenolic compounds using the Folin–Ciocalteu reagent in a basic environment and then assessing the resulting blue color using a spectrophotometer. In the analysis, the translucent supernatant was used to determine the overall phenolic content after homogenate preparation. Briefly, a 2 mL sample was mixed with 10 mL of 2 N (10%) Folin–Ciocalteu reagent and incubated for 3 min in darkness. Then, 8 mL of 0.7 M sodium carbonate was added. Following a 2-h incubation at room temperature in the absence of light, the absorbance of the reaction mixture was measured at 765 nm using a spectrophotometer. The results are expressed as milligrams of gallic acid equivalents per kilogram of fresh pepper weight, following the method outlined by Singleton and Rossi in 1965 [53].

3. Results and Discussion

3.1. Chemical Analysis of Capia Pepper

When examining the Soluble Solid Content (SSC) values used to determine the ripening time and harvest date of fruits in terms of fruit quality, it was found that raw wastewater applications increased the SSC levels compared to tap water applications. The Amfora variety irrigated with wastewater had the highest SSC value at 9.37%, while the Amfora variety irrigated with tap water had the lowest value at 8.00% (Table 5). Dagianta et al. (2014) researched peppers grown under greenhouse conditions and irrigated with different wastewater sources to determine growth, yield, and fruit quality [54]. The research found that peppers irrigated with treated wastewater had higher SSC values than control plants.
Our research also found a statistically significant effect of wastewater on pH for both varieties, ranging between 5.03 and 5.37.
Research on tomato plants irrigated with treated wastewater found no statistically significant difference compared to control groups. However, it was suggested that pH values could vary depending on the variety of characteristics [55]. Bozkurt (2019) discovered that different organic fertilization applications on peppers, specifically the Postal and Elephant Ear varieties, resulted in pH levels ranging from 4.94 to 5.24, consistent with our research [56]. The bell peppers irrigated with wastewater had higher pH values, which can be attributed to the higher organic matter content in the wastewater.
The peppers’ titratable acidity (TA) values ranged from 1.13% to 2.26%. The highest TA value was observed in the varieties irrigated with tap water. Among the pepper varieties, the Yalova Yağlık variety irrigated with tap water had the highest value, while the Amfora variety irrigated with treated wastewater had the lowest value.
The research found that total phenol values of pepper varieties were high when irrigated with both raw and treated waters. A decrease in irrigation water treatment levels increased total phenol content. Another study investigated the impact of wastewater applications on yield quality parameters in pepper and eggplant varieties and found that an increase in wastewater treatment levels led to a decrease in total phenol content [37]. The level of phenolic compounds in plants and fruits is directly proportional to pollution and related stress.
Wastewaters contain higher levels of heavy metals than tap water, leading to the accumulation of toxic heavy metals in the soil [57]. This accumulation affects the environment and human health and disrupts plant growth [58]. Figure 2 shows the effect of drip irrigation wastewater treatments on heavy metals such as Cd, Pb, Ni, Mn, Co, and Mn in capia pepper.
In both the Amfora and Yalova Yağlık varieties, the WW1 treatments achieved the highest values for all heavy metals. This was followed by WW2 and MW, respectively. In another study [37] which investigated the impact of wastewater produced by the Kalecik wastewater treatment plant on heavy metal content in capia pepper applied with the flood irrigation method, Cd and Pb contents were found to be higher than those observed in our study using the drip irrigation method. This indicates that the heavy metal content also depends on the irrigation method. Furthermore, given that the plant stem, leaves, and fruit were not subjected to wetting in the drip irrigation method, it can be concluded that the heavy metal levels in the fruit were lower. The analyses revealed that the heavy metal contents of capia pepper samples irrigated with wastewater were below the threshold levels permitted for human nutrition.
The heavy metal content of the peppers irrigated with wastewater was examined, and it was found to be below the permissible limit values for vegetables according to the FAO/WHO stated in Table 6. This leads to the conclusion that there is no drawback to using the wastewater used in the study as irrigation water for capia peppers.

3.2. Aromatic Compounds of Capia Pepper

The analysis of volatile aroma components in capia pepper samples conducted through GC-MS revealed the identification of 25 different volatile aroma compounds in the samples (Table 7). This analysis, performed on two different pepper varieties subjected to three irrigation treatments, identified eight common components across all samples. These common components, namely para-dichlorobenzene, alpha-cubebene, hexyl-hexanoate, alpha-farnesene, n-docosane, Limonene, Butanoic acid, 2-methyl-4-methylpentyl ester, and n-hexadecane, characterized the typical aromatic profiles of capia peppers. In addition to these components, squalene was specific to the Amfora variety, while alpha-copaene was uniquely detected in the Yalova variety across all treatments.
Para-dichlorobenzene (p-DCB) is a chemical compound with molecular formula C6H4Cl2. The compound is a derivative of benzene, in which two hydrogen atoms are replaced by chlorine atoms at the para positions [59]. It is a colorless crystalline solid. Para-dichlorobenzene has a distinctive, somewhat sweet odor, contributing to its ability to mask or neutralize unpleasant smells. The odor is noticeable at room temperature and is generally described as pungent and somewhat aromatic [59,60]. The para-dichlorobenzene level was higher in the Yalova variety compared to the Amfora variety; however, no significant difference was detected among the treatments (Table 7, Figure 3).
Alpha-cubebene is a sesquiterpene, a natural organic compound in various plants. It is commonly extracted for its potential applications in perfumery and flavoring due to its sweet and woody fragrance, with subtle hints of spiciness [61,62]. The Yalova variety exhibited a higher alpha-cubebene level than the Amfora variety. Furthermore, an increase in the amount of this component was observed in samples irrigated with wastewater in both varieties (Table 7, Figure 3).
Hexyl-hexanoate, a compound belonging to the ester class, is known for its fruity and sweet aroma. This volatile compound is commonly found in various fruits, contributing to their characteristic scents. Hexyl-hexanoate is often described as having a pleasant, ripe, fruity fragrance with notes reminiscent of apples, pears, and other tropical fruits. The hexyl group in its structure contributes to the compound’s fruity character [63,64]. The Yalova variety exhibited a higher level of hexyl-hexanoate than the Amfora variety. Furthermore, an increase in the amount of this component was observed in samples irrigated with wastewater in both varieties (Table 7, Figure 4).
N-docosane is typically odorless due to its linear and unbranched structure and its saturated nature. This compound is commonly used as a reference or standard in analytical chemistry and can be found in various natural sources, such as certain plant waxes. Although n-docosane itself does not contribute to the aroma of substances, it is valuable for scientific purposes as it serves as a baseline for comparison in studies of other volatile compounds. In aroma analysis or fragrance formulation, n-docosane is more commonly used as an inert substance than for its olfactory characteristics [60,67]. The content of n-docosane was higher in the Yalova variety than the Amfora variety; however, no significant difference was detected among the treatments (Table 7, Figure 5).
Limonene is a cyclic monoterpene hydrocarbon present in the peels of citrus fruits, including lemons, oranges, and limes [65]. This colorless liquid has a strong citrus scent, which is refreshing and zesty. Limonene is known for its potential health benefits, including antioxidant and anti-inflammatory effects. Its aromatic properties are also noteworthy [68]. The Amfora variety exhibited a higher Limonene level than the Yalova variety. Furthermore, an increase in the amount of this component was observed in samples irrigated with wastewater in both varieties (Table 7, Figure 5).
Isoamyl butyrate is an ester compound that contributes to the aroma of certain fruits, particularly in small quantities. This compound is colorless and has a fruity, banana-like odor. It is commonly used in the food and beverage industry to impart a sweet and fruity character to products such as candies, chewing gum, and artificial banana flavorings [69,70]. The Yalova variety exhibited a higher level of isoamyl butyrate than the Amfora variety. Furthermore, an increase in the amount of this component was observed in samples irrigated with wastewater in both varieties (Table 7, Figure 6).
N-hexadecane is a straight-chain alkane with a 16-carbon backbone. This hydrocarbon is colorless, odorless, and part of the larger family of alkanes, known for their saturated and non-aromatic structures. N-hexadecane has been detected in all spices, cucumbers, tea, orange capia peppers, and herbs and spices [71]. It has been determined that neither the varieties nor the different irrigation methods applied significantly affect the level of hexadecane (Table 7, Figure 6).
Squalene was identified in samples from all irrigation regimes specifically applied to the Amfora variety. Squalene is a triterpene, a natural organic compound commonly found in shark liver oil, olive oil, and various plant sources. Despite its numerous biological functions, squalene is generally odorless or has a neutral odor [72]. It has been observed that the level of the squalene component is higher in capia pepper samples of the Amfora variety that are irrigated with wastewater (Table 7, Figure 6).
Alpha-copaene was detected in samples from all irrigation regimes applied specifically to the Yalova variety. Alpha-copaene is a sesquiterpene hydrocarbon commonly found in various plant essential oils, contributing to their aromatic profiles. This compound possesses a woody and sweet scent with subtle hints of spiciness. The alpha form of alpha-copaene imparts a warm and earthy fragrance, often described as reminiscent of cedarwood or sandalwood [61,73]. It has been determined that the level of the alpha-copaene component is higher in capia pepper samples of the Yalova variety irrigated with purified water (Table 7).

4. Conclusions

In conclusion, this research aimed to investigate the impact of wastewater irrigation on aromatic compounds in two varieties of capia peppers in the Kalecik District of Ankara. With the increase in the global population and an accompanying six-fold increase in global water demand over the past century, the sustainable management of water resources, particularly in agriculture, has become a critical concern.
The research examined the crucial role of water in agriculture, particularly in Türkiye, the fourth largest producer of fresh vegetables worldwide. It analyzed the aromatic compounds of the capia pepper, a widely used vegetable in the food industry. It is worth noting that peppers, which belong to the Solanaceae family, are sensitive to soil and water conditions and therefore require careful irrigation practices.
The research discusses the challenge of climate change and predicts that Türkiye will be one of the countries most affected by changes in water usage by 2070. The study investigates the potential of wastewater, specifically from the Kalecik Wastewater Treatment Plant, for sustainable agricultural practices.
The research used a rigorous experimental design to investigate the effects of various irrigation waters, including primary and secondary treated wastewater and tap water, on the aromatic compounds of capia peppers. The results showed that using raw wastewater increased the Soluble Solid Content (SSC) levels, which affected the fruits’ ripening time and harvest date. Wastewater irrigation had a statistically significant effect on the pH levels of both pepper varieties.
Titratable acidity (TA) values varied among pepper varieties and irrigation water sources, providing insights into the impact of different water qualities on fruit acidity. Furthermore, the research found high total phenol values in plants irrigated with raw and treated waters, highlighting the correlation between wastewater irrigation and phenolic content.
When the heavy metal data obtained from pepper fruits in our study were analyzed, WW1 resulted in the highest value of all heavy metals. This was followed by WW2 and MW, respectively. Therefore, it was determined that as the wastewater treatment level used as irrigation water decreases, the heavy metal content in the product increases. However, all heavy metal data obtained were below the permissible levels. Therefore, our study revealed that irrigation of capia-type peppers with wastewater is not objectionable regarding heavy metals. Wastewater must be analyzed before being used as irrigation water. The heavy metal content accumulated in the crop is directly related to the heavy metal content of the wastewater to be used as irrigation water.
The research extended beyond conventional analyses by exploring the volatile aroma components through GC-MS, identifying 25 compounds, and highlighting variations in their levels based on pepper variety and irrigation water source.
The research conducted an in-depth investigation into the effects of wastewater irrigation on the aromatic profile of capia peppers, revealing significant alterations in several key aroma components. Specifically, the study identified that para-dichlorbenzene, a compound known for its sharp and somewhat medicinal scent, exhibited noticeable changes under wastewater irrigation. Similarly, alpha-cubebene, which contributes a woody and spicy character to the peppers, showed a distinct shift in its concentration.
The analysis also highlighted modifications in hexyl-hexanoate levels, a component that imparts a sweet and fruity aroma, enhancing the sensory appeal of capia peppers. Additionally, alpha-farnesene, which provides a green, citrus-like fragrance, was affected, suggesting an impact on the fresh and vibrant notes of the peppers. Limonene, another critical component recognized for its bright, lemony scent, experienced significant variations, potentially altering the overall aromatic balance.
Further, the study reported changes in isoamyl butyrate, a compound known for its fruity, banana-like aroma, and squalene, which adds a subtle earthy undertone to the peppers. The presence of alpha-copaene, contributing a woody and spicy scent, was also influenced by wastewater irrigation, indicating a broad spectrum of aromatic components being affected.
In contrast, the study found that hexadecane, a compound with a less pronounced aroma, remained stable and showed no significant response to wastewater treatment. This finding underscores the selective nature of wastewater irrigation’s impact on the aromatic profile of capia peppers.
It is crucial to emphasize that these findings are grounded in rigorous scientific analysis, ensuring the objectivity and reliability of the results. The comprehensive examination conducted in this study provides a clear understanding of how wastewater irrigation can modulate the complex aroma profile of capia peppers, highlighting the nuanced and multifaceted nature of agricultural practices on food quality.
In summary, this research demonstrates that wastewater irrigation significantly influences the aromatic compounds in capia pepper, yielding both positive and negative effects. Notably, certain aromatic components, including para-dichlorobenzene, alpha-cubebene, hexyl-hexanoate, alpha-farnesene, limonene, isoamyl butyrate, squalene, and alpha-copaene, were enhanced, contributing to the peppers’ distinct aroma and fragrance. While wastewater irrigation increased the Soluble Solid Content (SSC) and phenolic content, which could improve some quality attributes, it also significantly affected the pH and titratable acidity (TA) levels. The heavy metal content remained within permissible limits, indicating no immediate health risk. These findings suggest that while wastewater irrigation can enhance certain desirable aromatic qualities in capia pepper, careful monitoring and controlled application are necessary to mitigate potential negative impacts. As the world faces the challenge of feeding a growing population amidst water scarcity, studies such as these provide insight into informed and sustainable agricultural practices.

Author Contributions

Conceptualization, H.E.P. and Y.G.; methodology, H.E.P., O.Z. and Y.G.; validation, H.E.P., O.Z. and A.S.A.; formal analysis, O.Z. and Y.G.; investigation, H.E.P.; resources, H.E.P.; data curation, O.Z.; writing—original draft preparation, H.E.P., O.Z. and Y.G.; writing—review and editing, H.E.P. and A.S.A.; visualization, O.Z. and A.S.A.; supervision, H.E.P.; project administration, H.E.P. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Acknowledgments

The laboratory analyses were conducted with the assistance of Ozan Halisçelik who also provided the materials used in the experiments. We express our gratitude for his contribution. Also, the authors thank the editor and anonymous reviewers for their useful comments and suggestions.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Kelebek, H.; Sevindik, O.; Uzlasir, T.; Selli, S. LC-DAD/ESI MS/MS characterization of fresh and cooked Capia and Aleppo red peppers (Capsicum annuum L.) phenolic profiles. Eur. Food Res. Technol. 2020, 246, 1971–1980. [Google Scholar] [CrossRef]
  2. Govindarajan, V.S.; Salzer, U.J. Capsicum-production, technology, chemistry, and quality part 1: History, botany, cultivation, and primary processing. Crit. Rev. Food Sci. Nutr. 1985, 22, 109–176. [Google Scholar] [CrossRef] [PubMed]
  3. Materska, M. Flavone C-glycosides from Capsicum annuum L.: Relationships between antioxidant activity and lipophilicity. Eur. Food Res. Technol. 2015, 240, 549–557. [Google Scholar] [CrossRef]
  4. Korkmaz, A.; Hayaloglu, A.A.; Atasoy, A.F. Evaluation of the volatile compounds of fresh ripened Capsicum annuum and its spice pepper (dried red pepper flakes and isot). LWT 2017, 84, 842–850. [Google Scholar] [CrossRef]
  5. Uçkan Çakır, M.; Özbay, G. A Short History of Spices: An Overview on Pepper History. In Proceedings of the International Pepper and Spices Conference, Villahermosa, Mexico, 26 April 2022; pp. 23–35. [Google Scholar]
  6. Cui, M.; Wang, F.; Xu, H. Response of Physiological-biochemical Characters of Sweet Pepper Seedlings. Chin. Agric. Sci. Bull. 2005, 21, 225. [Google Scholar]
  7. Reyes, L.M.; Sanders, D.C.; Buhler, W.G. Evaluation of slow-release fertilizers on bell pepper. HortTechnology 2008, 18, 393–396. [Google Scholar] [CrossRef]
  8. Berke, T.; Black, L.; Morris, R.; Talekar, N.; Wang, J. Suggested cultural practices for sweet pepper. Int. Coop. Guide AVRDC Publ. 2003, 5, 99–497. [Google Scholar]
  9. Yadav, P.K.; Kumar, S.; Dwivedi, D.K.; Turkar, G.P. Soil Requirements for Horticultural Crop. In Modern Trends in Horticulture, 1st ed.; Golden Leaf Publishers: Lucknow, India, 2023; Chapter 3. [Google Scholar]
  10. Khatun, M.; Sarkar, S.; Era, F.M.; Islam, A.M.; Anwar, M.P.; Fahad, S.; Islam, A.A. Drought stress in grain legumes: Effects, tolerance mechanisms and management. Agronomy 2021, 11, 2374. [Google Scholar] [CrossRef]
  11. FAO. Making agrifood systems more resilient to shocks and stresses. In The State of Food and Agriculture 2021; FAO: Rome, Italy, 2021. [Google Scholar] [CrossRef]
  12. TSI. Sebze Üretim İstatistikleri (Vegetable Production Statistics). 2023. Available online: https://data.tuik.gov.tr/Bulten/Index?p=Bitkisel-Uretim-1.Tahmini-2023-49534 (accessed on 3 February 2024).
  13. Özdikmenli, S.; Zorba, N.N.D. Közlenmiş kırmızı biber (kapya) konservesi üretiminde gıda güvenliği. Tekirdağ Ziraat Fakültesi Derg. 2015, 12, 55–64. [Google Scholar]
  14. Corcoran, E.; Nellemann, C.; Baker, E.; Bos, R.; Osborn, D.; Savelli, H. The central role of wastewater management in sustainable development. A Rapid Response Assessment. United Nations Environment Programme, UN-HABITAT, GRID-Arendal. J. Environ. Prot 2010, 3, 12–29. [Google Scholar]
  15. Wada, Y.; Flörke, M.; Hanasaki, N.; Eisner, S.; Fischer, G.; Tramberend, S.; Satoh, Y.; Van Vliet, M.T.H.; Yillia, P.; Ringler, C. Modeling global water use for the 21st century: The Water Futures and Solutions (WFaS) initiative and its approaches. Geosci. Model Dev. 2016, 9, 175–222. [Google Scholar] [CrossRef]
  16. Nouri, M.; Homaee, M.; Pereira, L.S.; Bybordi, M. Water management dilemma in the agricultural sector of Iran: A review focusing on water governance. Agric. Water Manag. 2023, 288, 108480. [Google Scholar] [CrossRef]
  17. Koç, D.L.; Kapur, B.; Mustafa, Ü.; Kanber, R. The Situation of Water Resources and Agricultural Irrigation in Turkey. Çukurova Tarım Gıda Bilim. Derg. 2022, 37, 112–122. [Google Scholar]
  18. Dorji, K.; Behboudian, M.; Zegbe-Dominguez, J. Water relations, growth, yield, and fruit quality of hot pepper under deficit irrigation and partial rootzone drying. Sci. Hortic. 2005, 104, 137–149. [Google Scholar] [CrossRef]
  19. Kumari, R.; Kaushal, A. Drip fertigation in sweet pepper: A review. Int. J. Eng. Res. Appl. 2014, 4, 144–149. [Google Scholar]
  20. Demirel, K.; Genç, L.; Saçan, M. Effects of different irrigation levels on pepper (Capsicum annum cv. kapija) yield and quality parameters in semi-arid conditions. J. Tekirdag Agric. Fac. 2012, 9, 7–15. [Google Scholar]
  21. Candido, V.; Miccolis, V.; Rivelli, A.R. Yield traits and water and nitrogen use efficiencies of bell pepper grown in plastic-greenhouse. Ital. J. Agron. 2009, 4, 91–100. [Google Scholar] [CrossRef]
  22. Dalla Costa, L.; Gianquinto, G. Water stress and watertable depth influence yield, water use efficiency, and nitrogen recovery in bell pepper: Lysimeter studies. Aust. J. Agric. Res. 2002, 53, 201–210. [Google Scholar] [CrossRef]
  23. Tanaskovik, V.; Cukaliev, O.; Romić, D.; Ondrašek, G. The influence of drip fertigation on water use efficiency in tomato crop production. Agric. Conspec. Sci. 2011, 76, 57–63. [Google Scholar]
  24. Çolak, Y.B.; Yazar, A.; Çolak, İ.; Akça, H.; Duraktekin, G. Evaluation of crop water stress index (CWSI) for eggplant under varying irrigation regimes using surface and subsurface drip systems. Agric. Agric. Sci. Procedia 2015, 4, 372–382. [Google Scholar] [CrossRef]
  25. Sezen, S.M.; Yazar, A.; Tekin, S. Physiological response of red pepper to different irrigation regimes under drip irrigation in the Mediterranean region of Turkey. Sci. Hortic. 2019, 245, 280–288. [Google Scholar] [CrossRef]
  26. Gisbert-Mullor, R.; Martín-García, R.; Bažon Zidarić, I.; Pascual-Seva, N.; Pascual, B.; Padilla, Y.G.; Calatayud, Á.; López-Galarza, S. A Water Stress–Tolerant Pepper Rootstock Improves the Behavior of Pepper Plants under Deficit Irrigation through Root Biomass Distribution and Physiological Adaptation. Horticulturae 2023, 9, 362. [Google Scholar] [CrossRef]
  27. Keleş, D. Biber Yetiştiriciliği. 2015. Available online: https://arastirma.tarimorman.gov.tr/alata/Belgeler/Diger-belgeler/BiberYeti%C5%9Ftiricili%C4%9FiDKele%C5%9F.pdf (accessed on 3 February 2024).
  28. Şen, E. The Effect of Drip Irrigation Applications of Some Yield and Quality Parameters of Processing Pepper (Capsicum annuum L.). Master’s Dissertation, Adnan Menderes University, Aydın, Türkiye, 2015; p. 57. [Google Scholar]
  29. Liu, Y.; Yang, Y. Advances in the quality of global soil moisture products: A review. Remote Sens. 2022, 14, 3741. [Google Scholar] [CrossRef]
  30. Cakmakcı, T.; Sahın, U. Yield, Physiological Responses and Irrigation Water Productivity of Capia Pepper (Capsicum annuum L.) at Deficit Irrigation and Different Biochar Levels. Gesunde Pflanz. 2023, 75, 317–327. [Google Scholar] [CrossRef]
  31. Hashem, M.S.; Qi, X. Treated Wastewater Irrigation—A Review. Water 2021, 13, 1527. [Google Scholar] [CrossRef]
  32. Polat, A. Su kaynaklarının sürdürülebilirliği için arıtılan atıksuların yeniden kullanımı. Türk Bilimsel Derlemeler Derg. 2013, 6, 58–62. [Google Scholar]
  33. Erel, R.; Eppel, A.; Yermiyahu, U.; Ben-Gal, A.; Levy, G.; Zipori, I.; Schaumann, G.E.; Mayer, O.; Dag, A. Long-term irrigation with reclaimed wastewater: Implications on nutrient management, soil chemistry and olive (Olea europaea L.) performance. Agric. Water Manag. 2019, 213, 324–335. [Google Scholar] [CrossRef]
  34. Arora, S.; Kazmi, A.A. The effect of seasonal temperature on pathogen removal efficacy of vermifilter for wastewater treatment. Water Res. 2015, 74, 88–99. [Google Scholar] [CrossRef] [PubMed]
  35. Jaramillo, M.F.; Restrepo, I. Wastewater reuse in agriculture: A review about its limitations and benefits. Sustainability 2017, 9, 1734. [Google Scholar] [CrossRef]
  36. Saraoglu, E. Reuse of Treated Waste Water in Agricultureal Irrigation—Successful Examples from Our Country and the World and Implementation Suggestions for Türkiye. Environment and Urbanization. Expertise Thesis, Republic of Türkiye Ministry of Environment, Urbanization and Climate Change, Ankara, Türkiye, 2014; p. 104. [Google Scholar]
  37. Zambi, O. Bazı Sebzelerde Atık Sularla Sulamanın Kalite Üzerine Etkisi. Ph.D. Thesis, Bursa Uludag University, Bursa, Turkey, 2022. [Google Scholar]
  38. Hamilton, K.; Hamilton, M.; Johnson, W.; Jjemba, P.; Bukhari, Z.; LeChevallier, M.; Haas, C. Health risks from exposure to Legionella in reclaimed water aerosols: Toilet flushing, spray irrigation, and cooling towers. Water Res. 2017, 134, 261–279. [Google Scholar] [CrossRef] [PubMed]
  39. Becerra-Castro, C.; Lopes, A.R.; Vaz-Moreira, I.; Silva, E.F.; Manaia, C.M.; Nunes, O.C. Wastewater reuse in irrigation: A microbiological perspective on implications in soil fertility and human and environmental health. Environ. Int. 2015, 75, 117–135. [Google Scholar] [CrossRef]
  40. Cui, B.; Hu, C.; Fan, X.; Cui, E.; Li, Z.; Ma, H.; Gao, F. Changes of endophytic bacterial community and pathogens in pepper (Capsicum annuum L.) as affected by reclaimed water irrigation. Appl. Soil Ecol. 2020, 156, 103627. [Google Scholar] [CrossRef]
  41. Hamilton, K.A. Quantitative Microbial Risk Assessment for Sustainable Water Resources. 2016. Available online: https://www.proquest.com/dissertations-theses/quantitative-microbial-risk-assessment/docview/1859928829/se-2 (accessed on 7 February 2024).
  42. Öztürk, A.; Çolak, M.S. A Quantitative and Qualitative Assessment of Türkiye’s Water Resources Potential. J. Agric. Sci. 2024, 30, 1–34. [Google Scholar] [CrossRef]
  43. Ayers, R.S.; Westcot, D.W. Water Quality for Agriculture; Irrigation and Drainage Paper; Food and Agriculture Organization (FAO): Rome, Italy, 1985; Volume 29, p. 174. [Google Scholar]
  44. Turkes, M. Climate and drought in Turkey. In Water Resources of Turkey; Springer: Boston, MA, USA, 2020; pp. 85–125. [Google Scholar]
  45. Siyal, A.A.; Bristow, K.L.; Šimůnek, J. Minimizing nitrogen leaching from furrow irrigation through novel fertilizer placement and soil surface management strategies. Agric. Water Manag. 2012, 115, 242–251. [Google Scholar] [CrossRef]
  46. Flores, J.H.N.; Faria, L.C.; Rettore Neto, O.; Diotto, A.V.; Colombo, A. Methodology for determining the emitter local head loss in drip irrigation systems. J. Irrig. Drain. Eng. 2021, 147, 06020014. [Google Scholar] [CrossRef]
  47. Yang, P.; Wu, L.; Cheng, M.; Fan, J.; Li, S.; Wang, H.; Qian, L. Review on drip irrigation: Impact on crop yield, quality, and water productivity in China. Water 2023, 15, 1733. [Google Scholar] [CrossRef]
  48. Abou Zakhem, B.; Al Ain, F.; Hafez, R. Assessment of field water budget components for increasing water productivity under drip irrigation in arid and semi-arid areas, Syria. Irrig. Drain. 2019, 68, 452–463. [Google Scholar] [CrossRef]
  49. Chen, X.; Qi, Z.; Gui, D.; Gu, Z.; Ma, L.; Zeng, F.; Li, L.; Sima, M.W. A model-based real-time decision support system for irrigation scheduling to improve water productivity. Agronomy 2019, 9, 686. [Google Scholar] [CrossRef]
  50. Lau, H.; Liu, S.Q.; Xu, Y.Q.; Lassabliere, B.; Sun, J.; Yu, B. Characterising volatiles in tea (Camellia sinensis). Part I: Comparison of headspace-solid phase microextraction and solvent assisted flavour evaporation. LWT 2018, 94, 178–189. [Google Scholar] [CrossRef]
  51. Cliff, M.A.; King, M.C.; Schlosser, J. Anthocyanin, phenolic composition, colour measurement and sensory analysis of BC commercial red wines. Food Res. Int. 2007, 40, 92–100. [Google Scholar] [CrossRef]
  52. Doğanlar, C.; Vural, G.E.; Zengin, S.; Karakuş, T.; Ellialtıoğlu, Ş.Ş. Determination of Eggplant Pure Lines Suitable for Drying by Different Methods. Ekin J. Crop Breed. Genet. 2023, 9, 1–18. [Google Scholar]
  53. Singleton, V.L.; Rossi, J.A. Colorimetry of total phenolics with phosphomolybdic-phosphotungstic acid reagents. Am. J. Enol. Vitic. 1965, 16, 144–158. [Google Scholar] [CrossRef]
  54. Dagianta, E.; Goumas, D.; Manios, T.; Tzotzakis, N. The use of treated wastewater and fertigation in greenhouse pepper crop as affecting growth and fruit quality. J. Water Reuse Desalination 2014, 4, 92–99. [Google Scholar] [CrossRef]
  55. Al-Lahham, O.; El Assi, N.M.; Fayyad, M. Impact of treated wastewater irrigation on quality attributes and contamination of tomato fruit. Agric. Water Manag. 2003, 61, 51–62. [Google Scholar] [CrossRef]
  56. Bozkurt, S.B. The Effect of Organic Fertilizers Used in Red Pepper (Capsicum annuum L. cv. Kapya) Cultivation on Plant Growth and Fruit Quality. Master’s Thesis, Bursa Uludağ University, Bursa, Türkiye, 2019. [Google Scholar]
  57. Rehman, Z.U.; Sardar, K.; Shah, M.T.; Brusseau, M.L.; Khan, S.A.; Mainhagu, J. Transfer of heavy metals from soils to vegetables and associated human health risks at selected sites in Pakistan. Pedosphere 2018, 28, 666–679. [Google Scholar] [CrossRef]
  58. Mohammadi, A.; Zarei, A.; Esmaeilzadeh, M.; Taghavi, M.; Yousefi, M.; Yousefi, Z.; Sedighi, F.; Javan, S. Assessment of heavy metal pollution and human health risks assessment in soils around an industrial zone in Neyshabur, Iran. Biol Trace Elem Res. 2020, 195, 343–352. [Google Scholar] [CrossRef] [PubMed]
  59. BYJUS. BYJU’S, Para Dichlorobenzene—C6H4Cl2. 2024. Available online: https://byjus.com/chemistry/para-dichlorobenzene/ (accessed on 3 February 2024).
  60. HMDB. Showing Metabocard for Docosane (HMDB0061865) and P-Dichlorobenzene (HMDB0041971). 2024. Available online: https://hmdb.ca/metabolites/HMDB0061865 (accessed on 7 February 2024).
  61. TGSCa. The Goods Cents Company, (-)-Alpha-Cubebene, Alpha-Copaene. 2024. Available online: http://www.thegoodscentscompany.com/data/rw1054531.html (accessed on 3 February 2024).
  62. Li, Z.; Howell, K.; Fang, Z.; Zhang, P. Sesquiterpenes in grapes and wines: Occurrence, biosynthesis, functionality, and influence of winemaking processes. Compr. Rev. Food Sci. Food Saf. 2020, 19, 247–281. [Google Scholar] [CrossRef]
  63. El Hadi, M.A.M.; Zhang, F.J.; Wu, F.F.; Zhou, C.H.; Tao, J. Advances in Fruit Aroma Volatile Research. Molecules 2013, 18, 8200–8229. [Google Scholar] [CrossRef] [PubMed]
  64. Dennis, E.G.; Keyzers, R.A.; Kalua, C.M.; Maffei, S.M.; Nicholson, E.L.; Boss, P.K. Grape contribution to wine aroma: Production of hexyl acetate, octyl acetate, and benzyl acetate during yeast fermentation is dependent upon precursors in the must. J. Agric. Food Chem. 2012, 60, 2638–2646. [Google Scholar] [CrossRef]
  65. NIH. National Library of Medicine, Limonene, (+/-)-. 2024. Available online: https://pubchem.ncbi.nlm.nih.gov/compound/Limonene (accessed on 20 February 2024).
  66. Javidnia, K.; Miri, R.; Soltani, M.; Khosravi, A.R. Essential oil composition of Tripleurospermum disciforme from Iran. Chem. Nat. Compd. 2008, 44, 800–801. [Google Scholar] [CrossRef]
  67. El Henshir, A.K. The Fractionation of Crude Petroleum using Chromatography, Extrography and Supercritical Fluid Extraction. Ph.D. Thesis, University of South Wales, Wales, UK, 1997. [Google Scholar]
  68. Sobel, A. What Is Limonene? Everything You Need to Know. Healthline 2023. Available online: https://www.healthline.com/nutrition/d-limonene (accessed on 22 February 2024).
  69. TGSCb. The Goods Cents Company, 3-Methylbutyl Butanoate. 2023. Available online: http://www.thegoodscentscompany.com/data/rw1006752.html (accessed on 5 February 2024).
  70. Matthews, A.C. Beverage flavourings and their applications. In Food Flavourings; Ashurst, P.R., Ed.; Springer: Boston, MA, USA, 1991. [Google Scholar] [CrossRef]
  71. FOODB. Food Browse, Showing Compound Hexadecane (FDB011952). 2020. Available online: https://foodb.ca/compounds/FDB011952 (accessed on 5 February 2024).
  72. Huang, Z.R.; Lin, Y.K.; Fang, J.Y. Biological and pharmacological activities of squalene and related compounds: Potential uses in cosmetic dermatology. Molecules 2009, 14, 540–554. [Google Scholar] [CrossRef]
  73. Lull, C.; Gil-Ortiz, R.; Cantín, Á. A Chemical Approach to Obtaining α-copaene from Clove Oil and Its Application in the Control of the Medfly. Appl. Sci. 2023, 13, 5622. [Google Scholar] [CrossRef]
Sustainability 16 04992 g001
Figure 1. Total and net irrigation water requirements throughout the capia pepper growth period.
Figure 1. Total and net irrigation water requirements throughout the capia pepper growth period.
Sustainability 16 04992 g001
Sustainability 16 04992 g002
Figure 2. Heavy metal content of capia-type pepper samples. Data are means ± standard error, n = 3. Different letters in each column indicate that they are statistically different (p ≤ 0.05; LSD test). The non-letters are not statistically significant (p > 0.05; LSD test). MW, Municipal water; WW1, Physical treatments; WW2, Physical + biological treatment; N.C, not calculated.
Figure 2. Heavy metal content of capia-type pepper samples. Data are means ± standard error, n = 3. Different letters in each column indicate that they are statistically different (p ≤ 0.05; LSD test). The non-letters are not statistically significant (p > 0.05; LSD test). MW, Municipal water; WW1, Physical treatments; WW2, Physical + biological treatment; N.C, not calculated.
Sustainability 16 04992 g002
Sustainability 16 04992 g003
Figure 3. The amount para-dichlorobenzene and alpha-cubebene in capia peppers irrigated with different wastewaters. MW, Municipal water; WW1, Physical treatments; WW2, Physical + biological treatment.
Figure 3. The amount para-dichlorobenzene and alpha-cubebene in capia peppers irrigated with different wastewaters. MW, Municipal water; WW1, Physical treatments; WW2, Physical + biological treatment.
Sustainability 16 04992 g003
Sustainability 16 04992 g004
Figure 4. The amount of hexyl-hexanoate and alpha-farnesene in capia peppers irrigated with different wastewater. MW, Municipal water; WW1, Physical treatments; WW2, Physical + biological treatment. Alpha-farnesene is a sesquiterpene compound commonly found in various plants, particularly in the essential oils of fruits and flowers. This natural organic compound contributes a distinct, sweet, and fruity aroma to the substances in which it is present. The alpha form of alpha-farnesene imparts a pleasant and slightly floral fragrance, often reminiscent of apples and other orchard fruits [65,66]. The Amfora variety exhibited a higher alpha-farnesene level than the Yalova variety. Furthermore, an increase in the amount of this component was observed in samples irrigated with wastewater in both varieties (Table 7, Figure 4).
Figure 4. The amount of hexyl-hexanoate and alpha-farnesene in capia peppers irrigated with different wastewater. MW, Municipal water; WW1, Physical treatments; WW2, Physical + biological treatment. Alpha-farnesene is a sesquiterpene compound commonly found in various plants, particularly in the essential oils of fruits and flowers. This natural organic compound contributes a distinct, sweet, and fruity aroma to the substances in which it is present. The alpha form of alpha-farnesene imparts a pleasant and slightly floral fragrance, often reminiscent of apples and other orchard fruits [65,66]. The Amfora variety exhibited a higher alpha-farnesene level than the Yalova variety. Furthermore, an increase in the amount of this component was observed in samples irrigated with wastewater in both varieties (Table 7, Figure 4).
Sustainability 16 04992 g004
Sustainability 16 04992 g005
Figure 5. The amount of n-docosane and Limonene capia peppers irrigated with different wastewater. MW, Municipal water; WW1, Physical treatments; WW2, Physical + biological treatment.
Figure 5. The amount of n-docosane and Limonene capia peppers irrigated with different wastewater. MW, Municipal water; WW1, Physical treatments; WW2, Physical + biological treatment.
Sustainability 16 04992 g005
Sustainability 16 04992 g006
Figure 6. The amount of isoamyl butyrate, n-hexadecane, and alpha-copaene capia peppers irrigated with different wastewater. MW, Municipal water; WW1, Physical treatments; WW2, Physical + biological treatment.
Figure 6. The amount of isoamyl butyrate, n-hexadecane, and alpha-copaene capia peppers irrigated with different wastewater. MW, Municipal water; WW1, Physical treatments; WW2, Physical + biological treatment.
Sustainability 16 04992 g006
Table 1. Soil characteristics of the trial parcels (Kalecik, Ankara, Türkiye).
Table 1. Soil characteristics of the trial parcels (Kalecik, Ankara, Türkiye).
Depth (cm)0–3030–60
TextureClayClay
Sand (%)28.1081724.07214
Silt (%)24.9060122.94990
Clay (%)46.9858149.97796
Clay + silt (%)71.8918372.92786
OM (%)3.162.53
CaCO322.7819.88
pH8.448.63
EC (dS m−1)0.3970.439
Table 2. Water utilized in the research conducted in Kalecik, Ankara, Türkiye.
Table 2. Water utilized in the research conducted in Kalecik, Ankara, Türkiye.
Wastewater (WW)
Analysis Parameters		 Municipal Water (MW)
Analysis Parameters
WW1WW2MW
pH7.57.1Turbidity (NTU)0.30
Total hardness (CaCO3) (mg L−1)341.00307.00Chlorine (mg L−1)0.20
Conductibility (EC) (25 °C, mS m−1)124.790.3Conductibility (EC) (25 °C, mS m−1)57.0
Total suspended solid matter (TSS) (mg L−1)451<10Ammonium (mg L−1)<0.06
Total dissolved solids (TDS) (mg L−1)81199247Nitrite (mg L−1)<0.006
K (mg L−1)13.213.1SO4 (mg L−1)47.1
Na (mg L−1)108.0111.00
SO4 (mg L−1)73.181.30
Total N (T-N) (mg L−1)53.2021.40
Total P (T–P) (mg L−1)0.880.93
MW, Municipal water; WW1, Physical treatments; WW2, Physical + biological treatment.
Table 3. Heavy metal content of treated wastewater used in the study (mg L−1).
Table 3. Heavy metal content of treated wastewater used in the study (mg L−1).
Heavy Metals
Irrigation WaterCdPbNiCoMn
WW10.822.243.440.6531.26
WW20.240.501.670.372.60
Threshold values, [40]10500020050200
WW1, Physical treatments; WW2, Physical + biological treatment.
Table 4. Long-term average meteorological data for the research area—Kalecik, Ankara.
Table 4. Long-term average meteorological data for the research area—Kalecik, Ankara.
ParameterJanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecemberAnnual
Avg. Temp. (°C)1.34.87.812.717.621.324.925.420.714.17.22.813.4
Highest Temp. (°C)19.122.72531.935.937.541.739.840.834.125.417.641.7
Lowest Temp. (°C)−19.3−13.2−8.4−3.43.46.19.611.20−1.9−9.6−12.9−19.3
Avg. Number of Rainy Days (mm)11.88.49.48.112.412.52.94.44.26.85.1995
Monthly Avg. Total Precipitation (mm)5.3723.0542.418.6257.6868.718.5320.8419.1318.5919.5133.61376.04
Table 5. Effect of wastewater applications on chemical properties.
Table 5. Effect of wastewater applications on chemical properties.
Wastewater ApplicationTotal Phenolic Matter (mg kg−1)Water Soluble Dry Matter (%)pHTitratable Acidity (%)
AMFORA
MW149.26 ± 7.63 c8.00 ± 0.05 c5.06 ± 0.01 c1.37 ± 0.03 a
WW2230.31 ± 11.45 b8.50 ± 0.09 b5.20 ± 0.03 b1.13 ± 0.03 b
WW1303.49 ± 4.81 a9.37 ± 0.10 a5.36 ± 0.04 a1.20 ± 0.04 b
YALOVA YAGLIK
MW186.45 ± 4.29 c8.37 ± 0.12 b5.03 ± 0.02 b2.26 ± 0.03 a
WW2249.10 ± 7.77 b8.87 ± 0.03 ab5.12 ± 0.01 b1.39 ± 0.07 b
WW1319.31 ± 8.05 a9.03 ±0.18 a5.37 ± 0.05 a1.30 ± 0.01 b
Data are means ± standard error, n = 3. Different letters in each column indicate that they are statistically different (p ≤ 0.05; LSD test). The non-letters are not statistically significant (p > 0.05; LSD test). MW, Municipal water; WW1, Physical treatments; WW2, Physical + biological treatment.
Table 6. Threshold values for vegetables according to FAO/WHO (mg kg−1).
Table 6. Threshold values for vegetables according to FAO/WHO (mg kg−1).
CdPbNiMnCo
FAO/WHO0.20.0367.95050
Cd, Cadmium; Pb, Lead; Ni, Nickel; Co, Copper; Mn, Manganese.
Table 7. Volatile aromatic compounds of capia pepper samples (% peak areas).
Table 7. Volatile aromatic compounds of capia pepper samples (% peak areas).
Aromatic CompoundsAmforaYalova Yaglık
WW1MWWW2WW1MWWW2
para-dichlorobenzene18.0218.0422.3327.5522.8724.64
nonanoic acid--5.61---
alpha-cubebene13.337.888.4221.8612.5513.18
hexyl-hexanoate5.222.712.777.053.332.96
alpha-, trans-bergamotene--1.1---
alpha-farnesene21.8610.374.168.916.746.99
squalene2.661.142.01---
n-octadecane9.7-13.49---
n-docosane2.571.421.9211.441.79
Limonene1.421.11.022.662.021.81
butyl-hexanoate2.36--5.417.18-
isoamyl butyrate1.961.471.245.163.872.02
n-pentadecane2.17-----
n-hexadecane16.5815.7717.4414.9616.6120.9
n-heptadecane3.76-----
methyl-salicylate-6.42---1.77
n-dodecane-1.59---2.77
alpha-copaene-9.96-1.021.221.41
hexyl-butyrate------
n-tridecane------
4-vinyl-guaiacol------
n-nonadecane------
naphthalene---1.041.14-
alpha-bulnesene---1.762.01-
(E)-dihydro apofarnesal-----1.56
MW, Municipal water; WW1, Physical treatments; WW2, Physical + biological treatment.
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Polat, H.E.; Zambi, O.; Güçer, Y.; Anli, A.S. Impact of Drip Irrigation with Recycled Wastewater on Aromatic Compound Composition in Capia Pepper (Capsicum annum L.). Sustainability 2024, 16, 4992. https://doi.org/10.3390/su16124992

AMA Style

Polat HE, Zambi O, Güçer Y, Anli AS. Impact of Drip Irrigation with Recycled Wastewater on Aromatic Compound Composition in Capia Pepper (Capsicum annum L.). Sustainability. 2024; 16(12):4992. https://doi.org/10.3390/su16124992

Chicago/Turabian Style

Polat, Havva Eylem, Ozan Zambi, Yalçın Güçer, and Alper Serdar Anli. 2024. "Impact of Drip Irrigation with Recycled Wastewater on Aromatic Compound Composition in Capia Pepper (Capsicum annum L.)" Sustainability 16, no. 12: 4992. https://doi.org/10.3390/su16124992

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop