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Article

Characteristics of Microplastic Pollution in Agricultural Soils in Xiangtan, China

by
Cong Ye
1,
Jing Lin
2,
Zhenguo Li
1,*,
Guanghuai Wang
1 and
Zeling Li
1
1
School of Earth Science and Spatial Information Engineering, Hunan University of Science and Technology, Xiangtan 411201, China
2
Yuhua Branch of Changsha Municipal Ecology and Environment Bureau, Changsha 410000, China
*
Author to whom correspondence should be addressed.
Sustainability 2024, 16(17), 7254; https://doi.org/10.3390/su16177254 (registering DOI)
Submission received: 5 July 2024 / Revised: 19 August 2024 / Accepted: 19 August 2024 / Published: 23 August 2024
Browse Figures
Versions Notes

Abstract

:
Microplastic pollution in agricultural soils has drawn significant attention in recent years. The objective of this study is to investigate the forms and characteristics of microplastic pollution in agricultural soils, specifically focusing on rice and vegetable soil in Xiangtan City. Various analytical techniques including stereomicroscopy, SEM, and FTIR spectroscopy were used to analyze the color, particle size, abundance, and types of microplastics in the study area. The findings indicated that the average abundance of microplastics in the soils in the study area was 4377.44 items/kg, with a maximum of 12,292.33 items/kg. Microplastics with smaller particle sizes were more prevalent, with their colors mainly being yellow, transparent, and black. The shapes of the microplastics were mainly thin-filmy and fibrous, and the types mainly included PE and PP. The abundance of microplastics in the vegetable soil with agricultural films applied was four times more than that without agricultural films. In the research area, the use of agricultural films was the most significant source of microplastics. The study’s findings describe the characteristics of microplastic pollution in agricultural soils in Xiangtan City. The findings could serve as a reference for establishing standardized assessments of microplastic pollution in agricultural soils, in addition to offering data support for Xiangtan City’s future efforts to safeguard agricultural soils and regulate microplastic pollution.

1. Introduction

Plastics are widely used because of their high durability, corrosion resistance, low manufacturing costs, and light weight [1]. Statistics show that the global annual production of plastic exceeds 359 million tons [2]; however, the majority of plastics are not recycled and as such enter into the environment [3]. The extensive utilization of plastic products also leads to the creation of substantial quantities of plastic garbage. This plastic waste, if not processed properly, will be gradually decomposed into fragments following long-term mechanical action, natural weathering, biodegradation, photodegradation, and other physical and chemical processes together with their human activities [4]. Among the different types of fragments, plastic fragments less than 5 mm in size are defined as microplastics [5]. Microplastics are small in particle size, light in texture, and chemically stable [6], and are difficult to be removed once they enter the environment. Thus far, microplastics have been found in soil [7], the atmosphere [8], freshwater [9], oceans [10], sediments [11], and even in remote locations like the Antarctic [12] and Arctic Ocean [13]. The results of different studies show that inhaling and ingesting microplastics may induce oxidative stress, cell damage, DNA damage, inflammation, and immune response, and also cause serious physical effects such as abrasions, ulcers, and digestive tract obstruction [14]. Because of the small size and large specific surface area of microplastics, organic contaminants, antibiotics, and heavy metals may adhere and accumulate on their surface, causing more severe compound contamination [15]. Therefore, the issue of microplastic pollution has received more attention and has become a research hotspot in recent years.
Soil may act as a reservoir for microplastics derived from various sources, with them being statistically 4 to 23 times more abundant in the soil than in the ocean [16]. Microplastics enter the soil through sewage sludge [17], composting [18], wastewater irrigation [19], atmospheric deposition [20], and agricultural films [21]. Microplastics may have effects on soil health and function, such as altering soil pH, soil structure, and nutrients, thus affecting soil plant growth. Additionally, microplastics have the capacity to be transferred down the food chain, which poses a potential hazard to human well-being [22]. Hence, it is imperative to study the prevalence of microplastic pollution in soils (especially agricultural soils) in various regions. At present, many domestic and international scholars have conducted studies on microplastic pollution in agricultural soils in different regions, including Germany [23], Canada [24], Shanghai [25], Harbin [26], and Shenyang [27].
In the following study, agricultural soils in Xiangtan City were used as the research object, and a mixture of NaCl: NaI = 1:1 was used for density separation [28] and Fenton reagent was used for ablation [29]. The color, particle size, abundance, and type of microplastics were analyzed in combination with stereomicroscope, scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy, and the potential sources of microplastics were further analyzed, to determine the pollution characteristics of microplastics in agricultural soils in Xiangtan City. The results of this study can be used as a reference for establishing standardized assessments of microplastic pollution in farmland soil. Additionally, they can offer data support for Xiangtan City’s future efforts to safeguard agricultural soils and regulate microplastic pollution.

2. Materials and Methods

2.1. Overview of the Study Area

Xiangtan is a prefecture-level city in Hunan Province, situated on the lower part of the Xiangjiang River. It is positioned between the longitudes 111°58′–113°05′ E and latitudes 27°21′–28°05′ N. The study area is the largest “vegetable basket” production base in Xiangtan—the Jiangshe Modern Agricultural Demonstration Park. The demonstration garden is located in the suburbs of Xiangtan City, characterized by a subtropical monsoon climate including four distinct seasons, ample precipitation, and adequate warmth. The mean annual temperature stands at 17.5 °C, while the average yearly rainfall ranges from 1200 to 1450 mm. Additionally, the average annual sunshine amounts to 1262.9 h. The soil of the demonstration garden is mainly sandy loam with thick layers and a high utilization rate, which is mainly used for the production of agricultural products such as vegetables, grains, and edible fungi. Vegetables mainly include beetroot, plow lettuce, chili, broccoli, and Chinese cabbage, and the grain grown at this location is rice.

2.2. Experimental Reagents

NaCl, NaI, ferrous sulfate (FeSO4∙7H2O), H2SO4, and 30% H2O2 were all analytically pure.
The preparation of reagents is detailed below:
Saturated NaCl solution: Add greater than or equal to 361 g NaCl to 1 L of water at room temperature and stir to dissolve until the solid pellets are no longer dissolved.
Saturated NaI solution: Add greater than or equal to 1840 g NaI to 1 L of water at room temperature and stir to dissolve until the solid pellets are no longer dissolved.
Fenton reagent: Prepared from 0.05 M Fe (II) and 30% H2O2 in a 1:1 ratio by volume [29].

2.3. Experimental Instruments

The experimental instruments used in the experiment described herein are shown in Table 1.

2.4. Soil Sample Collection and Pretreatment

In the following study, rice soil and vegetable soil were collected from Jiangshe Modern Agricultural Demonstration Park in Xiangtan City using a stainless steel shovel. Rice soil was naturally grown in the open, and the vegetable soil included four types: one type grown in the open without agricultural films, one type grown in the open with agricultural films, one type grown under greenhouses without agricultural films, and one type grown under greenhouses with agricultural films. The five types of soil were numbered from T1 to T5, and three sampling sites were set for each type, totaling 15 sampling sites. The specific location distribution and basic information of the sampling locations are depicted in Figure 1 and Table 2, respectively.
A sample plot of 1 m × 1 m was chosen at each sampling point; five points were selected based on the plum blossom sampling method, where equal amounts of 0–10 cm of surface soil were collected, mixed into a single soil sample positioned in the center of the plum blossom, and placed using a GPS to record the coordinates of the center point [27]. The soil samples were returned to the laboratory in clean aluminum boxes, spread out evenly in a clean, light-proof environment, and allowed to dry naturally. The dried soil samples were passed through a 5 mm sieve to facilitate the removal of impurities such as sand, gravel, stones, and plant debris visible to the naked eye, and 1 kg of soil was gathered in quadrants.
Afterward, 1 kg of collected soil was sifted using a 2 mm sieve. The soil that passed through the sieve (<2 mm) was sealed and stored for subsequent separation and digestion experiments aimed at extracting microplastics. For soil samples with a particle size ranging from 2 to 5 mm, visible microplastics were manually selected and their quantity, color, and shape were initially documented. Subsequently, stereomicroscopy, scanning electron microscopy, and FTIR spectroscopy were used for further analysis and identification.

2.5. Separation and Digestion of Soil Microplastics

Next, a conical flask was used to weigh 50 g of soil sample (<2 mm), and 200 mL of NaCl: NaI = 1:1 mixed solution was added. The solution was agitated for 30 min using a magnetic stirrer and then allowed to stand for 24 h to separate the solution [28]. Lighter-density microplastics and some soil organic matter remained suspended in the supernatant. The supernatant was then filtered using a vacuum filtration unit, with the microplastics collected on a 0.45 µm nylon membrane and air-dried in a glass dish. This density separation process was repeated three times for each group.
The mixture was gently scraped off of the air-dried filter membrane and washed with a tiny quantity of distilled water if it adhered. Next, the scraped mixture was digested with 60 mL Fenton reagent in a shaking chamber at 40 °C for 6 h to prevent interference from soil organic matter. Following digestion, the microplastics were collected on a filter membrane via vacuum filtration. Lastly, the filter membrane was put in a glass dish to dry naturally and stored for the subsequent identification of microplastics.

2.6. Identification and Analysis of Microplastics

A stereomicroscope was used to observe and identify the microplastics in the range of a 2–5 mm particle size that were identified by the naked eye and all of the microplastics (<2 mm) on the filter membrane after digestion. Images of the microplastics were captured using a microscopic imaging system, and the numbers, shapes, colors, and particle sizes of the microplastics were recorded and classified. Microplastics that were difficult to distinguish were further analyzed using SEM and FTIR spectroscopy. To determine the composition of the microplastics, FTIR spectroscopy was used for identification in the attenuated total reflection mode (ATR), setting the spectral range to cover 600–4000 cm−1 with a resolution of 4.00 cm−1, and 32 scans were conducted. All spectra were processed offline using OMNIC 8 software with automatic baseline correction. The spectrograms were then compared with the standard spectrogram of the database. The composition of the microplastics could be determined when the match was ≥70%.

2.7. Data Processing

All data processing procedures were completed using Excel 2016 and SPSS 27.0. The distribution of sampling sites was mapped using ArcGIS 10.8; that of the other figures was performed using Origin 8.0.

2.8. Quality Control

All experimental procedures were carried out in a fume hood and the following measures were taken to avoid background interference from microplastics: (1) during sampling and experimentation, all plastic products were avoided and only stainless steel, metal, or glass products were used; (2) the required instruments were rewashed three times and wrapped in aluminum foil immediately after washing to prevent potential contamination from airborne microplastics; (3) following each step, all materials and containers were covered with aluminum foil for closure; (4) the microplastic identification site was cleaned up; (5) a blank control was established in the experiment. Except for not adding soil samples, the other operations remained the same to monitor possible microplastic pollution in the laboratory atmosphere. One plastic fiber was monitored during the analysis of the samples from sampling site 7; therefore, the blank was used to correct the number of fibers in the sample.

3. Results and Analysis

3.1. Abundance of Microplastics

Microplastic abundance in the sampling area ranged from 776.33 to 12,292.33 items/kg, with an average abundance of 4377.44 items/kg. Figure 2 displays the abundance of microplastics in T1–T5. The abundance of microplastics in rice soil (T1) ranged from 776.33 to 1774.33 items/kg, with an average abundance of 1279.89 items/kg. In vegetable soil in greenhouses with agricultural films (T2), the abundance ranged from 6313.33 to 8904.33 items/kg, with an average abundance of 7971.33 items/kg. For vegetable soil in open fields with agricultural films (T3), the microplastic abundance ranged from 5978.67 to 12,292.33 items/kg, averaging 8134.89 items/kg. The abundance of microplastics in vegetable soil in greenhouses without agricultural films (T4) varied from 1590.67 to 3955.33 items/kg, with an average abundance of 2455.22 items/kg. Lastly, for vegetable soil in open fields without agricultural films (T5), the abundance of microplastics ranged from 1246.67 to 2610.67 items/kg, with an average abundance of 2045.89 items/kg.

3.2. Color of Microplastics

The microplastics found in the soils of the sampling area exhibited a diverse range of colors, such as yellow, transparent, black, red, blue, and green, as depicted in Figure 3. Additionally, a few other colors such as purple, white, orange, and brown were also observed. The distribution of each microplastic color is illustrated in Figure 4. Notably, yellow, black, and transparent microplastics were the most prevalent, constituting 50.12%, 21.92%, and 18.50% of the total, respectively. Specifically, the largest percentage of yellow microplastics was observed in vegetable soil in greenhouses with agricultural films (T2), vegetable soil in open fields with agricultural films (T3), and vegetable soil in greenhouses without agricultural films (T4), accounting for 62.66%, 55.47%, and 39.79% of the total, respectively. In contrast, the primary colors of microplastics in the rice soil (T1) and vegetable soil in open fields without agricultural films (T5) were black and transparent, respectively.

3.3. Particle Size of Microplastics

The microplastics were categorized into five groups according to their particle size: <100 μm, 100–500 µm, 500–1000 µm, 1000–2000 µm, and 2000–5000 µm [30]. The particle size distribution of the microplastics is illustrated in Figure 5. In the sampling area, the particle size of microplastics varied from 4.69 to 4931.22 µm, and there was an inverse relationship between the proportion of microplastics and their particle size. The highest proportion of microplastics with sizes <100 µm was found in rice soil (T1), vegetable soil in greenhouses with agricultural films (T2), and vegetable soil in open fields with agricultural films (T3), with values of 32.82%, 42.60%, and 45.99%, respectively. Microplastics in vegetable soil in greenhouses without agricultural films (T4) and vegetable soil in open fields without agricultural films (T5) were found to be mostly in the range of 100–500 µm, with values of 45.50% and 52.60%, respectively.

3.4. Shapes of Microplastics

In the study area, microplastics of five different shapes were examined: filmy, granular, fibrous, fragmented, and foamed (Figure 6). The distribution of each shape is illustrated in Figure 7. The proportion of microplastic shapes was ranked as follows: film (41.21%) > fiber (27.10%) > fragment (20.11%) > granular (10.91%) > foam (0.67%). Notably, rice soil (T1), vegetable soil in greenhouses without agricultural films (T4), and vegetable soil in open fields without agricultural films (T5) contained the largest concentration of fibrous microplastics. Conversely, the predominant shape in vegetable soil in greenhouses with agricultural films (T2) and vegetable soil in open fields with agricultural films (T3) was filmy.

3.5. Types of Microplastics

The types of microplastics were identified using FTIR spectroscopy with an 84.21% detection rate. Although 6.38% of the remaining materials were defined as microplastics, the infrared spectrum matched less than 70% of the standard spectra in the database. Nine types of microplastics were identified and analyzed, including PE, PP, PA, PS, PVC, PET, PC, PAN, and PMMA. Among them, PE, PP, PS, PA, and PVC were the main types of microplastics (Figure 8). To simplify the classification, the microplastics were grouped into six categories: PE, PP, PS, PA, PVC, and others. Furthermore, variations such as PA-6, PA-66, and PA-12 were all consolidated under PA; in comparison, LDPE, PE, and HDPE were all grouped under PE.
The percentages of different types of microplastics are shown in Figure 9. Predominantly, PE and PP accounted for 42.71% and 37.06%, respectively. For different types of soil from T1 to T5, the two types of microplastics with the highest proportion in T1 to T4 were also PE and PP. Only in T5 was the proportion of PA slightly higher than PE. In addition, only seven and two microplastics of PMMA and PAN were detected, respectively.

4. Discussion

4.1. Pollution Status of Microplastics in Agricultural Soils in Xiangtan

In current research on soil microplastics, the units used to evaluate their abundance are not unified; thus, comparisons can only be made with a few studies utilizing the same units. In the present study, the abundance of microplastics in agricultural soils in Xiangtan City ranged from 776.33 to 12,292.33 items/kg, with an average abundance of 4377.44 items/kg. This result exceeded the levels found in agricultural soils in Hangzhou Bay, Zhejiang Province (average 571 items/kg; maximum 2760 items/kg) [31] and in nine areas of Shaanxi Province (1430–3410 items/kg) [32]. However, the abundance was lower than the levels observed in vegetable soils in Wuhan (1.6 × 105 items/kg) [33] and in agricultural soils and fallow wetlands in the lake basin area of southern Dianchi (7100–42,960 items/kg) [34]. The variations in microplastic abundance across different study areas may be related to factors such as plastic pollution sources, fertilization practices, cropping patterns, and human activities.
The research area had the highest concentration of microplastics in yellow, black, and transparent colors. It was observed that the yellow microplastics were often unevenly distributed, appearing mostly white and yellow or partially transparent. This uneven distribution may be attributed to the prolonged interaction of white and transparent microplastics with soil components, leading to discoloration. Analysis of microplastic particle sizes indicated that particles smaller than 500 μm were most prevalent, aligning with previous research by Zhang [25] on microplastics in agricultural soils in Shanghai. Furthermore, a significant portion of microplastics smaller than 500 μm exhibited filmy and fibrous shapes, explaining the high proportion of filmy (39.51%) and fibrous (28.80%) shapes among the five microplastic shapes.
Shi et al. [27] found that in agricultural soils around Shenyang, PP, PE, and PS accounted for 43.26%, 28.78%, and 27.96% of all microplastics, respectively. In a separate study, Zhang [25] identified PP, PE, and PVC as the predominant microplastic forms found in agricultural soils in Shanghai. Chen et al. [35] studied the primary categories of microplastics in suburban vegetable soils in Wuhan, finding mainly PA (32.5%), PP (28.8%), PS (16.9%), PE (4.2%), and PVC (1.9%). The results of the microplastics study in three different areas indicated that PP, PE, PA, PS, and PVC were the predominant types of microplastics found in agricultural soils, aligning closely with the results of the current study.

4.2. Comparison of Microplastic Characteristics of Agricultural Soils

We found that vegetable soil with agricultural films contained a significantly higher abundance of microplastics compared to those soils without, roughly four times as high. This result indicated that agricultural films cracked and then accumulated on the soil surface due to weathering and UV exposure [36]. This result also showed that agricultural film was a significant contributor to the presence of microplastics in agricultural soils [37]. The agricultural films in the research area consisted of PE and PP, with colors ranging from white and transparent to black. This finding helped to clarify why there was a higher abundance of PE and PP microplastics compared to other types and why yellow, transparent, and black colors collectively make up over 80% of the microplastic colors.
The average abundance of microplastics was slightly higher in the vegetable soil in greenhouses without agricultural films (T4) than in the vegetable soil in open fields without agricultural films (T5), with a significant increase in PVC microplastics. This discrepancy may be ascribed to the utilization of PVC shed films at sampling sites 10 and 12, which might have degraded due to long-term use and artificial damage, leading to PVC fragments settling into the soil [38]. In comparison, the abundance of microplastics in the vegetable soil in greenhouses with agricultural films (T2) (average abundance of 7971.33 items/kg) was a bit lower than in the vegetable soil in open fields with agricultural films (T3) (average abundance of 8134.89 items/kg), primarily due to the exceptionally high abundance at sampling site 8 in T3 (average abundance of 12,292.33 items/kg). The elevated abundance at site 8 was a result of frequent film use and prolonged film cover [37], contributing to the overall higher average abundance of microplastics in T3.
The mean concentration of microplastics in the vegetable soil in open fields without agricultural films (T5) was 1.60 times more than that in rice soil (T1). This difference could be attributed to the increased need for fertilization, tillage, and irrigation in vegetable soil, all of which could potentially introduce microplastics [39,40]. The average abundance of microplastics in rice soil in the suburbs of Shanghai investigated by Liu [41] was 190.00 ± 31.22 items/kg. This value was significantly lower than the average abundance found in the current investigation. This disparity might be attributed to the proximity of the sampling locations in this study to a highway, where high human and vehicular activity may have caused the extensive distribution of microplastics. It is possible that microplastics from the highway migrated to the soil [42], and variations in soil composition across different regions may have also played a role [40]. Yu et al. [43] also highlighted in their study that the quantity of microplastics is influenced by the mechanical composition of the soil. The predominant shape of microplastics found in T1 and T5 was fibrous, with particle sizes ranging from 100 to 500 µm, most of which were identified as PA. Therefore, PA appears to be the primary type of fibrous microplastics in soil cultivated in open fields.
In general, there are certain variations in the characteristics of microplastics in agricultural soils, which are mainly reflected in the differences in abundance and type of microplastics. Differences in color, particle size, and shape are fundamental differences in types.

4.3. Potential Sources of Soil Microplastics

The prevalence of PE and PP microplastics suggested that agricultural films were a significant source of microplastics, as all films in the sampling areas were made of these materials. The higher concentrations of PE and PVC near greenhouses indicated that shed fragmentation may contribute to microplastic deposition in soil through airborne transport [38]. Microplastics could also originate from irrigation water in the sampling area, where numerous small rivers and ponds serve as natural sources of irrigation [40]. Plastic garbage, including woven and plastic bags, could be seen floating on the water’s surface, eventually breaking down into microplastics due to prolonged exposure to ultraviolet radiation and microorganisms in the water [36]. The authors of previous studies have also identified high levels of microplastics in rivers [44,45] and lakes [46,47], further supporting the role of natural irrigation water in delivering microplastics to the soil. Some irrigation water may come from domestic wastewater, used by farmers for field irrigation following cleaning activities. This finding was corroborated by the presence of microplastic PA in the study area, a material commonly found in clothing and textiles [35]. De Falco et al. [48] demonstrated that washing 1 kg of clothing can release 124–308 mg of microplastics, with effluent containing a variable amount of microfibers ranging from 640,000 to 1,500,000. In addition, many discarded plastic items including beverage bottles, plastic bags, packaging boxes, and disposable lunch boxes were found near the abandoned soil in the study areas (Figure 10). These items break down into microplastics through cracking and crushing, and due to their lightweight nature, they can be carried into agricultural soil by the wind [49]. Among the six main types of microplastics identified at the sampling locations, PE is commonly used in plastic bags, PP is a key component in woven bags, food packaging, and automotive parts, PA is frequently utilized in clothing and textile production, PS is extensively found in cosmetic product and daily necessity packaging, PVC is employed in water pipe manufacturing, and PET is predominantly used in beverage bottle production [26,50]. These findings indicate that the sources of the microplastics PE, PP, PA, PS, PVC, and PET are linked to these discarded plastic products.

5. Conclusions

(1)
Microplastics were found in each of the 15 sampling locations of agricultural soils in Xiangtan, China. The average abundance of microplastics was 4377.44 items/kg, with a maximum abundance of 12,292.33 items/kg. Microplastics of a small and medium size (<500 μm) dominated, and their colors were mainly yellow, transparent, and black; their shapes were mainly filmy and fibrous; and their types mainly included PE and PP.
(2)
Variations in the prevalence of microplastics were observed in the soil across different farming techniques. The abundance of microplastics in the vegetable soil with agricultural films was four times higher than that without agricultural films, the number of microplastics in the vegetable soil in greenhouses was slightly higher than that in the open fields, and the average abundance of microplastics in the vegetable soil in the open fields without agricultural films was 1.60 times more than that in the rice soil.
(3)
The main factor that led to the presence of microplastics in agricultural soils in Xiangtan was the utilization of agricultural films. Additionally, irrigation water and waste plastic products were also being noted as potential sources of microplastics.

Author Contributions

Conceptualization, C.Y. and J.L.; methodology, J.L.; software, C.Y.; validation, C.Y., J.L., and G.W.; formal analysis, C.Y.; investigation, G.W.; resources, Z.L. (Zhenguo Li); data curation, C.Y. and Z.L. (Zeling Li); writing—original draft preparation, C.Y.; writing—review and editing, Z.L. (Zhenguo Li); visualization, C.Y.; supervision, Z.L. (Zhenguo Li); project administration, Z.L. (Zhenguo Li); funding acquisition, Z.L. (Zhenguo Li). 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 original contributions presented in the study are included in the article; further inquiries can be directed toward the corresponding author.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Schematic diagram of sampling site’s location distribution.
Figure 1. Schematic diagram of sampling site’s location distribution.
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Figure 2. Figure detailing the abundance of microplastics.
Figure 2. Figure detailing the abundance of microplastics.
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Figure 3. Color of several common microplastics in experimental soil.
Figure 3. Color of several common microplastics in experimental soil.
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Figure 4. Figure depicting the color distribution of microplastics.
Figure 4. Figure depicting the color distribution of microplastics.
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Figure 5. Figure depicting particle size distribution of microplastics.
Figure 5. Figure depicting particle size distribution of microplastics.
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Figure 6. Five different shapes of microplastics: (a) fibrous; (b) filmy; (c) foamed; (d) granular; (e) fragmented.
Figure 6. Five different shapes of microplastics: (a) fibrous; (b) filmy; (c) foamed; (d) granular; (e) fragmented.
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Figure 7. Figure depicting shape distribution of microplastics.
Figure 7. Figure depicting shape distribution of microplastics.
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Figure 8. FTIR results of several common microplastics in the study area.
Figure 8. FTIR results of several common microplastics in the study area.
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Figure 9. Figure depicting type distribution of microplastics.
Figure 9. Figure depicting type distribution of microplastics.
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Figure 10. Waste discarded randomly in the area near the sampling sites.
Figure 10. Waste discarded randomly in the area near the sampling sites.
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Table 1. List of experimental instruments.
Table 1. List of experimental instruments.
InstrumentModel
Vacuum Filtration PumpSHZ-D (III)
(Shanghai Huichuang Chemical Instrument Co., Shanghai, China)
Constant Temperature Heating Magnetic Stirrer85-2A
(Changzhou Yuexin Instrument Manufacture Co., Changzhou, China)
Electronic Analytical BalanceTD20002A
(Tianjin Tianma Hengji Instrument Co., Tianjin, China)
Electric Heating Blast DryerDHG-9023A
(Shanghai Yiheng Scientific Instrument Co., Shanghai, China)
Water Bath Thermostat OscillatorSHA-B
(Changzhou Guowang Instrument Manufacturing Co., Changzhou, China)
StereomicroscopySZN71
(Sunny optical technology (group) Co., LTD, Ningbo, China)
Fourier Transform Infrared SpectroscopyNicoletTM iS20
(Thermo Fisher Scientific, Waltham, MA, USA)
Table 2. Basic information of the sampling sites.
Table 2. Basic information of the sampling sites.
Sampling Site No.Soil TypeForm of CultivationUse of Agricultural Films
T11Rice soilOpen fieldNot used
2
3
T24Vegetable soilGreenhouseUsed
5
6
T37Vegetable soilOpen fieldUsed
8
9
T410Vegetable soilGreenhouseNot used
11
12
T513Vegetable soilOpen fieldNot used
14
15
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Ye, C.; Lin, J.; Li, Z.; Wang, G.; Li, Z. Characteristics of Microplastic Pollution in Agricultural Soils in Xiangtan, China. Sustainability 2024, 16, 7254. https://doi.org/10.3390/su16177254

AMA Style

Ye C, Lin J, Li Z, Wang G, Li Z. Characteristics of Microplastic Pollution in Agricultural Soils in Xiangtan, China. Sustainability. 2024; 16(17):7254. https://doi.org/10.3390/su16177254

Chicago/Turabian Style

Ye, Cong, Jing Lin, Zhenguo Li, Guanghuai Wang, and Zeling Li. 2024. "Characteristics of Microplastic Pollution in Agricultural Soils in Xiangtan, China" Sustainability 16, no. 17: 7254. https://doi.org/10.3390/su16177254

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