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Article

Characteristics and Significance of Natural Nanoparticles in the Groundwater of the Baotu Spring Area in Jinan, Shandong Province, Eastern China

by
Caiping Hu
1,2,
Rui Liu
1,2,3,*,
Peng Zhang
3,
Yaqin Wang
3,
Lei Zuo
3,
Xiaoheng Zhang
3 and
Changsuo Li
1,2,*
1
801 Institute of Hydrogeology and Engineering Geology, Shandong Provincial Bureau of Geology & Mineral Resources (Shandong Provincial Geo-Mineral Engineering Exploration Institute), Jinan 250014, China
2
Shandong Engineering Research Center for Environmental Protection and Remediation on Groundwater, Jinan 250014, China
3
School of Resources and Environmental Engineering, Shandong University of Technology, Zibo 255000, China
*
Authors to whom correspondence should be addressed.
Water 2024, 16(13), 1820; https://doi.org/10.3390/w16131820
Submission received: 8 May 2024 / Revised: 19 June 2024 / Accepted: 20 June 2024 / Published: 26 June 2024
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Abstract

:
Karst groundwater is a crucial water source, but it has faced significant environmental risks in recent years. The complexity of the groundwater system necessitates innovative approaches to studying karst groundwater. This paper focuses on the karst groundwater of the Baotu Spring area in Jinan. Using the nanoparticle tracking analysis instrument, it is observed that the collected groundwater contains many natural nanoparticles, with particle sizes mainly ranging from 76.3 to 621.8 nm and concentrations primarily between 0.31 and 5.0 × 105 Particles/L. The transmission electron microscope (TEM) is used to study the characteristics of naturally occurring nanoparticles in the karst groundwater. The results show that the karst groundwater mainly contains particles of Ca, Na, Fe, Al, Si, and other elements, which exist in granular and irregular forms. The size of individual particles varies from 40 to 600 nm, and they are mostly amorphous and monocrystalline. The characteristics of the particles suggest that the direct recharge area mainly receives infiltration from atmospheric precipitation, with minimal influence from human activities and agriculture. In contrast, the indirect recharge and discharge areas are more significantly affected by external environments, including domestic sewage, industrial wastewater discharge, and agricultural fertilizers. These findings also suggest that elements can be transported in particle form during water-rock interactions, potentially playing a significant role in the cycling of elements between water and rocks. The particles in the study area are situated in a relatively oxidized environment, suggesting that fracture and oxidation are the main processes for particle formation. Particles can effectively transport metallic elements in groundwater, offering fresh perspectives on the migration of these elements and acting as carriers for inorganic substances, thereby increasing their mobility in aquatic environments. Given the widespread presence of natural nanoparticles in the water cycle system, some stable nanoparticles can serve as new types of groundwater tracing agents during the groundwater migration process.

1. Introduction

Water is one of the fundamental resources for the survival of all life on Earth, and water resources are key elements of the natural ecological environment [1,2]. Groundwater, essential to freshwater resources, holds a pivotal role within the broader water resource system [3]. As an essential part of urban water cycles, groundwater quality directly affects the life, health, and safety of urban residents. Karst aquifers, which provide nearly 25% of the world’s drinking water [4], are significant water resources. In China, karst regions are extensive, covering about one-third of the country’s territory, making it one of the most karst-rich nations in the world. Among these regions, the Jinan Spring area is a prominent and representative large karst spring in the north. The spring water emerges from the karst groundwater in an almost vertical motion to the surface [5]. The primary water supply in the Jinan Spring area is karst water [6], which is a crucial form of groundwater [7]. With rapid economic development and urbanization, infrastructure expansion, environmental pollution, and ecological destruction have increasingly disrupted the karst water system. This disruption has led to the breakdown of the natural chemical balance of groundwater, reduced the recharge area of the spring, and deteriorated the aquatic ecological environment. Despite significant research on the groundwater of the Baotu Spring area, there remains considerable debate over issues such as the recharge, flow, and discharge pathways of karst water, as well as the impact of flow processes on water quality. Therefore, studying the groundwater in the Baotu Spring area requires the exploration of new research methods for further in-depth investigation.
Nanomaterials are an essential component of the Earth’s system, formed by atoms and molecules at the nanoscale [8]. These materials are ubiquitous in the natural environment and exist stably across various spheres of the Earth’s system (including the lithosphere, pedosphere, biosphere, hydrosphere, and atmosphere), particularly within the Earth’s critical zone [9]. Nature itself is a major producer of nanoparticles, with many natural processes generating nanoparticles, such as mineralization [10], oxidation and reduction [11,12], fault activities [13,14], microbial actions [15] and volcanic eruptions [16]. According to Wiggington et al. [17], these nanoparticles derive from both geochemical and biological processes and are commonly found in soil and groundwater. Moreover, research has indicated that environmental nanoparticles are present in a wide range of natural aquatic systems, including underground aquifers, surface lakes, and rivers. Because of their unique physicochemical properties, natural nanoparticles can offer distinctive insights into their environment, maintain this information for prolonged periods [18,19], and have the capability to transport elements [20,21]. Numerous previous studies confirm that contaminant and suspended particles (such as TiO2 nanoparticles, graphene nanoparticles, and biocolloids) can cotransport in groundwater, also indicating that elements can be stably transported as nanoparticles in the groundwater [22,23,24,25,26].
Based on this, the study observes and analyzes the characteristics of nanoparticles in the groundwater of the Baotu Spring area in Jinan City. It focuses on the ultrastructural features (morphology, size, crystal type, crystalline state, and aggregation state) of nanoparticles in this region’s groundwater, as well as their chemical composition and element distribution patterns. Additionally, the research investigates how nanoparticles can indicate groundwater sources across different strata in this area. The study confirms the existence of natural nanoparticles in the groundwater and identifies their sources. Furthermore, it demonstrates the role of these nanoparticles in revealing the factors influencing groundwater quality and the evolution of the water cycle in this region.

2. Geological Setting

Jinan City, the capital of Shandong Province, is located at 36°40′ N latitude and 117°00′ E longitude, in the central part of Shandong (Figure 1). Known internationally as the “City of Springs”, Jinan is situated on the alluvial and inclined land at the northern foothills of the Tai Mountain range. This area has undergone multiple tectonic movements, primarily during the Yanshan period, leading to well-developed karst formations. The Jinan Spring area is situated at the intersection of the northern edge of the central mountains in Shandong and the adjacent sloping plains. The terrain slopes from high in the south to low in the north. The southern part consists of steep mid-low mountain areas, the central part features low mountains and hilly areas with gentler slopes, and the northern part includes the sloping plains in front of the mountains and the Yellow River alluvial plains, characterized by flat terrain. The Baotu Spring area in Jinan is found in a mid-latitude inland region, experiencing a warm temperate continental climate marked by distinct seasons. The average annual precipitation and evaporation in the study area are 698 mm and 1475.6 mm, respectively.
The geological structure of the research area is a north-dipping monocline dominated by Paleozoic carbonate rock layers. The monocline structure features a large number of fractures, with several being extensive. Stratigraphically, the area comprises the Archean Taishan Group, Paleozoic Cambrian, Ordovician, Carboniferous–Permian, Cenozoic Tertiary, and Quaternary systems, arranged from oldest to youngest. The Archean Taishan Group, primarily composed of mixed gneiss such as biotite plagioclase gneiss, amphibolite, and biotite metagranite, is extensively distributed in the southern part of the region, forming the base layer of the Jinan Spring area. The Paleozoic Cambrian, mainly distributed in a near east–west belt in the central and southern part of the region and unconformably overlying the pre-Sinian strata, is the most complete sedimentary formation in Jinan, consisting of limestone, marly limestone, and sandstone. The Ordovician, conformably overlying the Cambrian, is distributed in the central and northern parts of the area and consists of shallow marine to coastal carbonate rocks. The Carboniferous–Permian is largely concealed beneath the Quaternary in the north, mainly composed of shale and claystone. Quaternary deposits are found extensively throughout the region, primarily in the piedmont inclined plains, the northern Yellow River alluvial plain, and inter-mountain river valleys, with lithology mainly consisting of sandy clay, clayey sand, and clay. The Jinan area not only has complex types of igneous rocks but also a long evolutionary history. The igneous rocks are mainly Yanshanian intrusive bodies, composed of intermediate to basic intrusive rocks, primarily including gabbro and diorite.
The research area lies within the hydrogeological region characterized by a northward dipping monocline structure situated in the northern part of Mount Tai, with higher terrain to the south and lower terrain to the north. The inclination of the strata directs groundwater flow generally from south to north. The area can be divided into four major aquifers: the loose rock porous aquifer, the carbonate rock fracture-karst aquifer, the clastic rock with carbonate fracture-karst aquifer, and the massive rock fracture aquifer. The loose rock porous aquifer is mainly distributed in intermountain valleys, and alluvial plains formed by rivers originating from the piedmont and along the Yellow River zone. It is primarily composed of gravel, clay, and sandstone. The carbonate rock fracture-karst aquifer consists of Cambrian and Ordovician aquifers. The Cambrian aquifer comprises limestone and shale, while the Ordovician aquifer comprises highly soluble limestone, dolomitic limestone, dolomite, and mudstone limestone. This aquifer is characterized by well-developed karst fractures that facilitate groundwater recharge, flow, and enrichment. The clastic rock with carbonate fracture-karst aquifer, formed by Cambrian strata, consists of limestone and shale layers or interbedding, with poorly developed fractures and poor water richness. The massive rock fracture aquifer includes intrusive and metamorphic rock porous fractured aquifers. The intrusive rock porous fracture aquifer is mainly composed of gabbro, diorite, and granite. The metamorphic rock porous fracture aquifer mainly consists of gneiss and amphibolite. Groundwater movement primarily occurs within the pores and fractures of the weathered rock zone. Due to the fine nature of the fractures, the aquifer exhibits poor water richness and uneven distribution.
The sources of karst groundwater recharge in the Jinan Spring area mainly include atmospheric precipitation, surface water infiltration, irrigation return flow, and Quaternary porous water. Atmospheric precipitation is the main source of karst water recharge in Jinan. The Cambrian–Ordovician limestone, which is widely distributed in the southern mountainous area, facilitates the development of surface and underground karst features due to its solubility. Surface karst formations provide highly favorable conditions for direct infiltration of atmospheric precipitation into the groundwater, while well-developed underground karst voids offer extensive space and channels for groundwater storage and movement. The main discharge methods of groundwater in the research area include spring discharge, artificial extraction, subsurface flow discharge, and surface flow discharge.
The hydrochemical type of groundwater in the Jinan Spring area is mainly characterized by HCO3-SO4-Ca, with a variety of types coexisting, demonstrating a complex hydrochemical system [28]. Under the dual influence of natural and human-induced factors, such as groundwater extraction, irrigation, and wastewater discharge, etc., the hydrochemical field of karst groundwater in the Jinan Spring area has undergone significant changes. The hydrochemical characteristics of the study area are mainly influenced by precipitation dissolution and cation exchange processes, with the intensity of dissolution precipitation being greater than that of cation exchange [29].

3. Sampling and Analytical Methods

In this study, a total of 18 groundwater samples were collected from both the recharge and discharge areas of the Baotu Spring region in Jinan (Figure 2). The containers were rinsed with source water at least three times during the sampling process. Samples were taken from wells (holes) that are frequently pumped, generally involving 50 min of pumping (about 3.5 m3 of water at a pumping rate of 4.2 m3/h [30]) before sampling to ensure that the groundwater obtained corresponds to the aquifer. We used a 50 mL volumetric flask to initially collect a small amount of groundwater, rinsed the flask once, then filled it with more than 30 mL of groundwater, capped it, and sealed it for storage.
Initially, the groundwater samples’ particle sizes and concentrations were meticulously determined using nanoparticle tracking analysis (NTA) with a ZetaView PMX 110 instrument (Particle Metrix, Meerbusch, Germany) and the ZetaView 8.04.02 software. Measurements across 11 distinct positions were captured and thoroughly analyzed. To ensure precision, the system was calibrated using 110 nm polystyrene particles, under ambient temperature conditions ranging from approximately 23 °C to 30 °C.
For investigation at nanoscale, we primarily use transmission electron microscopy (TEM) with a maximum acceleration voltage of 200 kV. TEM foils are prepared by extracting samples, attaching them to Cu grids with Pt welding, and thinning them to 50–70 nm. Based on the TEM, we can image at nanoscale, study crystal structure, and dislocations, and analyze the morphology and size of nanoparticles. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging is performed using an FEI Titan Themis TEM. The model of HAADF-STEM is standard HAADF-STEM. High-resolution TEM (HRTEM) images are processed and analyzed with Gatan’s Digital Micrograph software (version 3.7.4). Elemental distribution was determined using energy-dispersive X-ray spectrometry (EDS). Model of EDS is standard EDS system. Selected area electron diffraction (SAED), which provides detailed information about the crystal structure, phase composition, and defects present in nanoparticles, is used software tools for digital analysis and enhancement of diffraction patterns. All analyses, including TEM and EDS, are carried out at the Sinoma Institute of Materials Research in Guangzhou, China.

4. Results and Discussion

4.1. Characteristics of Nanoparticle in the Groundwater of the Baotu Spring Area

Based on the experimental data results of the NTA test (Table 1), groundwater collected from different locations contains many nanoparticles. The particle size range in different types of groundwater is mainly concentrated between 76.3 and 621.8 nm, and the concentration of nanoparticles is primarily focused at 0.31–5.0 × 105 Particles/mL (Table 1).
There are 14 samples of karst groundwater, with approximately 200 particles analyzed in total. The EDS spectral analysis of nanoparticles shows that nanoparticles mainly contain C, O, Ca, Fe, Si, Mg, N, K, and Na (Table 2). In addition, there are some trace elements occurring in these nanoparticles, such as S, P, Cl, Mn, Cr, Ni, Mn, and Te. In the transmission electron microscope (TEM) images, the size of individual particles varies from 40 to 600 nm (Figures S1–S18). The selected area electron diffraction (SAED) patterns show that these particles are mostly amorphous and monocrystalline (Figures S1–S18).

4.2. Comparison of Nanoparticle in the Groundwater from Recharge Area and Discharge Area

Results show that the groundwater in the recharge area and discharge area contains a large number of nanoparticles, with the main components of the particles being Ca, Na, and Fe. The particles mostly exist in granular and irregular forms, with individual particle sizes ranging from 76.3 to 621.8 nm, and are mostly amorphous and single crystals. Specific characteristics are as follows:
Ca-bearing nanoparticles: Calcium-bearing nanoparticles in the groundwater of the Baotu Spring area are widely found, often in near-spherical, granular, and irregular shapes. Compositionally, they are mostly carbonates, sulfates, and calcite (CaCO3) of calcium, with the carbonates of calcium often containing impurities of metal elements such as Mg, Na, and Al, and non-metal elements such as Si and Cl. The mixtures of Ca-bearing carbonates and sulfates are often adulterated with metal elements, such as Mg and Na, and non-metal elements, such as Si and Cl. Ca-bearing nanoparticles of the same type have a certain regularity in morphology; carbonate particles of calcium are mostly in near-spherical shapes (Figure 3), mixtures of Ca-bearing carbonate and sulfate are in granular shapes (Figure 4), and calcite particles are in granular shapes (Figure 5).
Fe-bearing nanoparticles: Iron nanoparticles are often in the form of cubic and irregular aggregates in the groundwater of the Baotu Spring area. Compositionally, they are predominantly hematite (Fe2O3), iron-bearing carbonates, and iron-containing oxides, with hematite often containing impurities of metal elements, such as Ti, Al, and Mg, and non-metal elements, such as Si. The Fe-bearing carbonates often include adulterations of metal elements, such as Ca and Mg, and non-metal elements, such as Si. The Fe-bearing oxides are frequently mixed with metal elements, such as Ca, Mg, and Al, and non-metal elements, such as Si and Cl. Iron-bearing particles of the same type exhibit certain regularities in morphology; hematite particles often appear as cubic aggregates (Figure 6), and iron oxide particles are in aggregate forms (Figure 7).
The above research indicates that the composition of the nanoparticles in groundwater from the recharge area and discharge area is relatively consistent, which is also the same as the nanoparticles found in the hot spring in Northern Jinan (see the details in Zuo et al. [27]). These findings indicate that the recharge area and discharge area, as well as the northern geothermal zone, indeed have certain hydraulic connections.

4.3. Genesis Nanoparticles in the Groundwater of the Baotu Spring Area

Many natural activities can produce nanoparticles, leading to a significant natural reserve of nanoparticles in the environment [10,11,12,13,14,15,16]. The nanoparticles in the study area mainly exist in the form of carbonates, sulfates, halite, and oxides, indicating that these particles are in a relatively oxidized environment [32]. This is speculated to be related to the developed fracture zones in the study area. During the faulting process, changes in the surrounding pressure and temperature can cause chemical reactions in the nearby mineral components, such as oxidation reactions. The study area is characterized by the development of faulted structural belts. Faults also provide channels for oxygen to enter deep strata, increasing the oxygen fugacity between rock layers. At the same time, fault activity often fractures, grinds, and oxidizes the surrounding rocks, promoting the formation of oxide nanoparticles. Some nanoparticles exist in the form of sulfates, which is believed to be due to the oxidation of sulfides (e.g., pyrite, etc.), to form sulfates. The topography of the study area slopes from south to north, and its geological structure is generally a north-dipping monocline structure dominated by Paleozoic strata. The direct recharge area can form hydraulic connections through intra-area faults, magmatic rock fracture zones, and other structures. The groundwater flow system in the direct recharge area is affected by topography, geological structure, and extraction, leading to a long pathway for groundwater flow. Therefore, under hydrogeological conditions with a certain stability, the previously formed elemental nanoparticles can achieve long-distance migration.

4.4. The Characteristics and Significance of the Composition within Nanoparticles in the Groundwater

Nanomaterials present enhanced reactivity and thus better effectiveness when compared to their bulkier counterparts due to their higher surface-to-volume ratio. In addition, nanomaterials offer the potential to leverage unique surface chemistry as compared to traditional approaches. Therefore, the nanomaterials can contain many elements, that have a close relationship with the environment in which the nanomaterials occur.
In this study, the composition of some nanoparticles (e.g., G15) in the direct recharge area is relatively simple, and it is the same as the composition with the groundwater. This finding indicates that the groundwater at the sampling point is not contaminated. In addition, the composition of the groundwater and nanoparticles is mainly affected by the atmospheric precipitation and aquifers. On the contrary, the composition of some nanoparticles (e.g., JS12) in the direct recharge area is relatively complex. Metal elements, such as Mg, Al, K, Ca, Fe, and Ti are widely present, and there are many heavy metal elements (e.g., Mn, Cr, and Ni) occurring in some particles. In addition, nanoparticles in JS12-2 have higher contents of N element. The sampling point of JS12 is located in the villages and industrial areas. Therefore, we favor that the presence of some heavy metal elements in the nanoparticle may be caused by domestic sewage and industrial wastewater. The N occurring in the nanoparticles is impacted by the nitrate which is considered to be the largest pollutant affecting the quality of the groundwater environment in the Jinan area [33].
Similarly, some nanoparticles (e.g., YR39 and YR41) in indirect recharge areas are also relatively simple, and these particles usually contain common elements in groundwater (such as Mg, Na, Cl, K, etc.). This indicates that human activities have a relatively small impact on these sampling points. However, some nanoparticles contain many other metal elements, such as Mn, Cr, Ni, and Te. These elements mainly come from the aquifers where the sampling point is located. For example, the LX44 aquifer consists primarily of diorite, composed mainly of feldspar and dark minerals. Therefore, the nanoparticles in these samples contain Mn, Cr, and Ni. The aquifer of the YR41-2 contains more dolomite which is the important carrier of Te. This may be the reason that the nanoparticles in this sample contain Te. The N occurring in many nanoparticles also indicates that the groundwater in these sampling sites has been contaminated with nitrate.
The discharge area of the Baotu Spring area is located in the residential areas, and the groundwater in this area is easily affected by the daily life of residents (e.g., such as food and metabolites). Therefore, the nanoparticles in the discharge area usually contain P, which has a close relationship with human activities.
All these findings indicate that the composition of nanoparticles in the groundwater has a close relationship with the aquifer and environment. The nanoparticles can reflect the composition of the aquifer and perhaps be an indicator of water quality.

4.5. The Application Prospects of Nanoparticles in Researching the Water Cycle

Groundwater tracer experiments are an effective method to obtain the hydrogeological conditions and regional groundwater flow field, such as groundwater recharge sources, runoff paths, and discharge pathways [34]. Tracers can usually be divided into natural tracers and artificial (applied) tracers, and their role is to obtain groundwater flow field and physical migration information [35]. In the study of groundwater systems, inert chemical components are used to reflect changes in rainfall input and paleoclimatic conditions. The most important inert chemical components are Cl− and Br− (under aerobic conditions), which reflect what happened along the runoff path and the water–rock interaction [36,37,38,39]. Using the changing patterns of environmental isotopes in different times and spaces, quantitative research can be completed on the recharge, runoff, and discharge conditions of regional groundwater [40,41,42,43]. Hydrogen- and oxygen-stable isotopes form a significant portion of natural water molecules and are ideal water tracer agents [44]. During the groundwater runoff process, various minerals are continuously dissolved, leading to changes in the ion concentration in the groundwater through interactions with the surrounding rock. Such ions can be regarded as reaction tracers (such as Mg2+, Ca2+, Na+, K+, HCO3−, and SO42−, etc.) [45,46].
By analyzing the ultrastructure and chemical components of nanoparticles in groundwater from different locations, it has been found that the nanoparticles contained in water samples from the recharge area and the discharge area exhibit a degree of similarity, but there are also notable differences. Affected by topography, groundwater flows from south to north. However, due to the influence of the surrounding environment and human production and living activities during the runoff process, the chemical element composition has certain differences. By analyzing the characteristics and chemical components of all nanoparticles, it can be found that some nanoparticles with strong stability can be detected in the supply and excretion area. Therefore, some mineral nanoparticles can also be used as a new type of groundwater tracing reagent, and such mineral nanoparticles that naturally exist in the water environment will not cause harm to the water environment (Figure 8).
Research findings suggest that natural nanoparticles can persist in groundwater in a stable manner, serving as carriers for transporting elements in nanoparticle form. Liang et al. [47] believe that nanoparticles can selectively adsorb metals and have high adsorption properties. Nanoparticles can fully carry heavy metal elements (e.g., Pb, Cd, Cu, Zn, and Ni) during groundwater transport [48]. In this study, nanoparticles contain Ca, Na, Fe, Ti, Mn, Cr, Ni, and Te in composition, showing that the nanoparticles can fully carry metal elements during groundwater transportation. This offers new insights into the movement of metal elements in groundwater, with nanoparticles serving as carriers for inorganic substances, thereby enhancing their mobility in aquatic environments. This perspective opens new avenues for deeper comprehension of groundwater systems.

5. Conclusions

In this study, natural nanoparticles in the groundwater of the Baotu Spring area in Jinan City are analyzed using nanoparticle tracking analysis and transmission electron microscopy. Based on the characteristics of the nanoparticles, we draw the following conclusions:
(1)
A significant number of nanoparticles have been detected in the groundwater samples of the study area. These nanoparticles mainly consist of Ca, Na, Fe, Al, and Si. They typically exhibit granular and irregular shapes, with individual sizes ranging from 76.3 to 621.8 nm. They are predominantly in both amorphous and crystalline forms.
(2)
Compared to the characteristics of nanoparticles in indirect recharge area, direct recharge area, and discharge area, the same nanoparticles exhibit certain similarities in morphology, size, structure, aggregation state, and elemental composition, indicating that there are hydraulic connections between the recharge area and discharge area.
(3)
Based on the geological background and the composition of nanoparticles, we propose that the nanoparticles observed in this study are formed in a relatively oxidizing environment, likely as a result of fracturing and oxidation processes.
(4)
The composition of some nanoparticles is relatively simple, while others are more complex. This suggests that the composition of nanoparticles in the groundwater is closely related to the aquifer and environmental conditions. Nanoparticles can reflect the composition of the aquifer and may serve as indicators of water quality.
(5)
The presence of certain metal elements in nanoparticles suggests that nanoparticles can effectively transport metal elements in groundwater, offering new insights into the migration of metal elements in groundwater systems. Nanoparticles can act as carriers of inorganic substances, enhancing their mobility within water systems. Additionally, stable nanoparticles can be detected in both supply and discharge areas. Therefore, nanoparticles can also serve as a novel groundwater tracer agent for assessing water quality.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/w16131820/s1, Figure S1: (a) Particle morphology (yellow circle) and (b) diffraction pattern of BQ-1. Figure S2: (a) Particle morphology (yellow circle) and (b) diffraction pattern of BTQ-1. (c) Particle morphology (yellow circle) and (d) diffraction pattern of BTQ-2. Figure S3: (a) Particle morphology (yellow circle) and (b) diffraction pattern of BTQ-4. Figure S4: (a) Particle morphology (yellow circle) and (b) diffraction pattern of BTQ-6. Figure S5: (a) Particle morphology (yellow circle) and (b) diffraction pattern of BTQ-9. Figure S6: (a) Particle morphology (yellow circle) and (b) diffraction pattern of BTQ-11. Figure S7: (a) Particle morphology and (b) diffraction pattern of LX44-1. Figure S8: (a) Particle morphology and (b) diffraction pattern of LX44-3. Figure S9: (a) Particle morphology (yellow circle) and (b) diffraction pattern of YR33-2. Figure S10: Particle morphology (yellow circle) of YR38-1 (a) and YR38-4 (b). Figure S11: Particle morphology (yellow circle) of YR38-6. Figure S12: (a) Particle morphology and (b) diffraction pattern of YR39-2. Figure S13: (a) Particle morphology and (b) diffraction pattern of YR41-1. Figure S14: (a) Particle morphology (yellow circle) and (b) diffraction pattern of YR41-2. Figure S15: Particle morphology (blue circle) of G15-5. Figure S16: Particle morphology (blue circle) of ZETJ-2. Figure S17: Particle morphology of JS12-2 (a) and JS12-3 (b). Figure S18: (a) Particle morphology and (b) diffraction pattern of JS12-6.

Author Contributions

Methodology, C.H.; resources, L.Z.; data curation P.Z. and Y.W.; writing—original draft preparation, C.H. and R.L.; visualization, X.Z.; supervision, C.L.; funding acquisition, R.L. All authors have read and agreed to the published version of the manuscript.

Funding

This work was jointly supported by the National Natural Science Foundation of China (Grant Nos. 42102076 and 42077129), Shandong Province Natural Science Foundation under Grant No. ZR2021QD037 and ZR2020ZD19, and SDUT and Zibo City Integration Development Project (NO. 2021SNPT0012).

Data Availability Statement

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

Conflicts of Interest

The authors declare no conflict of interest.

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Water 16 01820 g001
Figure 1. Locations of the Baotu Spring area in Jinan, Shandong province, Eastern China (a,b modified from the Zuo et al. [27]). (a) Location of Shandong province in Chian; (b) Location of Jinan city in Shandong province; (c) Geological sketch of the Baotu Spring area.
Figure 1. Locations of the Baotu Spring area in Jinan, Shandong province, Eastern China (a,b modified from the Zuo et al. [27]). (a) Location of Shandong province in Chian; (b) Location of Jinan city in Shandong province; (c) Geological sketch of the Baotu Spring area.
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Figure 2. (a) The sampling location and the land use and geological schematic diagram (modified from the Zuo et al. [31]), and (b) section map of the research area.
Figure 2. (a) The sampling location and the land use and geological schematic diagram (modified from the Zuo et al. [31]), and (b) section map of the research area.
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Figure 3. Particle morphology of Ca-bearing carbonate particles in groundwater (a: BQ-1, b: YR38-1, c: YR38-4).
Figure 3. Particle morphology of Ca-bearing carbonate particles in groundwater (a: BQ-1, b: YR38-1, c: YR38-4).
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Figure 4. Particle morphology of mixtures of Ca-bearing carbonate and sulfate (in blue circle) in groundwater. (a: BTQ-4, b: BTQ-6, c: G15-5, d: ZETJ-2).
Figure 4. Particle morphology of mixtures of Ca-bearing carbonate and sulfate (in blue circle) in groundwater. (a: BTQ-4, b: BTQ-6, c: G15-5, d: ZETJ-2).
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Figure 5. Particle morphology of aragonite particles (a,b in bule circle) in groundwater (a: BTQ-1, b: BTQ-2, c: YR39-2).
Figure 5. Particle morphology of aragonite particles (a,b in bule circle) in groundwater (a: BTQ-1, b: BTQ-2, c: YR39-2).
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Figure 6. Particle morphology of hematite particles in groundwater (a: BTQ-9, b: LX44-1, c: YR38-6).
Figure 6. Particle morphology of hematite particles in groundwater (a: BTQ-9, b: LX44-1, c: YR38-6).
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Figure 7. Particle morphology of Fe-bearing oxide particles in groundwater (a: JS12-2, b: JS12-3).
Figure 7. Particle morphology of Fe-bearing oxide particles in groundwater (a: JS12-2, b: JS12-3).
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Figure 8. Model pattern of relationship between nanoparticles and environment.
Figure 8. Model pattern of relationship between nanoparticles and environment.
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Table 1. The results of NTA analysis of the groundwater in Baotu Spring are.
Table 1. The results of NTA analysis of the groundwater in Baotu Spring are.
SamplesSize (nm)Concentration (Particles/mL)Groundwater TypeArea
BQ *155.9–537.81.50–4.10 × 105SpringDischarge area
BTQ *151.5–621.80.45–1.90 × 105SpringDischarge area
LX4586.2–391.20.32–2.00 × 105Karst waterIndirect recharge area
ZETJ122.1–365.31.00–5.20 × 105Karst waterIndirect recharge area
G15188.6–509.20.98–5.10 × 105Karst waterDirect recharge area
JS12 *76.3–299.40.31–1.50 × 106Karst waterDirect recharge area
Note: * date is from the Zuo et al. (2024) [24].
Table 2. EDS results (wt.%) of sample nanoparticles.
Table 2. EDS results (wt.%) of sample nanoparticles.
SamplesCNPOCaSClSiMgFeAlNaKCrMnNiTe
BQ-128.63 0.3263.457.44 0.17
BTQ-135.23 45.3019.48
BTQ-236.15 6.3439.5116.72 1.28
BTQ-47.02 49.6619.9816.531.89 1.54 1.921.47
BTQ-67.97 47.7221.9416.091.450.732.08 1.230.78
BTQ-923.12 47.19 0.57 29.13
BTQ-11 0.95
LX44-14.84 48.18 46.99
LX44-312.87 16.27 0.47 1.15 43.83 10.9711.811.95
YR33-25.4322.32 51.19 0.45 19.96
YR38-129.59 52.2318.19
YR38-445.36 30.1217.492.78 3.25 0.99
YR38-65.55 37.46 57.00
YR39-237.74 43.8218.06 0.39
YR41-163.27 23.7211.99 0.610.40
YR41-234.76 22.5019.261.330.250.392.50 1.140.47 17.40
G15-513.15 49.4219.0015.450.530.401.05 1.00
ZETJ-222.50 43.0017.2614.75 0.210.62 1.280.39
JS12-210.30 48.961.410.140.285.370.4532.140.94
JS12-317.022.950.1929.481.46 3.520.4241.022.75 0.13
JS12-625.43 15.01 0.85 36.08 10.488.802.83
Note: BQ, BTQ, LX, YR, G, ZETJ, and JS are the abbreviations of the sampling locations.
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Hu, C.; Liu, R.; Zhang, P.; Wang, Y.; Zuo, L.; Zhang, X.; Li, C. Characteristics and Significance of Natural Nanoparticles in the Groundwater of the Baotu Spring Area in Jinan, Shandong Province, Eastern China. Water 2024, 16, 1820. https://doi.org/10.3390/w16131820

AMA Style

Hu C, Liu R, Zhang P, Wang Y, Zuo L, Zhang X, Li C. Characteristics and Significance of Natural Nanoparticles in the Groundwater of the Baotu Spring Area in Jinan, Shandong Province, Eastern China. Water. 2024; 16(13):1820. https://doi.org/10.3390/w16131820

Chicago/Turabian Style

Hu, Caiping, Rui Liu, Peng Zhang, Yaqin Wang, Lei Zuo, Xiaoheng Zhang, and Changsuo Li. 2024. "Characteristics and Significance of Natural Nanoparticles in the Groundwater of the Baotu Spring Area in Jinan, Shandong Province, Eastern China" Water 16, no. 13: 1820. https://doi.org/10.3390/w16131820

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