Surface Water Samples Research Articles

Quality Of Drinking Water In An Area With High Gold Panning Activity In Côte d'Ivoire (Daloa, Centre-West)

Background: Gold panning has experienced remarkable growth in recent decades in Côte d’Ivoire. This activity contributes substantially to local economies. However, the use of toxic chemicals has an impact on human health and the environment, particularly water resources. The aim of this study was to evaluate the level of contamination of drinking water by metallic trace elements, cyanide and pesticides in an area with high gold panning activity in Côte d'Ivoire. Materials and Methods: Five (5) surface water samples and 5 well water samples were collected in the area of the gold panning sites and then analyzed. The metallic trace elements were measured by atomic absorption spectrometry. Total cyanides were measured according to the NF EN ISO 14403-1 standard and the pesticides were analyzed using a UV-visible HPLC chain. Results:The average concentrations of the metallic trace elements found were 0.125; 0.002; 0.046; 0.036 and 0.009 µg/L respectively for arsenic, Cadmium, Iron, Lead and mercury in surface waters. In the well water, the concentrations of arsenic, cadmium, iron, lead and mercury were respectively 0.025; 0.001; 0.009; 0.007 and 0.002 µg/L. The average concentration of arsenic in all surface water samples and three well water samples was higher than the standard set by WHO (0.01 mg/Kg) for drinking water. Lead and mercury levels in surface water were also higher than recommended standards for drinking water. Cyanide has been found in surface and well waters at relatively low concentrations. Twenty-five pesticides belonging to the chemical families of organochlorines, organophosphates, carbamates and other compounds derived from urea and atrazine were found in the water samples analyzed. Farmer’s well water was qualitatively the most contaminated with the simultaneous presence of several pesticides. The sum of the measured pesticide concentrations for each sample complied with the recommendations for drinking water, set at 0.50 µg/L. Conclusion: Drinking water in this locality is contaminated by metallic trace elements, cyanide and pesticides. The quality of drinking water in this locality must be subject to permanent monitoring in order to protect the health of the population.

Quality and health impact of groundwater in a coastal region: a case study from west coast of southern India.

Seawater intrusion seriously threatens the quality of coastal groundwater, affecting nearly 40% of the world's population in coastal areas. A study was conducted in the Kamini watershed situated in the Udupi district of Karnataka to assess the groundwater quality and extent of seawater intrusion. During the pre-monsoon period, 57 groundwater and 3 surface water samples were analyzed to understand the impact of seawater on the groundwater and surface water. The analysis revealed that the groundwater in the study area is slightly alkaline. The weighted overlay analysis map indicated that 11% of the study area is unsuitable for drinking water due to the influence of seawater. The Piper plot analysis revealed that the groundwater is predominantly CaMgCl facies. The hydrogeochemical facies evolution diagram (HFED) showed that 62% of the groundwater is affected by seawater. The HFED and Piper plots also indicate that the surface water is also affected by seawater. These results are also supported by various molar ratios such as Cl- vs. Cl⁻/HCO3⁻, Cl⁻ vs. Na⁺/Cl⁻, Cl- vs. SO42-/Cl-, and Cl⁻/HCO3- vs. Mg2+/Ca2+, suggesting that the majority of the water sample has been affected by seawater. The saturation indices indicated that mineral dissolution has significantly contributed to groundwater salinization. The correlation between sulfate concentration and calcite and dolomite dissolution suggested the influence of seawater intrusion in the coastal aquifer. The process of reverse ion exchange mainly influences the groundwater chemistry according to chloroalkali indices. The total hazard index (THI) values of nitrate and fluoride exceeded limits, posing health risks to adults and children. Studies suggest that with time and space, seawater intrusion is increasing in some pockets of the study area, especially along the west coast.

First report of Acanthamoeba spp. isolation in a recreational hot spring in the Philippines.

Natural hot springs are ideal places and environmental matrices that offer relaxation to people and microorganisms of different types. A total of 40 surface water samples were collected from the five identified collection sites, eight water samples for each site. Collection sites are designated 200 m apart to cover the entire study site. Surface water samples were collected approximately 10-20 cm from the surface. Water samples were filtered, cultured, and microscopically observed for 14 days. After 14 days of cultivation, eight (20%) water samples revealed cystic and trophozoite stages. Polymerase chain reaction using JDP1 and JDP2 specific primers confirmed the presence of Acanthamoeba spp. from two of our isolates in the hot spring, isolates 1.1 and 5.1. Further sequencing revealed that the isolates are Acanthamoeba T20 and Acanthamoeba genotype T7. Sequences were deposited to GenBank and were assigned accession numbers PP741726 and PP741727, respectively. The isolation of Acanthamoeba spp. in hot springs has significant health implications, especially for those who use it for recreational activity. Private resort owners are highly encouraged to regularly monitor and maintain hot spring resorts to avoid future infections.

Contamination of toxic elements in the sediments, water, and igneous rocks of the Sefid-rud River in Northern Iran using contamination indicators, with a specific focus on Ti-rich coastal sediments

The Sefid-rud River is a significant river on the southern coast of the Caspian Sea in Iran. In this study, we collected 28 samples of surface sediments and water to assess the level of metal contamination. Chemical analysis revealed that the average concentrations of heavy metals in both sediments and water increase from upstream to downstream. There is no clear significant relationship observed between changes in the values of investigated elements in sediments and water. The levels of these elements in the sediments, exceed toxic response thresholds. In the water samples, As, Ni and V concentrations exceed the WHO standard values. According to the Igeo, EF and PLI indices, the sediments at most stations are not contaminated by any of the elements. The CF and Dc indices suggest low contamination levels at all stations. The NIPI and ecological risk indices (Er and RI) indicate non-polluted conditions at all stations except SF22, SF20, SF11, and SF6. The MI and HEI indices indicate pollution in all water samples of the Sefid-rud, but critical values are only observed at SF5 and SF15. The other stations show no contamination. The Cf index indicates high pollution levels for all elements except Cu, Zn, and Pb. The upstream area poses a relatively high and considerable ecological risk according to the PERI index. In conclusion, the sediments of the Sefid-rud River have a higher potential for the exchange of toxic substances compared to the aquatic environment.

Simultaneous determination of 61 hormones in water by solid phase extraction-ultra performance liquid chromatography-tandem mass spectrometry

Concerns over the emergence of steroid hormones as pollutants in water have grown. Steroid hormone compounds present challenges in the simultaneous detection of total residual hormones owing to their analogous structures and diverse types. In this study, we established a rapid and high-throughput continuous online method based on solid phase extraction (SPE) coupled with ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) for the simultaneous determination of 61 hormone components, including 48 glucocorticoids, 1 mineralocorticoid, 4 androgens, and 8 progesterones, in water. Various SPE columns were investigated to assess their extraction efficiency for enriching and purifying target compounds in a large sample volume (1 L). An HC-C18 SPE column was selected because of its superior performance. Acetonitrile was used as a washing solution during SPE to ensure that the majority of the tested substances achieved recoveries exceeding 70% and effectively avoid interferences from water-soluble components. Various C8 and C18 columns were tested, and the optimal HPLC conditions for hormone retention were established. We systematically evaluated different UPLC columns and mobile phases, including methanol-water and acetonitrile-water systems with 0.1% formic acid added to the aqueous phase. The optimized UPLC conditions were as follows: BEH C18 column (100 mm×2.1 mm, 1.7 μm); column temperature, 40 ℃; flow rate, 0.3 mL/min; injection volume, 5 μL; mobile phase A: 0.1% formic acid aqueous phase; mobile phase B: acetonitrile. Gradient elution was performed as follows: 0-0.5 min, 30%B; 0.5-15.0 min, 30%B-75%B; 15.0-18.0 min, 75%B-98%B; 18.0-19.0 min, 98%B; 19.0-19.1 min, 98%B-30%B; 19.1-20.0 min, 30%B. Both positive- and negative-ion modes were explored in the UPLC-MS/MS experiment to obtain the full scan of the parent ions, and positive mode was finally selected for electrospray ionization (ESI). Two product ions exhibiting strong signals and minimal interference were selected for quantitative and qualitative ion analyses, using an external standard method for quantification. MS/MS was performed in positive-ion (ESI+) mode with multiple reaction monitoring (MRM) scanning. The MS/MS parameters were as follows: atomizing gas pressure, 379 kPa; curtain air pressure, 241 kPa; spray voltage, 5500 V; desolvation temperature, 550 ℃; collision exit voltage (CXP), 13 V; intake voltage (EP), 10 V; and residence time of each ion pair, 0.5 ms. Other instrument settings, such as the collision energy and declustering voltage, were also optimized. The 61 hormones exhibited excellent linear relationships within their corresponding concentration ranges, with correlation coefficients greater than 0.99. The method detection limits (MDLs) were in the range of 0.05-1.50 ng/L. The average recoveries of the 61 hormones across three spiked levels ranged from 62.3% to 125.2%, with relative standard deviations (RSDs, n=6) of 1.1%-10.5%. Using this method, we successfully detected 10 hormone components (cortisone, fluticasone propionate, ciclesonide, betamethasone dipropionate, clobetasone butyrate, diflucortolone valerate, halobetasol propionate, isoflupredone, difluprednate, and hydroxyprogesterone caproate) in various surface water and groundwater samples collected from the Taihu Basin region. The SPE-UPLC-MS/MS method presented in this paper is simple, highly sensitivity, and exceptionally accurate. Thus, it exhibits promising potential for tracing targeted hormone residues in water and will be of great value in monitoring and ensuring water safety. Finally, a regional analysis was conducted on the hormone levels in water, and suggestions were made for the targeted treatment of hormone residues in future sewage treatment processes.

Hydrochemical processes and inorganic nitrogen sources of shallow groundwater in the Sanjiang Plain, northeast China.

This study investigates the chemical characteristics, formation, and sources of inorganic nitrogen (IN) of shallow groundwater across the Sanjiang Plain, aiming to enhance drinking water safety management and pollution control. A total of 167 groundwater and 27 surface water samples were collected for constituents and isotopes (H2 and O18). The hydrogeochemical characteristics showed that the major type is HCO3- Ca·Mg, with low total dissolved solids and a neutral to weak alkaline nature. Rock weathering processes govern the hydrochemical composition of groundwater. Hydrogen and oxygen stable isotopes analyses revealed that precipitation serves as the main water source. In alluvial areas, oxidative conditions lead to the enrichment of NO3-N concentrations, with sewage, manure, and fertilizers being the primary IN sources. In lacustrine areas, intensive rice cultivation results in reductive conditions and strong denitrification processes, causing the loss of NO3-N and leaving NH4-N as the dominant IN form. Organic matter mineralization is likely a more significant contributor to NH4-N concentrations than ammonium fertilizers. These findings provide valuable information for further research on natural sources and groundwater pollution in areas with similar hydrogeological conditions. PRACTITIONER POINTS: Rock weathering processes govern the hydrochemical composition of groundwater, and precipitation serves as the main water source. In alluvial areas, oxidative conditions lead to the enrichment of NO3-N. In lacustrine areas, intensive rice cultivation results in reductive conditions and strong denitrification processes. Organic matter mineralization is likely a more significant contributor to NH4-N concentrations than ammonium fertilizers. These findings provide references for water management and information for further research on natural sources and groundwater pollution in areas with similar hydrogeological conditions.

Evaluating the sources of microplastic contamination and quantifying its abundance in the Balu River, Dhaka, Bangladesh.

Microplastics (MPs) are prevalent environmental pollutants due to their durable composition, extensive use, and improper disposal. Despite their widespread presence, rivers have received less attention in microplastic research than other water bodies. This study focused on investigating the origins, prevalence, spatial distribution, and physicochemical characteristics of microplastics in the surface waters of the Balu River, located in Dhaka, Bangladesh. Surface water samples were collected at six sampling sites of Balu River (each about 1-5km apart) adjacent to the footwear industry, jute factory, textile mill, paper mill, agro and beverage factory, and cement plant. The study found that the average concentration of microplastics in the sampled water bodies was 102.5 ± 12.83 (items/l). Samples near the textile mill had the highest microplastic abundance (122 ± 18 items/l), while the cement plant had the lowest (58.5 ± 8 items/l). Analysis using a stereomicroscope revealed that fibers (29%), microplastics smaller than 100µm (45%), and transparent microplastics (19%) were the most prevalent types observed in terms of shape, size, and color, respectively. Furthermore, scanning electron microscopy (SEM) observation suggested the potential for additional degradation of these microplastics into smaller particles, potentially reaching the nanoplastic scale. Additionally, Fourier transform infrared (FTIR) analysis identified 07 distinct polymer types among the microplastics: nylon (24%), polyvinyl chloride (19%), high-density polyethylene (17%), low-density polyethylene (14%), polystyrene (12%), polypropylene (7%), and nitrile (7%). The findings of this study serve as a crucial indicator of microplastic contamination, providing valuable insights into the sources and magnitude of microplastic pollution within the significant freshwater ecosystem of Balu River, Bangladesh, particularly focusing on its river systems.

Phytoplankton community structure at the eastern entrance of the Gulf of California during El Niño 2023

This work aims to report the phytoplankton species composition and cell density in the Mazatlán coastal region (eastern entrance of the Gulf of California (GC), Mexico) during the strong El Niño event of 2023. Surface water samples (at 2 m depth) for phytoplankton cell determinations were collected in December of 2023, a month in which the numerical value of the Oceanic Niño Index was 2.0. The results showed a total of 197 species, including 113 diatoms (with a total cell density of 51,444 cells L-1), 76 dinoflagellates (with a total cell density of 31,260 cells L-1), four silicoflagellates (with a total cell density of 420 cells L-1), two cyanobacteria (with a total cell density of 2,020 cells L-1), one Euglenophyta (with a total cell density of 900 cells L-1) and one ciliate (with a total cell density of 7,820 cells L-1). The diatom Dactyliosolen phuketensis (B.G.Sundström) G.R. Hasle, 1996 and the dinoflagellate Gyrodinium fusiforme (Kofoid & Swezy, 1921) presented the highest cell densities with 4,100 and 5,900 cells L-1, respectively, species that have been previously reported in high abundances in Mexican waters in years of warming events, including El Niño. The results presented here contribute to understanding the effects of strong El Niño events on the phytoplankton community structure of the southeastern GC. This topic still needs to be fully addressed. This study also provides an update on the taxonomic lists available for the region of a group of organisms whose nomenclature has been constantly changing in recent years.

Distribution, flux, and risk assessment of microplastics at the Anzali Wetland, Iran, and its tributaries.

Microplastic pollution has raised significant concerns among scientific communities and society in recent years due to its increase and lesser-known effects on the environment. To improve the knowledge of microplastic pollution in freshwater, we investigated microplastics in Anzali Wetland, a Ramsar site in northern Iran, as well as its nine main entering rivers. The extracted microplastics were characterized via visual identification, SEM-EDX, and μ-Raman methods. Microplastics (size range: 50-5000 μm) were found in all water and sediment samples with concentration of fibrous particles as well as polypropylene and polyethylene polymers. The mean concentration of microplastics in bottom sediment and surface water samples of the wetland was 301 ± 222 particles∙kg-1 d.w. and 235 ± 115 particles∙m-3 (0.23 particles∙L-1), respectively. The microplastic concentration in the central and eastern parts of the wetland was higher than in other areas; however, the mean concentrations revealed homogeneity across the wetland area. Water properties (dissolved oxygen, pH, temperature, electrical conductivity, and salinity in water) did not affect the concentration of microplastic particles, though correlational analysis revealed a strong positive association between microplastic quantity and turbidity. There was a significant positive relationship between microplastic concentration and the percentage of clay in sediment samples. The quantity of microplastics in river water was higher than in wetland water, but the difference between the results was not significant. However, the quantity of microplastics in the river's littoral sediment was higher than in the bottom sediment of the wetland where the difference between the results was significant. Microplastic ecological risk assessment showed high potential ecological risk. The findings underscore the importance of effective management strategies and the implementation of policies to mitigate the negative impact of MP pollution on ecosystems and human health.

Petroleum spills and assessment of heavy metals in water, sediment, soil from Afiesere River, Ughelli, Delta State, Nigeria

The study which was to determine the concentrations of heavy metals in water, sediment and soil of Afiesere river because of the anthropogenic activities of petroleum exploration and attendant spills in the area. Surface water, sediment, surface soil and sub-surface soil samples were collected from Afiesere River, Ughelli, Delta State. Some physiochemical parameters of water were analysed using standard methods and Hanna water quality checker. The concentrations of five heavy metals, namely; lead (Pb), cadmium (Cd), zinc (Zn), copper (Cu) and nickel (Ni) were determined in water, sediment, surface soil, and sub-surface soil using Flame Atomic Absorption Spectrophotometer (Flame-AAS). The results obtained show the mean values of pH, temperature, total dissolved solid, conductivity, dissolved oxygen, biological oxygen demand, phosphate, nitrate, and sulphate as follows: 6.87 ± 0.18, 27.40 ± 0.28oC, 4.00 ± 0.00 mg/L, 8.67 ± 0.25 µs/cm, 4.23 ± 0.08 mg/L, 0.65 ± 0.17 mg/L, 0.01 ± 0.00 mg/L, 0.01 ± 0.03 mg/L, and 2.17 ± 0.18 mg/L respectively. The heavy metals; Pb, Cd, Zn, Cu and Ni mean concentrations are as follows: in water, 0.06 ± 0.02, 0.02 ± 0.01, 0.46 ± 0.01, 0.03 ± 0.01 and 3.56 ± 0.07 mg/L; in sediment, 0.52 ± 0.03, 0.02 ± 0.00, 0.21 ± 0.02, 0.07 ± 0.01 and 0.26 ± 0.01 mg/kg; in surface soil, 0.50 ± 0.03, 0.02 ± 0.00, 0.07 ± 0.01, 0.03 ± 0.00 and 2.91 ± 0.03 mg/kg; in sub-surface soil, 0.55 ± 0.02, 0.02 ± 0.01, 0.26 ± 0.02, 0.06 ± 0.01 and 0.36 ± 0.08 mg/kg respectively. The results showed a significant difference at P<0.05. The results obtained in this study were within and above the set standard for water, sediment and soil by World Health Organization (WHO). The metals are toxic, can bio-accumulate and are potential carcinogens; therefore treatment of water is very important. Periodic medical examination of the inhabitants of the area must be a top priority.

Components of dissolved organic carbon in relation to environmental factors in lakes along an altitudinal gradient in central China.

Dissolved organic carbon (DOC) is an important organic substance that affects biogeochemical processes and underwater light conditions in aquatic ecosystems. To explore altitudinal variations in DOC components and water quality, 66 surface water samples were collected along an altitudinal gradient (10-1857m) in three regions of central China, including a montane region (Enshi Prefecture) and two floodplain regions (Dongting Lake Basin and Wuhan City). DOC components were measured using a three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy, in conjunction with fluorescence regional integration (FRI) and fluorescence indices. Generally, lakes at high elevations (Enshi Prefecture) had higher DOC concentrations (a mean value of 6.43mgL-1) than floodplain lakes in Dongting Basin (4.51mgL-1) and Wuhan City (3.89mgL-1). Fluorescence index (FI, a range of 1.37-1.92) and biological index (BIX, a range of 0.47-0.74) indicated that DOC mainly originated from allochthonous sources in the three regions. Enshi Prefecture had relatively lower FI and BIX values, suggestive of a larger contribution of allochthonous carbon in this montane region in comparison with the floodplain regions. Humic-like substances were more abundant than other four fluorescent components, including tyrosine-like, tryptophan-like, fulvic acid-like, microbial-like substances. Spearman rank correlation analyses showed that tryptophane-like substances were positively correlated with K+, Mg2+, and Na+, while humic-like substances were negatively correlated with these cations. Taken together, the results can improve our understanding on altitudinal variations in DOC components and potential driving forces.

Per- and polyfluoroalkyl substances (PFAS) fate and transport across a groundwater-surface water interface

Per- and polyfluoroalkyl substances (PFAS) are emerging contaminants of concern whose fate and transport in environmental media are incompletely understood. In the 1960s, PFAS were dumped in the House Street Disposal Site, an unlined landfill on the crest of a glacial end moraine near Rockford, Michigan, USA. In 2017, PFAS were discovered in groundwater and subsequently, a network of monitoring wells delineated a 2 mi (3 km) PFAS plume migrating downgradient toward the Rogue River. Today, the Michigan Department of Natural Resources (MDNR) operates fish-rearing ponds in the area where the plume intersects the groundwater-surface water interface (GSI). Each year, the MDNR fills these man-made ponds using water from a nearby creek. Springs in the ponds prevent them from draining completely at the end of fish-rearing each fall.We sampled surface water and modeled groundwater flow to investigate PFAS transport across the GSI. Numerical models constructed with and without the fishponds did not substantially change MODFLOW model calibration curves or predicted MODPATH flow lines, indicating that PFAS transport is dominated by the regional flow system with limited influence from semiannual changes to boundary conditions at the GSI. Surface water samples collected from five locations within and adjacent to the fishponds were analyzed using EPA Draft Method 1633. PFAS were detected at all locations with the highest total PFAS >60 ng/L in the fishponds. Mixing models based on total PFAS indicate that approximately 10 % of the fishpond water is sourced by groundwater. However, similar analyses with perfluoroalkyl carboxylic acids (PFCA) and perfluoroalkyl sulfonic acids (PFSA) imply that groundwater comprises as much as 30 % of water in the ponds, suggesting differential movement of individual PFAS across the groundwater-surface water interface. Additional investigation of PFAS within the pond sediments is needed to better understand partitioning and differential transport behavior across the GSI.

Tracing Acinetobacter baumannii's Journey from Hospitals to Aquatic Ecosystems.

This study provides a comprehensive analysis of Acinetobacter baumannii in aquatic environments and fish microbiota by integrating culture-dependent methods, 16S metagenomics, and antibiotic resistance profiling. A total of 83 A. baumannii isolates were recovered using culture-dependent methods from intra-hospital infections (IHI) and wastewater (WW) and surface water (SW) samples from two southern Romanian cities in August 2022. The antibiotic susceptibility was screened using disc diffusion, microdilution, PCR, and Whole Genome Sequencing assays. The highest microbial load in the analyzed samples was found in Glina, Bucharest, for both WW and SW samples across all investigated phenotypes. For Bucharest isolates, the resistance levels corresponded to fluoroquinolones > aminoglycosides > β-lactam antibiotics. In contrast, A. baumannii from upstream SW samples in Târgoviște showed the highest resistance to aminoglycosides. The blaOXA-23 gene was frequently detected in IHI, WW, and SW isolates in Bucharest, but was absent in Târgoviște. Molecular phylogeny revealed the presence of ST10 in Târgoviște isolates and ST2 in Bucharest isolates, while other minor STs were not specifically correlated with a sampling point. Using 16S rRNA sequencing, significant differences in microbial populations between the two locations was identified. The low abundance of Alphaproteobacteria and Actinobacteria in both locations suggests environmental pressures or contamination events. These findings indicate significant fecal contamination and potential public health risks, emphasizing the need for improved water quality monitoring and management.

Rapid Determination of 12 Classes of Per- and Polyfluoroalkyl Substances in Water Samples from Environmental Forensic Cases.

The widespread use of per- and polyfluoroalkyl substances (PFASs) with different physico-chemical properties poses a great threat to the environment and human health. Simultaneous detection of different classes of PFASs is a difficult task, especially for rapid analysis of polluted water samples in environmental forensic cases. In this study, a simple sample preparation ultrahigh-performance liquid chromatography coupled with quadrupole Orbitrap high-resolution mass spectrometry was established for the detection of PFASs in a wide range of water matrices. By optimizing the conditions of pretreatment and the parameters of the instrument, the developed method provided good linearity of calibration standards (R2 > 0.99), and demonstrated excellent MLOQ (0.008-1.2 µg/L), with spiked recoveries ranging from 57.7% to 151% for 47 targets in surface water samples, and from 45.7 to 165% for 46 targets in ground and waste water samples, respectively. This method required an injection volume of 3 µL and an analysis time of only 18 min per sample. The validation method was successfully applied to the analysis of 20 environmental water samples, in which 15 target substances with different concentrations were detected, with total concentrations of 0.082 to 262.455 μg/L. The method is simple and exclusive, and can rapidly confirm the occurrence of PFASs in different water samples, providing a convenient and fast high-throughput analysis, which is especially suitable for the application in the environmental forensic investigation of PFASs pollution.

Implication of heavy metal(loid)s contamination for human health and preliminary application of water treatment in floodplain area along Mekong River, Lao PDR

Groundwater is widely used for domestic purposes, especially as a reliable source of drinking water in rural areas of the Lao People’s Democratic Republic (Lao PDR). This preliminary study aims to examine heavy metal(loid)s contamination leading to human health risks while also focusing on a method that can improve drinking water quality in floodplain areas along the Mekong River in Lao PDR. Groundwater and surface water samples were collected during the monsoon season in 2022 in Attapeu and Champasak provinces. Heavy metal(loid)s concentrations and human health risks were investigated using inductively coupled plasma mass spectrometry (ICP-MS) and the USEPA method, respectively. A nanofiltration membrane technique was introduced to optimize the quality of groundwater. Results showed that groundwater quality was significantly poor (p < 0.05), particularly in Attapeu province, with high levels of electrical conductivity, total dissolved solids, and manganese, exceeding WHO standards of 400 µS cm−1, 300 mg L−1, and 80 µg L−1, respectively. With the groundwater ingestion pathway, children were found to be more vulnerable to non-carcinogenic risk than adults (Hazard Quotient, Hazard Index >1), but adults had a higher carcinogenic risk (Incremental Lifetime Cancer Risk >1E-04). The removal of fecal bacteria and heavy metal(loid)s was achieved using the nanofiltration membrane, demonstrating its potential as a practical point-of-use technology to provide cleaner water sources and enhance the health status of Lao residents.

Impact of microplastics on microbial community structure in the Qiantang river: A potential source of N2O emissions

This study aimed to investigate the spatial distribution of microplastics (MPs) and the features of the bacterial community in the Qiantang River urban river. Surface water samples from the Qiantang River were analyzed for this purpose. The results of the 16S high-throughput sequencing indicated that the microbial community diversity of MPs was significantly lower than in natural water but higher than in natural substrates. The biofilm of MPs was mainly composed of Enterobacteriaceae (28.00%), Bacillaceae (16.25%), and Phormidiaceae (6.75%). The biodiversity on MPs, natural water, and natural substrates varied significantly and was influenced by seasonal factors. In addition, the presence of MPs hindered the denitrification process in the aquatic environment and intensified N2O emission when the nitrate concentration was higher than normal. In particular, polyethylene terephthalate (PET) exhibited a 12% residue of NO3−-N and a 4.2% accumulation of N2O after a duration of 48 h. Further findings on gene abundance and cell viability provided further confirmation that PET had a considerable impact on reducing the expression of nirS (by 0.34-fold) and nosZ (by 0.53-fold), hence impeding the generation of nicotinamide adenine dinucleotide (NADH) (by 0.79-fold). Notably, all MPs demonstrated higher the nirK gene abundances than the nirS gene, which could account for the significant accumulation of N2O. The results suggest that MPs can serve as a novel carrier substrate for microbial communities and as a potential promoter of N2O emission in aquatic environments.

Distribution characteristics and risk assessment of fluoride in surface water of urban typical rivers

Recent research on fluoride in water primarily focuses on groundwater; however, the potential environmental risks of fluoride in urban rivers should not be overlooked. In 2023, this study collected 135 surface water samples from the Ershibu River in Hefei, China, during various flood periods. Through descriptive statistical analysis, correlation analysis, principal component analysis-multiple linear regression (PCA-MLR) modeling, hazard quotient (HQ) assessment, and Monte Carlo simulation analysis, the spatial and temporal distribution, potential sources, and health risks of fluoride were investigated. The results showed that fluoride concentrations in the Ershibu River ranged from 0 to 1.38 mg/L. According to the PCA-MLR calculations, industrial pollution (73.92 %) was identified as the main source, followed by hydrogeochemical evolution (16.10 %) and agricultural activities (9.98 %). The HQ analysis revealed that the average exceedance rates of HQ for the five exposed populations were as follows: infants (64.45 %) > young children (2.22 %) = adults (2.22 %) > children (0) = teenagers (0). Therefore, relevant authorities should improve defluoridation facilities to reduce fluoride levels in industrial and agricultural wastewater and implement measures to protect public health. Future research should investigate the migration processes and toxicity mechanisms of fluoride more thoroughly.

In-stream attenuation and enantioselective fractionation of psychiatric pharmaceuticals in a wastewater effluent-dominated river basin

Wastewater effluent is the main contributor of psychiatric pharmaceuticals (PPs) pollution in surface waters. However, little is known about its spatial evolution dynamics in effluent-dominated rivers. Herein, 10 representative PPs, including 6 chiral pharmaceuticals and 4 achiral pharmaceuticals, were explored in the Beiyun River, a typical wastewater effluent-dominated river, to explore their occurrence, in-stream attenuation and enantioselective fractionation behaviors at a watershed scale. Among the target substances, 8 and 9 drugs were detected in surface water and sediment samples with the ΣPPs concentrations ranging from 78.4 to 260.1 ng/L and 4.8 to 43.4 ng/g dw in surface water and sediments, respectively. Along the mainstream of the Beiyun River, only several PPs detected in surface water, e.g., citalopram, O-demethylvenlafaxine, and fluoxetine, exhibited in-stream attenuation behaviors when reaching rural area, while all PPs detected in sediments displayed in-stream attenuation behavior. Four chiral PPs detected in surface water exhibited an enantioselective attenuation phenomenon, while in sediments, only citalopram displayed an enantioselective fractionation behavior. The differences in the in-stream attenuation and enantioselective environmental behavior of individual PPs caused complex contaminant evolution along the stream reach. This work provides enantiomeric profiles of chiral pollutants for evaluating their in-stream attenuation processes, which would facilitate better understanding of the changing contaminant exposure conditions in complex natural environments.

Assessing surface water quality in Hungary’s Danube basin using geochemical modeling, multivariate analysis, irrigation indices, and Monte Carlo simulation

Evaluation of water quality is crucial for managing surface water effectively, ensuring its suitability for human use, and sustaining the environment. In the lower Danube River basin, various methods were employed to assess surface water quality for irrigation, drinking, human health risk purposes and the main mechanism control the surface water chemistry. These methods included water quality indicators (WQIs), complex statistical analyses, geographic information systems (GIS), Monte Carlo simulation, and geochemical modeling. Physicochemical analyses of surface water samples revealed primarily Ca–Mg–HCO3− is the dominant water types. Principal component analysis (PCA), ionic ratios and piper, chloro alkaline index, Chadha, and Gibbs diagrams identified three distinct water characteristics influenced by water-rocks interaction, evaporation, ions exchange, and human activities. The geochemical modeling showed Danube River water’s strong ability to dissolve gypsum, halite, and anhydrite (SI < 0) and precipitate aragonite, dolomite, and calcite with saturation index (SI) value greater than 0 along its flow path. The irrigation water quality index (IWQI = 99.6–107.6), sodium adsorption ratio (SAR = 0.37–0.68), sodium percentage (Na% = 13.7–18.7), soluble sodium percentage (SSP = 12.5–17.5), Potential Salinity (PS = 0.73–1.6), and Residual Sodium Carbonate (RSC = − 1.27–0.58) values were used, mainly indicating acceptable quality with some limitations. Danube River water was unsuitable for drinking based on WQI value (WQI = 81–104). Oral exposure of children to specific components showed a higher hazard index (HI > 1) compared to adults, indicating a 2.1 times higher overall non-carcinogenic risk hazard index. However, Monte Carlo simulation demonstrated negligible iron, manganese, and nitrate health hazards for both age groups. These findings are valuable for water quality management decisions, contributing to long-term resource sustainability.

Dissolved trace elements in the upper reaches of Lancang River, southeast Qinghai-Tibet Plateau: Current status and distribution, risk and source

The environmental impact of dissolved trace element (DTE) pollution is becoming increasingly well understood. The southeastern edge of the Qinghai-Tibet Plateau is a region with high environmental vulnerability, making it highly susceptible to various anthropogenic disturbances. The Lancang River (LCR), as the most representative river in this area, serving as the largest international river in Southeast Asia, the LCR is crucial for the downstream regions, supporting fisheries, agriculture, and even economic development, earning it the title of the “water tower” for these areas. This study mainly focuses on the upstream unbuilt dam area. In this study, we gathered 25 surface water samples from the upstream of the LCR and examined the geographical distribution, primary sources, and associated human health risks of seven dissolved trace elements (Mn, Cr, Fe, Co, Cu, Ni, Zn). Cr, Fe, Co, Ni, and Cu in the main stream are primarily associated with natural sources, including rock weathering, soil erosion, and similar processes. Mn, however, predominantly originates from human activities such as industrial construction and road transportation. Zn mainly originates from the specialized fertilizers used for highland barley in plateau regions. Almost all DTE concentrations exhibited a downward trend from upstream to downstream. However, due to inputs from various sources along the way, there will be some abnormal points. The concentrations of DTE in the study area were within the acceptable limits set by drinking water standards in China, the USA, and the WHO. Overall, the water quality in this region is considered good. The results from a Monte Carlo simulation assessing health risks indicate that the non-carcinogenic health risk caused by DTE in the upper reaches of Lancang River was very weak. The primary pathway through which DTE can harm human health is ingestion, with children being particularly vulnerable. These findings offer a critical scientific basis for understanding the migration of DTE in aquatic environments and for the ecological stewardship of the Lancang River.