Heavy Metals In Surface Water Research Articles

Heavy Metal Concentrations in Surface Water of the Lower Mekong River Basin (Vietnam)

Heavy Metal Concentrations in Surface Water of the Lower Mekong River Basin (Vietnam)

Heavy metal contamination and environmental risk assessment: a case study of surface water in the Bahr Mouse stream, East Nile Delta, Egypt

Water, as an indispensable constituent of life, serves as the primary source of sustenance for all living things on Earth. The contamination of surface water with heavy metals poses a significant global health risk to humans, animals, and plants. Sharkiya Governorate, situated in the East Nile Delta region of Egypt, is particularly susceptible to surface water pollution due to various industrial, agricultural, and urban activities. The Bahr Mouse Stream, crucial for providing potable water and supporting irrigation activities in Sharkiya Governorate, caters to a population of approximately 7.7 million inhabitants. Unfortunately, this vital water source is exposed to many illegal encroachments that may cause pollution and deteriorate the water resource quality. In a comprehensive study conducted over two consecutive seasons (2019–2020), a total of 38 surface water samples were taken to assess the quantity of heavy metals in surface water destined for human consumption and other applications, supported by indices and statistics. The assessment utilized flame atomic absorption spectrophotometry to determine the concentration of key heavy metals including iron (Fe), manganese (Mn), cadmium (Cd), copper (Cu), lead (Pb), zinc (Zn), nickel (Ni), cobalt (Co), and chromium (Cr). The calculated mean value of the Water Quality Index (WQI) was found to be 39.1 during the winter season and 28.05 during the summer season. This value suggests that the surface water maintains good quality and is suitable for drinking purposes. Furthermore, the analysis indicated that the concentrations of heavy metals in the study area were below the recommended limits set by the World Health Organization and fell within the safe threshold prescribed by Egyptian legislation. Despite the identification of localized instances of illegal activities in certain areas, such as unauthorized discharges, the findings affirm that the Bahr Mouse stream is devoid of heavy metal pollution. This underscores the importance of continued vigilance and regulatory enforcement to preserve the integrity of these vital water resources.

Surface water pollution by some heavy metals in a remote island, Hatiya, northern Bay of Bengal

IntroductionMetal contamination in surface water in urban cities has become a common scenario in underdeveloped and developing countries. Nowadays, the extent of this contamination is suspected to be traced in remote islands due to the transportation of metals with downward water flow. Unfortunately, we found a dearth of research on our remote island, where thousands of people live and use surface water for their daily needs. ObjectivesThe current study aims to investigate the status of heavy metals in surface water from a remote island, Hatiya Coast, to determine the existence of heavy metals and their risks to human health. Ten surface water samples were collected, and their concentrations were measured using AAS. Later, various pollution indices were analyzed to understand their pollution level. ResultsThe mean metal concentrations were ranked in descending order of Mg (65.44 mg.L−1)> Fe (0.375 mg.L−1)> Zn (0.139 mg.L−1)>Mn (0.016 mg.L−1)> and Cu was below the detection limit (BDL). According to different metal pollution indexes, the surface water of the Hatiya coast is low to moderately polluted. The standard HEI value was 1.58, and the range was 1.29–2.25, indicating that all sampling stations had a low level of metal contamination. The mean and range of HPI values were found at 44.58 and 34.33–69.33, respectively. All of the sampling stations indicated low pollution levels except sampling station 6. NPI values revealed moderate contamination in stations 2, 3, and 7. According to the hazard quotient (HQ) and hazard index (HI) for adults and children, heavy metals were found to have no carcinogenic risks for children and adults through dermal exposure. ConclusionAlong with the metals coming from upstream, several local sources of heavy metals were identified during fieldwork, including metallurgical businesses, oil spills from the ship, and some trawlers associated with fishing activities. Overall, these findings would be valuable for aquaculture sectors and future researchers to compare, correlate, and understand the pollution level of the island and serve as a foundation for conducting further investigations in similar island environments, both locally and globally.

Pollution Assessment and Spatial Distribution of Heavy Metals in Surface Waters and Bottom Sediments of the Krzna River (Poland)

Due to their toxicity, lack of bioaccumulation and biodegradability, and ease of binding to sediments, heavy metals are considered the main pollutants of rivers. It is, therefore, necessary to control and monitor these pollutants. The present study analyzed the Krzna River, which flows in southeastern Poland and has an outlet to the Bug River. Over much of its length, the Bug River forms Poland’s border with Belarus, while its origin is in Ukraine. The main purpose of the conducted research was a qualitative and quantitative analysis of selected heavy metals, i.e., Ni, Pb, Zn, Cd, and Cu, in bottom sediments and surface waters of the Krzna River. The secondary objectives were to evaluate the level of contamination of the studied matrices and identify the sources of pollution. Eighty samples of water and bottom sediments from the Krzna River were collected for the analysis. Due to the varying distribution of metals under the influence of changes in temperature, precipitation, and humidity, the samples were collected in May and August 2023. The average cadmium content in the sediments studied was the same in both May and August, at 0.6 mg/kg. In contrast, the nickel content of the sediments ranged from 4.6 to 6.1 mg/kg in May and from 4.8 to 6.8 in August. Only nickel and cadmium of the five heavy metals tested were present in amounts exceeding the geochemical background value. Analysis of the results indicates that only a minimal amount of heavy metals remain dissolved in the surface waters, and the remainder contaminates the sediments. The average concentrations of metals in the studied bottom sediments and surface waters were as follows: zinc > lead > nickel > copper > cadmium. The content of metals in the studied sediments was not high, but at the same time, their presence above the geochemical background indicates anthropogenic human activity. Any changes in hydrodynamic conditions and various environmental factors may result in the re-release of heavy metals contained in sediments into surface waters.

Source-specific probabilistic health risk assessment of heavy metals in surface water of the Yangtze River Basin

The detrimental effects of heavy metal accumulation on both ecosystems and public health have raised widespread concern. Source-specific risk assessment is crucial for developing effective strategies to prevent and control heavy metal contamination in surface water. This study aims to investigate the contamination characteristics of heavy metals in the Yangtze River Basin, identifying the pollution sources, assessing the risk levels, and further evaluating the health risks to humans. The results indicated that the average concentrations of heavy metals were ranked as follows: zinc (Zn) > arsenic (As) > copper (Cu) > chromium (Cr) > cadmium (Cd) > nickel (Ni) > lead (Pb), with average concentrations of 38.02 μg/L, 4.34 μg/L, 2.53 μg/L, 2.10 μg/L, 1.17 μg/L, 0.84 μg/L, and 0.32 μg/L, respectively, all below the WHO 2017 standards for safe drinking water. The distribution trend indicates higher concentrations in the upper and lower reaches and lower concentrations in the mid-reaches of the river. By integrating the Absolute Principal Component Scores-Multiple Linear Regression (APCS-MLR) receptor model and Positive Matrix Factorization (PMF) model, the main sources of heavy metals were identified as industrial activities (APCS-MLR: 41.3 %; PMF: 42.1 %), agricultural activities (APCS-MLR: 30.1 %; PMF: 27.4 %), and unknown mix sources (APCS-MLR: 29.1 %; PMF: 30.4 %). The calculation of the hazard index (HI) for both children and adults was <1, indicating no non-carcinogenic or carcinogenic risks. Based on the source-specific risk assessment, agricultural activities contribute the most to non-carcinogenic risks, while industrial activities pose the greatest contribution to carcinogenic risks. This study offers a reference for monitoring heavy metals and controlling health risks to residents, and provides crucial evidence for the utilization and protection of surface water in the Yangtze River Basin.

Spatial and Temporal Distribution and Risk Assessment of Heavy Metals in Surface Water of Changshou Lake Reservoir, Chongqing

To understand the water pollution status and environmental risks of Changshou Lake, the concentrations of heavy metals (Cr, Cu, Zn, As, Cd, and Pb) in the water were collected and analyzed during different seasons. The study investigated temporal and spatial variations, distribution characteristics, pollution levels, and health risks associated with heavy metals in Changshou Lake. The results showed that all six heavy metals were below than the Class Ⅰ standard of the Surface Water Environmental Quality Standard (GB 3838-2002), but recent years have witnessed an increasing trend, with Cu, As, and Pb showing a significant increase (P<0.05). The temporal and spatial distributions of these heavy metals were different. Temporally, Cr and Cd concentrations in surface water were higher in summer, As and Zn were higher in spring, and Pb and Cu were higher in autumn and winter. Spatially, the concentrations of Cr, As, Cu, Zn, and Pb showed higher concentrations in the southern outlet of the reservoir, the northwestern Longxi River inlet, and the central part of the reservoir, whereas Cd was higher in the northern stagnant area. The overall levels of heavy metals in the water body of Changshou Lake were low, with Cr and Cu slightly polluted, while other heavy metals were identified as having an insignificant pollution level. Drinking water was the primary exposure pathway to carcinogenic and non-carcinogenic heavy metals in surface water bodies. The health risk values of Cr and As in water bodies were high, ranging from 6.2×10-10 to 3.0×10-4 and 5.1×10-8 to 3.9×10-5, respectively. The corresponding contribution rates for children and adults to the total health risk were high, with Cr accounting for 87.18% and 87.20%, respectively, while As accounted for 12.73% and 12.71%, respectively. Therefore, it is crucial to prioritize environmental risks associated with Cr and Cu, as well as the health risks associated with Cr and As in Changshou Lake These findings provide a scientific foundation for water pollution control and environmental quality improvement in Changshou Lake, and rational development and utilization of water resources.

Contamination level and ecological risk assessment of selected heavy metals in surface water and sediments from Mudi River, Blantyre, Malawi

Contamination level and ecological risk assessment of selected heavy metals in surface water and sediments from Mudi River, Blantyre, Malawi

New approach into human health risk assessment associated with heavy metals in surface water and groundwater using Monte Carlo Method

This study assessed the environmental and health risks associated with heavy metals in the water resources of Egypt's northwestern desert. The current approaches included the Spearman correlation matrix, principal component analysis, and cluster analysis to identify pollution sources and quality-controlling factors. Various indices (HPI, MI, HQ, HI, and CR) were applied to evaluate environmental and human health risks. Additionally, the Monte Carlo method was employed for probabilistic carcinogenic and non-carcinogenic risk assessment via oral and dermal exposure routes in adults and children. Notably, all water resources exhibited high pollution risks with HPI and MI values exceeding permissible limits (HPI > 100 and MI > 6), respectively. Furthermore, HI oral values indicated significant non-carcinogenic risks to both adults and children, while dermal contact posed a high risk to 19.4% of samples for adults and 77.6% of samples for children (HI > 1). Most water samples exhibited CR values exceeding 1 × 10–4 for Cd, Cr, and Pb, suggesting vulnerability to carcinogenic effects in both age groups. Monte Carlo simulations reinforced these findings, indicating a significant carcinogenic impact on children and adults. Consequently, comprehensive water treatment measures are urgently needed to mitigate carcinogenic and non-carcinogenic health risks in Siwa Oasis.

Micro-essential and toxic heavy metals in surface water of Harike wetland - India

Wetlands are consequential habitats with diverse flora and fauna. The overutilization of these habitats led to the implementation of conservational strategies which includes Ramsar convention. Harike wetland is the largest wetland in northern India, declared as a Ramsar site. However, the recent industrialization and anthropogenic activities may result in the ecological degradation of this wetland. The wetland is eminently polluted due to industrial discharges, therefore the present study was undertaken to investigate heavy metal status of Harike wetland. The analysis included bio-essential (chromium, manganese, iron, cobalt, nickel, copper, zinc) and non-essential (arsenic, mercury, cadmium, lead) heavy metals. The concentration of heavy metals in the surface water was determined using inductively Coupled Plasma-Mass Spectrometry and the recovered values were compared to the global and national standards. Among all the heavy metals analysed the mean concentrations of iron (437.983 µg/l), mercury (4.011 µg/l) and lead (156.719 µg/l) were recorded to be alarming. The higher concentration of heavy metals may be directly related to the inlet from river Sutlej, as the water is contaminated by various industrial, domestic and agricultural sources. Therefore, continuous monitoring and adequate measures need to be implemented to improve the water quality of internationally recognized wetland.

Suspended particulate matter affects the distribution and migration of heavy metals in the Yellow River

Suspended particulate matter (SPM) is an important heavy metal transporter in water. As a well-known high-SPM river, its impact on the distribution and migration of heavy metals in the Yellow River (YR) deserves special attention. In this study, the spatial distributions of heavy metals in surface water and SPM of the YR were investigated. The results indicate that the concentrations (dissolved and particulate phases) and bioavailability (particulate phase) of most heavy metals were higher during the rainy season than during the dry season. A considerable proportion of heavy metals (>70 %) was transported by SPM and fine particles (clay) controlled the pollution status of heavy metals in the YR. This could lead to higher heavy metal concentrations in the SPM midstream and downstream during the rainy season and higher heavy metal concentrations in upstream during the dry season. Heavy metal adsorption experiments showed that specific combination methods (such as binding with carbonate) between Cd and SPM may cause SPM to act as a source of Cd midstream and downstream. This study provides a new perspective on the effects of SPM on heavy metal distribution and migration in the YR.

Assessment of Elemental Contamination of Selected Major Dams from Osun State, Nigeria by Multivariate and Hazard Index Analyses

Dams and their environment, interrelate with a degree of complexity that often affects the availability of potable water. In Nigeria, dams are an important source of drinking water in many communities but are vulnerable to contamination from different sources. This study assessed the possible elemental (Cd, Cr, Cu, Fe, Ni, Pb, Mn, and Zn) contamination sources of selected dams in a total of 126 samples comprising 54 surface water, and 72 sediment samples collected from six main dams in Osun State using multivariate analyses like Principal Component Analysis (PCA) and Cluster Analysis (CA). Generally, the average elemental concentration was in the decreasing order of Cr > Ni > Cd > Pb > Cu > Fe > Zn > Mn and Pb > Cr > Ni > Cd > Zn > Mn > Fe > Cu for surface water and sediment samples respectively. Furthermore, statistical analysis showed that the average concentrations of the potentially toxic elements (PTEs) did not differ significantly (p < 0.05) across the sampling sites, indicating similar PTEs profiles. The PCA and CA revealed possible sources of elemental contamination to the dam quality as weathering of bedrocks, uncontrolled farming activities, abandoned equipment, boat fueling, maintenance, and repairs. Although only 13.9% of the hazard quotients (HQ) were higher than one for all the studied heavy metals in surface water, 91.7% of the hazard index (HI) were higher than one. This suggests an unacceptable risk of non-carcinogenic effects from the direct consumption of dam water. Furthermore, the oral target cancer risk, TCRoral in children > adults and > 1 × 10−4 for cancer risk set by USEPA, however, the % contribution of Cr to ∑TCRoral in adults which is > 1 × 10−4 ranged between 98.9 to 99.5%, indicating that Cr is the most dominant carcinogens in the overall cancer risk in adults.

Bacterial nanocellulose, a sustainable alternative, to implement cleaner production in the design of biosensors to detect heavy metals in surface waters

Bacterial nanocellulose, a sustainable alternative, to implement cleaner production in the design of biosensors to detect heavy metals in surface waters

Levels of Heavy Metals in Surface Water of Oge-Etche River, Etche, Rivers State, Nigeria

The levels of heavy metals in surface water of Oge-Etche River, Etche, Rivers State, Nigeria was assessed. Analysis of the heavy metals was performed after due laboratory procedures with a thermo Atomic Elemental Absorption Spectrophotometer (model SE-71906). The average levels of the investigated heavy metals in the surface water of the river within the stations in the months of investigations were in the range as follows; Fe; 1.6585±0.069-3.8758±0.123mg/L, Pb; 1.7164±0.078-2.2913±0.101mg/L, Cu; 1.4271±0.068-3.7419±0.188mg/L, Cr; 4.6070±0.284- 6.2551±0.241mg/L, Cd; 0.0246±0.018-1.5386±0.051mg/L, Ni; 3.0057±0.040-4.4311±0.135mg/L, and As; 0.0473±0.056-1.3072±0.063mg/L. The average occurrence of heavy metals in the stations of the river during the period of investigation were in the order Cr &gt; Ni &gt; Fe &gt; Cu &gt; Pb &gt; Cd &gt; As. The pollution assessment indices adopted in the evaluation of the influence of anthropogenic input on the level of heavy metals in the river using WHO maximum acceptable limit as basis were, contamination factor, pollution load index, contamination degree, and modified contamination degree. These indices indicated that the heavy metals examined have contaminated the river to a high degree and the river may not be suitable for domestic use.

Comprehensive evaluation of heavy metals in surface water of the upper Banar River, Bangladesh

The main focus of the research was to examine the dispersion of elements and evaluate the possible ecological impact of heavy metals in the water of the Upper Banar River. To achieve this, water samples were obtained from ten different locations along the river, and the concentrations of Cr, Ni, Cu, Cd, Pb, and As were analyzed using an atomic absorption spectrophotometer (AAS). Results exhibited that the abundance of Cr, Ni, Cu, Cd, Pb, and As in water varied from 1.10 to 3.20, 0.11 to 1.30, 1.30 to 13.50, 1.14 to 1.91, 0.39 to 0.75 and 1.44 to 2.56 µgL-1, respectively. Mean (±SD) concentrations of considered metals declined with the following downward direction: Cu (5.07±4.11) &gt; As (1.94±1.15) &gt; Cr (1.81±0.63) &gt; Cd (1.42±0.23) Pb (0.55±0.12) &gt; Ni (0.54±0.41), indicated that concentrations were reasonably assorted throughout the observed region. Moreover, the Upper Banar River water was contaminated with heavy metals, but the pollution level was not significant based on HPI analysis. Based on the computed HEI values, water quality is deemed low hazard and lower degrees of contamination. Overall, the river's water was still in good condition and had low levels of contamination, as per PI and CD ratings. Upper Banar River water's computed ERI ranged from 7.24 to 12.16, which showed a low-risk level. The study concluded that the Upper Banar River experienced some metallic pollution because of anthropogenic disturbances. Thus, responsible authorities should immediately implement appropriate management strategies and conduct routine water quality monitoring. Int. J. Agril. Res. Innov. Tech. 13(1): 110-122, June 2023

Distribution, Site-Specific Water Quality Criteria, and Ecological Risk Assessment of Heavy Metals in Surface Water in Fen River, China.

Due to a lack of toxicity reference values that match the regional environmental characteristics, the ecological risk of metals in water bodies cannot be accurately assessed. The Fen River is the second-largest tributary of the Yellow River in China, and the sustainability of this area is threatened by heavy metal pollution caused by intensive industrial and agricultural activities. In this study, site-specific water quality criteria (WQCs) for heavy metals in the Fen River were derived considering toxicity data from native aquatic organisms and regional water quality factors (e.g., water hardness). Short-term WQCs for Mn, Cu, Cd, Zn, Cr, Pb, and Ni were 2026.15, 98.62, 10.02, 63.07, 6.06, 166.74, and 132.73 μg/L, respectively, and long-term WQCs were 166.53, 29.71, 2.18, 19.29, 4.15, 6.38, and 14.76 μg/L, respectively. The distribution characteristics of these metals during the wet season in 2020 were explored, and their average concentrations in the river water did not exceed the environmental quality standards for surface water in China but were higher than the world average levels. Cr was the main pollutant in the sampling sites of Yaodu region, Hongdong Shitan, Xiao River, and Duanchun River, as was Pb in Duanchun River. Based on the site-specific WQCs, using hazardous quotient (HQ) and margin of safety (MOS10) approaches, a high risk of Pb was identified in the Duanchun River, and a medium risk of Cr might occur at midstream and downstream of Yaodu and Xiaodian. The results will provide a reference basis for heavy metal pollution control and water quality management in the Fen River.

Seasonal Variation Characteristics and Pollution Assessment of Heavy Metals in Water and Sediment of Taipu River

Taipu River is a river spanning two provinces and one city in a demonstration area in the Yangtze River Delta on an ecologically friendly developmentand an important water source in the upper reaches of the Huangpu River in Shanghai. To understand the multi-media distribution characteristics, pollution status, and ecological risk of heavy metals in the Taipu River, the contents of heavy metals (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sb, and Zn) in the sediments of Taipu River were analyzed, and the pollution status and potential ecological risk were evaluated using the Nemerow comprehensive pollution index, geo-accumulation index, and potential ecological risk index methods. In addition, the health risk assessment model was used to assess the health risk of heavy metals in surface water of Taipu River. The results showed that the concentrations of Cd, Cr, Mn, and Ni in the surface water of Taipu River exceeded the class Ⅲ water limit at the upstream point in spring; the concentrations of Sb exceeded the class Ⅲ water limit at all points in winter; the average value of As exceeded the class Ⅲ water limit in overlying water during the wet season; and the average values of As and Cd exceeded the class Ⅲ water limit in pore water during the wet season. The health risk assessment of surface water implied that both adults and children had higher health risk in spring and lower health risk in other seasons. The health risk of children was significantly higher than that of adults, and it mainly came from chemical carcinogenic heavy metal elements As, Cd, and Cr. The average contents of Co, Mn, Sb, and Zn in Taipu River sediments in the four seasons all exceeded the Shanghai soil baseline; the average contents of As, Cr, and Cu in summer, autumn, and winter exceeded the Shanghai soil baseline; and the average contents of Cd, Ni, and Pb in summer and winter exceeded the Shanghai soil baseline. The evaluation results of the Nemerow comprehensive pollution index and geo-accumulation index showed that the pollution degree of the middle reaches of Taipu River was higher than that of the upper and lower reaches, and the Sb pollution was more serious. The potential ecological risk index method revealed that the Taipu River sediment was at a low risk. Cd had a high contribution in both the wet and dry seasons and could be regarded as the main heavy metal of potential ecological risk in the Taipu River sediment.

The Influence of DOC on the Migration Forms of Elements and Their Sedimentation from River Waters at an Exploited Diamond Deposit (NW Russia)

The development of mineral deposits causes changes that are comparable to natural exogenous geological processes, and prevail over the latter in local areas of intensive mining activity. In this article, a diamond deposit is selected, developed by quarries of great depth, and a forecast is made of the impact of drainage water discharge on changes in the composition of surface water and bottom sediments during the entire period of development of the deposit. Modeling was performed according to various scenarios, taking into account changes in the total dissolved solids of groundwater from 0.5 to 21.7 g/kg H2O. Thermodynamic calculations were carried out using the HCh software package. The role of dissolved organic carbon in the migration of chemical elements and the effect of DOC on the precipitation of chemical elements from mixed solutions is given. It has been established that fulvic acid completely binds to Fe in the Fe(OH)2FA− complex in all types of natural waters and under all mixing scenarios. With humic acid, such a sharp competitive complex formation does not occur. It is distributed among the various elements more evenly. It was determined that the mass of precipitating iron in the presence of DOC decreases by 18–27%, and its precipitation in winter is more intense. In contrast to Fe, the precipitation of Ca, Mg, and C from solutions with DOC is higher in summer, and there are more of them in the solutions in winter. This study contributes to a better understanding of the behavior of heavy metals in surface waters and sediments under anthropogenic pressures in order to improve the sustainable management of water resources in the face of anthropogenic activities.

Comprehensive Monitoring and Ecological Risk Assessment of Heavy Metals in Soil and Surface Water of Chishui River Basin in Upper Reaches of the Yangtze River

Chishui River is an important ecological security barrier area in the upper reaches of the Yangtze River in China. Therefore, it is of great significance to conduct research on soil and water ecological risks in the Chishui River basin. In this paper, the risk of heavy metals pollution and its control factors was evaluated systematically by using surface water and soil samples from 16 tributaries in the Yunnan section of the Chishui River basin. The method of soil environmental capacity and ecological risk index were studied. The results showed that the average concentration of heavy metals in the surface water of the main stream was in the order of Fe &gt; Mn &gt; Zn &gt; Cu &gt; Pb &gt; Cd &gt; Hg. Except for Hg, all the concentrations of heavy metals were far lower than the Class I water limits in the Environmental Quality Standards for Surface Water (GB3838-2002) issued by the Ministry of Ecology and Environment, PRC. The average concentration of Hg concentration was 0.056 μg·L−1, which was slightly higher than the limit value of Class II. Heavy metals in the surface water were distributed in a point-like manner in the main stream of the Chishui River, which was mainly affected by mining drainage, township sewage, and human production activities. Meanwhile, the environmental capacity study showed that the heavy metals in soil were in the order of Zn &gt; Pb &gt; Cr &gt; Ni &gt; As &gt; Hg &gt; Cu &gt; Cd, and the environmental capacity were significant differences among different soils: purple soil &gt; limestone soil &gt; loess &gt; yellow-brown soil. Soil Cd tended to migrate out of the soil under the control of the occurrence form, vegetation coverage, and human production activities, while Cr, Cu, and Ni tended to accumulate in the soil. The average comprehensive ecological risk index (RI) of heavy metals in all tributaries ranged from 44.86 to 154.15, mainly distributed in medium and low ecological risk. Therefore, it is recommended to dynamically monitor and control these pollution points in the Chishui River basin to prevent the risk of heavy metals from escalating.

Heavy Metal Dispersion in a Hydrological Sub-Basin as Consequence of Mining Activity in Taxco, Guerrero (Southern Mexico)

The mining industry generates high concentrations of heavy metals (HMs) susceptible to being released into surface and ground water. The objective of this work was to determine the concentration and dispersion of HMs in surface water and ground water in a hydrological sub-basin located in southwest Mexico. The samples were collected as following: 24 samples from streams, rivers, and one lake, and 15 samples from springs, located along the Taxco-Cocula sub-basin. A total of 78 samples were collected in the dry and rainy seasons. Physicochemical parameters, major ions, and HMs were analyzed. The pH, Eh, electrical conductivity, and total dissolved solids were analyzed in situ, while the concentrations of anions, cations, and HMs were measured in the laboratory. The results were treated with multivariate analysis and PHREEQC simulation. The highest recorded values (in mg/L) were in surface water, where the HMs in the dry season were Al (28.63), As (0.60), Cd (1.78), Cu (1.10), Fe (68.27), Mn (21.47), Pb (0.02), and Zn (208.80). These high concentrations exceed the limits established by national and international regulations for drinking water. The ground water did not indicate pollutants associated to the mining industry. On the other hand, in the rainy season, the surface water showed a decrease in the concentrations of the measured heavy metals. The hypsometric gradient and the hydrogeological and meteorological characteristics of the Taxco-Cocula sub-basin are the factors that contribute to the dilution and dispersion of the HMs along the 60 km of its length.

Occurrence and spatial distribution of microplastic contaminated with heavy metals in a tropical river: Effect of land use and population density

Microplastics are of concern due to their potential environmental risks. This research aims to find the effect of land use (agriculture, urban, and aquaculture) and population density on the abundance of microplastics contaminated with heavy metals in surface water and sediment of the Chao Phraya River in Thailand. Results indicated that population density is directly correlated with increased microplastic abundance. Most microplastics were found in the urban zone (water: 80 ± 38 items/m3 and sediment: 62 ± 11 items/kg) and were small fragments (0.05 to 0.3 mm). Polymer types of polypropylene and polyethylene were commonly found. Heavy metals of Cr, Cu, Cd, Pb, Zn, Ni, and Ti were detected in microplastics in water and sediment, with Cu, Pb, and Zn being the most dominant. Heavy metals in microplastics were highest in the agriculture zone. In general, the presence of metals on microplastics may potentially impact the ecosystem and human health.