Variations In Heavy Metal Concentrations Research Articles

Cascading effects of Pb on the environmental and symbiotic microbiota and tadpoles' physiology based on field data and laboratory validation

Heavy metal pollution poses a serious threat to ecosystems. Currently, there is a lack of field data that would enable us to gain a systematic understanding of the influences of heavy metals on aquatic ecosystems, especially the interactions between environments and animals. We studied the relationships between the variations in heavy metal concentrations (10 species including Pb in sediments and surface water), the community structure of environmental and symbiotic microbiota, and the gut traits of Bufo gargarizans tadpoles across 16 sampling sites on the Chengdu Plain through rigorous statistical analysis and laboratory validation. The results show that heavy metal concentrations, especially the Pb concentration of the sediment, are linked to the variations in sediment and tadpoles' gut microbiomes but not to water microbiota. For the sediment microbiota, Pb causes a trade-off between the proportions of Burkholderiales and Verrucomicrobiae and affects the methane, sulfide, and nitrate metabolisms. For tadpoles, a high sediment Pb content leads to a low abundance of gut aerobic bacteria and a large relative gut weight under both field and laboratory conditions. In addition, Pb promotes the growth of B. gargarizans tadpoles under laboratory conditions. These effects seem to be beneficial to tadpoles. However, a high Pb content leads to a low abundance of probiotic bacteria (e.g., Verrucomicrobiae, Eubacteriaceae, and Cetobacterium) and a high abundance of pathogenic bacteria in the gut and environment, suggesting potential health risks posed by Pb. Interestingly, there is a causal relationship between Pb-induced variations in sediment and symbiotic microbiotas, and the latter is further linked to the variation in relative gut weight of tadpoles. This suggests a cascading effect of Pb on the ecosystem. In conclusion, our results indicate that among the heavy metals, the Pb in sediment is a critical factor affecting the aquatic ecosystem through an environment-gut-physiology pathway mediated by microbiota.

A Dual Media Filter using Zeolite and Mortar for the Efficient Removal of Heavy Metals in Stormwater Runoff

Stormwater runoff from expressways contains high concentrations of various heavy metals. However, heavy metal removal in most current runoff treatment facilities, using infiltration and filtration, is limited and poses substantial risks. Therefore, this study proposes and evaluates a dual media system of mortar and Na-zeolite, which are inexpensive and readily available, using long-term continuous column experiments for the removal of heavy metals. The results showed significant Cu2+ removal with Na-zeolites that was improved by the addition of a thin mortar layer, while a sand layer provided negligible improvements. The removal of Cu was further enhanced by increasing mortar layer thickness. The removal of Cu2+, Zn2+, Fe3+, and Ni2+ in a mixture was enhanced as the mortar layer’s thickness increased, while the contribution of Na-zeolite was significant in 232 h experiments with a fixed empty bed contact time (EBCT) of 1.8 min. Moreover, the media were not saturated with Fe throughout the operation period. These results suggest that the dual media system is cost-effective and efficient in the removal of heavy metals from stormwater runoff via precipitation, filtration, and adsorption with a short EBCT.

Variation in Road Dust Heavy Metal Concentration, Pollution, and Health Risk with Distance from the Factories in a City-Industry Integration Area, China.

Road dust samples around three typical factories, F1, F2, and F3, in the National Zhengzhou Economic and Technology Development Zone (ZETZ), China, were collected to study the variation in heavy metal concentration (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn), pollution, and health risk with distance from the factories. The results indicated that the concentrations of all the elements near F1 were higher than near both F2 and F3. Apart from Co, Mn, and Cu in some dust samples, all the element concentrations were higher than the corresponding background values (BCs), to varying degrees. The spatial distributions of the heavy metals surrounding the factories followed the normal distribution. The peak values of element concentrations occurred at 300~400 m away from the factories, except for Hg, which continued increasing more than 500 m away from the factories. The fluctuation curves of the pollution load index value calculated according to the BCs for F1, F2, and F3 all had two peaks, a "small peak" and a "large peak", appearing at about 30 m and 300 m, respectively. For the hazard index and the total carcinogenic risk, the peak values all appeared at 400 m, with the curves following the normal distribution. Exposure to road dust containing non-carcinogenic and carcinogenic elements around F1 was greater than around F2 or F3. In conclusion, our results provide a reference for pursuing effective prevention of dust heavy metal pollution around modern manufacturing factories.

Seasonal variation of heavy metal contents in road dust from residential, industrial and rural areas of Hong Kong

Heavy metal contents in road dust have been an important indicator of heavy metal pollution arising from traffic-related activities. In this study, 108 road dust samples were collected from four locations of Hong Kong, namely Kwai Hing (industrial area), Sau Mau Ping (residential area), Sai Kung and Tai Lam (rural area), over a one-year period and analysed for zinc (Zn), nickel (Ni), copper (Cu), lead (Pb), chromium (Cr), cadmium (Cd), and arsenic (As). The geo-accumulation indices (Igeo) and contamination factors indicated zinc, copper, chromium, to a lesser extent, nickel, and cadmium pollution of road dust in industrial and residential areas. The potential ecological risks of Cu were found to be particularly high in both areas. Residential and industrial areas are prone to considerable and very high risks, respectively, based on the risk indices (RI). The sources of heavy metals may vary slightly between the areas based on Pearson's correlation analysis. It was found that the metal contents in the road dust samples vary differently between the dry and wet seasons. The concentrations of Zn were higher in the dry season while those of Cu, Cr and Ni were generally higher in the wet season.

Soil heterogeneity influence on the distribution of heavy metals in soil during acid rain infiltration: Experimental and numerical modeling

Acid rain is a global environmental problem that mobilizes heavy metals in soils, while the distribution and geochemical fraction of heavy metals during acid rain infiltration in heterogeneous soils are still unclear. In this study, we performed column experiments to investigate the distribution and geochemical fraction of Cu, Pb, Ni and Cd in heterogeneously layered soils during continuous acid rain infiltration. Chloride ion used as a conservative tracer was found to be uniformly distributed during acid rain infiltration, showing insignificant preferential flow effects in the column. In contrast, however, the distribution of heavy metals was highly non-uniform, especially in the silty soil at the lower part of the column, indicating a heterogeneous distribution of adsorption capacity. In addition, in the control experiments with neutral rain infiltration, uniform distribution of heavy metals was observed, indicating that the heterogeneous distribution of adsorption coefficient during acid rain infiltration was mainly caused by different pH buffering capacities. A numerical model considering water flow and solute transport was developed, where the average water-solid distribution coefficient (Kd) in Layer 2 was only 1.5–12.5% of that in Layer 1 during acid rain infiltration. The model could predict the variation of heavy metal concentrations in soil with the majority of error less than 35%, confirming that different Kd induced the heterogeneous distribution of heavy metals. In addition, the geochemical fraction of heavy metals in the upper coarse sand layer remained stable, while the acid-extractable fractions in the lower loam and silt loam layer gradually increased. Our findings suggest that soil heterogeneity, especially chemical heterogeneity affected by rainfall acidity, has an important influence on the infiltration, migration and geochemical fraction of heavy metals in soils. This study could help guide the risk assessment of heavy metal-contaminated sites that were polluted by acid rain or landfill leachate.

THE BACKGROUND CONCENTRATION OF SOME HEAVY METALS AT NYSC ORIENTATION CAMP LAYOUT, KATSINA

An anthropogenic activities leads to the presence of heavy metals in an environment which lead to environmental pollution. The area has become gradually engage with various waste such as animal waste, refused dump, spilling of petrol, kerosene, engine oil etc which can introduces the trace heavy metals. The research of background concentration of various heavy metals in soil samples taken from the NYSC orientation camp layout, which is situated in Katsina state, Nigeria, at latitudes of 643.7 m to 798.5 m and longitudes of 18 21I32IIE to 18 28I37II, was conducted. At intervals of 100 m, soil samples were taken from the locations, and each 100 m was divided into 10 m. (A1A10). In order to determine the concentration of the five examined heavy metals, a flame atomic absorption spectrophotometer (FAAS) was used (Co, Cr, Pb, Cd, Cu). The locations have an average heavy metal concentration of:- 0.16009, 0.55449, 0.02804, 0.00231, and 0.10406 ppm Respectively. Significant differences were observed by comparing the mean concentration of the heavy metals in the study areas with world health organization (W.H.O) threshold limit, national and international studies and it was suggested that the samples were not contaminated with the heavy metals. But the metals were detected and there is no need for immediate implementation and remediation measures by the relevant authority. It was and recommended that industries, factories and filling station should not be located at the area in order to minimize human activities so as to maintain stable environment free from pollutants

Accumulation Characteristics and Pollution Evaluation of Soil Heavy Metals in Different Land Use Types: Study on the Whole Region of Tianjin.

Heavy metal pollution in soil has received much attention in recent decades. Many studies have analyzed the interaction between specific soil quality and soil heavy metal pollution. However, there is little information about the pollution status, spatial distribution and pollution sources of heavy metals in the province of Tianjin. In this paper, the distribution characteristics and pollution sources of heavy metals in soil were studied by means of the surface soil of Tianjin, as the study area and object, conducted in combination with land use types, using multiple data analysis and multivariate statistics, while the pollution levels were evaluated by various indices. The results showed the mean contents of the seven heavy metals of the studied elements followed an increasing order of Cd (0.15 mg/kg) < As (11.9 mg/kg) < Cu (24.3 mg/kg) = Pb (24.3 mg/kg) < Ni (27.9 mg/kg) < Cr (70.7 mg/kg) < Zn (79.1 mg/kg). The median values of Cr and Ni were lower than the background values and did not exceed the screening values at the points, and the median values of Cu, Zn and Pb were close to the background values, while the median contents of As and Cd were higher than the background values. The highest accumulation of heavy metals was found in grassland, and the coefficient of variation of heavy metal contents were higher in garden land, industrial and mining storage land, residential land and transportation land, indicating that the soil heavy metal contents under these land use types were more significantly disturbed by human factors. The evaluation results of the ground accumulation index method showed that the soil in Tianjin was free of pollution, except for Cd, which was at the non-polluted to moderately polluted level. The Nemero integrated pollution index evaluation method and the pollution load index evaluation method together showed that the integrated pollution levels of heavy metals in Tianjin soils were both at no pollution level/safety level. Apart from Cd and As, which were not correlated, the other heavy metals were correlated with each other two by two. Cd, Pb and Zn were the main pollution contributors from traffic, industry and other anthropogenic factors, while Cr and Ni were the main pollution contributors from soil parent material, and Cu was the main pollution contributor from mining and metal smelting. In addition, As was presumed to be the main source of pollution contribution from agriculture and surface runoff.

A comprehensive review of heavy metal pollution in the coastal areas of Bangladesh: abundance, bioaccumulation, health implications, and challenges.

The coastal zone of Bangladesh, with a population density of 1278 people per square kilometer, is under serious threat due to heavy metal pollution. To date, many studies have been conducted on the heavy metal contamination in soils, water, aquatic animals, and plants in the coastal zone of Bangladesh; however, the available information is dispersed. In this study, previous findings on the contamination levels, distributions, risks, and sources of heavy metals in sediments and organisms were summarized for the first time to present the overall status of heavy metal pollution along coastal regions. Earlier research found that the concentrations of various heavy metals(HMs), particularly Co, Cd, Pb, Cu, Cr, Mn, Fe, and Ni in water, sediment, and fish in most coastal locations, were above their permissible limits. High concentrations of HMs were observed in sediments and water, like Cr of 55mg/kg and 86.93mg/l in the ship-breaking areas and Karnaphuli River, respectively, in coastal regions of Bangladesh. Heavy metals severely contaminated the Karnaphuli River estuary and ship-breaking area on the Sitakundu coast, where sediments were the ultimate sink of high concentrations of metals. Sedentary or bottom-dwelling organisms like gastropods and shrimp had higher levels of heavy metals than other organisms. As a result, the modified PRISMA review method was used to look at the critical research gap about heavy metal pollution in Bangladesh's coastal areas by analyzing the current research trends and bottlenecks.

Seasonal variations of heavy metal concentrations in tissues of Talang Queenfish (Scomberoides commersonianus) from Iraqi marine and coastal waters, Northwestern Arabian Gulf

This study was carried out during the period from Winter 2010 to Winter 2011 to evaluate the concentrations of heavy metals (Fe, Co, Ni, Cu and Pb) in tissues of commercially valuable coastal fishes (Talang Queenfish, Scomberoides commersonianus) from Iraqi coastal areas around the Faw Peninsula which receives petrochemical wastes. Thus, it is important to identify the extent of concentrations of heavy metals in fish and consider potential impacts on the food chain and risks to human health. Fe had the highest level of accumulation in the four tissues examined (gill, muscle, liver and gonad) of S. commersonianus whilst Pb had the lowest (p &lt; 0.05). The order of the heavy metal concentrations in the gills, muscles, liver and gonad tissues of S. commersonianus across all the stations was Fe (198.27 μg/g) &gt; Co (21.07 μg/g) &gt; Cu (7.89 μg/g) &gt; Ni (5.43 μg/g) &gt; Pb (1.85 μg/g). This study suggests that additional measures must be taken to monitor waste and ambient water quality, and to prevent contamination of fish for human consumption

Accumulation of some heavy metals in Tenualosa ilisha (Hamilton, 1822) collected from Shatt Al-Arab River

In the present study, the concentrations of various heavy metals including copper, nickel, lead, cadmium, iron and manganese were investigated in several organs (muscles of head, muscles of trunks, muscles of tails, liver, gills, gonads and intestine) of Tenualosa ilisha (Hamilton, 1822) which was collected from Shatt Al-Arab river during the period between February 2013 and September 2013. Heavy metal concentrations were measured by using Flame Atomic Absorption Spectrophotometer. The results of the heavy metals during study period showed that the highest concentration was 41.910 µg/g (dry weight) for iron between February and March, whereas the least concentration was 0.036 µg/g (dry weight) for lead between June and July. Also, they showed that the highest concentration was 27.470 µg/g (dry weight) for iron in liver, whereas the least concentration was 0.003 µg/g (dry weight) for lead in muscles of tails.

Temporal and spatial variation of heavy metal concentration in four limpet species along the southeast coast of South Africa

Rocky shores are experiencing heavy metal (HM) pollution as a result of anthropogenic activities. The information on the use of limpets Scutellastra spp. and Cellana sp. as bioindicators is limited. This study aimed to assess HM concentration in water samples, soft and shell tissues of four limpet species, Scutellastra granularis, S. longicosta; S. cochlear and Cellana capensis along the southeast coast of South Africa. Individual species were collected between 2019 and 2020 in four sites and four seasons during spring low tide. The physico-chemical parameters were simultaneously measured in situ with limpet species collection for correlation with HM. Concentration of Zn, As, Cd, Cu, Fe, Pb, Hg and Ni in limpet tissues were analysed using inductively coupled plasma optical emission spectrometry (ICP-OES). Data were explored using SPSS v26, GraphPad Prism v5, Primer v7 and MS-excel 2016. Temporal/spatial differences of physico-chemicals and HM in limpet tissues were evident. Heavy metal concentration was species specific e.g. Fe, Ni and were high in S. granularis, and Hg, As, Pb in C. capensis. The lower shore species S. longicosta and S. cochlear were notable accumulators of Zn and Cd. Limpet soft tissues concentrated 5–10 times magnitude of HM than shell tissues. This study provided a baseline information on the concentration of HM in marine limpets along the southeast coast of South Africa and suggest limpets as bioindicator species.

Phytoprevention of Heavy Metal Contamination From Terrestrial Enhanced Weathering: Can Plants Save the Day?

Enhanced weathering is a promising approach to remove carbon dioxide from the atmosphere. However, it may also pose environmental risks through the release of heavy metals, in particular nickel and chromium. In this perspective article I explore the potential role of plants in modulating these heavy metal fluxes. Agricultural basaltic soils may be valuable study sites in this context. However, the effect of biomass harvesting on the accumulation of heavy metals is currently not well studied. Mostly caused by different parent rock concentrations, there is a large variability of heavy metal concentrations in basaltic and ultramafic soils. Hence, to minimize environmental risks of enhanced weathering, basalts with low heavy metal concentrations should be favored. Existing phytoremediation strategies may be used to “phytoprevent” the accumulation of nickel and chromium released from enhanced weathering in soils. As a result, elevated nickel and chromium concentrations in rocks must not preclude enhanced weathering in all settings. In particular, hyperaccumulating plants could be used as part of a crop rotation to periodically remove heavy metals from soils. Enhanced weathering could also be employed on fields or forests of (non-hyper) accumulating plants that have a high primary production of biomass. Both approaches may have additional synergies with phytomining or bioenergy carbon capture and storage, increasing the total amount of carbon dioxide drawdown and at the same time preventing heavy metal accumulation in soils.

Remediation Efficiency of the In Situ Vitrification Method at an Unidentified-Waste and Groundwater Treatment Site

The subject of this study was the dust collected from an electric arc furnace at an unidentified-waste treatment site in southern Taiwan. The dust underwent an in situ vitrification (ISV) process and was tested using the toxicity characteristic leaching procedure (TCLP), at the end of which the final product was analyzed for its stability and weather resistance. This study then examined the above results to determine whether the ISV process helps to enhance the efficiency and economic benefits of said waste-treatment site. A TCLP test conducted on the dust that had been treated with ISV revealed that concentrations of various heavy metals were not only far below those of the unprocessed sample dust but also fell below the limit stipulated in the TCLP regulation of Taiwan’s Environmental Protection Administration. The results show that after undergoing ISV treatment, heavy metals in the dust were either encapsulated or bound in silicon lattices and thus barely leached from the dust. Analyses using scanning electron microscopy (SEM) and an energy dispersive spectrometry (EDS) indicate that the surface of the dust appeared more compacted after going through the ISV process. In addition, the highly contaminated dust that underwent ISV treatment saw a pronounced decrease in or elimination of wave crests. Another analysis applying X-ray diffraction (XRD) showed that the SiO2 crests disappeared in the processed dust, suggesting that the crystal structure was replaced with quasi-vitreous products after ISV treatment. In the event that pollutants were extant, they were usually characterized by smaller size, high stability, excellent weather resistance, an innocuous nature, and recyclability.

Assessment of the variation of heavy metal pollutants in soil and crop plants through field and laboratory tests

Heavy metal contamination in cultivated land is turning out to be a major problem these days. This paper presents the experimental results of the variation of heavy metal concentration in the cultivated land before and after planting different crops and accumulation of heavy metal concentration in the crops. Six crops including corn, potato, broad beans, oats, beans and soybeans were planted in 13 test fields (15,686.75 m2) in Wushan County, Gansu, China in 2020. In total, 26 subsurface soil specimens and 47 crops samples were collected for which the concentration of heavy metals such as arsenic (As), lead (Pb), cadmium (Cd), chromium (Cr) and mercury (Hg) and pH were analyzed. The results showed that the average concentration of As, Cd, Cr, Hg and Pb in 26 subsurface soil samples were 58.9, 0.251, 72.4, 0.0342 and 32.2 mg/kg, respectively. The concentration of As in the study area was even higher than the average concentration of As in Gansu Province. It was also detected from the test results of crops that Hg was mostly accumulated in corn, broad beans, soybeans and oats, while Cd was most likely accumulated in potato. The ecological risk of heavy metal contamination was assessed using index of geoaccumulation (Igeo), pollution index (Pi), potential ecological risk index (RI) and bioconcentration factor (BCF). The reason of high heavy metal concentration in the study area was also explored and suitable crops and planting strategies were recommended. This paper provided a comprehensive approach to investigate the heavy metal contamination in cultivated land soil and crops and offered a reasonable method to mitigate heavy metal contamination.

Health Risk Assessment of Heavy Metals Due to Wheat, Cabbage, and Spinach Consumption at Cold-Arid High Altitude Region.

Soil and water from the trans-Himalayan high-altitude region contain high concentrations of various heavy metals. Vegetables and cereals such as cabbage, spinach, and wheat are most prone to heavy metal accumulation from soil and water which can be toxic for human consumption. It has yet to be studied how consumption of vegetables and cereal with excess heavy metal content can affect human health in high altitude areas. To this end, the objectives of this study are (a) quantify the concentrations of Aluminum (Al), Iron (Fe), Cobalt (Co), Boron (B), Lead (Pb), Arsenic (As), Cadmium (Cd), Selenium (Se), Copper (Cu), and Zinc (Zn) in three crops (wheat, cabbage, and spinach), and (b) evaluate the health risk of excess dietary heavy metal consumption in the local adult population using non-carcinogenic and carcinogenic parameters. A total of 60 samples were analyzed for minerals and potentially toxic elements using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). Results found that spinach has a high mineral content than wheat and cabbage. The estimated daily intake (EDI) of each metal in each crop was less than the limit of permissible value. The hazard index (HI) of three plant species, and target hazard quotient (THQ) were less than the threshold level (< 1). The carcinogenic risk (CR) value in all the crops was less than the unacceptable risk level (1 × 10-4). These findings suggest that consumption of wheat, spinach, and cabbage does not have any significant effect on human health due to presence of elevated heavy metals at this high altitude region. .

Heavy metals in Venezuelan marine sediments: concentrations, degree of contamination, and distribution

Venezuelan oil exploration and exploitation activities have been taking place since the 18th century. These long-term activities are closely related to heavy metal contamination because of the increasing input of toxic pollutants. Variations in heavy metal concentrations can cause, among other things, changes in metal distribution patterns, alterations in biogeochemical cycles, and increments in environmental and biological risks. The need for a complete baseline on heavy metal concentrations along the Venezuelan coast is critical. For this reason, we present the concentrations, distribution, and degree of contamination of 9 heavy metals (barium, mercury, copper, nickel, chromium, cadmium, zinc, lead, and vanadium) in marine sediments along the Venezuelan coast. We used the enrichment factor, the geoaccumulation index, and the mean effects range median quotients to evaluate the degree of contamination, comparing areas with and without intervention. Our results indicate that higher concentrations of these heavy metals are associated with places with greater anthropic activity, especially on the central and eastern coasts of Venezuela. Only cadmium showed extremely severe enrichment and a high degree of contamination. The biohazard potential was between 12% and 30% and was primarily associated with locations having high oil activity, which suggests that these places must be monitored, given the potential hazard they represent. This work encompasses the distribution and concentration of 9 heavy metals along the Venezuelan coast and takes relevance as a baseline for heavy metal concentrations and pollution indicators in marine sediments for Venezuela and the Caribbean.

Integrated ecological risk assessment of heavy metals in an oil shale mining area after restoration

Although the mining area has been restored, the environmental problems caused by years of large-scale oil shale mining are still continuing, coupled with the intensive distribution of the surrounding petrochemical industry, posing a serious threat to the local ecological environment. In this study, we investigated eight heavy metals (Cu, Ni, Pb, Cd, As, Cr, Mn and Zn) contamination and distribution around mining area, evaluated the potential risks of environment, identified the main sources of metal pollution and performed source apportionment. The results showed that the original north and south dumps were seriously polluted, and the CF values were significantly higher than other sampling sites. Ni, Zn and Mn have high coefficients of variation, which may be greatly affected by human factors and especially the waste slag piled up. The concentration of heavy metals in the water was lower than in the soil; soil particles, pH, Eh and acid mine drainage influence the variation of heavy metal concentrations. As and Cd have very high RAC values, and accordingly they were mainly present in the exchangeable and reduced fractions. Mn was exposed to higher ecological risks, followed by Pb, although there were high loads on carbonate bound and oxidizable fractions. APCS-MLL receptor model was used to identify and apportionment three main sources of contamination. The mean contribution rates of industrial activity, atmospheric deposition and mixed sources accounted for 39.77%, 22.24% and 37.99%, respectively. Cluster analysis further classified the metal pollution sources according to the spatial distance of sampling points.

Transfer of heavy metals from soils to curly mustard (Brassica juncea (L.) Czern.) grown in an agricultural farm in Brunei Darussalam

Determination of heavy metal concentrations in vegetables and agricultural soils is crucial because high levels of heavy metals could affect soil quality, crop production and safe consumption of crops. A field study was conducted to determine the heavy metal concentrations and their transfer from agricultural soils to different parts (leaf, stem, and root) of Brassica juncea (L.) Czern. In addition, potential health risks of contamination in the vegetables grown in the field were evaluated. Acid digestion method USEPA 3050B in combination with ICP-OES were used to analyze heavy metal (Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) contents in both pre- and post-harvest soils and vegetable samples. Results showed that none of the heavy metals in soils had concentrations above the maximum safety limits based on the WHO, USEPA and CCME guidelines. Calculated metal transfer factor (MTF >1) showed B. juncea accumulated Cd, Co, Ni, Pb and Zn in leaves, stems and roots, but Cu and Mn, as well as Cr were only accumulated in stems and roots, respectively. There were variations in heavy metal contents between the different parts of B. juncea, but only Cd and Pb contents were above the maximum allowable limit recommended by FAO/WHO. PCA analysis was able to identify 4 major components corresponding to 38.38%, 28.98%, 14.39% and 10.67% of the total variance and PC1 was clearly associated to leaves of B. juncea. Based on the MTF values, only Cd was found to have a value of HRI >1 compared to the other heavy metals, implying potential health risk associated with long-term ingestion of the vegetable.

Vertical and Lateral Distribution of Heavy Metals in the Euphrates River Sediments between Heet and Fallujah, Western Iraq

In recent decades, significant attention has been paid to heavy metal contamination as a dangerous environmental problem because of the toxicity, abundance, persistence and bioaccumulation of these elements (Chen et al., 2016,) (Islam et al., 2017 and ) (Jin et al., 2019). In general, the contamination state of the environment is evaluated by the total concentration of heavy metals (Kanda et al., 2018). The riverine sediments are considered as the main basins for various pollutants following the largely uncontrolled discharge of contamination resulting from human activities and geogenic processes (Liu et al., 2018). The sediment contamination is an important indicator of environmental variation as a result of anthropogenic influence (Gao et al., 2019). River sediments serve as not only a major sink and carrier of heavy metals but also as potential sources of secondary pollution, which can reflect their contamination level (Tang et al., 2014 and ) (Hsu et al., 2016). The heavy metals are released into the aquatic environments from geogenic and anthropogenic sources. The geogenic sources include chemical leaching of bedrock, water drainage basins and runoff from banks (Raj et al., 2017). The anthropogenic sources of heavy metals pollution in aquatic systems include mining activities, industrial wastes disposal and pesticides use, (Chakravarty &amp; Patgiri, 2009). The heavy metals pollution of sediments is an indicator of the aquatic systems water quality (Zhao et al., 2012). The heavy metal distribution in sediments and pollution levels supplies a base for consideration of sediments treatment methods and evaluation of the potential releasing of heavy metals into water and transport downstream (Nawrot et al., 2020). The vertical and spatial distribution of heavy metals and pollution levels have been evaluated in sediments of many world rivers, such as the Yinma River, China (Guan et al., 2018), the Voghji River, Armenia (Gabrielyan et al., 2018), the Barigui River, Brazil (Machado et al., 2017), the Harazdan River, Armenia (Petrosyan et al., 2019), the Thames River, the UK (Vane et al., 2020), the Yang River, China (Tang et al., 2020), and the Lu Lu River, China (Ye et al., 2020). The spatial distribution of heavy metals in sediments of the Euphrates River in Iraq has been investigated by many authors (Issa &amp; Qanbar, 2016); (Al-Taher et al., 2020); and (Hussain &amp; Al-Jaberi, 2020). The spatial variation of heavy metal concentrations in sediments of the Euphrates River along the studied area between Heet and Ramadi Cities has been studied by (Al-Bassam &amp; Al-Mukhtar, 2008) and (Salah et al., 2012). The aim of the study is to investigate how heavy metals are laterally and vertically distributed in sediments of the given study area of Euphrates River between Heet and Fallujah Cities. This study represents the first attempt to investigate the vertical distribution of heavy metals in the Euphrates River sediments.

Geochemistry of Dissolved Heavy Metals in Upper Reaches of the Three Gorges Reservoir of Yangtze River Watershed during the Flood Season

Dissolved heavy metals (HMs), derived from natural and anthropogenic sources, are an important part of aquatic environment research and gain more international concern due to their acute toxicity. In this study, the geochemistry of dissolved HMs was analyzed in the upper Three Gorges Reservoir (TGR) of the Yangtze River (YZR) watershed to explore their distribution, status, and sources and further evaluate the water quality and HM-related risks. In total, 57 water samples were collected from the main channel and tributaries of the upper TGR. The concentrations of eight HMs, namely V, Ni, Cu, Zn, As, Mo, Cd, and Pb, were measured by ICP-MS. The mean concentrations (in μg/L) of eight HMs decreased in the order: As (1.46), V (1.44), Ni (1.40), Mo (0.94), Cu (0.86), Zn (0.63), Pb (0.03), and Cd (0.01). The concentrations of most HMs were 1.4~8.1 times higher than that in the source area of the YZR, indicating a potential anthropogenic intervention in the upper TGR. Spatially, the concentrations of V, Cu, As, and Pb along the main channel gradually decreased, while the others were relatively stable (except for Cd). The different degrees of variations in HM concentrations were also found in tributaries. According to the correlation analysis and principal component (PC) analysis, three PCs were identified and explained 75.1% of the total variances. combined with the concentrations of each metal, PC1 with high loadings of V, Ni, As, and Mo was considered as the main contribution of human inputs, PC2 (Cu and Pb) was primarily attributed to the contribution of mixed sources of human emissions and natural processes, and Zn and Cd in PC3 were controlled by natural sources. Water quality assessment suggested the good water quality (meeting the requirements for drinking purposes) with WQI values of 14.1 ± 3.4 and 11.6 ± 3.6 in the main channel and tributaries, respectively. Exposure risk assessment denoted that the health effects of selected HMs on the human body were limited (hazard index, HI &lt; 1), but the potential risks of V and As with HI &gt; 0.1 were non-negligible, especially for children. These findings provide scientific support for the environmental management of the upper TGR region and the metal cycle in aquatic systems.