Variation Of Arsenic Concentration Research Articles

Arsenic variation in soil layers in Bandung Regency, Indonesia: A statistical approach for identifying potential sources

This research investigates the arsenic concentrations in 96 soil samples from a regency in Indonesia using a statistical approach. Soil samples were collected from three depth layers (topsoil [10–20 cm], subsoil [50–60 cm], and deep soil [90–100 cm]), with each layer consisting of 32 samples. Statistical analysis using SPSS was employed to analyze potential arsenic sources based on the proximity of study locations to geothermal system areas, land use, distance from industry, and the presence of study locations on fault lines.The findings indicate that the potential source of arsenic contamination in the soil are suspected to be associated with geothermal system activities and the presence of soil samples on fault lines. The arsenic concentration in locations near to the geothermal system (5-10 km) was 45 times higher (OR = 45, 95% CI = 45–362.57, p < 0.01). Arsenic was found to be 3.828 times higher in study areas situated on fault zones (OR = 3.828, 95% CI = 1.507–9.719, p < 0.01). Additionally, the research suggests that arsenic in the soil may also originate from anthropogenic activities, such as agriculture and industry, as the highest concentrations were found in subsoil or topsoil layers compared to deep soil. The variation in arsenic concentration from highest to lowest in agricultural soil layers was subsoil > topsoil > deep soil, whereas in residential soil, it was subsoil > deep soil > topsoil. The arsenic concentration variation at near distances from industrial areas was topsoil > subsoil > deep soil, contrasting with medium to far distances from industry (subsoil > deep soil > topsoil). Therefore, these findings can be utilized to prioritize remediation efforts and provide input for future research on arsenic contamination in the region.

An analysis of arsenic concentrations associated with sargassum influx events in Barbados

Tropical Atlantic blooms of pelagic Sargassum spp. present major socioeconomic and ecological challenges for Caribbean and West African nations. Valorisation of sargassum provides an opportunity to ameliorate some of the damage to national economies; however, the active uptake of arsenic by pelagic sargassum creates significant barriers to its use. When defining valorisation pathways, it is important to understand arsenic speciation in pelagic sargassum, given the different levels of toxicity associated with different arsenic species. In this study, we assess the temporal variability of total arsenic and inorganic arsenic in pelagic sargassum arriving in Barbados; and test whether arsenic concentrations are linked to oceanic sub-origins. Results indicate that inorganic arsenic, the most toxic form, represents a consistent and substantial percentage of the total arsenic present in pelagic sargassum, and that variability in arsenic concentration does not appear to be driven by sample months, years or oceanic sub-origins/transport pathways.

Hotspots of geogenic arsenic and manganese contamination in groundwater of the floodplains in lowland Amazonia (South America)

Arsenic enrichment in groundwater resources in deltas and floodplains of large sediment-rich rivers is a worldwide natural hazard to human health. High spatial variability of arsenic concentrations in affected river basins limits cost-effective mitigation strategies. Linking the chemical composition of groundwater with the topography and fluvial geomorphology is a promising approach for predicting arsenic pollution on a regional scale. Here we correlate the distribution of arsenic contaminated wells with the fluvial dynamics in the Amazon basin. Groundwater was sampled from tube wells along the Amazon River and its main tributaries in three distinct regions in Peru and Brazil. For each sample, the major and trace element concentrations were analyzed, and the position of the well within the sedimentary structure was determined. The results show that aquifers in poorly weathered sediments deposited by sediment-rich rivers are prone to mobilization and accumulation of aqueous arsenic and manganese, both in sub-Andean foreland basins, and in floodplains downstream. Two zones at risk are distinguished: aquifers in the channel-dominated part of the floodplain (CDF) and aquifers in the overbank deposits on the less-dynamic part of the floodplain (LDF). Some 70 % of the wells located on the CDF and 20 % on the LDF tap groundwater at concentrations exceeding the WHO guideline of 10 μg/L arsenic (max. 430 μg/L), and 70 % (CDF) and 50 % (LDF) exceeded 0.4 mg/L manganese (max. 6.6 mg/L). None of the water samples located outside the actual floodplain of sediment-rich rivers, or on riverbanks of sediment-poor rivers exceed 5 μg/L As, and only 4 % exceeded 0.4 mg/L Mn. The areas of highest risk can be delineated using satellite imagery. We observe similar patterns as in affected river basins in South and Southeast Asia indicating a key role of sedimentation processes and fluvial geomorphology in priming arsenic and manganese contamination in aquifers.

Assessment of organic and inorganic arsenic species in Sengcu rice from terraced paddies and commercial rice from lowland paddies in Vietnam

As a toxic metalloid and nonthreshold carcinogen, arsenic in rice has become a serious concern worldwide due to the risks of chronic human exposure through food. In this study, we aimed to assess the variation in arsenic concentration between Sengcu rice planted in a mountainous terrain and lowland commercial rice available for sale in markets around Vietnam. An optimized protocol using microwave-assisted extraction in combination with an HPLC-ICP-MS/MS system was employed for species-specific arsenic extraction from rice samples, and experimental conditions were determined by response-surface methodology for optimal extraction of all arsenic species. Multivariate analysis with generalized linear models was performed to test the hypothesis of intergroup variation in arsenic concentration. Our method yielded high productivity for all arsenic species with >95% accuracy and <6.1% precision for the certified-reference NIST® SRM® 1568b material. The method determination limits for As(III), As(V), DMA and MMA were 0.1, 0.2, 0.5 and 0.1 μg kg−1, respectively, thus ensuring the concentration stability of each arsenic species. As(III) was the predominant species in both Sengcu and commercial rice, which may be due to its abundance in the aquatic environment of paddy fields, thus being readily absorbed by rice roots. In contrast, differences in irrigation practices, microbial activities of farming fields and soil properties may lead to variations in As(V) and DMA concentrations between Sengcu and commercial rice. A further detailed investigation is necessary to provide a comprehensive understanding of the effect of farming practices on arsenic assimilation in rice grains.

Metal and metalloid concentrations in marine fish marketed in Salvador, BA, northeastern Brazil, and associated human health risks

The research aims to determine the content of arsenic, mercury, cadmium and lead in 13 species of marine fish marketed in Salvador, Bahia, northeastern Brazil and assess the risk to human health associated with the consumption of these fish by using the Target Hazard Quotient (THQ) as a tool. The levels of these metals in fish are of great interest to the public health due to the toxicity of these elements and biomagnification in the food chain. The elements arsenic, cadmium and lead were determined by inductively coupled plasma mass spectrometry (ICP-MS) and mercury by cold vapor atomic absorption spectrometry (CVAAS). In general, intra and interspecific variations in arsenic concentrations were observed (0.01 - 1.85 mg kg −1), cadmium (0.03 to 0.32 mg kg −1), lead (< 0.01 - 0.10 mg kg −1) and mercury (0.001 - 1.85 mg kg −1), with arsenic having the highest levels in the vast majority of fish species, followed by mercury, cadmium and lead. THQ¿1 value was observed only for mercury in Seriola spp. and Mycteroperca intertitialis indicating a potential risk of consumption of these species.

Recommended Sampling Intervals for Arsenic inPrivate Wells.

Geogenic arsenic in drinking water is a worldwide problem. For private well owners, testing (e.g., private or government laboratory) is the main method to determine arsenic concentration. However, the temporal variability of arsenic concentrations is not well characterized and it is not clear how often private wells should be tested. To answer this question, three datasets, two new and one publicly available, with temporal arsenic data were utilized: 6370 private wells from New Jersey tested at least twice since 2002, 2174 wells from the USGS NAWQA database, and 391 private wells sampled 14 years apart from Bangladesh. Two arsenic drinking water standards are used for the analysis: 10µg/L, the WHO guideline and EPA standard or maximum contaminant level (MCL) and 5µg/L, the New Jersey MCL. A rate of change was determined for each well and these rates were used to predict the temporal change in arsenic for a range of initial arsenic concentrations below an MCL. For each MCL and initial concentration, the probability of exceeding an MCL over time was predicted. Results show that to limit a person to below a 5% chance of drinking water above an MCL, wells that are ½ an MCL and above should be tested every year and wells below ½ an MCL should be tested every 5 years. These results indicate that one test result below an MCL is inadequate to ensure long-term compliance. Future recommendations should account for temporal variability when creating drinking water standards and guidance for private well owners.

Seasonal variation of arsenic concentrations in tubewells in west Bengal, India.

This study was conducted to monitor the changes in arsenic concentration during different seasons in a one-year period during 2002-2003 in selected tubewells in an arsenic-affected area in the district of South 24 Parganas in West Bengal, India, and to map the location of the wells. Seasonal variations in concentrations of arsenic in water were measured from 74 selected tubewells, ranging in depth from 40 to 500 feet. Water samples were collected from these wells during winter, summer, monsoon, and the following winter in 2002-2003. A global positioning system was used for locating the tubewells, and a geographic information system was used for mapping. There was evidence of seasonal variation in concentrations of arsenic in water (p=0.02) with the minimum average concentration occurring in the summer season (694 microg/L) and the maximum in the monsoon season (906 microg/L). From the winter of 2002 to the winter of 2003, arsenic concentrations increased, irrespective of the depth of the tubewells, from an average of 464 microg/L to 820 microg/L (p<0.001). This extent of variation in arsenic concentration, if confirmed, has important implications for both epidemiological research and mitigation programmes.

Arsenic variability and groundwater age in three water supply wells in southeast New Hampshire

Three wells in New Hampshire were sampled bimonthly over three years to evaluate the temporal variability of arsenic concentrations and groundwater age. All samples had measurable concentrations of arsenic throughout the entire sampling period and concentrations in individual wells had a mean variation of more than 7 μg/L. The time series data from this sampling effort showed that arsenic concentrations ranged from a median of 4 μg/L in a glacial aquifer well (SGW-65) to medians of 19 μg/L and 37 μg/L in wells (SGW-93 and KFW-87) screened in the bedrock aquifer, respectively. These high arsenic concentrations were associated with the consistently high pH (median ≥ 8) and low dissolved oxygen (median <0.1 mg/L) in the bedrock aquifer wells, which is typical of fractured crystalline bedrock aquifers in New Hampshire. Groundwater from the glacial aquifer often has high dissolved oxygen, but in this case was consistently low. The pH also is generally acidic in the glacial aquifer but in this case was slightly alkaline (median = 7.5). Also, sorption sites may be more abundant in glacial aquifer deposits than in fractured bedrock which may contribute to lower arsenic concentrations.Mean groundwater ages were less than 50 years old in all three wells and correlated with conservative tracer concentrations, such as chloride; however, mean age was not directly correlated with arsenic concentrations. Arsenic concentrations at KFW-87 did correlate with water levels, in addition, there was a seasonal pattern, which suggests that either the timing of or multiple sampling efforts may be important to define the full range of arsenic concentrations in domestic bedrock wells.Since geochemically reduced conditions and alkaline pHs are common to both bedrock and glacial aquifer wells in this study, groundwater age correlates less strongly with arsenic concentrations than geochemical conditions. There also is evidence of direct hydraulic connection between the glacial and bedrock aquifers, which can influence arsenic concentrations. Correlations between arsenic concentrations and the age of the old fraction of water in SGW-65 and the age of the young fraction of water in SGW-93 suggest that water in the two aquifers may be mixing or at least some of the deeper, older water captured by the glacial aquifer well may be from a similar source as the shallow young groundwater from the bedrock aquifer. The contrast in arsenic concentrations in the two aquifers may be because of increased adsorption capacity of glacio-fluvial sediments, which can limit contaminants more than fractured rock. In addition, this study illustrates that long residence times are not necessary to achieve more geochemically evolved conditions such as high pH and reduced conditions as is typically found with older water in other regions.

Identification of Hydrobiogeochemical Processes Controlling Seasonal Variations in Arsenic Concentrations Within a Riverbank Aquifer at Jianghan Plain, China

AbstractThe arsenic concentration in groundwater varies significantly with time and space in groundwater‐surface water exchange zones. Various processes have been identified that control arsenic concentration distribution and mobility in laboratory systems. However, it is still challenging to identify important processes controlling arsenic concentration distribution at the field scale due to the complex coupling of hydrobiogeochemical processes. In this study, a reactive flow and transport model was used to identify dominant processes controlling arsenic distribution and seasonal variations in groundwater‐surface water exchange zones using Jianghan Plain, China, as an example. The results revealed the importance of river water and groundwater interactions on seasonal changes in arsenic concentration; however, the affected region is limited to within 50‐m distance to the river. The modeling results, unexpectedly, revealed the predominant importance of groundwater extraction to the seasonal variation in arsenic concentration. The groundwater extraction changed the groundwater flow pattern and induced vertical leakage of oxygen‐containing surface water into the aquifer, which triggered a series of biogeochemical reactions that changed groundwater redox conditions and promoted arsenic sorption, resulting in a rapid decrease in arsenic concentrations in groundwater. After groundwater extraction ceased, aquifer recovered to anoxic condition, promoting arsenic release from the sorbed phase, leading to a rapid rebounding in groundwater arsenic concentrations. Overall, this study provided a tool to identify coupled hydrobiogeochemical processes on arsenic spatiotemporal distribution and migration in groundwater.

Vertical variability of arsenic concentrations under the control of iron-sulfur-arsenic interactions in reducing aquifer systems

High spatial variability of arsenic (As) concentration in geogenic As-contaminated groundwater has been commonly observed worldwide, but the underlying reasons remain not well understood. Selecting a sulfate-containing, As-affected aquifer at the Datong Basin, northern China as the study area and combining hydrogeochemical investigation and sediment extraction with reactive transport modeling, this work elucidated the roles of Fe-S-As interactions in regulating the vertical variation of As concentration in the groundwater. Dissolved As concentration varied between 0.05 and 18 μmol/L, but generally increased in the depth of 20–25 m and then decreased in 25–30 m. The high-As groundwater contained low Fe(II) (<0.007 mmol/L) and up to 15 μmol/L sulfide, in contrary to the S/SE Asian deltas/floodplains where high Fe(II) and As jointly occur in the groundwater devoid of sulfate reduction. The reductive dissolution of As-bearing Fe(III) oxides coupled to the degradation of organic matter with an estimated maximum rate of 0.22 mmol C/L/yr, mainly accounted for the depth-dependent increase of As concentration in the upper part of the shallow aquifer (<25 m deep). However, the decreasing reactivity of Fe(III) oxides together with the increase of pH over depth rendered the majority of electrons being transferred to sulfate reduction. The Fe(II) sulfides formed as a consequence not only helped to restrict the build-up of Fe(II) in the groundwater but also probably co-precipitated As to prompt As decrease in the depth of 25–30 m. Arsenite adsorbed on remaining Fe(III) oxides and newly-formed Fe(II) sulfides is another important pool of As in the aquifer, which varies in response to the extents of Fe(III)-oxide and sulfate reduction and consequently alters As distribution coefficient between the solid and the aqueous phases. This study highlights the importance of coupled geochemical cycling of Fe, S and As for As mobilization and reveals how it regulates As partitioning between groundwater and sediments.

Seasonal Variation in Arsenic Concentration and its Bioremediation Potential of Marine Bacteria Isolated from Alang-Sosiya Ship-Scrapping Yard, Gujarat, India

This work investigates seasonal variations in arsenic concentration at Alang-Sosiya, world’s largest ship-scrapping yard situated on the Gulf of Khambhat. Annually, hundreds of ships have been dismantled, which lead to discharge large amounts of detrimental and persistent pollutants at this location. In all seasons, the arsenic concentration was significantly elevated in sediments and seawaters in the intertidal zone of Alang-Sosiya ship-scrapping yard as compared to the reference station at Ghogha, 42 km away towards the northeast. The highest arsenic concentrations in seawater and sediment samples were observed during the Winter season and Summer season respectively. The marine environment affected by ship-scrapping activity and contaminated with arsenic is the potential location to get arsenic hyper-tolerant bacterial isolates. Out of 16 isolated bacterial strains, KKDK-1 and KKDK-2 sustained 600 mM and 500 mM arsenate respectively. The 16S rRNA ribotyping identified strains KKDK-1 and KKDK-2 as Halomonas species. The strain KKDK-1 showed the maximum arsenic accumulation of 21.7±3.3 mg g-1 cell dry weight at exponential phase (60 h), followed by sudden extrusion of arsenic during stationary phase (84 h) of bacterial growth. Whereas, strain KKDK-2 accumulated 6.8±1.12 mg Arsenic g-1 cell dry weight during exponential phase (72 h), which remains almost invariable during stationary phase (96-144 h) of bacterial growth. These results indicate the hypertolerance of arsenic by KKDK-1 and KKDK-2 with its higher accumulation capacity, signifying them as potential candidates for arsenic detoxification of arsenic contaminated sites.

Study on the variation of arsenic concentration in groundwater and chemical characteristics of arsenic in sediment cores at the areas with endemic arsenic poison disease in Jianghan Plain

To understand the variation of arsenic concentration in underground water at the endemic arsenic poison disease area of Jianghan Plain so as to better understand the spatial distribution of high arsenic groundwater, hydro-chemical evolution and source of arsenic in this region. Thirty underground water samples were collected respectively around 3 km radius of the two houses where arsenic poisoning patients lived, in Xiantao and Honghu. Sediment cores of three drillings were collected as well. Both paired t-test or paired Wilcoxon Signed Ranking Test were used to compare the arsenic concentration of water. The arsenic concentration in 2011-2012 appeared lower than that in 2006-2007 at the Nanhong village of Xiantao (t = 4.645 3, P < 0.000 1), but was higher (S = -150, P < 0.000 1) in the Yaohe village of Honghu. The pH value showed weak acidity with Eh as weak oxidated. Positive correlations were observed between arsenic concentration and Cl, HCO3(-), Fe, Mn. However, negative correlations were found between As and SO4(2-), NO3(-). The range of arsenic content in the sediment was 1.500 mg/kg to 17.289 mg/kg. The maximum arsenic content existed in the soil layer, while the minimum arsenic content existed in the sand layer. The concentration of arsenic varied widely with time and space at endemic arsenic poison disease area of Jianghan Plain. Characteristics of these water chemicals showed significant differences, when compared to the groundwater from Datong Basin, Shanxi Shanyin and Hetao Plain of Inner Mongolia, which presented a typical environment with high arsenic contents in the groundwater. The arsenic content in the sediment samples seemed related to the lithologic structure.

Variation of arsenic concentration on surfaces of in-service CCA-treated wood planks in a park and its influencing field factors.

Wood preservatives can protect wood from dry rot, fungi, mould and insect damage, and chromated copper arsenate (CCA) has been used as an inorganic preservative for many years. However, wood treated with CCA has been restricted from residential uses in the EU from June 30, 2004, due to its potential toxicity. Such a regulation is not in place in China yet, and CCA-treated wood is widely used in public parks. A portable XRF analyser was used to investigate arsenic (As) concentration on surfaces of in-service CCA-treated wood planks in a popular park as well as the influencing field factors of age in-service, immersion and human footfall. With a total of 1207 readings, the observed As concentrations varied from below the detection limit (<10 mg/kg) to 15,746 mg/kg with a median of 1160 mg/kg. Strong variation of As concentrations were observed in different wood planks of the same age, on the surface of the same piece of wood, inside the same piece of wood, and different surfaces of walkway planks, hand rails and poles in the field. The oldest planks exhibited high As concentrations, which was related to its original treatment with high retention of CCA preservative. The effect of immersion in the field for about 4 months was insignificant for As concentration on the surfaces. However, a significant reduction of As was observed for immersion combined with human footfall (wiping by shoes). Human traffic in general caused slightly reduced and more evenly distributed As concentrations on the wood surfaces. The strong variation, slow aging and relatively weak immersion effects found in this study demonstrate that the in-service CCA-treated wood poses potential health risks to the park users, due to easy dermal contact especially when the wood is wet after rainfall. It is suggested that further comprehensive investigations and risk assessments of CCA-treated wood in residential areas in China are needed, and precautionary measures should be considered to reduce the potential risks to residents and visitors, especially children.

A Preliminary Study on Genetic Variation of Arsenic Concentration in 32 Different Genotypes of Leafy Vegetable

Leafy vegetables are a food crop with higher protein and are also important source of minerals which are essential for good health. Due to the large consumption, it is necessary to decrease the arsenic (As) concentration in leafy vegetable to avoid the potential risk to human health. The current study is aimed at assessing arsenic (As) accumulation ability and identification of cultivars with less As concentration that could be grown in As contaminated farmland for food safety. A set of thirty two leafy vegetable cultivars from 5 species were compared in hydroponics for 2 weeks having moderate level of 0- control and 6 mg As L -1 . At harvest, plants were sampled and analyzed for As concentration. Significant genotypic variations were observed in the shoots As concentration, translocation and bioaccumulation factors revealing more than 8 and 25 times cultivar differences in shoot As concentration, and in translocation factors respectively. This result revealed that As concentration in shoot was in part governed by the greater ability of root-shoot translocation. Cultivar Sijibaiye (SJBY) had the lowest shoot As concentration while the highest was detected in Dayekongxincai (DYKXC). The average As concentration in roots were found to be ten to twenty times higher than those observed in shoots, indicating that there is restricted transport of As from the root system to the shoot of cultivars. Therefore, it has been suggested that there is possibility to lower the As concentration in leafy vegetables by selecting and breeding cultivars with less As concentration that can be safely grown in contaminated soils with the slight and moderate levels of As for safe consumption.

Factors affecting temporal variability of arsenic in groundwater used for drinking water supply in the United States

The occurrence of arsenic in groundwater is a recognized environmental hazard with worldwide importance and much effort has been focused on surveying and predicting where arsenic occurs. Temporal variability is one aspect of this environmental hazard that has until recently received less attention than other aspects. For this study, we analyzed 1245 wells with two samples per well. We suggest that temporal variability, often reported as affecting very few wells, is perhaps a larger issue than it appears and has been overshadowed by datasets with large numbers of non-detect data. Although there was only a slight difference in arsenic concentration variability among samples from public and private wells (p=0.0452), the range of variability was larger for public than for private wells. Further, we relate the variability we see to geochemical factors—primarily variability in redox—but also variability in major-ion chemistry. We also show that in New England there is a weak but statistically significant indication that seasonality may have an effect on concentrations, whereby concentrations in the first two quarters of the year (January–June) are significantly lower than in the second two quarters (July–December) (p<0.0001). In the Central Valley of California, the relation of arsenic concentration to season was not statistically significant (p=0.4169). In New England, these changes appear to follow groundwater levels. It is possible that this difference in arsenic concentrations is related to groundwater level changes, pumping stresses, evapotranspiration effects, or perhaps mixing of more oxidizing, lower pH recharge water in wetter months. Focusing on the understanding the geochemical conditions in aquifers where arsenic concentrations are concerns and causes of geochemical changes in the groundwater environment may lead to a better understanding of where and by how much arsenic will vary over time.

Predicting arsenic concentrations in groundwater of San Luis Valley, Colorado: implications for individual-level lifetime exposure assessment

Consumption of inorganic arsenic in drinking water at high levels has been associated with chronic diseases. Risk is less clear at lower levels of arsenic, in part due to difficulties in estimating exposure. Herein we characterize spatial and temporal variability of arsenic concentrations and develop models for predicting aquifer arsenic concentrations in the San Luis Valley, Colorado, an area of moderately elevated arsenic in groundwater. This study included historical water samples with total arsenic concentrations from 595 unique well locations. A longitudinal analysis established temporal stability in arsenic levels in individual wells. The mean arsenic levels for a random sample of 535 wells were incorporated into five kriging models to predict groundwater arsenic concentrations at any point in time. A separate validation dataset (n = 60 wells) was used to identify the model with strongest predictability. Findings indicate that arsenic concentrations are temporally stable (r = 0.88; 95 % CI 0.83-0.92 for samples collected from the same well 15-25 years apart) and the spatial model created using ordinary kriging best predicted arsenic concentrations (ρ = 0.72 between predicted and observed validation data). These findings illustrate the value of geostatistical modeling of arsenic and suggest the San Luis Valley is a good region for conducting epidemiologic studies of groundwater metals because of the ability to accurately predict variation in groundwater arsenic concentrations.

Predicting arsenic concentration in groundwater of Bangladesh using Bayesian geostatistical model

The pattern of the spatial variation in arsenic concentration in groundwater of Bangladesh is usually needed for the planning of safe drinking water. Often a model-based prediction is required for this purpose. In this paper, we fit a Bayesian hierarchical geostatistical model by utilizing data from the project, ‘Groundwater studies of arsenic concentration in Bangladesh’ conducted by the British Geological Survey and the Department of Public Health Engineering of Bangladesh. We also develop a predictive model for arsenic concentration at different levels of well-depth using the same approach. The resulting predictive model has been cross-validated by appropriate statistical tools. Finally, we obtained reliable spatially continuous predictive maps and predictive probability maps showing the areas with high probability of arsenic concentration for different levels of well-depth. Results indicate that our model fits the data well and captures a substantial amount of spatial variation. Moreover, well-depth is found to have a significant contribution in explaining the observed variation in arsenic concentration. The predictive maps that have been produced are observed to be different for various levels of well-depths and are expected to be helpful to the policy makers in preparing proper regional planning for safe drinking water.

Arsenic residues in soil at cattle dip tanks in the Vhembe district, Limpopo Province, South Africa

Arsenic-based compounds have been used for cattle dipping for about half a century to combat East Coast Fever in cattle in South Africa. The government introduced a compulsory dipping programme in communal areas to eradicate the disease in 1911. Concern has been raised regarding the ecological legacy of the use of arsenic-based compounds in these areas. We investigated the incidence of arsenic residue in soil at 10 dip sites in the Vhembe district of Limpopo Province, South Africa. We found high levels of arsenic contamination at a depth of 300 mm at some sites. Control samples indicated that these high arsenic levels are the result of the application of inorganic arsenic. Variation of arsenic concentrations is attributed to duration of exposure to the chemical, soil properties and distance from the dip tank. Concerns are raised regarding the structural condition of the dip tanks, encroaching villages and possible health threats to the human population in the area.

Arsenic concentration variability, health risk assessment, and source identification using multivariate analysis in selected villages of public water system, Lahore, Pakistan

This paper reports high levels and variability in arsenic (As) levels at locations identified as one of the highest As-contaminated locations in Pakistan. Groundwater pollution related to arsenic has been reported since many years in the areas lying in outskirts of District Lahore, Pakistan. A comparative study is done to determine temporal variations of As from three villages, i.e., Kalalanwala (KLW), Manga Mandi (MM), and Shamki Bhattian (SKB). Seventy-three percent of the 30 investigated samples ranging in depth from 20 to 200 m, show an increasing trend in variations of As concentration over a time span of 4 years and 87% of samples exceeded the WHO standard of 10 μg/L for As while 77% of samples have As concentration >50 μg/L (national standard). Further results indicate that high levels of As is accompanied with increase pH (r = 0.8) favoring desorption of As from minerals at higher pH under oxidizing conditions. For health risk assessment of arsenic, the average daily dose, hazard quotient (HQ), and cancer risk were calculated. The residents of the studied areas had toxic risk index in the order of SKB>KLW>MM, with 87% of samples exceeding the typical toxic risk index 1.00 (ranging from 2.3-48.6) which was 83% (ranging from 0.3-41) 4 years before. The results of the present study therefore indicate that arsenic concentrations are increasing in the area, which needs an immediate attention to provide alternate sources of water to save people at risk.

Spatial variability of Arsenic Concentrations in Baltic Sea surface sediments in relation to Sea Dumped Chemical Munitions

Arsenic concentration in marine areas are higher than in terrestrial environment, because most of its compounds are water soluble, and water bodies serve as a sink for this element. Arsenic compounds, though naturally present in the sediments, are considered a threat to the environment, due to possible transformation to its toxic species – As 3+ and As 5+ . Natural background concentration of arsenic compounds is highly variable, as it differs both with the type of sediments, presence of ferromanganese nodules, iron sulphides or proximity to sources. In the Baltic Sea, majority of As originates from river runoff, while additional source of arsenic compounds in some areas of the Baltic are arsenic containing chemical warfare agents dumped into the sea after second world war.