Speciation of arsenic in bulk and rhizosphere soils from artisanal cooperative mines in Bolivia

Negative Impacts of Arsenic on Plants and Mitigation Strategies

Arsenic (As) is a metalloid prevalent mainly in soil and water. The presence of As above permissible levels becomes toxic and detrimental to living organisms, therefore, making it a significant global concern. Humans can absorb As through drinking polluted water and consuming As-contaminated food material grown in soil having As problems. Since human beings are mobile organisms, they can use clean uncontaminated water and food found through various channels or switch from an As-contaminated area to a clean area; but plants are sessile and obtain As along with essential minerals and water through roots that make them more susceptible to arsenic poisoning and consequent stress. Arsenic and phosphorus have many similarities in terms of their physical and chemical characteristics, and they commonly compete to cause physiological anomalies in biological systems that contribute to further stress. Initial indicators of arsenic's propensity to induce toxicity in plants are a decrease in yield and a loss in plant biomass. This is accompanied by considerable physiological alterations; including instant oxidative surge; followed by essential biomolecule oxidation. These variables ultimately result in cell permeability and an electrolyte imbalance. In addition, arsenic disturbs the nucleic acids, the transcription process, and the essential enzymes engaged with the plant system's primary metabolic pathways. To lessen As absorption by plants, a variety of mitigation strategies have been proposed which include agronomic practices, plant breeding, genetic manipulation, computer-aided modeling, biochemical techniques, and the altering of human approaches regarding consumption and pollution, and in these ways, increased awareness may be generated. These mitigation strategies will further help in ensuring good health, food security, and environmental sustainability. This article summarises the nature of the impact of arsenic on plants, the physio-biochemical mechanisms evolved to cope with As stress, and the mitigation measures that can be employed to eliminate the negative effects of As.

The role of various ameliorants on geochemical arsenic distribution and CO2-carbon efflux under paddy soil conditions

Climate change is a global challenge that is accelerated by contamination with hazardous substances like arsenic (As), posing threat to the agriculture, ecosystem and human health. Here, we explored the impact of various ameliorants on geochemical distribution of As in two soils with contrasting textures (sandy clay loam (Khudpur Village) and clay loam (Mattital Village)) under paddy soil conditions and their influence on the CO₂-carbon efflux. The exchangeable As pool in clay loam soil increased as: lignite (0.4%) < biogas slurry (6%) < cow dung (9%), and < biochar (20%). However, in the sandy clay loam soil exchangeable soil As pool was found to be maximum with farmyard manure followed by biogas slurry, biochar and cow dung (17%, 14%, 13% and 7%, respectively). Interestingly, in the sandy clay loam soil the percentage As distribution in organic fraction was: biochar (38%) > cow dung (33%) > biogas slurry (23%) > sugarcane bagasse (22%) > farmyard manure (21%) that was higher compared to the clay loam soil (< 6% for all the amendments). In addition to the highest As immobilization by biochar in sandy clay loam soil, it also led to the lowest CO₂-carbon efflux (1470 CO₂-C mg kg^-1) among all the organic/inorganic amendments. Overall, the current study advances our understanding on the pivotal role of organic amendments, notably biochar, in immobilizing As under paddy soil conditions with low (CO₂) carbon loss, albeit it is dependent on soil and ameliorant types.

Arsenic contribution of poultry manure towards soils and food plants contamination and associated cancer risk in Khyber Pakhtunkhwa, Pakistan

Exposure to high level of arsenic (As) through the ingestion of contaminated soil, dust and food plants can pose health risk to humans. This study investigates the total arsenic (As), arsenobetaine (AsB), monomethylarsenate (MMA), dimethylarsenate (DMA), arsenite (As³⁺) and arsenate (As⁵⁺) concentrations in poultry feed, manure, agricultural soils and food plants collected from Khyber Pakhtunkhwa Province, Pakistan. The total mean As concentrations in the edible parts of food plants ranged from 0.096 mg kg^-1 to 1.25 mg kg^-1 with percentile (P) values (P25-0.039, P50-0.0765, P75-0.165 1 mg kg^-1 to P25-0.95, P50-1.23, P75-1.6 1 mg kg^-1) and exceeded the food safety limit (0.1 mg kg^-1) of Food & Agriculture Organization (FAO) and World Health Organization (WHO) in all plant species except Pisum sativum (pea) and Mentha arvensis (mint). The risk to human health was assessed through the average daily intake (ADI), hazards quotient (HQ), health risk index (HRI) and lifetime cancer risk (LTCR). The highest average daily intake of As via the ingestion of Malva neglecta (mallow, a leafy plant) was observed for adults and children. The ADI for adults and children (2.36 × 10^-4 mg kg^-1 day^-1 and 6.33 × 10^-4 mg kg^-1 day^-1) was about 13% and 5%, respectively, of the Bench Mark Dose Limit (BMDL_0.5) of 3.00 × 10^-3 mg kg^-1 day^-1 set by WHO. The HRI was 3 times more in the children (2.1) than the adults (0.79), posing non-cancer health risks (health risk index > 1) for children. The LTCR values were slightly higher (1.53 × 10^-4) relative to USEPA and WHO limits (1 × 10^-6 to 1 × 10^-4) for children whereas a minimal cancer risk was observed for adults via consumption of selected food plants. The results showed that poultry manure can contaminate food plants that may lead to cancer and non-cancer risks in agricultural areas, Pakistan. Thus, it is important to minimize As concentration in poultry feed to safeguard human health and environment from adverse effects.

Transdisciplinary Communities of Practice to Resolve Health Problems in Southeast Asian Artisanal and Small-Scale Gold Mining Communities

Artisanal and small-scale gold mining (ASGM) has been a major part of people's livelihood in the rural areas of many developing countries, including those in Southeast Asia (SEA). Nevertheless, because of the use of mercury, ASGM activities have significant local and global adverse impacts on the environment and ASGM community health. Although there have been many monodisciplinary projects by academic researchers and governments to solve the environmental and health problems in SEA ASGM communities, they have not been sufficient to solve the complex socioeconomic problems. This review first outlines the nature of the SEA ASGM activities and the consequent environmental, community health, and socioeconomic problems and then introduces an approach using transdisciplinary communities of practice that involves both academic and nonacademic participants to relieve these wicked ASGM problems and to improve the environmental governance and community health in ASGM communities in SEA.

Vertical Distributions and Bioavailabilities of Heavy Metals in Soil in An-Tea Plantations in Qimen County, China

Heavy metals mainly enter tea from the soil. In this study, stratified soil samples were collected, at a depth of 0–60 cm, using a soil drill in An-tea plantations. Speciation of As, Cd, Cr, Cu, Ni, Pb, and Zn was determined using the European Community Bureau of Reference sequential extraction method, and the heavy metal concentrations in the extracts were determined by inductively coupled plasma−mass spectrometry. Compared with other soil layers, the mean Cd, Cu, Pb, and Zn concentrations were highest in the 0–20 cm layer, the Ni concentrations were highest in the 20–40 cm layer, and the As and Cr concentrations were highest in the 40–60 cm layer. The mean contributions of the non-residual fractions, including the acid-soluble, reducible, and oxidizable fractions, to the total concentrations were higher than those of the residual fraction for Cr, Cu, and Ni at all depths in soil from a flat area, as well as for Cd and Zn at all depths in soil from a sloping area. The contributions of non-residual fractions to the total As and Pb concentrations were higher than those of the residual fraction in soil from a depth of 0–20 cm from the flat area and soil from a depth of 20–60 cm from the sloping area. The total heavy metal concentrations correlated well with the acid-soluble fraction and reducible fraction concentrations in soil from 0–40 cm.

Application of Biochar for the Restoration of Metal(loid)s Contaminated Soils

Biochar has recently aroused great interest for the restoration of contaminated soils since it improves soil properties and induces the immobilization of pollutants. This study evaluates the use of biochar from plant pruning, applied as an amendment, for immobilizing metal(loid)s in a highly contaminated soil as well as for reducing the phytotoxicity of these pollutants by promoting natural revegetation. For this purpose, a bioassay with Trifolium pratense L. was used to test the effectiveness of the soil amendment in greenhouse conditions. Three treatments were carried out including soil contaminated with metal(loid)s (RA), and this soil was amended with biochar at different dosage: 4% (RA4B) and 8% (RA8B). A non-contaminated soil (NC) from a nearby area not affected by contamination was used as a control. The results show that biochar increased soil pH by several units depending on the dose used, 8% being the most effective one. Biochar treatments also reduced soluble and bioavailable forms of Zn and Cu. Likewise, phytotoxicity was significantly reduced, promoting seed germination and biomass with plant growth values similar to the non-polluted soil. In light of the results obtained, the evaluation of the bioremediation potential of biochar under field conditions can be considered.

Research progress on speciation analysis of arsenic in traditional Chinese medicine

Traditional Chinese medicine contains arsenic (As), which in the natural environment accumulates in plants during the growth of Chinese medicinal materials; there are mineral medicines containing As in Chinese patent medicine such as As4S4, As2S3, etc. Due to the toxicity of As-containing compounds and its role in inflammation and treatment of cancers such as leukemia, it is necessary to analyze the chemical form of As. A comprehensive investigation of the compound forms of heavy metals rather than the simple total amount of elements will lay the foundation for the scientific and objective evaluation of the safety of heavy metals. This article summarizes the speciation of As in bulk Chinese medicinal materials and Chinese patent medicines in recent years, and reviews the main research methods of As speciation analysis. The separation and detection combined analysis method focuses on the high-performance liquid chromatography-plasma mass spectrometry and high-performance liquid chromatography-hydride generation-atomic fluorescence spectroscopy, etc. Taking the advanced synchrotron radiation source as the research platform, the use of X-ray near edge absorption fine structure spectrum and micro-area X-ray fluorescence analysis as a microscopic analysis technique supports direct analysis of the As speciation in situ. It is the most promising morphological analysis method.

Heavy Metals and As in Ground Water, Surface Water, and Sediments of Dexing Giant Cu-Polymetallic Ore Cluster, East China

Heavy metals and As (HMs) pollution in mining areas are a widespread environmental concern. In this study, ground water, surface water, and sediment samples around the Dexing area, one of the largest Cu-polymetallic ore clusters in China, were collected to examine the concentrations and distributions of As, Cd, Cr, Cu, Hg, Pb, and Zn. Pollution indices, geo-accumulation index, and potential ecological risk index were used to estimate the pollution characteristics and ecological risk of HMs. The results show that the major pollutants in the surface water were Cd, Cu, Zn, and Pb, while the dominant ecological risk of HMs in the sediments originated from Cu, As, Hg, and Cd. Moreover, HMs in the surface water and sediments exhibited substantial spatial heterogeneity in the study area, indicating a severely disturbed environment due to mining activities. The proportions of HM pollutions were higher in the Dexing River and its tributaries than in the Le’an River and its tributaries. The surface water pollution was predominant at the tributaries closest to the mine area, while the sediment contamination has been expanded several kilometers downstream of the major rivers. Overall, the ecological risk of HMs was higher in the sediments than in the surface water.

Accumulation of As, Ag, Cd, Cu, Pb, and Zn by Native Plants Growing in Soils Contaminated by Mining Environmental Liabilities in the Peruvian Andes

The capability of native plant species grown in polluted post-mining soils to accumulate metals was evaluated in view of their possible suitability for phytoremediation. The study areas included two environmental liabilities in the Cajamarca region in the Peruvian Andes. The content of As, Ag, Cd, Cu, Pb, and Zn was determined in individual plant organs and correlated with soil characteristics. The degree of the pollution depended on the metal with results ranging from uncontaminated (Cd) to moderately (Zn), strongly (As, Cu), and extremely contaminated (Pb, Ag) soils. The metals were mainly present in the fractions with limited metal mobility. The bioaccumulation of the metals in plants as well the translocation into overground organs was determined. Out of the 21 plants evaluated, Pernettya prostrata and Gaultheria glomerate were suitable for Zn, and Gaultheria glomerata and Festuca sp. for Cd, phytostabilization. The native species applicable for Cd phytoremediation were Ageratina glechonophylla, Bejaria sp., whereas Pernettya prostrata Achyrocline alata,Ageratina fastigiate, Baccharis alnifolia, Calceolaria tetragona, Arenaria digyna, Hypericum laricifolium, Brachyotum radula, and Nicotiana thyrsiflora were suitable for both Cd and Zn. None of the studied plants appeared to be suitable for phytoremediation of Pb, Cu, As and Ag.

Spatial assessment of heavy metals contamination in household garden soils in rural Limpopo Province, South Africa

Heavy metal pollution in soil poses a serious health threat to humans living in close proximity and in contact with contaminated soil. Exposure to heavy metals can result in a range of adverse health effects, including skin lesions, cardiovascular effects, lowering of IQ scores and cancers. The main objectives of this study were to (1) use a portable XRF spectrophotometer to measure concentrations of lead (Pb), arsenic (As), mercury (Hg) and cadmium (Cd) in residential soils in rural Giyani in the Limpopo province of South Africa; (2) to assess the spatial distribution of soil metal concentrations; and (3) to assess pollution levels in residential soils. There were elevated levels of As at one of the sites where 54% of soil samples exceeded the Canadian reference levels for As of 20 mg/kg. Using the geoaccumulation index (I_geo) to determine contamination levels of As, 57% of soil samples from the most polluted site were found to be moderately to heavily and extremely contaminated with As (I_geo class 2-5). The site is located near the Giyani Greenstone Belt, which is characterized by abandoned mines and artisanal mining activities. Gold ores are closely associated with sulphide minerals such as arsenopyrite, and these have been found to contain high amounts of As. This study highlighted the potential for soil contamination and the importance of site-specific risk assessment in the context of environment and health impact assessments prior to major developments, including human settlement developments.

Toxic Metal Implications on Agricultural Soils, Plants, Animals, Aquatic life and Human Health

The problem of environmental pollution is a global concern as it affects the entire ecosystem. There is a cyclic revolution of pollutants from industrial waste or anthropogenic sources into the environment, farmlands, plants, livestock and subsequently humans through the food chain. Most of the toxic metal cases in Africa and other developing nations are a result of industrialization coupled with poor effluent disposal and management. Due to widespread mining activities in South Africa, pollution is a common site with devastating consequences on the health of animals and humans likewise. In recent years, talks on toxic metal pollution had taken center stage in most scientific symposiums as a serious health concern. Very high levels of toxic metals have been reported in most parts of South African soils, plants, animals and water bodies due to pollution. Toxic metals such as Zinc (Zn), Lead (Pb), Aluminium (Al), Cadmium (Cd), Nickel (Ni), Iron (Fe), Manganese (Mn) and Arsenic (As) are major mining effluents from tailings which contaminate both the surface and underground water, soil and food, thus affecting biological function, endocrine systems and growth. Environmental toxicity in livestock is traceable to pesticides, agrochemicals and toxic metals. In this review, concerted efforts were made to condense the information contained in literature regarding toxic metal pollution and its implications in soil, water, plants, animals, marine life and human health.

Simplex-Centroid mixture design applied to arsenic (V) removal from waters using synthetic minerals

Arsenic (As) is a toxic and carcinogenic element. Therefore, it is necessary to carry out research on As-contaminated water management in order to achieve the World Health Organization (WHO) standard for drinking water (0.010 mg L^-1). A Simplex-Centroid mixture design (SCMD) was used to determine the best mineral composition for both maximum adsorption capacity of As(V) (MAC-As) and residual concentration of As(V) (RC-As), using synthetic poorly crystallized aluminum hydroxide (pAlHyd), calcined layered double hydroxide (cLDH), and two-line ferrihydrite (2ℓFh). The analysis of variance results and the predicted values of models showed a good agreement with the experimental data, indicating that SCMD is a reliable method to optimize As removal through determination of the best mineral composition. The ability of pure synthetic minerals to remove As from water was different among those mixtures thereof, which indicate that the mineral components interacted with each other. Results showed that cLDH was the best As adsorbent. However, it showed a RC-As higher than the WHO standard. The pAlHyd and 2ℓFh exhibited smaller MAC-As, but they lowered RC-As to below 0.010 mg L^-1, showing no direct relationship between high MAC-As and low RC-As. Therefore, mineral compositions which combine high adsorption capacity with low residual concentration should work better for removing As from drinking water, ensuring it meets the WHO potability standard. Ternary diagrams for MAC-As and RC-As showed that the best combination for maximizing MAC-As and reducing RC-As should be a mixture of 75-90% of cLDH, 10-20% of pAlHyd, and 0-5% of 2ℓFh.

Residual pollution and vegetation distribution in amended soils 20 years after a pyrite mine tailings spill (Aznalcóllar, Spain)

The present work assesses the residual pollution in the Guadiamar Green Corridor (SW, Spain) after a long-term aging process (18 years) since the accident of the Aznalcóllar pyrite mine. We have focused on the study of trace elements (Cu, Zn, Cd, As and Pb) in soils, their fractionation and the transference to the surrounding vegetation. The residual polluted areas are characterized by scattered plots with absence of vegetation, presenting high concentrations of trace elements, acidic pH and low organic carbon content. Surrounding these polluted plots, two vegetation gradient belts are clearly identified by changes in plant cover and richness. The inhibition of plant growth in the bare soils is related to the highest mobility of soluble and exchangeable Cu, Zn and Cd forms, which significantly decrease with the distance to the polluted plots. Plant richness and cover show differences between belts; bioaccumulation of trace elements in plants also differs, with a preferential accumulation in roots. Despite the low bioavailability of As and Pb in soils, bioaccumulation factors in plants for these elements are significantly higher in belt 1 in relation to belt 2. High Cu and Cd potential toxic concentrations in aerial parts of vegetation are found, posing a risk for livestock and a potential entrance to the food-chain. On the other hand, Lamarckia aurea (L.) Moench (in belt1) and Trifolium campestre Schreb. (in belt2) were the most dominant species in severely polluted soils. Elevated concentrations of trace elements in the vegetation growing in the area indicate plant adaptation mechanisms to live in these severely polluted soils, which can be used as a good bioindicator of pollution in similar polluted areas.

The soil-plant transfer of risk elements within the area of an abandoned gold mine in Libčice, Czech Republic

Abandoned gold mines are often suggested as potential sources of environmental pollution. Thus, the soils within the area of a gold mine in Libčice, Czech Republic, were monitored. Elevated element contents were found of As, Cd, Cu, Hg, Pb, and Zn. The risk assessment codes (RACs) indicated high environmental risk from soil Cd, and moderate risk from Zn, whereas the risk of As, Cu, and Pb was low. It was supported by the analysis of 134 samples of aboveground biomass of plants, where the levels of As and Pb were below the detection limit. For Cd, the plant uptake reflected the high mobility of this element, where the bioaccumulation factors (BAFs) varied in range 0.032 (Fragaria vesca) and 1.97 (Circia arvensis). For 11% of samples the BAF values for Cd exceeded 1. For Hg, although the maximum BAF did not exceed 0.37 (Lotus corniculatus), the Hg contents in plants occasionally exceeded the threshold limits for Hg contents in raw feedstuffs. The investigated gold mine does not represent a direct environmental risk, but the fate of Cd and Hg in the soils and plants suggests the necessity of a deeper understanding of the penetration of these elements into the surrounding environment.

A Case Study of Heavy Metal Pollution in Water of Bone River by Artisanal Small-Scale Gold Mine Activities in Eastern Part of Gorontalo, Indonesia

Bone River, which is located in the eastern part of Gorontalo, Indonesia, has an issue of contamination by heavy metals due to artisanal small-scale gold mine (ASGM) activities. This river is used as a source of water by inhabitants living along the river, due to the lack of another clean water supply. The purpose of this study is to investigate the concentration of As from the mining site alongside Bone River, and to reveal the As pollution source. Water and sediment samples were collected from ASGM and along Bone River to the delta. The concentrations of As, Hg, and Pb in water samples were identified by inductively coupled plasma mass spectroscopy (ICP–MS), while concentrations in sediment samples were determined by particle-induced X-ray emission (PIXE). Results showed that the concentrations of As, Hg, and Pb in water ranged from 66 to 82,500 µg/L, 17 to 2080 µg/L, and 11 to 1670 µg/L, respectively. These levels exceeded, by 1000 to 10,000 times, the safe limits of drinking water defined by the World Health Organization, which indicated that Bone River water is not safe for drinking or cooking purposes.

Preliminary data on arsenic and trace metals concentrations in wetlands around artisanal and industrial mining areas (Cote d'Ivoire, West Africa)

This data article is issued from the research article ‘’Distribution trends and ecological risks of arsenic and trace metals in wetland sediments around gold mining activities in central-southern and southeastern Côte d’Ivoire’’ [1]. It presents arsenic and trace metal Cd, Pb, Cu, Zn, Cr, Co, Fe, Al, Mn, and Ni loadings in surface sediments collected from industrial mining, artisanal and small scale mining, and non-mining areas (West Africa). Are also provided, hierarchical dendrograms and factor loadings derived from the Hierarchical Clustering Analysis (HCA) and the principal component analysis (PCA), respectively. Data ranged from <LD-561 µg/g for As, 0.10–2.70 µg/g for Cd, 1.10–16.9 µg/g for Pb, 2.00–71.8 µg/g for Cu, 5.60–116 µg/g for Zn, 16.3–439 µg/g for Cr, 0.70–46.4 µg/g for Co, 11.9–175 mg/g for Fe, 7.49–93.3 mg/g for Al, 4.30–6442 µg/g for Mn, and 3.10–68.6 µg/g for Ni. These data are relevant for future research and sediment quality policy making at a regional level.

Characterization and risk of exposure to elements from artisanal gold mining operations in the Bolivian Andes

Artisanal and small-scale gold mining (ASGM) offers low-skilled workers an opportunity to elevate themselves out of poverty. However, this industry operates with little to no pollution controls and the cost to the environment and human health can be large. The objectives of this study were to measure levels of arsenic (As), manganese (Mn), cobalt (Co), lead (Pb), and mercury (Hg) in the environment and characterize health risks to miners and residents in an area with active ASGM operations. An exposure assessment was conducted at two different mining sites and a nearby village in the Bolivian Anders. The resulting measurements were then used to quantify cancerous and noncancerous health risks to children and adults working at and living near ASGM areas. Soil concentrations of As were well above background levels and showed great variations between the village and mining area. Mercury vapor levels at the two mining sites were approximately 30 times larger than the EPA reference concentration. The risk of developing non-cancerous health effects were primarily due to exposure to As and Hg. The probability of individuals developing cancer was considerably increased with adult miners having a probability of 1.3 out of 100. Cancer potential was driven by exposure to As, with de minimus cancer risk from all other elements. Based on the environmental characterization of elements in soils and Hg vapors, the risk of developing cancerous and non-cancerous health outcomes were above a level of concern based on EPA risk assessment guidance. Personal protective equipment was not worn by workers and Hg amalgam is commonly heated in workers' homes. Better education of the risks of ASGM is needed as well as simple controls to reduce exposure.

Understanding arsenic dynamics in agronomic systems to predict and prevent uptake by crop plants

This review is on arsenic in agronomic systems, and covers processes that influence the entry of arsenic into the human food supply. The scope is from sources of arsenic (natural and anthropogenic) in soils, biogeochemical and rhizosphere processes that control arsenic speciation and availability, through to mechanisms of uptake by crop plants and potential mitigation strategies. This review makes a case for taking steps to prevent or limit crop uptake of arsenic, wherever possible, and to work toward a long-term solution to the presence of arsenic in agronomic systems. The past two decades have seen important advances in our understanding of how biogeochemical and physiological processes influence human exposure to soil arsenic, and this must now prompt an informed reconsideration and unification of regulations to protect the quality of agricultural and residential soils.

Novel mesoporous FeAl bimetal oxides for As(III) removal: Performance and mechanism

In this study, novel mesoporous FeAl bimetal oxides were successfully synthesized, characterized, and employed for As(III) removal. Batch experiments were conducted to investigate the effects of Fe/Al molar ratio, dosage, and initial solution pH values on As(III) removal. The results showed that the FeAl bimetal oxide with Fe/Al molar ratio 4:1 (shorten as FeAl-4) can quickly remove As(III) from aqueous solution in a wide pH range. The FeAl-4 before and after reaction with As(III) was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED), Brunauer-Emmett-Teller (BET) surface area measurement, and X-ray photoelectron spectroscopy (XPS). The BET results showed that the original FeAl-4 with a high surface area of 223.9 m²/g was a mesoporous material. XPS analysis indicated that the surface of FeAl-4 possessed a high concentration of M-OH (where M represents Fe and Al), which was beneficial to the immobility of As(III). The excellent performance of FeAl-4 makes it a potentially attractive material for As(III) removal from aqueous solution.

Micro-distribution of arsenic species in tissues of hyperaccumulator Pteris vittata L

Arsenic (As) contamination and its harmful consequences have gained increasing attention in research. Phytoextraction, which uses the As hyperaccumulator Pteris vittata L., is a well-established technology adopted in many countries. However, the hyperaccumulation mechanisms of this plant remain controversial. This study investigated the species and the micro-distribution of As species in three P. vittata L. ecotypes after exposure to arsenite (AsIII) and arsenate (AsV) for 7d. Arsenic-accumulating abilities and preferences to As species varied among different ecotypes. The reduction of AsV into AsIII, oxidation of AsIII into AsV, and chelation of AsIII with thiols were all observed in P. vittata. The reduction of As mainly occurred in the rhizoid, whereas oxidation and chelation mainly occurred in the aboveground parts. Correlation analyses showed that the As concentration in pinna was significantly correlated with the AsV percentage in paraxial and abaxial epidermis (positive), AsIII-GSH percentage in paraxial epidermis (positive), and AsIII percentage in paraxial and abaxial epidermis (negative). Results indicated that oxidation and chelation reactions contributed to the accumulation of As in P. vittata.

Quantification of inorganic arsenic exposure and cancer risk via consumption of vegetables in southern selected districts of Pakistan

Human exposures to arsenic (As) through different pathways (dietary and non-dietary) are considered to be one of the primary worldwide environmental health risks to humans. This study was conducted to investigate the presence of As in soil and vegetable samples collected from agricultural lands located in selected southern districts of Khyber Pakhtunkhwa (KPK) Province, Pakistan. We examined the concentrations of total arsenic (TAs), organic species of As such as monomethylarsonic acid (MMA) and dimethylarsonic acid (DMA), and inorganic species including arsenite (AsIII) and arsenate (AsV) in both soil and vegetables. The data were used to determine several parameters to evaluate human health risk, including bioconcentration factor (BCF) from soil to plant, average daily intake (ADI), health risk index (HRI), incremental lifetime cancer risk (ILTCR), and hazard quotient (HQ). The total As concentration in soil samples of the five districts ranged from 3.0-3.9mgkg(-1), exhibiting minimal variations from site to site. The mean As concentration in edible portions of vegetable samples ranged from 0.03-1.38mgkg(-1). It was observed that As concentrations in 75% of the vegetable samples exceeded the safe maximum allowable limit (0.1mgkg(-1)) set by WHO/FAO. The highest value of ADI for As was measured for Momordica charantia, while the lowest was for Allium chinense. The results of this study revealed minimal health risk (HI<1) associated with consumption of vegetables for the local inhabitants. The ILTCR values for inorganic As indicated a minimal potential cancer risk through ingestion of vegetables. In addition, the HQ values for total As were <1, indicating minimal non-cancer risk.