Effectiveness and reliability of arsenic field testing kits: are the million dollar screening projects effective or not?

Advances in Nanomaterials and Colorimetric Detection of Arsenic in Water: Review and Future Perspectives

Arsenic, existing in various chemical forms such as arsenate (As(V)) and arsenite (As(III)), demands serious attention in water and environmental contexts due to its significant health risks. It is classified as "carcinogenic to humans" by the International Agency for Research on Cancer (IARC) and is listed by the World Health Organization (WHO) as one of the top 10 chemicals posing major public health concerns. This widespread contamination results in millions of people globally being exposed to dangerous levels of arsenic, making it a top priority for the WHO. Chronic arsenic toxicity, known as arsenicosis, presents with specific skin lesions like pigmentation and keratosis, along with systemic manifestations including chronic lung diseases, liver issues, vascular problems, hypertension, diabetes mellitus, and cancer, often leading to fatal outcomes. Therefore, it is crucial to explore novel, cost-effective, and reliable methods with rapid response and improved sensitivities (detection limits). Most of the traditional detection techniques often face limitations in terms of complexity, cost, and the need for sophisticated equipment requiring skilled analysts and procedures, which thereby impedes their practical use, particularly in resource-constrained settings. Colorimetric methods leverage colour changes which are observable and quantifiable using simple instrumentation or even visual inspection. This review explores the colorimetric techniques designed to detect arsenite and arsenate in water. It covers recent developments in colorimetric techniques, and advancements in the role of nanomaterials in colorimetric arsenic detection, followed by discussion on current challenges and future prospects. The review emphasizes efforts to improve sensitivity, selectivity, cost, and portability, as well as the role of advanced materials/nanomaterials to boost the performance of colorimetric assays/sensors towards combatting this pervasive global health concern.

Sensitive and Environmentally Friendly Field Analysis of Waterborne Arsenic by Electrochemical Hydride Generation Microplasma Optical Emission Spectrometry

To avoid polluting the environment, it is desirable to develop methods consuming as few chemicals as possible for field elemental analysis. In this work, a lithium-ion battery supplied, compact handheld optical emission spectrometer (OES) (0.3 kg, length 18 cm × width 5 cm × height 10 cm) was fabricated for the sensitive field analysis of waterborne arsenic by utilizing electrochemical hydride generation (ECHG) and miniaturized ballpoint discharge (μPD) as sample introduction means and excitation source, respectively. The high ECHG efficiency of arsenic was obtained using a superior cathode of Fe@PbO/Pb and the generated arsine was separated from an aqueous phase and further swept to the μPD microplasma for detection. It is worth noting that the Fe@PbO/Pb cathode not only retains advantages of large specific surface area, robust stability, and excellent reproducibility for the ECHG of arsenic but also accomplishes the preconcentration of As(III), thus improving the kinetics of the surface chemistry at the cathode, alleviating the corrosion of the electrode, and minimizing the release of Pb. A limit of detection of 1.0 μg L^-1 was obtained with a relative standard deviation of 4.2% for 20 μg L^-1 As(III). Owing to the advantages of ECHG and μPD-OES, the system retains a promising potential for the sensitive, cost-effective, and environmentally friendly field analysis of waterborne arsenic.

A blue arsenomolybdic acid-crystal violet ion-associate pair paving the way for the field detection of arsenic in groundwater

A simple visual colorimetric method based on arsenomolybdic acid-crystal violet ion-associate pair formation is described for the detection of As in groundwater at about 10, 25 and 50 μg L^-1 levels. The pair exhibits light green coloration at ≤5 μg L^-1 and blue colorations of distinctly different intensities at about 10, 25 and 50 μg L^-1 concentrations of arsenic. High sensitivity is achieved by the preconcentration of As that entails simultaneous sorption of both As(III) and As(V) from groundwater on covellite (CuS) and, later, their elution as As(V), which subsequently participates in the formation of arsenomolybdic acid. The interference in the color development from PO₄^3-ions that are as efficiently sorbed on CuS and eluted as the oxyanions of As is eliminated by their selective removal by Ce⁴⁺ ions under basic (pH ∼ 8.5) conditions. The removal is caused by the formation of cerium phosphate and its co-precipitation with calcium hydroxide. SiO₄^2- ions do not interfere in the process as they are not sorbed by CuS. Groundwater containing ≤0.5 mg L^-1 P and ≥200 mg L^-1 total dissolved solid can be conveniently analysed by the method. The direct sensing of As(III) as well as As(V), the use of benign and easily available chemicals, the absence of any hazardous by-product, undiminished applicability in sunlight, the testing procedure lasting only for about 30 min, and rapidity are the major advantages of the method. Thus, the method is potentially well-suited for the on-site testing of groundwater potability under different regulations.

Speciation of inorganic arsenic in aqueous samples using a novel hydride generation microfluidic paper-based analytical device (µPAD)

The development of the first microfluidic paper-based analytical device (µPAD) for the speciation of inorganic arsenic in environmental aqueous samples as arsenite (As(III)) and arsenate (As(V)) which implements hydride generation on a paper platform is described. The newly developed µPAD has a 3D configuration and uses Au(III) chloride as the detection reagent. Sodium borohydride is used to generate arsine in the device’s sample zone by reducing As(III) in the presence of hydrochloric acid or both As(III) and As(V) (total inorganic As) in the presence of sulfuric acid. Arsine then diffuses across a hydrophobic porous polytetrafluoroethylene membrane into the device’s detection zone where it reduces Au(III) to Au nanoparticles. This results in a color change which can be related to the concentration of As(III) or total inorganic As (i.e., As(III) and As(V)) concentration. Under optimal conditions, the µPAD is characterized by a limit of detection of 0.43 mg L⁻¹ for total inorganic As (As(III) + As(V)) and 0.41 mg L⁻¹ for As(III) and a linear calibration range in both cases of 1.2–8.0 mg As L⁻¹. The newly developed µPAD-based method was validated by applying it to groundwater and freshwater samples and comparing the results with those obtained by conventional atomic spectrometric techniques.

Determination of Arsenic Content in Water Using a Silver Coordination Polymer

In this report, we describe a practical method for the colorimetric determination of dissolved inorganic arsenic content in water samples, using a silver coordination polymer as the sensing material. We demonstrate that a crystalline polymer framework can be used to stabilize silver(I) ions, greatly reducing both photosensitivity and water solubility, while still affording sufficient reactivity to detect arsenic in water samples at low parts-per-billion (ppb) levels. Test strips fabricated with the silver-based polymer are shown to be effective for field tests of groundwater under real-world operating conditions and display performance that is competitive with commercially available mercury-based test strips. Spectroscopic methods are also used to probe the reaction products formed, in order to better understand the sensing mechanism. Thus, our work provides the foundation for an improved field test that could be deployed to help manage groundwater usage in regions where arsenic contamination is problematic but sophisticated lab testing is not readily available.

Low-cost electrochemical detection of arsenic in the groundwater of Guanajuato state, central Mexico using an open-source potentiostat

Arsenic is a carcinogenic groundwater contaminant that is toxic even at the parts-per-billion (ppb) level and its on-site determination remains challenging. Colorimetric test strips, though cheap and widely used, often fail to give reliable quantitative data. On the other hand, electrochemical detection is sensitive and accurate but considerably more expensive at the onset. Here, we present a study on arsenic detection in groundwater using a low-cost, open-source potentiostat based on Arduino technology. We tested different types of gold electrodes (screen-printed and microwire) with anodic stripping voltammetry (ASV), achieving low detection limits (0.7 μg L^-1). In a study of arsenic contaminated groundwaters in Mexico, the microwire technique provides greater accuracy than test strips (reducing the median error from -50% to +2.9%) and greater precision (reducing uncertainties from ±25% to ±4.9%). Most importantly, the rate of false negatives versus the World Health Organisation’s 10 μg L^-1 limit was reduced from 50% to 0% (N = 13 samples). Arsenic determination using open-source potentiostats may offer a low-cost option for research groups and NGOs wishing to perform arsenic analysis in-house, yielding superior quantitative data than the more widely used colorimetric test strips.

Arsenic in the geo-environment: A review of sources, geochemical processes, toxicity and removal technologies

Impact of arsenic (As) contaminated groundwater on human health, through drinking and irrigation practices, is of grave-concern worldwide. This paper present the review of various sources, processes, health effects and treatment technologies available for the removal of As from arsenic contaminated water. Groundwater with high As concentration is detrimental to human health and incidents of As contamination in groundwater had been reported from different parts of the globe. More serious known As contamination problem as well as largest population at risk are found in Bangladesh, followed by West Bengal state in India along the Indo-Gangetic plains. Large scale natural As contamination of groundwater is found in two types of environment such as strongly reducing alluvial aquifers (ex. Bangladesh, India, China and Hungary) and inland basins in arid or semi-arid areas (ex. Argentina and Mexico). The provisional guideline of 10 ppb (0.0 l mg/l) has been adopted as the drinking water standard by World Health Organization (WHO). In the aquatic environment, the release, distribution and remobilization of As depend on temperature, redox potential, speciation, and interaction between liquid solution and solid phases. As predicaments in the environment is due to its mobilization under natural geogenic conditions as well as anthropogenic activities. Arsenic mineral is not present in As contaminated alluvial aquifer but As occurs adsorbed on hydrated ferric oxide (HFO) generally coat clastic grains derived from Himalayan mountains. As is released to the groundwater mainly by bio-remediated reductive dissolution of HFO with corresponding oxidation of organic matter. The development of strongly reductive dissolution of mineral oxides (Fe and Mn) at near-neutral pH may lead to desorption and ultimately release of As into the groundwater. As release through geochemical process is more important factor in alluvial aquifers causing As contamination rather than sources of arsenic. As is a toxin that dissolves in the bloodstream, rendering the victim susceptible to disease of the skin, bones, and also cancer of liver, kidney, gall bladder and the intestines. It is necessary to adopt highly successful technology to treat As contaminated water into the acceptable limit for human consumption. Universally accepted solutions are not developed/available even after the lapse of almost forty years since slow As poisoning identification in tens of millions of people especially in Bengal delta. The issue poses scientific, technical, health and societal problems even today.

Arsenic biotransformation and mobilization: the role of bacterial strains and other environmental variables

Over several decades, arsenic (As) toxicity in the biosphere has affected different flora, fauna, and other environmental components. The majority of these problems are linked with As mobilization due to bacterial dissolution of As-bearing minerals and its transformation in other reservoirs such as soil, sediments, and ground water. Understanding the process, mechanism, and various bacterial species involved in these processes under the influence of some ecological variables greatly contributes to a better understanding of the fate and implications of As mobilization into the environments. This article summarizes the process, role, and various types of bacterial species involved in the transformation and mobilization of As. Furthermore, insight into how Fe(II) oxidation and resistance mechanisms such as methylation and detoxification against the toxic effect of As(III) was highlighted as a potential immobilization and remediation strategy in As-contaminated sites. Furthermore, the significance and comparative advantages of some useful analytical tools used in the evaluation, speciation, and analysis of As are discussed and how their in situ and ex situ applications support assessing As contamination in both laboratory and field settings. Nevertheless, additional research involving advanced molecular techniques is required to elaborate on the contribution of these bacterial consortia as a potential agronomic tool for reducing As availability, particularly in natural circumstances. Graphical abstract. Courtesy of conceptual model: Aminu Darma.

Detecting Arsenic Contamination Using Satellite Imagery and Machine Learning

Arsenic, a potent carcinogen and neurotoxin, affects over 200 million people globally. Current detection methods are laborious, expensive, and unscalable, being difficult to implement in developing regions and during crises such as COVID-19. This study attempts to determine if a relationship exists between soil’s hyperspectral data and arsenic concentration using NASA’s Hyperion satellite. It is the first arsenic study to use satellite-based hyperspectral data and apply a classification approach. Four regression machine learning models are tested to determine this correlation in soil with bare land cover. Raw data are converted to reflectance, problematic atmospheric influences are removed, characteristic wavelengths are selected, and four noise reduction algorithms are tested. The combination of data augmentation, Genetic Algorithm, Second Derivative Transformation, and Random Forest regression (R2=0.840 and normalized root mean squared error (re-scaled to [0,1]) = 0.122) shows strong correlation, performing better than past models despite using noisier satellite data (versus lab-processed samples). Three binary classification machine learning models are then applied to identify high-risk shrub-covered regions in ten U.S. states, achieving strong accuracy (=0.693) and F1-score (=0.728). Overall, these results suggest that such a methodology is practical and can provide a sustainable alternative to arsenic contamination detection.

Iron oxide xerogels for improved water quality monitoring of arsenic(III) in resource-limited environments via solid-phase extraction, preservation, storage, transportation, and analysis of trace contaminants (SEPSTAT)

Arsenic is a widespread trace groundwater contaminant that presents a range of health risks and has an acceptable level of only 10 μg L-1 in drinking water. However, in many countries arsenic quantification in water is limited to centralized laboratories because it requires the use of elemental analysis techniques with high capital cost. As a result, routine water samples are frequently not tested for trace contaminants such as arsenic. In order to facilitate improved arsenic monitoring, we present the use of iron oxide xerogels for adsorption of arsenic(iii) from water samples at neutral pH, dry storage for over 120 days, and desorption of stored arsenic at elevated pH. Iron oxide xerogels offer high surface area (340 m2 g-1) and an As(iii) adsorption capacity of 165 mg g-1. Using an extraction solution of 100 mM sodium hydroxide and 1 mM sodium phosphate, As(iii) is reliably eluted from iron oxide xerogels for initial As(iii) concentrations from 10 μg L-1 to 1000 μg L-1, with a calculated detection limit of less than 4 μg L-1 and less than 17% difference in recovered As(iii) between test solutions with low and high interfering ion concentrations. By demonstrating the ability for iron oxide xerogels to reliably adsorb, store, and release arsenic, we enable the development of protocols for solid-phase extraction, preservation, storage, transportation, and analysis of trace contaminants (SEPSTAT), where arsenic would be adsorbed from water samples onto xerogel-based sorbents and shipped to centralized laboratories for recovery and quantification.

Nano-Enabled sensors for detection of arsenic in water

The elevated cases of arsenic contamination reported across the globe have made its early detection and remediation an active area of research. Although, the World Health Organisation has set the maximum provisional value for arsenic in drinking water at 10 parts per billion, yet concentrations as high as 5000 parts per billion are still reported. In human beings, chronic arsenic exposure can culminate into lethal diseases such as cancer. Thus, there is a need for urgent emergence of efficient and reliable detection system. This paper offers an overview of the state-of-art knowledge on current arsenic detection mechanisms. The central agenda of this paper is to develop an understanding into the nano-enabled methods for arsenic detection with an emphasis on strategic fabrication of nanostructures and the modulation of nanomaterial chemistry in order to strengthen the knowledge into novel nano-enabled solutions for arsenic contamination. Towards the end prospects for arsenic detection in water are also prompted.

Evaluation of arsenic field test kits for drinking water: Recommendations for improvement and implications for arsenic affected regions such as Bangladesh

Arsenic field test kits are widely used to measure arsenic levels in drinking water sources, especially in countries like Bangladesh, where water supply is highly decentralized and water quality testing infrastructure is limited. From a public health perspective, the ability of a measurement technique to distinguish samples above and below relevant and actionable drinking water standards is paramount. In this study, the performance of eight commercially available field test kits was assessed by comparing kit estimates to hydride generation atomic absorption spectroscopy (HG-AAS) analyses. The results of tests that control for user-dependent color matching errors showed that two kits (LaMotte and Quick II kits) provided accurate and precise estimates of arsenic, four kits (Econo-Quick, Quick, Wagtech and Merck kits) were either accurate or precise, but not both, and two kits (Hach and Econo-Quick II kits) were neither accurate nor precise. Tests were performed for arsenic concentration ranges commonly found in natural waters and treated waters (such as community drinking water filter systems), and also on laboratory generated arsenic standards in DI water. For those kits that did not perform well, test strips often produced colors too light compared to manufacturer-provided arsenic color calibration charts. Based on these results, we recommend stakeholders carefully re-consider the use of poorly performing field test kits until better quality control of components of these kits is implemented. In addition, we recommend that field test kit manufacturers provide suitable internal standards in every kit box for users to verify the veracity of manufacturer provided color charts.

Arsenic contamination in Kolkata metropolitan city: perspective of transportation of agricultural products from arsenic-endemic areas

Arsenic exposure route for humans is through the drinking of contaminated water and intake of arsenic-contaminated foods, particularly in arsenic-exposed areas of Bengal delta. Transport of the arsenic-contaminated crops and vegetables grown using arsenic-contaminated groundwater and soil in arsenic-exposed areas to the uncontaminated sites and consequent dietary intakes leads to great threats for the population residing in non-endemic areas with respect to consumption of arsenic through drinking water. We have studied the food materials collected from 30 families and their dietary habits, apparently who consume arsenic-free drinking water as well as 9 well-known markets of Kolkata city. The total and inorganic arsenic intake has been estimated from the collected foodstuffs from the market basket survey (n = 93) and household survey (n = 139), respectively for human risk analysis. About 100% of the collected samples contained detectable amount of arsenic (range 24-324 μg/kg), since the origin of the food materials was somewhere from arsenic-endemic areas. The daily consumption of inorganic arsenic (iAs) from rice grain and vegetables for adult and children is 76 μg and 41.4 μg, respectively. Inorganic arsenic (mainly arsenite and arsenate) contributes approximately 88% of the total content of arsenic in vegetable. In most of the cases, insufficient nutrient intake by the studied population may lead to arsenic toxicity in the long run. An independent cancer risk assessment study on the same population indicates that the main risk of cancer might appear through the intake of arsenic-contaminated rice grain and cereals.

Field testing of over 30,000 wells for arsenic across 400 villages of the Punjab plains of Pakistan and India: Implications for prioritizing mitigation

Most of the rural population of 90 million in Punjab province in Pakistan and Punjab state in India drinks, and cooks with, untreated water drawn from shallow wells. Limited laboratory testing has shown that groundwater in the region can contain toxic levels of arsenic. To refine this assessment, a total of 30,567 wells from 383 villages were tested with a field kit in northern Punjab province of Pakistan and western Punjab state of India. A subset of 431 samples also tested in the laboratory show that 85% of wells were correctly classified by the kit relative to the World Health Organization guideline of 10 μg/L for arsenic in drinking water. The kit data show that 23% of the tested wells did not meet the WHO guideline for arsenic but also that 87% of households with a well high in arsenic live within 100 m of a well that meets the WHO guideline. The implication is that many households could rapidly lower their exposure if the subset of safe wells could be shared. In a follow-up conducted one year later in five villages where 59% of wells were elevated in arsenic, two-thirds of households indicated that they had switched to a neighboring well in response to the testing. The blanket testing of millions of wells for arsenic in the region should therefore be prioritized over much costlier water treatment and piped water supply projects that will take much longer to have a comparable impact.

Field tests of in-well electrolysis removal of arsenic from high phosphate and iron groundwater

Subsurface arsenic (As) removal has been proposed for in situ immobilizing As in aquifers at a low cost and without post-disposal of As-containing wastes. However, the results reported for field tests are very limited, particularly when high As, phosphate (P) and iron (Fe) coexist in the groundwater. Herein the performance of single- and multiple-well operations was evaluated for in situ removing groundwater As in Jianghan Plain, central China. To enhance groundwater oxygenation, in-well electrolysis was employed in both operation modes. The groundwater in confined aquifer in Jianghan Plain contains elevated concentrations of As (272-606 μg/L), Fe²⁺ (4.7-14.3 mg/L) and P (0.90-1.58 mg/L). In the single-well operation with cycles of injection and abstraction, groundwater Fe²⁺ was completely removed but As cannot be reduced to below the World Health Organization guideline (10 μg/L) due to the high concentration and the competition of coexisting P. In-well electrolysis is cost-effective for boosting dissolved oxygen (DO) and Fe²⁺ removal in single-well operations. In the multiple-well operation with one abstraction well surrounded by 6 in-well electrolysis wells, removals of groundwater As, Fe, P and Mn were not sufficient because of clogging of treatment wells and incomplete capture of groundwater flowing to the abstraction well. In comparison, single-well operation is more simple and efficient for in situ treatment of groundwater As and Fe than multiple-well operation. This study provides a field example of in situ removing high As in groundwater by both single- and multiple-well operations, and underscores the difficulty in treating the groundwater with coexistence of elevated As and P.

Impact of arsenic contaminated groundwater used during domestic scale post harvesting of paddy crop in West Bengal: Arsenic partitioning in raw and parboiled whole grain

The role of post harvesting procedures for producing parboiled rice grain using arsenic (As) contaminated groundwater in rural Bengal was investigated. Considerable high concentrations of As (mean: 186 μg/kg) were found in about 82% of parboiled rice grain samples compared to raw or non-parboiled rice grain samples (66 μg/kg in 75% samples) obtained from Deganga, a highly As affected zone located in West Bengal, India. This observation instigated to study the additional entry of As at various stages of parboiling. A maximum increase of 205% of As content in parboiled rice grain was observed. Significant increase in parboiled whole grain As concentration was dependent upon the large difference between As concentrations of the water and the raw whole grain used for parboiling. Arsenic concentrations of water samples collected at raw, half boiled and full boiled stages of parboiling increased, irrespective of their initial concentration due to reduction in final volume during parboiling process. Principle component analysis shows a positive correlation of As concentration of rice grain to that in the groundwater being used in post harvesting procedure. Moreover, partitioning studies of As in whole grain indicated higher accumulation of As content in individual rice grain than that in their respective husks implying higher risk of exposure on ingestion of these contaminated rice grains. It is therefore, suggested to employ novel methods such as rain water harvesting or surface water channelling to make As free water available for parboiling process to curtail the entry of additional As in parboiled rice.

Quantitative drinking water arsenic concentrations in field environments using mobile phone photometry of field kits

Arsenic (As) groundwater contamination is common yet spatially heterogeneous within most environments. It is therefore necessary to measure As concentrations to determine whether a water source is safe to drink. Measurement of As in the field involves using a test strip that changes color in the presence of As. These tests are relatively inexpensive, but results are subjective and provide binned categorical data rather than exact determinations of As concentration. The goal of this work was to determine if photos of field kit test strips taken on mobile phone cameras could be used to extract more precise, continuous As concentrations. As concentrations for 376 wells sampled from Araihazar, Bangladesh were analyzed using ICP-MS, field kit and the new mobile phone photo method. Results from the field and lab indicate that normalized RGB color data extracted from images were able to accurately predict As concentrations as measured by ICP-MS, achieving detection limits of 9.2μg/L, and 21.9μg/L for the lab and field respectively. Data analysis is most consistent in the laboratory, but can successfully be carried out offline following image analysis, or on the mobile phone using basic image analysis software. The accuracy of the field method was limited by variability in image saturation, and variation in the illumination spectrum (lighting) and camera response. This work indicates that mobile phone cameras can be used as an analytical tool for quantitative measures of As and could change how water samples are analyzed in the field more widely, and that modest improvements in the consistency of photographic image collection and processing could yield measurements that are both accurate and precise.

Paper-Based Microfluidic Device with a Gold Nanosensor to Detect Arsenic Contamination of Groundwater in Bangladesh

In this paper, we present a microfluidic paper-based analytical device (μPAD) with a gold nanosensor functionalized with α-lipoic acid and thioguanine (Au–TA–TG) to detect whether the arsenic level of groundwater from hand tubewells in Bangladesh is above or below the World Health Organization (WHO) guideline level of 10 μg/L. We analyzed the naturally occurring metals present in Bangladesh groundwater and assessed the interference with the gold nanosensor. A method was developed to prevent interference from alkaline metals found in Bangladesh groundwater (Ca, Mg, K and Na) by increasing the pH level on the μPADs to 12.1. Most of the heavy metals present in the groundwater (Ni, Mn, Cd, Pb, and Fe II) did not interfere with the μPAD arsenic tests; however, Fe III was found to interfere, which was also prevented by increasing the pH level on the μPADs to 12.1. The μPAD arsenic tests were tested with 24 groundwater samples collected from hand tubewells in three different districts in Bangladesh: Shirajganj, Manikganj, and Munshiganj, and the predictions for whether the arsenic levels were above or below the WHO guideline level agreed with the results obtained from laboratory testing. The μPAD arsenic test is the first paper-based test validated using Bangladesh groundwater samples and capable of detecting whether the arsenic level in groundwater is above or below the WHO guideline level of 10 μg/L, which is a step towards enabling the villagers who collect and consume the groundwater to test their own sources and make decisions about where to obtain the safest water.

Tuning DNA adsorption affinity and density on metal oxide and phosphate for improved arsenate detection

Arsenic (As) contamination in groundwater presents a major health and environmental concern in developing countries. Typically, As is found in two oxidation states. Most chemical tests for inorganic arsenic are focused on As(III), and few have been developed for As(V). We are interested in developing biosensors for As(V) based on its similarity with phosphate. Building upon previous work involving DNA-capped Fe₃O₄ nanoparticles for As(V) detection, we investigated two other nanomaterials: CeO₂ and CePO₄ in terms of DNA adsorption and As(V) induced DNA desorption. Fluorescently labeled DNA is physically adsorbed to the surface sites on the nanoparticle surface via its phosphate backbone. In the cases of CeO₂ and Fe₃O₄, the fluorescence was quenched due to electron transfer, whereas for the insulating CePO₄, no quenching was observed. Arsenate, being similar to phosphate, can also bind to the surface of the nanoparticles and displace the DNA, increasing the fluorescence signal. The length and sequence of DNA were systematically studied. Using this method, CeO₂ performed significantly better than Fe₃O₄, lowering the detection limit by almost 10-fold. In addition, for CeO₂ and CePO₄, using shorter DNA was more effective for As(V) detection than using the longer DNA since they both adsorb DNA more tightly than Fe₃O₄ does. Overall, CeO₂ has the best performance since it has an intermediate adsorption affinity of DNA, while CePO₄ adsorbs DNA too strongly.

Sensitive determination of As (III) and As (V) by magnetic solid phase extraction with Fe@polyethyleneimine in combination with hydride generation atomic fluorescence spectrometry

The magnetic nanomaterial Fe@polyethyleneimine (Fe@PEI) was successfully synthesized and used as an effective adsorbent material for magnetic solid phase extraction(MSPE) of As(III) and As(V) from water samples. Fe@SiO2 nanoparticles were prepared by one pot synthetic method using a borohydride reduction method, then modified with (3-chloropropyl)trimethoxysilane to obtain Fe@SiO2-Cl by chloropropylation, which was reacted with PEI to achieve Fe@polyethyleneimine (Fe@PEI). The microstructure and morphology of Fe@PEI were characterized by transmission electron microscoscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). The experimental results showed that Fe@PEI demonstrated excellent adsorption for As(III) and As(V). Based on this fact, the determination method for these two arsenic species earned good limits of detection (LODs) of 0.002μgL(-1) and wide calibration curves in the concentration range from 0.008 to 0.2μgL(-1). The precisions of As (III) and As (V)were 1.95% and 2.55% (RSD, n=6), respectively. The proposed method was validated with real samples and the spiked recoveries were in the range of 82.7-98.3% and the accuracies were in the range of 2-13.3%. The results demonstrated that the developed MSPE method had good advantages such as simplicity, rapid separation, low cost, easy to reuse and high-quality analytical performances, which made it attractive for rapid and efficient extraction of inorganic arsenic species in the environmental water samples.

Evaluation of bioavailable arsenic and remediation performance using a whole-cell bioreporter

The traditional method of evaluating the effects of soil contaminants on living organisms by measuring the total amount of contaminant has been largely inadequate, in part because testing contamination levels is hindered in real samples. Here we report a novel strategy for testing arsenic (As) bioavailability in soil samples by direct (in vivo) and indirect (in vitro) measurement using an Escherichia coli-based whole-cell bioreporter (WCB). The WCB was used to test As-amended Landwirtschaftliche Untersuchungs und Forschungsanstalt soils as well as field soils collected from a smelter area under remediation in order to evaluate the efficiency of bioavailable As removal. The percentage of bioavailable As in amended and field soils was 5.8% (range: 4.9%-7.6%) and 0.6% (0.08%-1.09%) of total As, respectively. In contaminated soils, total As was decreased, whereas bioavailable As was slightly increased after soil washing. These results emphasize the importance of considering ecotoxicological aspects of soil remediation; to this end, the WCB is a useful tool for evaluating the efficiency of soil remediation by assessing bioavailability along with the total amount of contaminant present.

Water Quality Index for measuring drinking water quality in rural Bangladesh: a cross-sectional study

BACKGROUND

Public health is at risk due to chemical contaminants in drinking water which may have immediate health consequences. Drinking water sources are susceptible to pollutants depending on geological conditions and agricultural, industrial, and other man-made activities. Ensuring the safety of drinking water is, therefore, a growing problem. To assess drinking water quality, we measured multiple chemical parameters in drinking water samples from across Bangladesh with the aim of improving public health interventions.

METHODS

In this cross-sectional study conducted in 24 randomly selected upazilas, arsenic was measured in drinking water in the field using an arsenic testing kit and a sub-sample was validated in the laboratory. Water samples were collected to test water pH in the laboratory as well as a sub-sample of collected drinking water was tested for water pH using a portable pH meter. For laboratory testing of other chemical parameters, iron, manganese, and salinity, drinking water samples were collected from 12 out of 24 upazilas.

RESULTS

Drinking water at sample sites was slightly alkaline (pH 7.4 ± 0.4) but within acceptable limits. Manganese concentrations varied from 0.1 to 5.5 mg/L with a median value of 0.2 mg/L. The median iron concentrations in water exceeded WHO standards (0.3 mg/L) at most of the sample sites and exceeded Bangladesh standards (1.0 mg/L) at a few sample sites. Salinity was relatively higher in coastal districts. After laboratory confirmation, arsenic concentrations were found higher in Shibchar (Madaripur) and Alfadanga (Faridpur) compared to other sample sites exceeding WHO standard (0.01 mg/L). Of the total sampling sites, 33 % had good-quality water for drinking based on the Water Quality Index (WQI). However, the majority of the households (67 %) used poor-quality drinking water.

CONCLUSIONS

Higher values of iron, manganese, and arsenic reduced drinking water quality. Awareness raising on chemical contents in drinking water at household level is required to improve public health.

Water Quality Monitoring in Developing Countries; Can Microbial Fuel Cells be the Answer?

The provision of safe water and adequate sanitation in developing countries is a must. A range of chemical and biological methods are currently used to ensure the safety of water for consumption. These methods however suffer from high costs, complexity of use and inability to function onsite and in real time. The microbial fuel cell (MFC) technology has great potential for the rapid and simple testing of the quality of water sources. MFCs have the advantages of high simplicity and possibility for onsite and real time monitoring. Depending on the choice of manufacturing materials, this technology can also be highly cost effective. This review covers the state-of-the-art research on MFC sensors for water quality monitoring, and explores enabling factors for their use in developing countries.

Colorimetric As (V) detection based on S-layer functionalized gold nanoparticles

Herein, we present simple and rapid colorimetric and UV/VIS spectroscopic methods for detecting anionic arsenic (V) complexes in aqueous media. The methods exploit the aggregation of S-layer-functionalized spherical gold nanoparticles of sizes between 20 and 50 nm in the presence of arsenic species. The gold nanoparticles were functionalized with oligomers of the S-layer protein of Lysinibacillus sphaericus JG-A12. The aggregation of the nanoparticles results in a color change from burgundy-red for widely dispersed nanoparticles to blue for aggregated nanoparticles. A detailed signal analysis was achieved by measuring the shift of the particle plasmon resonance signal with UV/VIS spectroscopy. To further improve signal sensitivity, the influence of larger nanoparticles was tested. In the case of 50 nm gold nanoparticles, a concentration of the anionic arsenic (V) complex lower than 24 ppb was detectable.

Introducing Simple Detection of Bioavailable Arsenic at Rafaela (Santa Fe Province, Argentina) Using the ARSOlux Biosensor

Numerous articles have reported the occurrence of arsenic in drinking water in Argentina, and the resulting health effects in severely affected regions of the country. Arsenic in drinking water in Argentina is largely naturally occurring due to elevated background content of the metalloid in volcanic sediments, although, in some regions, mining can contribute. While the origin of arsenic release has been discussed extensively, the problem of drinking water contamination has not yet been solved. One key step in progress towards mitigation of problems related with the consumption of As-containing water is the availability of simple detection tools. A chemical test kit and the ARSOlux biosensor were evaluated as simple analytical tools for field measurements of arsenic in the groundwater of Rafaela (Santa Fe, Argentina), and the results were compared with ICP-MS and HPLC-ICP-MS measurements. A survey of the groundwater chemistry was performed to evaluate possible interferences with the field tests. The results showed that the ARSOlux biosensor performed better than the chemical field test, that the predominant species of arsenic in the study area was arsenate and that arsenic concentration in the studied samples had a positive correlation with fluoride and vanadium, and a negative one with calcium and iron.

A step towards mobile arsenic measurement for surface waters

Surface modified quantum dots (QDs) are studied using a bio-inspired cysteine rich ligand (glutathione, GSH) and their quenching response and selectivity to arsenic examined. As predicted from As(3+) binding with highly crosslinked phytochelatin-(PCn)-like molecules, better arsenic selectivity is obtained for a thicker more 3-dimensional GSH surface layer, with exposed sulfhydryl groups. A detection limit of at least 10 μM can be achieved using CdSe/ZnS core-shell QDs capped with this GSH structure. The system is also demonstrated using a mobile phone camera to record the measurement, producing a detection limit of 5 μM. However, copper remains the main interferent of concern. Water-soluble CdTe QDs show little sensitivity to As(3+) even with a GSH surface, but they remain sensitive to Cu(2+), allowing a copper baseline to be established from the CdTe measurement. Despite anticipating that spectrally non overlapping fluorescence would be required from the two types of QDs to achieve this, a method is demonstrated using RGB channels from a mobile phone and processing the raw data for CdTe QDs, with an emission wavelength of 600 nm, and CdSe/ZnS QDs, with emission maximum of 630 nm. It is shown that As(3+) measurement remains feasible at the WHO guideline value of 10 μg L(-1) up to a copper concentration of around 0.3 μM Cu(2+), which corresponds to the highest recorded level in a selection of large rivers world-wide.

The potential risk assessment for different arsenic species in the aquatic environment

The different toxicity characteristics of arsenic species result in discrepant ecological risk. The predicted no-effect concentrations (PNECs) 43.65, 250.18, and 2.00×10(3)μg/L were calculated for As(III), As(V), and dimethylarsinic acid in aqueous phase, respectively. With these PNECs, the ecological risk from arsenic species in Pearl River Delta in China and Kwabrafo stream in Ghana was evaluated. It was found that the risk from As(III) and As(V) in the samples from Pearl River Delta was low, while much high in Kwabrafo stream. This study implies that ecological risk of arsenic should be evaluated basing on its species.

Biosensors for inorganic and organic arsenicals

Arsenic is a natural environmental contaminant to which humans are routinely exposed and is strongly associated with human health problems, including cancer, cardiovascular and neurological diseases. To date, a number of biosensors for the detection of arsenic involving the coupling of biological engineering and electrochemical techniques has been developed. The properties of whole-cell bacterial or cell-free biosensors are summarized in the present review with emphasis on their sensitivity and selectivity. Their limitations and future challenges are highlighted.

Whole-cell bioreporters for the detection of bioavailable metals

Whole-cell bioreporters are living microorganisms that produce a specific, quantifiable output in response to target chemicals. Typically, whole-cell bioreporters combine a sensor element for the substance of interest and a reporter element coding for an easily detectable protein. The sensor element is responsible for recognizing the presence of an analyte. In the case of metal bioreporters, the sensor element consists of a DNA promoter region for a metal-binding transcription factor fused to a promoterless reporter gene that encodes a signal-producing protein. In this review, we provide an overview of specific whole-cell bioreporters for heavy metals. Because the sensing of metals by bioreporter microorganisms is usually based on heavy metal resistance/homeostasis mechanisms, the basis of these mechanisms will also be discussed. The goal here is not to present a comprehensive summary of individual metal-specific bioreporters that have been constructed, but rather to express views on the theory and applications of metal-specific bioreporters and identify some directions for future research and development.

A prospective cohort study of the association between drinking water arsenic exposure and self-reported maternal health symptoms during pregnancy in Bangladesh

BACKGROUND

Arsenic, a common groundwater pollutant, is associated with adverse reproductive health but few studies have examined its effect on maternal health.

METHODS

A prospective cohort was recruited in Bangladesh from 2008-2011 (N = 1,458). At enrollment (<16 weeks gestational age [WGA]), arsenic was measured in personal drinking water using inductively-coupled plasma mass spectrometry. Questionnaires collected health data at enrollment, at 28 WGA, and within one month of delivery. Adjusted odds ratios (aORs) and 95% confidence intervals (95% CI) for self-reported health symptoms were estimated for each arsenic quartile using logistic regression.

RESULTS

Overall, the mean concentration of arsenic was 38 μg/L (Standard deviation, 92.7 μg/L). A total of 795 women reported one or more of the following symptoms during pregnancy (cold/flu/infection, nausea/vomiting, abdominal cramping, headache, vaginal bleeding, or swollen ankles). Compared to participants exposed to the lowest quartile of arsenic (≤0.9 μg/L), the aOR for reporting any symptom during pregnancy was 0.62 (95% CI = 0.44-0.88) in the second quartile, 1.83 (95% CI = 1.25-2.69) in the third quartile, and 2.11 (95% CI = 1.42-3.13) in the fourth quartile where the mean arsenic concentration in each quartile was 1.5 μg/L, 12.0 μg/L and 144.7 μg/L, respectively. Upon examining individual symptoms, only nausea/vomiting and abdominal cramping showed consistent associations with arsenic exposure. The odds of self-reported nausea/vomiting was 0.98 (95% CI: 0.68, 1.41), 1.52 (95% CI: 1.05, 2.18), and 1.81 (95% CI: 1.26, 2.60) in the second, third and fourth quartile of arsenic relative to the lowest quartile after adjusting for age, body mass index, second-hand tobacco smoke exposure, educational status, parity, anemia, ferritin, medication usage, type of sanitation at home, and household income. A positive trend was also observed for abdominal cramping (P for trend <0.0001). A marginal negative association was observed between arsenic quartiles and odds of self-reported cold/flu/infection (P for trend = 0.08). No association was observed between arsenic and self-reported headache (P for trend = 0.19).

CONCLUSION

Moderate exposure to arsenic contaminated drinking water early in pregnancy was associated with increased odds of experiencing nausea/vomiting and abdominal cramping. Preventing exposure to arsenic contaminated drinking water during pregnancy could improve maternal health.

Maternal arsenic exposure and birth outcomes: a comprehensive review of the epidemiologic literature focused on drinking water

Inorganic arsenic (iAs) is a human toxicant to which populations may be exposed through consumption of geogenically contaminated groundwater. A growing body of experimental literature corroborates the reproductive toxicity of iAs; however, the results of human studies are inconsistent. Therefore, we conducted a comprehensive review of epidemiologic studies focused on drinking water iAs exposure and birth outcomes to assess the evidence for causality and to make recommendations for future study. We reviewed 18 English language papers assessing birth weight, gestational age, and birth size. Thirteen of the studies were conducted among populations with frequent exposure to high-level groundwater iAs contamination (>10 μg/L) and five studies were conducted in areas without recognized contamination. Most studies comprised small samples and used cross-sectional designs, often with ecologic exposure assessment strategies, although several large prospective investigations and studies with individual-level measurements were also reported. We conclude that: (1) the epidemiologic evidence for an increased risk of low birth weight (<2500 g) is insufficient, although there exists limited evidence for birth weight decreases; (2) the evidence for increased preterm delivery is insufficient; and, (3) there exists minimal evidence for decreased birth size. In further investigation of birth weight and size, we recommend incorporation of individual susceptibility measures using appropriate biomarkers, with collection timed to windows of vulnerability and speciated arsenic analysis, as well as consideration of populations exposed primarily to drinking water iAs contamination <10 μg/L. Given the large potential public health impact, additional, high quality epidemiologic studies are necessary to more definitively assess the risk.

Biosensor for organoarsenical herbicides and growth promoters

The toxic metalloid arsenic is widely distributed in food, water, and soil. While inorganic arsenic enters the environment primarily from geochemical sources, methylarsenicals either result from microbial biotransformation of inorganic arsenic or are introduced anthropogenically. Methylarsenicals such as monosodium methylarsonic acid (MSMA) have been extensively utilized as herbicides, and aromatic arsenicals such as roxarsone (Rox) are used as growth promoters for poultry and swine. Organoarsenicals are degraded to inorganic arsenic. The toxicological effects of arsenicals depend on their oxidation state, chemical composition, and bioavailability. Here we report that the active forms are the trivalent arsenic-containing species. We constructed a whole-cell biosensor utilizing a modified ArsR repressor that is highly selective toward trivalent methyl and aromatic arsenicals, with essentially no response to inorganic arsenic. The biosensor was adapted for in vitro detection of organoarsenicals using fluorescence anisotropy of ArsR-DNA interactions. It detects bacterial biomethylation of inorganic arsenite both in vivo and in vitro with detection limits of 10(-7) M and linearity to 10(-6) M for phenylarsenite and 5 × 10(-6) M for methylarsenite. The biosensor detects reduced forms of MSMA and roxarsone and offers a practical, low cost method for detecting activate forms and breakdown products of organoarsenical herbicides and growth promoters.

Environmental arsenic contamination and its health effects in a historic gold mining area of the Mangalur greenstone belt of Northeastern Karnataka, India

This report summarizes recent findings of environmental arsenic (As) contamination and the consequent health effects in a community located near historic gold mining activities in the Mangalur greenstone belt of Karnataka, India. Arsenic contents in water, hair, nail, soil and food were measured by FI-HG-AAS. Elemental analyses of soils were determined by ICP-MS (inductively coupled plasma-mass spectrometry). Of 59 tube-well water samples, 79% had As above 10 μg L(-1) (maximum 303 μg L(-1)). Of 12 topsoil samples, six were found to contain As greater than 2000 mg kg(-1) possibly indicating the impact of mine tailings on the area. All hair and nail samples collected from 171 residents contained elevated As. Arsenical skin lesions were observed among 58.6% of a total 181 screened individuals. Histopathological analysis of puncture biopsies of suspected arsenical dermatological symptoms confirmed the diagnosis in three out of four patients. Based on the time-course of As-like symptoms reported by the community as well as the presence of overt arsenicosis, it is hypothesized that the primary route of exposure in the study area was via contaminated groundwater; however, the identified high As content in residential soil could also be a significant source of As exposure via ingestion. Additional studies are required to determine the extent as well as the relative contribution of geologic and anthropogenic factors in environmental As contamination in the region. This study report is to our knowledge one of the first to describe overt arsenicosis in this region of Karnataka, India as well as more broadly an area with underlying greenstone geology and historic mining activity.

Digital analysis technique for uncertainty reduction in colorimetric arsenic detection method

This article proposes an alternative to increase the reliability and reproducibility of a colorimetric method to measure arsenic (As) concentrations. The method of analysis developed incorporates a digital analysis technique to eliminate the operator dependence of results, and As concentrations are quantitatively determined from digital levels computed from photographs of the colorimetric reaction that emerges during the test. This technique allows the sensitivity of the detection to be increased at low concentration ranges, which is of fundamental importance for the detection of As given the current acceptable limit for drinking water. The results obtained show a very good correlation between As concentrations determined by means of analytical laboratory techniques and the method proposed in this research.

Field testing of arsenic in groundwater samples of Bangladesh using a test kit based on lyophilized bioreporter bacteria

A test kit based on living, lyophilized bacterial bioreporters emitting bioluminescence as a response to arsenite and arsenate was applied during a field campaign in six villages across Bangladesh. Bioreporter field measurements of arsenic in groundwater from tube wells were in satisfying agreement with the results of spectroscopic analyses of the same samples conducted in the lab. The practicability of the bioreporter test in terms of logistics and material requirements, suitability for high sample throughput, and waste disposal was much better than that of two commercial chemical test kits that were included as references. The campaigns furthermore demonstrated large local heterogeneity of arsenic in groundwater, underscoring the use of well switching as an effective remedy to avoid high arsenic exposure.

A novel colorimetric method for field arsenic speciation analysis

Accurate on-site determination of arsenic (As) concentration as well as its speciation presents a great environmental challenge especially to developing countries. To meet the need of routine field monitoring, we developed a rapid colorimetric method with a wide dynamic detection range and high precision. The novel application of KMnO4 and CH4N2S as effective As(III) oxidant and As(V) reductant, respectively, in the formation of molybdenum blue complexes enabled the differentiation of As(III) and As(V). The detection limit of the method was 8 microg/L with a linear range (R2 = 0.998) of four orders of magnitude in total As concentrations. The As speciation in groundwater samples determined with the colorimetric method in the field were consistent with the results using the high performance liquid chromatography atomic fluorescence spectrometry, as evidenced by a linear correlation in paired analysis with a slope of 0.9990-0.9997 (p < 0.0001, n = 28). The recovery of 96%-116% for total As, 85%-122% for As(III), and 88%-127% for As(V) were achieved for groundwater samples with a total As concentration range 100-800 microg/L. The colorimetric result showed that 3.61 g/L As(III) existed as the only As species in a real industrial wastewater, which was in good agreement with the HPLC-AFS result of 3.56 g/L As(III). No interference with the color development was observed in the presence of sulfate, phosphate, silicate, humic acid, and heavy metals from complex water matrix. This accurate, sensitive, and easy-to-use method is especially suitable for field As determination.

Iron and aluminium based adsorption strategies for removing arsenic from water

Arsenic is a commonly occurring toxic metal in natural systems and is the root cause of many diseases and disorders. Occurrence of arsenic contaminated water is reported from several countries all over the world. A great deal of research over recent decades has been motivated by the requirement to lower the concentration of arsenic in drinking water and the need to develop low cost techniques which can be widely applied for arsenic removal from contaminated water. This review briefly presents iron and aluminium based adsorbents for arsenic removal. Studies carried out on oxidation of arsenic(III) to arsenic(V) employing various oxidising agents to facilitate arsenic removal are briefly mentioned. Effects of competing ions, As:Fe ratios, arsenic(V) vs. arsenic(III) removal using ferrihydrite as the adsorbent have been discussed. Recent efforts made for investigating arsenic adsorption on iron hydroxides/oxyhydroxides/oxides such as granular ferric hydroxide, goethite, akaganeite, magnetite and haematite have been reviewed. The adsorption behaviours of activated alumina, gibbsite, bauxite, activated bauxite, layered double hydroxides are discussed. Point-of-use adsorptive remediation methods indicate that Sono Arsenic filter and Kanchan™ Arsenic filter are in operation at various locations of Bangladesh and Nepal. The relative merits and demerits of such filters have been discussed. Evaluation of kits used for at-site arsenic estimation by various researchers also forms a part of this review.

Development of a microfluidics biosensor for agarose-bead immobilized Escherichia coli bioreporter cells for arsenite detection in aqueous samples

Contamination with arsenic is a recurring problem in both industrialized and developing countries. Drinking water supplies for large populations can have concentrations much higher than the permissible levels (for most European countries and the United States, 10 μg As per L; elsewhere, 50 μg As per L). Arsenic analysis requires high-end instruments, which are largely unavailable in developing countries. Bioassays based on genetically engineered bacteria have been proposed as suitable alternatives but such tests would profit from better standardization and direct incorporation into sensing devices. The goal of this work was to develop and test microfluidic devices in which bacterial bioreporters could be embedded, exposed and reporter signals detected, as a further step towards a complete miniaturized bacterial biosensor. The signal element in the biosensor is a nonpathogenic laboratory strain of Escherichia coli, which produces a variant of the green fluorescent protein after contact to arsenite and arsenate. E. coli bioreporter cells were encapsulated in agarose beads and incorporated into a microfluidic device where they were captured in 500 × 500 μm(2) cages and exposed to aqueous samples containing arsenic. Cell-beads frozen at -20 °C in the microfluidic chip retained inducibility for up to a month and arsenic samples with 10 or 50 μg L(-1) could be reproducibly discriminated from the blank. In the 0-50 μg L(-1) range and with an exposure time of 200 minutes, the rate of signal increase was linearly proportional to the arsenic concentration. The time needed to reliably and reproducibly detect a concentration of 50 μg L(-1) was 75-120 minutes, and 120-180 minutes for a concentration of 10 μg L(-1).

Validation of analysis of arsenic in water samples using Wagtech Digital Arsenator

Groundwater, the only source of potable water for millions of people in Bangladesh during dry season, is often contaminated with arsenic (As) above the allowable drinking water limit of 50 μg/L. Testing well water--with arsenic field test kits (FTKs)--and switching to safe-wells can effectively reduce exposure to As. FTKs are low cost, provide fast results, and are commercially available. There are between 10 and 11 million shallow tubewells in Bangladesh. Approximately, 5 million have been tested using FTKs. FTKs with color comparator rely on visual identification for generating qualitative results, which may not be highly reliable at the lower range because human eyes have low sensitivity in this range and sensitivity varies from person to person. The Wagtech Digital Arsenator does not suffer from this limitation and should, in theory, be able to generate quantitative, accurate, and reliable results. The instrument has a linear range of 0-100 μg/L, an accuracy of ± 20% for the 50 μg/L quality control standards, and a detection limit of about 4.4 μg/L. All Arsenators employed in this investigation also displayed high bias for 50 μg/L arsenic standard and were calibrated in order to improve measurement accuracy and reliability. Analyses of 179 raw and 92 treated well waters in the field and in two analytical laboratories were found to be highly correlated with the Spearman rank correlation coefficient of ≥ 0.800, indicating that Arsenator results are perhaps nearly as accurate and reliable as those from analytical laboratories.

Application of geostatistics with Indicator Kriging for analyzing spatial variability of groundwater arsenic concentrations in Southwest Bangladesh

This article seeks to explore the spatial variability of groundwater arsenic (As) concentrations in Southwestern Bangladesh. Facts about spatial pattern of As are important to understand the complex processes of As concentrations and its spatial predictions in the unsampled areas of the study site. The relevant As data for this study were collected from Southwest Bangladesh and were analyzed with Flow Injection Hydride Generation Atomic Absorption Spectrometry (FI-HG-AAS). A geostatistical analysis with Indicator Kriging (IK) was employed to investigate the regionalized variation of As concentration. The IK prediction map shows a highly uneven spatial pattern of arsenic concentrations. The safe zones are mainly concentrated in the north, central and south part of the study area in a scattered manner, while the contamination zones are found to be concentrated in the west and northeast parts of the study area. The southwest part of the study area is contaminated with a highly irregular pattern. A Generalized Linear Model (GLM) was also used to investigate the relationship between As concentrations and aquifer depths. A negligible negative correlation between aquifer depth and arsenic concentrations was found in the study area. The fitted value with 95 % confidence interval shows a decreasing tendency of arsenic concentrations with the increase of aquifer depth. The adjusted mean smoothed lowess curve with a bandwidth of 0.8 shows an increasing trend of arsenic concentration up to a depth of 75 m, with some erratic fluctuations and regional variations at the depth between 30 m and 60 m. The borehole lithology was considered to analyze and map the pattern of As variability with aquifer depths. The study has performed an investigation of spatial pattern and variation of As concentrations.

Field based speciation of arsenic in UK and Argentinean water samples

A field method is reported for the speciation of arsenic in water samples that is simple, rapid, safe to use beyond laboratory environments, and cost effective. The method utilises solid-phase extraction cartridges (SPE) in series for selective retention of arsenic species, followed by elution and measurement of eluted fractions by inductively coupled plasma mass spectrometry (ICP-MS) for "total" arsenic. The method is suitable for on-site separation and preservation of arsenic species from water. Mean percentage accuracies (n = 25) for synthetic solutions of arsenite (As(III)), arsenate (As(V)), monomethylarsonic acid (MA), and dimethylarsinic acid (DMA) containing 10 μg l(-1) As, were 98, 101, 94, and 105%, respectively. Data are presented to demonstrate the effect of pH and competing anions on the retention of the arsenic species. The cartridges were tested in the UK and Argentina at sites where arsenic was known to be present in surface and groundwaters, respectively, at elevated concentrations and under challenging matrix conditions. In Argentinean groundwater, 4-20% of speciated arsenic was present as MA and 20-73% as As(III). In UK surface waters, speciated arsenic was measured as 7-49% MA and 12-42% DMA. Comparative data from the field method using SPE cartridges and the laboratory method using liquid chromatography coupled to ICP-MS for all water samples provided a correlation of greater than 0.999 for As(III) and DMA, 0.991 for MA, and 0.982 for As(V) (P < 0.01).