Arsenic Species In Groundwater Research Articles

Investigating water quality and arsenic contamination in drinking water resources in the Tavşanlı District (Kütahya, Western Turkey)

Arsenic is a natural component of the earth’s crust, and it is transported into surface water and groundwater through the dissolution of rocks, minerals and ores. In addition, arsenic leaching processes contaminate water sources and this geogenic arsenic contamination causes significant water quality problems in many parts of the world. In this study, water quality, arsenic contamination and human health risks of drinking water resources in the Tavsanli District were determined and the origins were discussed. For this purpose, geological and hydrogeological properties were investigated. In situ measurements and chemical analyses were carried out on water samples taken from drinking water sources such as wells, springs and surface waters for hydrogeochemical studies. According to the obtained results, water resources are Ca–Mg–HCO3, Mg–HCO3 and Na–HCO3 type. Total As (AsT) concentration of the water samples sometimes exceeds the permissible limit given by the TSI-266 (Standards for drinking waters, Turkish Standards Institution, Ankara, 2005) and WHO (Guidelines for drinking-water quality, World Health Organization, Geneva, 2008) for drinking water. H3AsO 3 0 and HAsO4 2− are dominant arsenic species in groundwater and surface water, respectively. Typically high total arsenic concentrations can be found in regions characterized by magmatic rocks. In addition, As concentrations in surface waters were found to be higher than in groundwater in the region, due to the anthropogenic influence of mining activities in the region.

As(III) adsorption and antimicrobial properties of Cu–chitosan/alumina nanocomposite

The objective of this work is to enhance the adsorption efficiency of chitosan toward As(III), a highly toxic and predominant arsenic species in groundwater, and to increase its antimicrobial activity at neutral pH values, the pHs of natural waters. Therefore, Cu–chitosan/alumina nanocomposite was prepared and tested as a new adsorbent for removal of As(III). The prepared adsorbent was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDX), Fourier transform Infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The modified adsorbent showed a more porous surface morphology compared to neat chitosan. The results of FTIR, EDX and XRD revealed that Cu2+ ions form a complex with amine groups on the chitosan surface. The adsorption behavior of As(III) on Cu–chitosan/nano-Al2O3, chitosan/nano-Al2O3 and neat chitosan was investigated using adsorption kinetics and isotherm studies at room temperature. The adsorption data for three types of adsorbents were fitted well by Freundlich model. The kinetic data showed good compliance with a pseudo-second-order kinetic model. The modified adsorbent exhibited a higher adsorption capacity and initial adsorption rate. Antimicrobial activity of the adsorbents was studied by minimum inhibitory concentration (MIC) method. The antimicrobial activity of Cu–chitosan/nano-Al2O3 was much higher than that of chitosan/nano-Al2O3 and neat chitosan.

Distribution of inorganic arsenic species in groundwater from Central-West Part of Santa Fe Province, Argentina

The distribution of inorganic arsenic species in groundwater used as drinking water supply by the peri-urban and rural population from central-western area of Santa Fe Province, Argentina, was studied. An analytical methodology based on an online system of atomic absorption spectrometry with hydride generation and flow injection (FI-HGAAS) was used for total inorganic arsenic determination. For speciation purposes, the distinction between As(V) and As(III) was performed through the on line coupling of FI-HGAAS to a solid phase system based on an anionic exchanger able to retain As(V) as oxyanion, allowing As(III) to be selectively determined. The concentration of As(V) was calculated as the difference between total arsenic and As(III) concentrations. Effects of matrix interference due to the nonselective behavior of the exchange resins were carefully laid. Results for 59 samples collected from 27 localities showed an almost exclusive predominance of pentavalent forms.

Superparamagnetic mesoporous ferrite nanocrystal clusters for efficient removal of arsenite from water

Contaminated groundwater with a high concentration of arsenic continues to pose health threats to millions of people worldwide, especially in Asia. As(III) is the dominant arsenic species in groundwater, and is more toxic, soluble, and mobile than As(V). Affected communities need accessible technologies to remove As(III) from drinking water, especially in rural areas. In this study, a strategy is adopted to assemble small-sized magnetic MnFe2O4 nanocrystal building blocks to form mesoporous clusters (NCs) with the advantage of increasing the magnetization while retaining superparamagnetic characteristics by using a solvothermal method, which is beneficial for efficient separation from treated water by a moderate magnetic field. The MnFe2O4 NCs combined with uniform mesoporous structure and small constituent nanocrystals (about 8–12 nm in size) provides a synergistic effect for enhanced adsorption performance toward As(III) with an adsorption capacity (>27.27 mg g−1) under neutral conditions. The analysis of Fourier transformed infrared spectra and X-ray photoelectron spectroscopy demonstrates that the adsorption of As(III) on MnFe2O4 NCs is through the formation of a surface complex.

Background species effect on aqueous arsenic removal by nano zero-valent iron using fractional factorial design

This study describes the removal of arsenic species in groundwater by nano zero-valent iron process, including As(III) and As(V). Since the background species may inhibit or promote arsenic removal. The influence of several common ions such as phosphate (PO43−), bicarbonate (HCO3−), sulfate (SO42−), calcium (Ca2+), chloride (Cl−), and humic acid (HA) were selected to evaluate their effects on arsenic removal. In particular, a 26−2 fractional factorial design (FFD) was employed to identify major or interacting factors, which affect arsenic removal in a significant way. As a result of FFD evaluation, PO43− and HA play the role of inhibiting arsenic removal, while Ca2+ was observed to play the promoting one. As for HCO3− and Cl−, the former one inhibits As(III) removal, whereas the later one enhances its removal; on the other hand, As(V) removal was affected only slightly in the presence of HCO3− or Cl−. Hence, it was suggested that the arsenic removal by the nanoiron process can be improved through pretreatment of PO43− and HA. In addition, for the groundwater with high hardness, the nanoiron process can be an advantageous option because of enhancing characteristics of Ca2+.

Arsenic Speciation Analysis in Environmental Water by HG-AFS after Solid-Phase Extraction Using Multiwalled Carbon Nanotubes

A simple, inexpensive, and sensitive method was developed for the determination of inorganic arsenic species As(III), As(V) and total arsenic in environmental water samples using multiwalled carbon nanotubes (MWCNTs) as solid phase extraction (SPE) adsorbents coupled with hydride generation atomic fluorescence spectrometry (HG-AFS). The procedure is based on selectively absorbance of the chelates of As(III)-ammonium pyrrolidine dithiocarbamate (APDC) on the MWCNTs at pH range of 2.0-5.0, while As(V) was passed through the microcolumn. The retention complexes of As(III)-APDC was eluted completely with 3 mL of 2.0 mol L-1 HCl solution at a flow rate 1.0 mL min-1, and then directly determined by HG-AFS. The effluent of As(V) was determined using thiourea and ascorbic acid as reducing agent for reduce As(V) to As(III). The different parameters that control the preconcention/separation step of As(III) and As(V) and determination have been investigated in detail. Under the optimized conditions, a linear range of 0.03-10.0 ng mL-1 for As(III), along with a detection limits of 0.0026 ng mL-1, and the relative standard deviations for As(III) and As(V) for 0.28-6.30%, were obtained. The proposed method was applied for the analysis of inorganic arsenic species in groundwater and lake water with the recovery of 98.00-102.0%.

Speciation analysis of inorganic arsenic in natural water by carbon nanofibers separation and inductively coupled plasma mass spectrometry determination

In this paper, carbon nanofibers (CNFs) as a novel solid phase extraction sorbent were developed for speciation preconcentration and separation of inorganic arsenic species As(III) and As(V) prior to determination by inductively coupled plasma mass spectrometry (ICP-MS). It was found that during all the steps of the separation, As(III) was selectively sorbed on the microcolumn packed with CNFs within a pH range of 1.0–3.0 in the presence of ammonium pyrroinedithiocarbamate (APDC), while As(V) was passed through the microcolumn without the retention. Various experimental parameters affecting the separation and determination of As(III) and As(V) have been investigated in detail. Under the optimized conditions, the detection limits of this method for As(III) were 0.0045 ng mL −1 with an enrichment factor of 33 and 0.24 ng mL −1 for As(V), and the relative standard deviations for As(III) and As(V) were 2.6% and 1.9% ( n = 9, c = 1.0 ng mL −1), respectively. In order to verify the accuracy of the method, a certified reference of water sample was analyzed, and the results obtained were in good agreement with the certified values. The proposed method was applied for the analysis of inorganic arsenic species in groundwater and lake water with the recovery of 92–106%.

Development of a field speciation method for inorganic arsenic species in groundwater

This research describes the development of a dual preservation and field speciation technique for the arsenic species arsenite [As(III)] and arsenate [As(V)] using ion exchange field speciation of a sample preserved with EDTA and acetic acid. The new method is compared with existing speciation methods and is shown to be simple, robust, free of hazardous chemicals, and capable of recovering >90% of As(III) and As(V) despite possible interference from ferrous iron in the sample. The method was further refined through testing on 20 drinking water wells in five states. Results indicated that As(III) measured by field speciation agreed with subsequent lab speciation (conducted two to four days later) on the preserved sample with a correlation coefficient of R2 = 0.997.

Preservation and Field Speciation of Inorganic Arsenic Species in Groundwater

Abstract This research describes the development of a dual preservation- and field-speciation technique for As(III) and As(V) speciation of a sample preserved with ethylenediaminetetraacetic acid (EDTA) and acetic acid (HAc). The new method was compared with existing preservation- and field-speciation methods and was shown to be accurate and precise in spite of possible interference from ferrous iron in the sample. The new preservation-speciation method was further evaluated on 55 drinking water wells (18 samples in triplicate) in Minnesota, North Dakota and California with the result that As(III) measured by field-speciation agreed with subsequent (within 1–3 d) laboratory speciation on the preserved sample with a slope of 0.98 and a correlation coefficient of r2 = 0.999. Preserved samples stored in the dark at room temperature (22–24°C) could maintain their species distribution for 30 to 85 d.

Preservation of Inorganic Arsenic Species in Groundwater

The objective of this research was to develop a robust preservation method for stabilizing inorganic As(IlI/V) species in synthetic and actual groundwaters. Ethylenediaminetetraacetic acid (EDTA), H2SO4, H3PO4, and EDTA-acetic acid (HAc) were evaluated in synthetic groundwater containing 3 mg/L Fe(ll) in the pH range 6.5-8.4 and Eh range -100 to +200 mV at room temperature. In the absence of strong UV light, only EDTA-HAc was found to be an effective preservative under all the experimental conditions tested. A total of 89 samples (including 16 samples in triplicate) from 55 drinking waterwells in Minnesota, California, and North Dakota were preserved with a combination of EDTA-HAc and speciated to evaluate its effectiveness for preserving inorganic arsenic species in actual groundwater samples. The preserved and field-speciated samples were repeatedly speciated and analyzed in the laboratory for up to 85 days after collection. Field-speciated As(lll) concentrations were compared with the As(lll) concentrations in the preserved samples. The results were highly correlated (slope 0.9773, R2 = 0.9986), which indicates that during sample transportation and storage the distribution of arsenic species did not change for samples preserved with EDTA-HAc.

Determination of inorganic arsenic species by flow injection hydride generation atomic absorption spectrometry with variable sodium tetrahydroborate concentrations

This work describes a study on the determination of inorganic arsenic species in ground water and synthetic experimental matrices, using a flow injection system with on-line hydride generation device coupled to an atomic absorption spectrometer with flame-heated quartz atomizer (FI HG AAS). Specific trivalent arsenic determination is based on the slow kinetics of As(V) on the hydride generation reaction using sufficiently low concentrations of sodium tetrahydroborate (NaBH 4) as reductant in highly acidic conditions (pH<0). Under these conditions, the efficiency of hydride generation from As(V) is much lower than that from As(III). The pentavalent form is determined by the difference between total inorganic arsenic and As(III). As(V) interferences were studied using As(III) solutions ranging from 0% to 50% of total inorganic As. The optimized NaBH 4 concentration was 0.035% (w/v). The detection limit was 1.4 μg l −1 As(III). As(V) interferences were 6% in the case of water samples with 6 μg l −1 As(III) in the presence of 54 μg l −1 As(V) (i.e. 10% As(III)). Interferences of methylated arsenic species (MMA and DMA) were evaluated. Speciation method was satisfactorily applied to 20 field arsenical water samples from Santa Fe, Argentina, with values ranging from 30 to 308 μg l −1 total As. We found from 0% to 36% As(III) in the 20 field samples. The developed methodology constitutes an economic, simple and reliable way to evaluate inorganic arsenic distribution in underground waters or similar systems with negligible or no content of organoarsenicals.

Relationship between molar volume and rejection of arsenic species in groundwater by low-pressure nanofiltration process

Rejection of arsenite, dimethyl arsinic acid (DMAA), arsenate, chloride, nitrate and sulfate ion by low-pressure nanofiltration was evaluated by the extended Nernst–Planck model coupled with steric hindrance and Donnan equilibrium. The partition coefficient of K i for each solute was introduced to Donnan equilibrium. They could be obtained from the curve fitting with experimental rejection of solutes. In the case of anionic solutes such as H 2AsO 3 −, H 2AsO 4 −, HAsO 4 −, (CH 3) 2AsO 2 −, NO 3 − and SO 4 2−, the partition coefficient K i was correlated with the molar volume. The empirical equation was obtained from the regression analysis between molar volume ( V A) and partition coefficient ( K i ) of anionic solutes for ES10 ( K i =3100 V A 0.64), NTR729HF ( K i =930 V A 0.44) and NTR7250 ( K i =1800 V A 0.63). The effective range of molar volume for the equation was from 0.5×10 −4 to 1.5×10 −4 m 3/mol. The gradient value of the regression line of K i with molar volume in log scale was closed to 2/3 for all membranes used. These results suggest that the interaction between anionic solute and membrane surface was affected mainly by the surface charge density corresponding to molar volume of ionic solute, although another factors need to be considered in order to account for a deviation from the 2/3.

Use of “red earth”-low cost remedial option for arsenic removal

High arsenic groundwater has emerged as a niggling environmental problem in the recent decades. Elevated levels of groundwater arsenic (>>50ppb) in the Bengal Delta Plain (BDP) threatens the lives of millions of people. The present study deals with the adsorption pattern of AsO 4 3- and AsO 3 3- , the predominant arsenic species in groundwater using red earth for the supply of potable water. The mineralogical study of red earth exhibits the predominance of iron and aluminium secondary phases. Cost calculated for the transportation of red earth approximates to US$16/ton/1000km whereas the treatment process estimates to US$0.6/100L contaminated water. Batch and column studies reveal the promising role of red earth in removing arsenic from water.

Preserving the distribution of inorganic arsenic species in groundwater and acid mine drainage samples.

The distribution of inorganic arsenic species must be preserved in the field to eliminate changes caused by metal oxyhydroxide precipitation, photochemical oxidation, and redox reactions. Arsenic species sorb to iron and manganese oxyhydroxide precipitates, and arsenite can be oxidized to arsenate by photolytically produced free radicals in many sample matrices. Several preservatives were evaluated to minimize metal oxyhydroxide precipitation, such as inorganic acids and ethylenediaminetetraacetic acid (EDTA). EDTA was found to work best for all sample matrices tested. Storing samples in opaque polyethylene bottles eliminated the effects of photochemical reactions. The preservation technique was tested on 71 groundwater and six acid mine drainage samples. Concentrations in groundwater samples reached 720 microg-As/L for arsenite and 1080 microg-As/L for arsenate, and acid mine drainage samples reached 13 000 microg-As/L for arsenite and 3700 microg-As/L for arsenate. The arsenic species distribution in the samples ranged from 0 to 90% arsenite. The stability of the preservation technique was established by comparing laboratory arsenic speciation results for samples preserved in the field to results for subsamples speciated onsite. Statistical analyses indicated that the difference between arsenite and arsenate concentrations for samples preserved with EDTA in opaque bottles and field speciation results were analytically insignificant. The percentage change in arsenite:arsenate ratios for a preserved acid mine drainage sample and groundwater sample during a 3-month period was -5 and +3%, respectively.

Separation of Inorganic Arsenic Species in Groundwater Using Ion Exchange Method

Separation of Inorganic Arsenic Species in Groundwater Using Ion Exchange Method

Separation of inorganic arsenic species in groundwater using ion exchange method.

Separation of inorganic arsenic species in groundwater using ion exchange method.

Evaluation of the Gas–Liquid Separation Efficiency of a Tubular Membrane and Determination of Arsenic Species in Groundwater by Liquid Chromatography Coupled With Hydride Generation Atomic Absorption Spectrometry

An experimental approach for evaluating the hydride separation efficiency of a tubular microporous poly(tetrafluoroethylene) (PTFE) membrane by flow injection hydride generation atomic absorption spectrometry (HGAAS) is described. A method is also proposed for determining arsenic species in groundwater by coupling ion-pair chromatography (IPC) with HGAAS. The evaluation was undertaken with a combined gas–liquid separator (GLS), consisting of a tubular PTFE membrane and a conventional U-shaped glass device. Two important controlling variables, viz ., the length of the microporous PTFE tubing and the ratio of the tubing id to the wall thickness, were investigated. The results showed that the absolute separation efficiency of the PTFE membrane can be effectively evaluated with the combined GLS. In addition, arsenic speciation in groundwater was also investigated by IPC–HGAAS. The chromatographic separation of arsenic species with this analytical system was examined in terms of the effects of pH and concentration of eluent. The absolute detection limits achieved with a 100 µl injection can be as low as 0.07, 0.11, 0.12 and 0.30 ng for arsenite (As III ), dimethylarsinic acid, monomethylarsonic acid and arsenate (As V ), respectively. A commercially available standard (NIST SRM 1643b Trace Elements in Water) and the spike additions method were used to confirm the analytical reliability of the method. The proposed method has already been routinely applied to the speciation of arsenic in groundwater samples.

Inorganic arsenic species in groundwater: A case study from Purbasthali (Burdwan), India

A regional groundwater quality survey from 20 tube wells in the Purbasthali area of the Burdwan district of West Bengal province (India) identified arsenic pollution in this area. Arsenic was detected in 19 cases at a concentration level 0.5 to 135.9 micrograms/L. Speciation studies indicate that As(III) is present in only one sample and organo-arsenic compounds have not been detected. Iron, antimony and pH of such water samples were also studied to see if there is any correlation of the presence of arsenic and these parameters. A high concentration of iron (0.3 to 10.7 mg/L) has been detected. Antimony is present in all these water samples (0.03 to 0.9 microgram/L). The pH value of the groundwater in this area shows that it is more or less neutral.