Sensitive inorganic arsenic speciation on a voltammetric platform in environmental water samples

A strategy for As(III) determination based on ultrafine gold nanoparticles decorated on magnetic graphene oxide

In this work, a new dendrimer modified magnetic graphene oxide (GO) was used as a substrate for electrodeposition of Au nanoparticles. The modified magnetic electrode was employed for sensitive measuring of As(III) ion as a well-established human carcinogen. The prepared electrochemical device exhibits excellent activity towards As(III) detection using the square wave anodic stripping voltammetry (SWASV) protocol. At optimum conditions (deposition potential at -0.5 V for 100 s in 0.1 M acetate buffer with pH 5.0), a linear range from 1.0 to 125.0 μgL-1 with a low detection limit (calculated by S/N = 3) of 0.47 μg L-1 was obtained. In addition to the simplicity and sensitivity of the proposed sensor, its high selectivity against some major interfering agents, such as Cu(II) and Hg(II) makes it an appreciable sensing tool for the screening of As(III). In addition, the sensor revealed satisfactory results for detection of As(III) in different water samples, and the accuracy of obtained data were confirmed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) setup. Accounting for the high sensitivity, remarkable selectivity and good reproducibility, the established electrochemical strategy has great potential for analysis of As(III) in environmental matrices.

Guilty by association: Assessment of environmental loadings on arsenic distribution in two Pacific Island rivers

This work evaluates the immediate risk of arsenic toxicity in two major river systems located in Western Viti Levu, Fiji and Guadalcanal, the Solomon Islands. Using principal component analysis, the associations between the major inorganic arsenic species, As (V) and As(III) and those of the controlling parameters, pH, dissolved oxygen and temperature were investigated in these aquatic systems. As(III) was found to be the dominant form of total inorganic As concentrations in five of the thirteen sites studied. There remains a high risk of As(III) exposure from these sites in the rivers. The study also examined the potential role of mine adits in influencing the distinct water chemistry at the sites. Over 50% of As was found to exist as the more toxic As(III) species at some sites (with higher levels near the gold mines) in both river systems. This finding implies that there may be health risk to populations relying on the river waters for agriculture. As(V) at most sites across both rivers exceeded 13 μg/L, defined as a trigger value for aquatic ecosystems by Australia and New Zealand standards. The PCA indicated that spatial variations play a significant role in water chemistries between sites further from the mine adit location in the Metapona River. In the Sabeto River system, there was also considerable intra-variability in the water chemistries between sites. Further detailed studies are necessary to determine a complete profile of As species and associated biogeochemical processes in these rivers which could lead on to identify appropriate containment or mitigation measures.

Sediment arsenic hotspots in an abandoned tailings storage facility, Gold Ridge Mine, Solomon Islands

Gold mining of arsenopyrite ore bodies result in waste tailings that contain elevated levels of arsenic. Disposal of these wastes in a Tailings Storage Facility (TSF) represents a substantial environmental risk if not properly managed. The Gold Ridge mine on Guadalcanal, in the Solomon Islands was abandoned from 2014 to 2018, leaving the TSF with little ongoing environmental management. Surface water quality monitoring observed a threefold increase in surface water arsenic concentrations over a 6-month period when no mining operations were occurring. This study aimed to investigate bottom sediments as the source of elevated concentrations of arsenic in the surface waters of the TSF during mine closure. This was achieved by analysing arsenic concentrations in the surface water, sediment porewaters and by quantifying sediment arsenic flux as dissolved oxygen availability declined. It was evident that bottom sediments of the TSF were the potential source of arsenic, having an average arsenic concentration of 437.9 mg kg^-1. In addition, average sediment porewater arsenic concentrations across the TSF were 1.07 mg L^-1, with a large central zone of highly elevated concentrations peaking at over 17 mg L^-1. Long term sediment core incubations demonstrated arsenic effluxes from all sites monitored under both oxic and hypoxic conditions, ranging from 0.72 mg m^-2 day^-1 to 7.01 mg m^-2 day^-1 respectively. These results suggest that arsenic hotspots within the TSF have the capability to contribute to increased arsenic concentrations in surface waters. Management of mine TSF's should consider these geochemical interactions that can occur in abandoned sites.

μ-Thin-layer chromatography coupled with laser ablation-inductively coupled plasma-mass spectrometry using tin(II)-imprinted polymer nanoparticles as a stationary phase for speciation of tin

A unique and novel μ-thin-layer chromatography method based on Sn(II) ion-imprinted polymer (Sn-IIP) for speciation of tin ion species in water and plasma samples is introduced for the first time. For this purpose, N-allylthiourea (NATU) and ethylene glycol dimethacrylate (EGDMA) were copolymerized in the presence of Sn(II). The obtained polymer particles were identified using multiple techniques like BET, FT-IR, XRD, and FESEM. The effects of different variables such as pH of the solution, mobile phase composition, and IIP per CaSO₄ mass ratio on the separation efficiency were also evaluated. After completion of the separation process on the plate, its surface was scanned by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Under the established optimal condition, the detection limit, relative standard deviation (RSD) of responses, and linear dynamic range (LDR) of the method were obtained as 0.3 μg L^-1, 3.5%, and 0.8-900 μg L^-1 for Sn(II) and 0.4 μg L^-1, 4%, and 1-740 μg L^-1 for Sn(IV) assay, respectively. The developed method was finally applied to the speciation of tin in various water and plasma samples. Graphical abstract Schematic representation of μ-thin-layer chromatography method based on tin(II) ion-imprinted polymer (Sn-IIP) for speciation of tin ion species in water and plasma samples and scanned separated casts by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS).