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Arsenic concentrations and speciation measurements were determined for six varieties of Australian-grown rice (n = 130), imported rice (n = 53) and rice products (n = 56) from supermarkets. Total As, inorganic As and dimethylarsinic acid (DMA) concentrations in Australian rice ranged from 16 to 630 µg As kg−1 (mean ± s.d.: 220 ± 122 µg kg−1), 16 to 250 µg As kg−1 (92 ± 52 µg As kg−1) and <5 to 432 µg As kg−1 (125 ± 109 µg As kg−1), respectively. Total As, inorganic As and DMA concentrations in imported rice ranged between 31 and 376 µg As kg−1 (130 ± 98 µg kg−1), 17 and 198 µg As kg−1 (73 ± 40 µg As kg−1) and <5 and 327 µg As kg−1 (84 ± 92 µg As kg−1) respectively. Few samples exceeded the guidelines for inorganic As in polished rice. In rice products, total As, inorganic As and DMA concentrations ranged between 21 and 480 µg As kg−1 (160 ± 110 µg As kg−1), 20 and 255 µg As kg−1 (92 ± 78 µg As kg−1) and <5 and 340 µg As kg−1 (65 ± 69 µg As kg−1) respectively. Sixteen samples exceeded the 100 µg kg−1 maximum for inorganic As concentration in rice foods for infants and young children. Ingestion of multiple serves of some rice products poses a potential risk. Environmental chemistry gaps, on processes influencing As occurrence in rice, are discussed.

The development of robust methods for determining the concentration and speciation of antimony (Sb) in natural samples is essential to understanding its distribution and cycling in nature. Here we discuss our experiences with a variety of approaches for measuring the content and speciation of Sb in environmental matrices. Total Sb concentration measurements in waters require digestion with HNO3–HCl to release Sb from particulate material and may require a preconcentration step to remove Sb from saline matrices or to obtain the required sensitivity. Plant analyses require the use of HNO3–HBF4 or HNO3–HF while sediments require the use of HNO3–HCl to solubilise Sb and prevent adsorption to silicates. Methods for Sb speciation should be fit for purpose. Volatile Sb species can be measured successfully using SPME-GCMS, waters via hydride generation-trapping ICPMS and sediment extracts using HPLC-ICPMS. Extraction of Sb from sediments and plants presents a challenge; however, the use of citrate is adequate for extraction of Sb from sediments predominately containing Sb associated with Fe–Mn oxyhydroxide phases. We have been unable to successfully quantify organic Sb species in plants because of the oxidation of Sb(III) to Sb(V) and the formation of artefact Sb species. The analysis of solid samples using X-ray absorption spectroscopy should be considered as it has been shown to discriminate between Sb(III) and Sb(V) as well as Sb minerals, oxides and adsorbed Sb species.

The importance of measuring arsenic (As) species has been appreciated for a long time mainly because of the wide spread knowledge of arsenic's toxicity and its use as a poison. Increasingly health, environmental and food regulations have been written around As species rather than total concentrations. Knowledge of As speciation is important as the chemical form of As controls its bioavailability, toxicity, mobility and therapeutic benefits. Arsenic is present as inorganic (arsenate, arsenite, thioarsenates), complexed (arsenic glutathionines and phytochelatins), low molecular weight (monomethylarsonate, dimethylarsenate, arsenobetaine, arsenocholine etc.) and high molecular weight (arsenic hydrocarbons and arsenic phospholipids) species. In this review we cover the intergrity of As species during collection, storage, sample preparation and measurement by HPLC-ICPMS and HPLC-HG-AFS. It is essential to ensure that As species, especially in waters and sediments, are not artefacts of the preservation or extraction procedure. Most samples can be stored frozen (-20 °C), but the stability of water and sediment samples is matrix dependent and depends on preservation technique applied. Arsenic cannot be extracted from samples using a single set of conditions but must be optimised for each sample type. Methanol-water mixtures with microwave heating are commonly used to extract polar As species from tissues while As-lipids required a non-polar solvent. Dilute acid can be used to increase the efficiencies of extraction of hard to extract tissue As species. Freeze drying is suitable for the drying of biotic material while sediments should not be dried before analysis. Extraction efficiencies are critically dependent on particle size. Polar As species have a wide variety of ionic characteristics thus complimentary chromatographic approaches utilising ion-exchange or reverse phase columns with modifiers are needed to separate all the As species. Arsenic-lipids require the use of a

In New South Wales (NSW), Australia, the availability of water from estuarine lakes combined with the use of coal as an energy source has resulted in coal-fired power stations on the margins of coastal lakes. The purpose of this study was to use a multi-proxy method to evaluate the extent and trends of historical metal inputs from a coal-fired power station to sediments in Lake Budgewoi. Metal concentrations in 15-cm sediment cores showed a uniform depth profile. The highest concentrations of zinc and copper were found close to the Munmorah Power Station outlet, while arsenic and lead were found in the deposition basin of sediments. Background values for metal concentrations of Zn < 80 mg/kg, As < 15 mg/kg, Se < 1 mg/kg, Cu < 16 mg/kg, Cd < 0.8 mg/kg and Pb < 20 mg/kg were used as the baseline for future studies in this lake. The history of sediment metal concentrations is consistent with power station activities in the lake. Maximum metal concentrations found in sediments of Lake Budgewoi were Zn 122 mg/kg, Cu 45 mg/kg, As 10 mg/kg, Se 1.8 mg/kg, Cd 0.2 mg/kg and Pb 41 mg/kg. The ratio of these values to the national interim sediment quality guidelines are Pb 0.8, Cu 0.7, Zn 0.6, As 0.5 and Cd 0.1. Although concentrations were below guideline values, the multi-proxy method applied in this study was sensitive enough to detect metal concentration changes over the 45 years of power station operation. The results of this study provide environmental regulators with a baseline of the past and current situation of power station metal contamination, and in the future will provide insights into how long it takes the environment to revert to background metal concentrations

Acid-sulfide hot springs are analogs of early Earth geothermal systems where microbial metal(loid) resistance likely first evolved. Arsenic is a metalloid enriched in the acid-sulfide hot spring Champagne Pool (Waiotapu, New Zealand). Arsenic speciation in Champagne Pool follows reaction paths not yet fully understood with respect to biotic contributions and coupling to biogeochemical sulfur cycling. Here we present quantitative arsenic speciation from Champagne Pool, finding arsenite dominant in the pool, rim and outflow channel (55-75% total arsenic), and dithio- and trithioarsenates ubiquitously present as 18-25% total arsenic. In the outflow channel, dimethylmonothioarsenate comprised ≤9% total arsenic, while on the outflow terrace thioarsenates were present at 55% total arsenic. We also quantified sulfide, thiosulfate, sulfate and elemental sulfur, finding sulfide and sulfate as major species in the pool and outflow terrace, respectively. Elemental sulfur concentration reached a maximum at the terrace. Phylogenetic analysis of 16S rRNA genes from metagenomic sequencing revealed the dominance of Sulfurihydrogenibium at all sites and an increased archaeal population at the rim and outflow channel. Several phylotypes were found closely related to known sulfur- and sulfide-oxidizers, as well as sulfur- and sulfate-reducers. Bioinformatic analysis revealed genes underpinning sulfur redox transformations, consistent with sulfur speciation data, and illustrating a microbial role in sulfur-dependent transformation of arsenite to thioarsenate. Metagenomic analysis also revealed genes encoding for arsenate reductase at all sites, reflecting the ubiquity of thioarsenate and a need for microbial arsenate resistance despite anoxic conditions. Absence of the arsenite oxidase gene, aio, at all sites suggests prioritization of arsenite detoxification over coupling to energy conservation. Finally, detection of methyl arsenic in the outflow channel, in conjunction with increased

In this review we present an overview of hyphenated techniques using an ICPMS detector with an emphasis on extraction techniques for the measurement of metalloids by high pressure liquid chromatography-inductively plasma mass spectrometry (HPLC-ICPMS). Five modes of using hyphenated ICPMS systems; HPLC-ICPMS, HPLC-hydride generation-ICPMS, Cryogenic trapping ICPMS, in-situ Cryogenic trapping ICPMS and Gas Chromatography-ICPMS are described together with their application for the measurement of arsenic, selenium, mercury and antimony species. Two classes of metalloid species are described; "Easy to extract species," stable species existing as discrete molecules or relatively weakly bound to cellular constituents, and Hard to extract species," unstable species that dissociate on extraction and species incorporated within cellular constituents such as proteins. Measurements described include, arsenic species: arsenobetaine, arsenoribosides, arsenic bound to lipids and phytochelatins and other minor arsenic species including thioarsenic species. Selenium species: selenocysteine and selenomethionine, Se-methyl selenomethionine, Se-methyl selenocysteine, y-glutamyl-Se-methylselenocysteine, dimethylselenide and dimethyldiselenide. Mercury species: inorganic Hg and methyl Hg. Antimony species: antimonite and antimonate. Germanium species: inorganic. Extraction methods are discussed in terms of their extraction efficiencies, stability of species and artifact formation.

If sponges are to be effective biomonitors we require a better understanding of the spatial scales over which metals vary in these organisms. We determined how concentration of Cd, Zn, Cu, Pb, Hg and Se varied over four spatial scales for two common estuarine sponge species in the Sydney region. We examined variability with a fully nested sampling design; between coastal lakes, within coastal lakes, between sponges and within sponges. Calculation of variance components confirmed that 'within-sponge' variation in Cd, Zn, Cu, Pb and Se concentrations were low (1-14%) relative to the two largest spatial scales (49-98%) examined. In contrast, Hg concentrations exhibited marked variability 'between-sponges' and were below detection at one location. There was little evidence that sponge size was a good predictor of metal concentration. Taken together, these outcomes confirm that fragments of these sponges could be successfully transplanted and therefore show promise as biomonitors of metal contamination.

Bioaccumulation and uptake of antimony (Sb) were investigated in a highly contaminated stream, Bakers Creek, running adjacent to mining and processing of Sb-As ores at Hillgrove Mine, NSW, Australia. Comparisons with arsenic (As) were included owing to its co-occurrence at high concentrations. Mean metalloid creek rhizome sediment concentrations were 777 115g g-1 Sb and 60 6g g-1 As, with water concentrations at 381 23g L-1 Sb and 46 2g L-1 As. Antimony and As were significantly elevated in aquatic autotrophs (96-212g g-1 Sb and 32-245g g-1 As) but Sb had a lower uptake efficiency. Both metalloids were elevated in all macroinvertebrates sampled (94-316g g-1 Sb and 1.8-62g g-1 As) except Sb in gastropods. Metalloids were detected in upper trophic levels although biomagnification was not evident. Metalloid transfer to riparian vegetation leaves from roots and rhizome soil was low but rhizome soil to leaf As concentration ratios were up to 2-3 times greater than Sb concentration ratios. Direct exposure to the rhizosphere sediments and soils, water ingestion and consumption of aquatic autotrophs appear to be the major routes of Sb and As uptake for the fauna of Bakers Creek.

Measurements of selenium in sediments and benthic infauna of Lake Macquarie, an estuary on the east coast of Australia, indicate that sediments are a significant source of selenium in the lake's food web. Analysis of surficial sediment samples indicated higher selenium concentrations near what are believed to be the main industrial sources of selenium to the lake: a smelter and a power station. Sediment cores taken from sediments in Mannering Bay, near a power station at Vales Point, contained an average of 12 times more selenium in surficial sections than sediment cores from Nord's Wharf, a part of the lake remote from direct inputs of selenium. The highest selenium concentration found in Mannering Bay sediments (17.2 μg/g) was 69 times the apparent background concentration at Nord's Wharf (0.25 μg/g). Pore water concentrations in Mannering Bay were also high, up to 5 μg/l compared to those at Nord's Wharf which were below detection limits (0.2 μg/l). Selenium concentrations in muscle tissues of three benthic-feeding fish species (Mugil cephalus, Platycephalus fuscus, Acanthopagrus australis) were significantly correlated (p < 0.05) with surficial sediment selenium concentration. Selenium concentrations in polychaetes and molluscs of Mannering Bay were up to 58 times higher than those from Nord's Wharf. Two benthic organisms, the eunicid polychaete Marphysa sanguinea and the bivalve mollusc Spisula trigonella, were maintained at different densities in selenium-spiked sediments. Both animals accumulated selenium from the spiked sediment, confirming that bioaccumulation from contaminated sediments occurs. Collectively, these data suggest that benthic food webs are important sources of selenium to the fish of Lake Macquarie.

Selenium is an essential trace element in humans, the majority of it occurring in selenoproteins. These proteins have several known physiologic functions; they are important antioxidants, maintain normal thyroid function, and are thought to play a role in inhibiting tumor growth. There has been considerable interest in studying selenoproteins in serum because the selenium concentrations reported for many populations are less than those required for optimum activity of selenoenzymes. This may have both long- and short-term consequences for human health.