Potential toxic elements in stream sediments, soils and waters in an abandoned radium mine (central Portugal)

The Alto da Várzea radium mine (AV) exploited ore and U-bearing minerals, such as autunite and torbernite. The mine was exploited underground from 1911 to 1922, closed in 1946 without restoration, and actually a commercial area is deployed. Stream sediments, soils and water samples were collected between 2008 and 2009. Stream sediments are mainly contaminated in As, Th, U and W, which is related to the AV radium mine. The PTEs, As, Co, Cr, Sr, Th, U, W, Zn, and electrical conductivity reached the highest values in soils collected inside the mine influence. Soils are contaminated with As and U and must not be used for any purpose. Most waters have pH values ranging from 4.3 to 6.8 and are poorly mineralized (EC = 41-186 µS/cm; TDS = 33-172 mg/L). Groundwater contains the highest Cu, Cr and Pb contents. Arsenic occurs predominantly as H2(AsO4)- and H(AsO4)2-. Waters are saturated in goethite, haematite and some of them also in lepidocrocite and ferrihydrite, which adsorbs As (V). Lead is divalent in waters collected during the warm season, being mobile in these waters. Thorium occurs mainly as Th(OH)3(CO3)-, Th(OH)2(CO3) and Th(OH)2(CO3) 22- , which increase water Th contents. Uranium occurs predominantly as UO2CO3, but CaUO2(CO3) 32- and CaUO2(CO3)3 also occur, decreasing its mobility in water. The waters are contaminated in NO2-, Mn, Cu, As, Pb and U and must not be used for human consumption and in agricultural activities. The water contamination is mainly associated with the old radium mine and human activities. A restoration of the mining area with PTE monitoring is necessary to avoid a public hazard.Thanks are due to Prof. Joao Coutinho for the determination of organic matter and cation exchange capacity in samples of stream sediments and soils and A. Rodrigues for the water analyses, EDM for some information on the Alto da Varzea mine area. This study had the support of Portuguese Fundacao para a Ciencia e Tecnologia (FCT), through the strategic projects UID/GEO/04035/2013 and UID/MAR/04292/2013 (MARE).info:eu-repo/semantics/publishedVersio

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 (AsIII), arsenate (AsV), 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 AsIII. 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 AsIII and DMA, 0.991 for MA, and 0.982 for AsV (P < 0.01)

Chemical speciation and ecological risk assessment of arsenic in marine sediments from Izmir Bay (Eastern Aegean Sea)

Total arsenic, arsenic(III) and (V), Fe, and Mn were measured in 17 surface sediment samples from Izmir Bay. The concentrations and ecological risk of As were characterized in the sediment affected by urban and agricultural activities. Total As ranged from 8.87 to 28.3 mu g g(-1) dry weight (96.5-99.9 % as inorganic As). Distribution of total As and total As/Fe followed a different trend in sediments at all sampling sites. Arsenite (As(III)) was the most dominant form followed by As(V), while organic arsenic represented a minor constituent (0.03 to 3.49 %). The highest concentration of total As was observed at Gediz River estuary and exceeded lower threshold value (threshold effects level (TEL)). Due to the biological reduction of As(V) and abundance of Fe (oxyhydr)oxides in the sediments, most inorganic As in the Izmir Bay was present as As(III). Besides, the levels of As were >TEL and <PEL at all stations, suggesting that As may not currently impose ecologically dangerous impacts in the sedimentary environment of Izmir Bay. At all sampling sites in the Izmir Bay, nevertheless, natural sources of As need to be considered to explain the distribution patterns. This work highlights the need for arsenic speciation analysis to accurately assess potential toxicity of marine resources and provides a crucial baseline to assess the impact of future development within this region