Arsenic mobilization from historically contaminated mining soils in a continuously operated bioreactor : Implications for risk assessment

Concentrations of soil arsenic (As) in the vicinity of the former Złoty Stok gold mine (Lower Silesia, southwest Poland) exceed 1000 μg g-1 in the area, posing an inherent threat to neighboring bodies of water. This study investigated continuous As mobilization under reducing conditions for more than 3 months. In particular, the capacity of autochthonic microflora that live on natural organic matter as the sole carbon/electron source for mobilizing As was assessed. A biphasic mobilization of As was observed. In the first two months, As mobilization was mainly conferred by Mn dissolution despite the prevalence of Fe (0.1 wt % vs 5.4 for Mn and Fe, respectively) as indicated by multiple regression analysis. Thereafter, the sudden increase in aqueous As[III] (up to 2400 μg L-1) was attributed to an almost quintupling of the autochthonic dissimilatory As-reducing community (quantitative polymerase chain reaction). The aqueous speciation influenced by microbial activity led to a reduction of solid phase As species (X-ray absorption fine structure spectroscopy) and a change in the elemental composition of As hotspots (micro X-ray fluorescence mapping). The depletion of most natural dissolved organic matter and the fact that an extensive mobilization of As[III] occurred after two months raises concerns about the long-term stability of historically As-contaminated sites.</p

Exploring Farm Investment Behaviour in Transition: The Case of Russian Agriculture

This paper analyses the investment behaviour of Russian farms during the period of economic stabilisation that followed Russia's financial crisis of 1998, and is the first to apply the error-correction investment model to describe farms' investment behaviour in the transitional context. Additionally, the paper employs the error-correction and the adjustment-cost model to test for differences in the investment behaviour between various farm categories. The results show that in general Russian farms exhibited an error-correcting behaviour in the period under investigation. From 1999 to 2005 the output-capital gap was closed by an average rate of 10% per year. Estimates of the adjustment-cost model show that Russian farm investments are very sensitive to the sales-capital ratio, suggesting that Russian farms exhibit increasing returns to scale and positive expectations about future revenues. Yet, such farm characteristics as ownership structure, access to input markets and also regional specifics were found to be decisive for farm investment not only in the short but long term too. Finally, the results show that the adjustment-cost model is adequate for the evaluation of differences in short-term investment behaviour, whereas it is noticeably less powerful for investigating differences in the farms' long-term investment behaviour. Copyright (c) 2009 The Authors. Journal compilation (c) 2009 The Agricultural Economics Society.