Arsenic and selenium mobilisation from organic matter treated mine spoil with and without inorganic fertilisation

Organic matter amendments are applied to contaminated soil to provide a better habitat for revegetation and remediation, and olive mill waste compost (OMWC) has been described as a promising material for this aim. We report here the results of an incubation experiment carried out in flooded conditions to study its influence in As and metal solubility in a trace elements contaminated soil. NPK fertilisation and especially organic amendment application resulted in increased As, Se and Cu concentrations in pore water. Independent of the amendment, dimethylarsenic acid (DMA) was the most abundant As species in solution. The application of OMWC increased pore water dissolved organic-carbon (DOC) concentrations, which may explain the observed mobilisation of As, Cu and Se; phosphate added in NPK could also be in part responsible of the mobilisation caused in As. Therefore, the application of soil amendments in mine soils may be particularly problematic in flooded systems. (C) 2012 Elsevier Ltd. All rights reserved.

High-affinity phosphate/arsenate transport in white lupin (Lupinus albus) is relatively insensitive to phosphate status

The development of proteoid roots under phosphorus deficiency by white lupin (Lupinus albus) may result in increased arsenate uptake, as arsenate is a phosphate analogue. This, together with its high biomass production, rapid growth and ability to survive in soils with low phosphate and nitrogen contents, low pH and high metal contents make them an interesting species to investigate with respect to revegetation, and possibly also for long-term phytoremediation, of arsenic contaminated soils. Kinetic parameters for arsenate uptake for P-deficient and P-sufficient plants, as well as for proteoid and nonproteoid roots were obtained. Down-regulation of arsenate uptake by phosphate, as well as phosphate/arsenate competition for P-deficient and P-sufficient plants was studied. Arsenate uptake was reduced by phosphate, but small differences were found between P-deficient and P-sufficient plants. Arsenate uptake by proteoid roots was higher than for nonproteoid roots of P-deficient plants, with higher V_max and similar K_m values. Down-regulation of the high affinity phosphate/arsenate uptake system by phosphate does take place but seems to be slower than in other plants. This study suggests that the low sensitivity of the phosphate/arsenate uptake system to regulation by phosphate may be related to the adaptations of white lupin to low P available environments. Such adaptation are absent in plants unable to develop proteoid roots.