Hg transfer from contaminated soils to plants and animals
Rodrigues, S.M. ; Henriques, B. ; Reis, A.T. ; Duarte, A.C. ; Pereira, E. ; Romkens, P.F.A.M. - \ 2012
Environmental Chemistry Letters 10 (2012)1. - ISSN 1610-3653 - p. 61 - 67.
potentially toxic elements - chloralkali plant - available pools - total mercury - part ii - speciation - transport - portugal - slovenia - samples
Understanding the transfer of mercury (Hg) from soil to crops is crucial due to Hg toxicity and Hg occurrence in terrestrial systems. Previous research has shown that available Hg in soils contributes to plant Hg levels. Plant Hg concentrations are related to soil conditions and plant characteristics. Mechanistic models describing such soil–plant interactions are however difficult to quantify. Here we performed a field study in agricultural, mining and industrial areas in Portugal to evaluate potential food chain risks. The uptake of Hg by Italian ryegrass, ryegrass, orchard grass, collard greens and rye was measured to calculate daily intakes (DI) of Hg for cows and sheep grazing. A total of 136 soil samples and 129 plant samples were analysed. Results show that total Hg concentrations ranged from 0.01 to 98 mg kg-1 in soils; 0.01–5.4 mg kg-1 in shoots and 0.01–42 mg kg-1 in roots. Calculated DI ranged from 0.18 to 132 mg d-1 for cows, and from 0.028 to 23 mg d-1 for sheep. In 27 grassland sites, daily intakes exceeded the acceptable daily intake of both cows and sheep in view of food safety considering Hg in animal kidneys evidencing potential risks to human health. The transfer of Hg from soil to crops was described using empirical Freundlich-type functions. For ryegrass, orchard grass and collard greens, the soil-to-root or soil-to-shoot transfer of Hg appeared to be controlled by the total soil Hg concentration and levels of Alox and Feox. Empirical functions allowed us to obtain realistic estimates of Hg levels in crops and can be used as an alternative to mechanistic models when evaluating food chain risks of Hg contamination in agricultural soils.
Soil-plant-animal transfer models to improve soil protection guidelines: A case study from Portugal
Rodrigues, S.M. ; Pereira, M.E. ; Duarte, A.C. ; Römkens, P.F.A.M. - \ 2012
Environment International 39 (2012)1. - ISSN 0160-4120 - p. 27 - 37.
potentially toxic elements - available pools - risk-assessment - food-chain - part ii - cadmium - mercury - lead - metals - sheep
Food chain models are essential tools to assess risks of soil contamination in view of product quality including fodder crops and animal products. Here we link soil to plant transfer (SPT) models for potentially toxic elements (PTEs) including As, Ba, Cd, Co, Cu, Hg, Ni, Pb, Sb, U and Zn with models describing accumulation in animal organs. Current EU standards for food products and acceptable daily intake levels (ADI) for humans were used as critical limits. The combined model is used to assess the impact of soil contamination on animal health, product quality and human health using data from 100 arable fields. Results indicate that 42 existing arable fields near industrial and mining sites are unsuitable for animal grazing in view of food safety due to elevated intake of Cd, Cu, Hg and Pb by cows and sheep. At 10 sites daily intake levels of As by cows exceeded threshold concentrations regarding the quality of animal products. The food chain model also was used inversely to derive soil threshold concentrations in view of EU fodder standards. Calculated threshold levels in soil for As, Cd, Cu, Pb, Hg and Zn appear to be in line with those proposed or used in other EU countries. As such the approach applied here can form a conceptual basis for a more harmonized risk assessment strategy regarding the protection of animal and human health. --------------------------------------------------------------------------------