Speciation of Cu and Zn in Drainage Water from Agricultural Soils

Abstract

Inputs of copper and zinc from agricultural soils into the aquatic system were investigated in this study, because of their heavy agricultural usage as feed additives and components of fertilizers and fungicides. As the mobility and bioavailability of these metals are affected by their speciation, the lipophilic, colloidal and organic fractions were determined in drainage water from a loamy and a humic soil treated with fungicides or manure. This study therefore investigates the impact of agricultural activity on a natural environment and furthers our understanding of the mobility of metals in agricultural soils and aquatic pollution in rural areas. Marked increases in the total dissolved metal concentrations were observed in the drainage water during rain events with up to 0.3 microM Cu and 0.26 microM Zn depending on the intensity of the rainfall and soil type. The mobile metal fractions were of a small molecular size (<10 kD) and mainly hydrophilic. Lipophilic complexes originating from a dithiocarbamate (DTC) fungicide could not be observed in the drainage water; however, small amounts of lipophilic metal complexes may be of natural origin. Cu was organically complexed to > 99.9% by abundant organic ligands (log K 10.5-11.0). About 50% of dissolved Zn were electrochemically labile, and the other 50% were complexed by strong organic ligands (log K 8.2-8.6). Therefore very little free metal species were found suggesting a low bioavailability of these metals in the drainage water even at elevated metal concentrations.

Soil factors affecting solubility and mobility of zinc in contaminated soils

“…Increasing content of SOC can increase the formation of organic metal complexes, while the solubility of metals may also increase (Aldrich et al 2002). The introduction of soil organic carbon into the model for free Zn 2?…”

Hydroclimatic control of sediment and metal export from a rural catchment in northwestern Spain

“…Thus, Al, Fe and Mn are abundant in earth's crust and relatively insoluble under oxidizing conditions in surface water (Förstner and Wittmann, 1981). Because of this, they are strongly dominated by the particulate phase while Cu and Zn are less abundant in natural environments and have high affinity for chelation to organic ligands, which favors their presence in the dissolved phase Aldrich et al, 2002;Miller et al, 2003).…”

Atributos químicos de Latossolo após sucessivas aplicações de composto orgânico de dejeto líquido de suínos

“…No entanto, também pode ocorrer o aumento dos teores de metais pesados no solo, como Cu e Zn Mattias et al, 2010;Basso et al, 2012;Popovic & Jensen, 2012;Tiecher et al, 2013), remanescentes de rações consumidas pelos suínos. Isso porque em torno de 90% do Cu e do Zn ingeridos pelos suínos por meio dos suplementos minerais são excretados nas fezes e na urina, estando presentes nos dejetos (Aldrich et al, 2002;Nicholson et al, 2003). Dessa forma, aplicações sucessivas de resíduos orgânicos, muitas vezes com suprimento de nutrientes acima das necessidades das culturas, podem promover acúmulos excessivos de nutrientes, como N, P, Cu e Zn, no solo, o que potencializa a transferência desses elementos por escoamento superficial e percolação, e, consequentemente, contamina mananciais de águas superficiais e subsuperficiais (Bergström & Kirchmann, 2006;Ceretta et al, 2010b;Girotto et al, 2013).…”