Leaching of Copper and Zinc in a Garden Soil Receiving Poultry and Livestock Manures from Intensive Farming

The leaching characteristics of a garden soil may be greatly affected by application of poultry and livestock manures from intensive farming. Packed soil columns of a garden soil (CK) and the soils after respectively receiving 2% pig manure (PM), chicken manure (CM), and commercial organic manure (OM) were leached with 0.05 mol L−1 Ca(NO3)2 and 0.01 mol L−1 EDTA solutions. The leachate EC (electric conductivity) values gradually increased at the beginning and then reached a stable value when the soil columns were leached with 0.05 mol L−1 Ca(NO3)2 solution. The leachate EC values showed a peak-shape when leached with 0.01 mol L−1 EDTA solution. In all the soil columns, the pH values of the leachates decreased with increase of displacement volumes when the Ca(NO3)2 solution was used. The total amounts of Cu and Zn eluted from the four soil columns were significantly correlated with the extracted soil Cu and Zn concentrations by 1.0 mol L−1 NH4NO3, but were not correlated with the leachate dissolved organic carbon (DOC) contents. The Zn concentration in the leachate of the PM-treated soil column with 0.05 mol L−1 Ca(NO3)2 solution was above the Quality Standard III for Ground Water of China (GB/T 14848-93, Zn < 1.0 mg L−1). When compared with 0.05 mol L−1 Ca(NO3)2, the EDTA solution significantly accelerated Cu and Zn elutions in the manure-treated columns. This suggested that applying poultry and livestock manures from intensive farming to farmland might pose a threat to the groundwater quality.