[Bioconcentration and translocation of Cu and Zn by Brassica sinensis L. planted in high Cu and Zn contaminated pig manure-applied soils].

In recent years, Cu and Zn have been widely used in pig fodders in large-scale animal feeding, causing Cu and Zn contamination in soils and effecting plants in land application of pig manure. It is of great concern to the world that pig manure is used in the dose greater than the organic fertilizer criterion. It is very important to clarify bioconcentration and translocation of Cu and Zn in vegetables in order to assess human health risk of these heavy metals accumulated in soil and to safely produce vegetables. Bioconcentration and translocation of Cu and Zn by Brassica sinensis L. planted in pig manure-applied soils were studied using pot experiments. Pig manure with great concentrations of Cu and Zn (Cu = 1114.7 mg x kg(-1), Zn = 1496.8 mg x kg(-1)) were applied to soils at six rates, i.e., 0, 25, 50, 100, 200 and 500 t x hm(-2). The results indicate that the concentration of Zn was greater than that of Cu in both aboveground and underground parts of B. sinensis. Both Cu and Zn concentrations in the underground part were greater than those in upper-ground for every treatment. There were significant differences for both Cu and Zn concentrations in shoots between CK and the treatment with application rate above 50 t x hm(-2). Bioconcentration factor of Cu in B. sinensis increased with pig manure application rate from 0.11 to 0.17, while that of Zn decreased from 0.47 to 0.11. The proportion of Cu and Zn transported from roots to shoots decreased 25% and 38% with the increase of pig manure application, respectively. It indicates that pig manure application can reduce bioconcentration of Zn in B. sinensis, and build up Cu accumulation which leads to human health risk. The ratio of Zn:Cu in every part of B. sinensis decreased with manure application rate increment. This result prompted that uptake and translocation capacity discrepancy of Cu and Zn decreased with manure application rate increment in B. sinensis.