Characteristics of Heavy Metals in Chicken Manure Organic Fertilizers in the Huang-Huai-Hai Region and related Environmental Risk Assessment

Abstract

One hundred and twenty types of chicken manure organic fertilizer samples were collected from five provinces and two cities in the Huang-Huai-Hai region, to investigate heavy metal content, fractionation, and environmental risk through toxicity characteristic leaching procedures. Results showed that content of heavy metals in chicken manure organic fertilizer varied greatly, in the order of Zn > Cu > Pb > As > Cd. When compared with the standard for organic manure, ratios of Cd, As, and Pb exceeded the standard by 6.7%, 47.05%, and 14.28%, respectively. Moreover, the content of heavy metals varied significantly in different provinces. Cd and Zn in organic manure fertilizers were mainly Fe and Mn oxide-bound fractions, accounting for 37.3% and 43.79%, respectively. However, the proportion of residual fractions of Pb, organically-bound fractions of Cu, and exchangeable forms of As were higher. Contents of TCLP-Zn,-Cu,-Cd,-Pb and-As in organic manure were 41.11, 33.3, 0.07, 1.25, and 0.21 mg·kg-1, respectively. The number of samples in which Zn and Pb in organic manure exceeded the standard was 6 and 5, respectively, with these mainly obtained from Hebei and Jiangsu provinces. There was a significant correlation between total content of Zn, Cu, Cd, and As in organic manure and content of TCLP (P<0.05). Based on an annual manure application rate of chicken manure of 15 t·hm-2, safe application of chicken manure is in the order of Henan > Tianjin > Anhui=Shandong=Jiangsu > Hebei > Beijin.