The Assessment Of Heavy Metal Safety Of Urban Sewage Irrigated Farmlands

In order to study the effect of heavy metal on agriculture environment and the quality of agriculture products in those farmlands with urban sewage irrigation and to supply some techniques on the reuse of sewage water to farmlands . From 2003 to 2005, Jiaozhou sewage irrigated regions were investigated and 90 samples including 15 water samples, 45 soil and 30 crops samples weres analyzed for 32 indices, and GB15618-1995 , NY/T395-2000 was compared as the evaluation standard. The results were as following:1, In the sewage irrigated farmlands,except the Pb, ? the contents of the other heavy metals were obviously higher. Among of them, only in one sampling site, the contents of the Cr and Ni were above national secondary soil quality . And the contents of those eight heavy metals showed decrease from the higher to the lower reaches, and especially for Hg, Cd, Cr and Zn.2. In the sewage irrigated farmlands, the average of Hg content was 0.196mg/kg, and variance of the content of Hg was existed between the sampled sites, and the highest was 1.27times the lowest sites, and the same trendy was found between the three sampling stage.3. In the sewage irrigated farmlands, the average of Cd content was 0.209mg/kg, and higher than the control farmlands, and the change range of Cd was smaller than that ofHg.4. As average content was 7.40mg/kg in the soil of back-irrigation regions, which was lower than the background value of Qingdao and whole country. The change of As content was small in the soil of the demonstrate area, and the differ value was only 49.13% between the highest and the lowest. The As-content had no obvious district...