Terrestrial environment

Effects of two sludge application on fractionation and phytotoxicityof zinc and copper in soil

HE Miao-miao , TIAN Guang-ming , LIANG Xing-qiang , YU Yi-tong , WU Jian-yang , ZHOU Gen-di


Received January 23, 2007,Revised August 26, 2007, Accepted , Available online

Volume 19,2007,Pages 1482-1490

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The potential harm of heavy metals is a primary concern in application of sludge to the agricultural land. A pot experiment was conducted to evaluate the e ect of two sludges on fractionation of Zn and Cu in soil and their phytotoxicity to pakchoi. The loamy soil was mixed with 0%, 20%, 40%, 60% and 80% (by weight) of digested sewage sludge (SS) and composted sludge (SC). The additions of the both sludges caused a significant raise in all fractions, resulting in that exchangeable (EXCH) and organic matter (OM) became predominance for Zn and organic bound Cu occupied the largest portion. There was more available amount for Zn and Cu in SS treatments than SC treatments. During the pot experiment, the concentration of Zn in EXCH, carbonate (CAR) and OM and Cu in EXCH and OM fractions decreased in all treatments, so their bioavailability reduced. Germination rate and plant biomass decreased when the addition rate was high and the best yield appeared in 20% mixtures at the harvest of pakchoi. The two sludges increased tissue contents of Zn and Cu especially in the SS treatments. Zn in pakchoi was not only in relationship to EXCH and CAR forms but also in OM forms in the sludge-soil mixtures. Tissue content of Cu in pakchoi grown on SC-soils could not be predicted by EXCH. These correlation rates between Zn and Cu accumulation in pakchoi and variation of di erent fractions increased with time, which might indicate that sludges represented stronger impacts on the plant in long-term land application.

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