title: Relationship between organic matter humification and bioavailability of sludge-borne copper and cadmium during long-term sludge amendment to soil.
abstract: Recycling of sludge as soil amendment poses certain risk of heavy metals contamination. This study investigated the relationship between organic matter in composted sludge and its heavy metals bioavailability over 7years. Periodic monitoring indicated a gradual increase in organic matter degradation, accompanied by changing degrees of polymerization, i.e., ratio of humic acid (HA)/fulvic acid (FA) coupled with incremental exchangeable fraction of copper (Cu) in sludge, with a growing rate of 74.7%, rather than that in soil. However, cadmium (Cd) in composted sludge exhibited an independent manner. Linear-regression analysis revealed that the total proportion of the Cu active fraction (exchangeable plus carbonate bound) was better correlated with the degree of polymerization (DP) and humification ratio (HR) than the degradation ratio of organic matter. Overall, amount of uptaken Cu was more dependent on the humification degree of organic matter, especially the proportion of HA in humus.
authors.affiliation: Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, PR China. Electronic address: liuht@igsnrr.ac.cn.
authors.forename: Hongtao
authors.initials: H
authors.lastname: Liu
mesh_terms: D000383:Agriculture; D001578:Benzopyrans / Q000737:chemistry; D001673:Biodegradation, Environmental; D001682:Biological Availability; D002681:China; D000076282:Composting; D006812:Humic Substances; D019216:Metals, Heavy / Q000737:chemistry*; D009930:Organic Chemicals / Q000737:chemistry*; D012621:Seasons; D012722:Sewage / Q000032:analysis*; D012989:Soil Pollutants / Q000737:chemistry*
chemical_list: D001578:Benzopyrans; D006812:Humic Substances; D019216:Metals, Heavy; D009930:Organic Chemicals; D012722:Sewage; D012989:Soil Pollutants; C005023:fulvic acid
keywords: Cadmium; Copper; Degree of polymerization (DP); Fraction; Organic matter; Sludge