Premium
Binding of cadmium, copper, and zinc to humic substances originating from municipal solid waste compost
Author(s) -
Kaschl Arno,
Römheld Volker,
Chen Yona
Publication year - 2002
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1560/j3br-d8j6-8ju3-0vb9
Subject(s) - chemistry , compost , humic acid , cadmium , zinc , environmental chemistry , dissolved organic carbon , organic matter , metal , titration , trace metal , soil water , copper , humus , inorganic chemistry , nuclear chemistry , organic chemistry , soil science , fertilizer , agronomy , environmental science , biology
The application of municipal solid waste (MSW) compost increases both the trace metal loading and the organic matter in the soil. To characterize the quality and metal‐binding capacity of the compost OM, we extracted humic acid (HA) and fulvic acid (FA) from mature MSW compost and analyzed them for elemental composition, acid‐titratable functional groups, total metal content, and structural components (by 13 C NMR). HA constituted 67% of all extracted humic substances and differed significantly from HAs of cultivated lands: The compost HA exhibited smaller molecular size, a higher N content, and lower aromaticity due to large amounts of saturated aliphatic components. Metal complexation studies of the extracted HA and FA were performed by equilibrium dialysis titration. The complexing capacity (CC) was highest for Cu: CC HA = 3357 and CC FA = 5221 μmol Cu g −1 of dissolved organic carbon (DOC) at pH 5. Zn and Cd were bound (at pH 7) in smaller concentrations: CC HA (Zn) = 2167, CC FA (Zn) = 2809, CC HA (Cd) = 2386, and CC FA (Cd) = 2468 μmol metal g −1 of DOC. Stability constants for binding on the strongest sites (pK int ) were determined as pK int HA = 6.6 and pK int FA = 7.3 for Cu at pH 5; and pK int HA = 8.0 and pK int FA = 6.4 for Cd at pH 7. Since these measured parameters fall within the ranges of values obtained for soil humic substances, we conclude that in soils with little organic matter, compost addition will significantly increase the amount of highly reactive organic complexing agents for trace metals in the soil.