Effect of molecular weight of dissolved organic matter on toxicity andbioavailability of copper to lettuce
Xudong Wang , Xianni Chen , Shuai Liu , Xizu Ge
DOI:
Received October 29, 2009,Revised March 06, 2010, Accepted , Available online
Volume 22,2010,Pages 1960-1965
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To clarify the e ects of molecular weight of dissolved organic matter (DOM) on the toxicity and bioavailability of copper (Cu) to
plants, DOM extracted from chicken manure was ultra-filtered into four fractions according to their molecular weights by means of
sequential-stage ultrafiltration technique. Lettuce seeds were germinated by being exposed to the solutions containing Cu2+ with or
without di erent fractions of DOM. The concentration of copper in roots, leaves, sprouts and the length of roots were investigated. The
results showed that not all fractions of DOM could improve copper availability or toxicity. The fraction of DOM with larger molecular
weight more than 1 kDa had higher complexation stability with Cu2+ and caused lower concentration of free Cu2+ ion in the solution of
copper plus the fraction, resulting in lower availability and toxicity of copper to lettuce, but the fraction with molecular weight less than
1 kDa had the opposite function. Therefore, the molecular weight of 1 kDa may be the division point to determine DOM to increase or
decrease copper availability and toxicity.
