Transformation of [ 14C] and [ 35S]labeled lignosulfonates during soil incubation

Abstract

[ 14C] and [ 35S]labeled lignosulfonates (LS) or [ 14C]labeled coniferyl alcohol dehydropolymer (DHP) were aerobically incubated in soil for 17 weeks. Respiratory 14CO 2 was compared with that from DHP or that from [U 14C]cellulose. Less CO 2 was released from ring and side chain carbons of LS than from DHP, though similar amounts of CO 2 were released from the methoxyl groups of both compounds. After incubation, the soil samples were exhaustively extracted with water and then with a sodium pyrophosphate-NaOH solution. The water solubility of the originally completely-soluble LS carbons was greatly decreased by incubation, and a large portion of the extracted 35S was detected as sulfate. The pyrophosphate extract was separated into humic and fulvie acids. The humic acid from soils incubated with LS contained low 35S activity and a similar 14C activity to that from soils incubated with DHP. The fulvic acid from the soils incubated with LS contained higher amounts of 14C (and 35S) than that of the soils incubated with DHP. More side chain 14C activity than other 14C activity was found in both, the water extract and the fulvic acid from soils incubated with LS. The high 35S together with the high side chain 14C activity probably indicates an elimination of the side chain carbons together with sulfonic acid groups. Anaerobic incubation of soil with LS or DHP promoted breakdown and incorporation of LS and DHP into humus much less than aerobic incubation. The possible reduction in potential pollution from lignosulfonates due to the observed transformations in soil are discussed.