Characteristics and distribution of low molecular weight organic acids in thesediment porewaters in Bosten Lake, China
Min Xiao , Fengchang Wu , Haiqing Liao , Wen Li , Xinqing Lee , Rongsheng Huang
DOI:
Received June 10, 2009,Revised October 26, 2009, Accepted , Available online
Volume 22,2010,Pages 328-337
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The composition and vertical profiles of low molecular-weight organic acids (LMWOAs) and the contribution of them to dissolved
organic matter (DOM) in sediment porewaters in Bosten Lake, Xinjiang, China were investigated. The results showed that total
concentration of LMWOAs was up to 94.5 mol/L and their proportion in DOM was 5.6%, suggesting that LMWOAs were
important chemical components in DOM in lake sediment porewaters. Among the seven LMWOAs, pyruvic and acetic acid had the
highest concentrations with 26.30 and 8.31 mol/L, accounting for 51.4% and 14.92% of LMWOAs, respectively. Trifluoroacetic
and sorbic acid had the lowest concentrations, indicating that the compositions of LMWOAs in relative reducing environments
were largely di erent from those reported in glacier, atmosphere and soils. The concentrations of lactic, acetic, formic, sorbic and
oxalic acid decreased with increasing depth, probably relating to stronger microbial activities in the initial stage of early diagenesis.
Trifluoroacetic acid was mainly anthropogenic with its concentration, showing a di usive trend from the surface to bottom sediments.
The concentrations of lactic acid and nitrate generally showed a consistent profile. The increasing concentration of pyruvic acid in the
vertical profile was just opposite to that of sulfate, revealing a significant negative relationship between them. Oxalic acid remained
constant except for an obvious peak at 6 cm depth. The results indicated the diversities in sources and behaviors for various LMWOAs
during early diagenesis in sediments.
