Temporal and spatial variations of low-molecular-weight organic acids inDianchi Lake, China
Min Xiao , Fengchang Wu , Runyu Zhang , Liying Wang , Xinqing Li , Rongsheng Huang
DOI:
Received October 18, 2011,Revised January 08, 2011, Accepted , Available online
Volume 23,2011,Pages 1249-1256
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Low-molecular-weight organic acids (LMWOAs) in eutrophic lake water of Dianchi, Southwestern China Plateau were investigated
diurnally and vertically using ion chromatography. Two profiles (P1 and P2) were studied due to the difference of hydrochemical
features. Lactic, formic, pyruvic and oxalic acid were detected as major components at P1 and P2 which were on average 7.98 and
6.53 mol/L, respectively, corresponding to their proportions of 2.68% and 2.48% relative to DOC. Pyruvic acid was regarded as the
uppermost species at P1 and P2, reaching up to 3.82 and 3.35 mol/L and accounting for 47.9% and 51.3%, respectively, in individual
TOA. Although humus were of biogenetic production at both sites, the significant negative correlation between diurnal variations
of TOAs, fluorescence intensity (FI) of protein-like components and humic-like components at P1 indicated LMWOAs were greatly
originated from bacterioplankton excretion and degradation. However, correlations between diurnal variations of humic-like FI and
physicochemical parameters demonstrated algal origination of LMWOAs at P2. Although content of humus was high, TOA at P2 was
1.45 mol/L lower than that at P1, due to the co-influence of more intense photo-oxidation and aggregation at P2. Therefore, TOAs
exhibited quite opposite diurnal variation trends of increasing-decreasing and decreasing-increasing at P1 and P2, respectively. Except
for impact of solar radiation, bacterial decomposition and assimilation rendered shifts of maximal LMWOAs along water column at
P1. Covering with massive algae, UV rays penetrated shallower depth that LMWOAs assembled in surface layer water before 18:00 at
P2 and represented decreasing profiles.
