TY - JOUR ID - 10.1016/S1001-0742(12)60042-4 TI - Investigation of low-molecular weight organic acids and their spatiotemporal variation characteristics in Hongfeng Lake, China AU - Min Xiao AU - Fengchang Wu AU - Liying Wang AU - Xinqing Li and Rongsheng Huang VL - IS - 2 PB - SP - 237 EP - 245 PY - JF - Journal of Environmental Sciences JA - J. Environ. Sci. UR - http://www.jesc.ac.cn/jesc_en/ch/reader/view_abstract.aspx?file_no=2013250201&flag=1 KW - Hongfeng Lake;low-molecular-weight organic acids;photochemical production;spatiotemporal variations;thermal stratification KW - Hongfeng Lake;low-molecular-weight organic acids;photochemical production;spatiotemporal variations;thermal stratification AB - The identities and concentrations of low-molecular-weight organic acids (LMWOAs) were determined by ion chromatography throughout a 20-m water column in Hongfeng Lake, China. The spatiotemporal variations of LMWOAs and their contributions to dissolved organic matter (DOM) in a research period of 24 hr were also investigated. The results demonstrated that five LMWOAs (lactic, acetic, pyruvic, sorbic, oxalic acid) were detected, and their total concentration and proportion in DOC were 6.55 μupmol/L and 7.47%. Their average levels were 2.50, 0.65, 2.35, 0.96 and 0.09 μupmol/L, respectively. LMWOAs were higher during daytime (10:00-18:00 on Jun 13, 2008) than nighttime (21:00-6:00 the next morning), in particular 4.99 μupmol/L high in the epilimnion (≤qslant 1 m water depth), reflecting the fact that direct import from terrigenous sources and photochemical production from humic materials were dominant during LMWOAs' origin and accumulation. The same factors caused LMWOAs to be 0.63 μupmol/L in the epilimnion higher than in the hypolimnion. The rapid decrease of total organic acid (TOA) up until 18:00 mainly resulted from bio-uptake and mineralization in the hypolimnion (>1 m water depth). Pyruvic acid increased with time in the epilimnion and decreased in the hypolimnion, largely related to the two contrary processes of continuous degradation and synthesis of macromolecular organic matter during life materials' cycle mediated by organisms. Simultaneously, plankton behavior and thermal stratification played a pivotal role in LMWOAs' behavior in the water column, causing decreasing and increasing profiles. The distribution of LMWOAs represents an interesting resource for biogeochemical research of DOM in aquatic ecosystems. ER -