桂林五里峡水库丰水期溶解有机碳特征

为更全面、准确把握岩溶碳循环特征,本文在获取桂林五里峡水库丰水期水化学及溶解有机碳(DOC)分布特征的基础上,还借助紫外吸收光谱技术对水体有机质分子量大小等进行分析.结果表明,五里峡水库丰水期水化学类型仍为HCO_3-Ca·Mg型,水体营养状态为中等营养型,未达到富营养状态;五里峡水库丰水期DOC质量浓度比枯水期低,DOC为TOC的主要组成部分,DOC质量浓度在垂直方向上呈表层至底层降低的趋势,这是Chl-a、DIC等水环境因子综合影响的结果;S_(275~295)、M、SUVA_(254)、E_(253)/E_(203)吸收光谱特征参数表征下的库区水体有机质以小分子量物质为主,富里酸所占比例高,腐殖酸所占比例低,芳香性较弱,苯环上脂肪族等非极性官能团含量较多,表明库区水体DOC内源特征较强,有机质生物活性较好,在水库碳循环中发挥了积极作用.

Water Chemistry and Characteristics of Dissolved Organic Carbon During the Wet Season in Wulixia Reservoir, SW China

In recent years, scientists have focused on the karst carbon cycle. To better understand the hydrochemical characteristics and the physical-chemical properties of DOC in the wet season in karst areas, the water chemistry and DOC distribution characteristics in Wulixia reservoir were analyzed. The molecular weight of the water organic matter was analyzed based on the UV absorption spectrum. The results showed that the water chemistry of Wulixia reservoir was HCO₃-Ca ·Mg, the nutrient status of the water body was of the medium nutrient type, and the water maintained a good quality. The DOC mass concentration was lower in the wet season than in the dry season, and DOC was the main component of TOC. The DOC mass concentration tended to decrease from the surface to the bottom in a vertical direction. Chl-a and DIC were the main factors affecting the DOC vertical distribution. The organic matter in the reservoir area related to the absorption spectrum parameters of S_275~295, M, SUVA₂₅₄, and E₂₅₃/E₂₀₃ showed that the water was dominated by constituents with small molecular weight, a high proportion of fulvic acid, low proportion of humic acid, and weak aroma. The results showed that the organic matter in the reservoir area was readily consumed by microbial bioactivity and that it played an active role in the carbon cycle of the reservoir. It also showed that the DOC endogenous characteristics of the reservoir were strong and provided a sufficient carbon source for heterotrophic microbes.