三峡库区内陆腹地典型水库型湖泊中DOM吸收光谱特征

溶解性有机质(DOM)是湖泊生态系统重要组成部分,其性质和结构决定了其在污染物(例如汞)环境行为中扮演着重要角色.本研究选取三峡库区内陆腹地典型水库型湖泊——长寿湖,采用吸收光谱表征方法,通过1年时间对DOM地球化学变化规律进行了定性定量分析,并结合汞观测数据,讨论了DOM对不同形态汞浓度的影响.结果表明,和1月相比,长寿湖4~11月DOC差异性低于CDOM,4~11月间差异性不显著.有色组分变化是解释DOM季节性变化的重要原因.DOM中主要生色团仍然来自于大分子量的芳香性组分.而CDOM三波长模型可较好对DOC的年际观测进行反演.同时,SUVA254和S275~295季节性变化特征较明显,1月芳香性和分子量均最小,4月上升.与其他类型湖泊相比,长寿湖水体DOM芳香性和分子量大小均低于森林湖泊,但高于高原湖泊.周边生态系统和土地利用类型对湖泊DOM差异影响明显.另外,SUVA254和DOC与各形态Hg无明显相关性,但水体生色组分和分子量大小是控制溶解态和活性汞的重要因素;而湖区甲基汞变化可能与湖泊初级生产力导致的有机质富集和迁移关系密切.

Absorption Spectral Characteristic Dynamics of Dissolved Organic Matter (DOM) from a Typical Reservoir Lake in Inland of Three Gorges Reservoir Areas: Implications for Hg Species in Waters

Dissolved organic matter (DOM) is an important component in lake eco-systems. It plays a crucial role in the environmental fate of pollutants such as mercury(Hg), because of its specific characteristics and functional structures. In this study, a typical reservoir lake from inland of Three Gorges Reservoir areas, Changshou Lake was selected to track the changes of DOM geochemical properties for one year by using UV-Vis absorption spectroscopy technique. Meanwhile, based on observed Hg data in Changshou Lake, it further validated the key environmental implications of DOM for Hg distributions in lake. The results showed that as compared to January, other months including April, June and September had significantly higher CDOM, but also higher DOC with a slightly decreasing significance. Dynamics of chromphoric component is an important reason to explain the seasonal changes of DOM concentration in Changshou Lake. Chromphores of DOM were mainly derived from high molecular weight (MW) materials with high aromaticity. Also, three wavelengths fitting model of CDOM could be used for inversion of DOC concentration in annual monitoring. Meanwhile, seasonal differences of SUVA₂₅₄ and S_275-295 were significant. Lowest aromaticity and MW size were observed in January following an obvious increase from April. In contrast to other types of lakes, DOM aromaticity and MW size in Changshou Lake were lower than forest lakes, but higher than plateau lakes. Eco-system and land use types surrounding lakes could have a heavily impact on the heterogeneous properties of DOM. Importantly, no clear differences between concentrations of Hg species and SUVA₂₅₄ and DOC respectively were observed, however chromphoric component and MW size controlled the dissolved Hg and reactive Hg in lake. Additionally, enrichment and migration of organic matter resulted from primary productivity in lake may be a substantial reason to explain the methylmercury changes.