辽河流域河流秋季CDOM光学特性及影响因素研究

了解有色溶解有机物(CDOM)的光学特性有助于对水生生态系统中溶解有机物(DOM)循环过程的研究,而环境要素对CDOM光学特性的影响会进一步影响水环境中的碳循环过程.利用2013年9月和10月辽河水体实测数据对水体反射特性、CDOM的吸收特性、荧光特性及各种水质参数对CDOM光学特性的影响进行研究.结果表明,辽河流域河流总氮(均值4.40 mg·L~(-1))、铬浓度(均值0.0065 mg·L~(-1))超过国家地表水V类标准.悬浮泥沙光谱特征较为明显的水样,其CDOM的吸收曲线非常相近,叶绿素a光谱特征较为明显的水样,其CDOM吸收曲线之间的差别较大.辽河流域水体CDOM的吸收斜率S275-295(0.0163~0.0191 nm-1)高于其他大多数河流,而低于湖泊、水库.对比辽河流域河流发现,东辽河与辽河水体CDOM组成物质的分子量相对较小,东辽河CDOM的芳香性最高,而西辽河最低.根据荧光指数、腐殖化指数及生物源指数分析发现,辽河流域水体主要以陆源的、高等植物DOM为主,太子河、大凌河CDOM具有较为明显的自生源特征.通过荧光峰的分布发现,辽河水体CDOM以类腐殖酸荧光峰(A峰、C峰)为主,部分河流(辽河干流)同时表现出较强的类蛋白质荧光峰(B峰、T峰).通过冗余分析(RDA)发现,水体中溶解有机碳(DOC)、总氮(TN)、总磷(TP)、总碱度(TAlk)、砷(As)及汞(Hg)与表征CDOM光学特性的参数之间存在显著的相关性(p0.05),是CDOM光学特征的主要影响因子.

CDOM optical characteristics and influences factors affected on them for rivers in Liaohe River watershed in autumn

Understanding the optical characteristics of chromophoric dissolved organic matter (CDOM) could help to study dissolved organic matter (DOM) cycling in aquatic ecosystems. In addition, environmental factors affected CDOM optical characteristics and resulted in influencing carbon cycle in aquatic environment. The spectral reflectance characteristics of riverine waters, CDOM absorption and fluorescent characteristic as well as environmental factors were analyzed for water samples collected in September 2013 and October 2014, respectively. Results showed that the water quality of Liaohe River watershed exhibited great variation. The concentrations of total nitrogen (TN, 4.40 mg·L^-1) and total dissolved chromium (0.0065 mg·L^-1) exceeded the GB3838-2002 (national quality standards for surface waters, China) standard for Class V waters of 2.0 mg·L^-1 and 0.005 mg·L^-1, respectively. Comparatively, samples with obvious characteristics of suspended sediments exhibited similar CDOM absorption curves while samples with obvious characteristics of chlorophyll a showed great differences. Values of S_275-295 obtained in this study, ranging from 0.0163 to 0.0191 nm^-1, were higher than many other rivers but lower than lakes and reservoirs. Relative lower molecular weight substances of CDOM in the East Liaohe River and the stem of Liaohe River were obtained compared with the other rivers. The SUVA₂₅₄ showed that the aromaticity of CDOM in the East Liaohe River was higher while the West Liaohe River was lower than the others investigated. According to fluorescence index (FI), the index of recent autochthonous contribution (BIX) and humification index (HIX), CDOM were mainly from terrestrial (allochthonous) substances and DOM originating from higher plants. However, CDOM in Taizihe and Dalinghe were derived from autochthonous substances. The humic-like and protein-like peaks were all observed in fluorescence excitation-emission matrices. Most samples exhibited fairly strong humic-like fluorophores (peak A and C) and number of samples showed strong protein-like fluorophores (peak B and T) at the same time. Redundancy analysis (RDA) indicated that dissolved organic carbon, TN, total phosphorus, total alkalinity, total dissolved arsenic and mercury concentrations strongly correlated with parameters that explained optical characteristics (p<0.05) and were the main factors affected CDOM characteristics.