长江中游典型河湖湿地主要水环境问题及生态环境地质风险评价区划

The Main Water Environmental Issues and Assessment-zonation of Eco-environmental Geology Risks for Typical River-lake-wetland Systems in the Central Yangtze River

为查明长江中游河湖湿地主要生态环境地质问题,选取鄱阳湖、洞庭湖、丹江口库区官山河流域等典型工作区开展了综合地质调查。从区域、流域尺度查明工作区主要水环境问题、评估官山河生态环境地质风险是项目主要任务之一,结果表明:(1)江汉-洞庭平原及鄱阳湖平原赋存区域性原生高砷、铵、铁、锰地下水,鄱阳湖平原发育高碘地下水;江汉-洞庭平原出现高磷地下水;Fe(Ⅲ)还原溶解是高砷、磷地下水形成的主要过程,微生物介导的有机质降解是高铵、磷、碘地下水形成的主要因素;土壤N、生活污水和化肥是鄱阳湖平原地下水硝酸盐主要来源;在洞庭湖平原,受污染的地下水向地表水排泄增加了后者污染物载荷,潜在的导致地表水污染。(2)官山河流域地表水体总氮、总磷浓度多劣于Ⅲ类水质标准,导致水质劣于Ⅲ类标准,有机氮对总氮贡献较大;其子流域存在不同等级的土壤侵蚀、地质灾害、人为污染、饮用水源、水环境、水生态、水生境风险。上述成果提升了典型河湖湿地区地质调查工作精度,为长江中游生态环境保护修复及水资源管理提供科学依据,支撑了长江大保护与长江经济带战略。

To reveal the main eco-environmental geological issues of the typical river-lake-wetland systems in the central Yangtze River, this program performed a comprehensive geological survey in the Poyang Lake,Dongting Lake, and Guanshan River Catchment of Danjiangkou reservoir. One of the primary objectives of this program is to discover the major water environmental issues of the survey areas and assess the ecoenvironmental geology risks in the Guanshan River Catchment from both the river basin and regional scales. The obtained results show that(1) regional geogenic high content of As, NH, Fe, and Mn have been detected in the groundwater in the Jianghan-Dongting and Poyang Lake plains, and groundwater with elevated I and P content have also been detected in the Poyang Lake and Jianghan-Dongting plains;Fe(Ⅲ)reduction is the primary mechanism responsible for genesis of the high As and P content in the groundwater,and microbial degradation of organic matter could be an important contribution for enrichment of NH_(4)^(+), P,and I in the groundwater;soil N, domestic wastewater, and chemical fertilizer are probably the major sources of groundwater NO_(3)^(-) in the Poyang plain;contaminated groundwater that discharged into the surface water would increases the contaminant loadings and, hence potentially causes contamination of the latter in the Dongting plain;(2) for the Guanshan River Catchment, the total N and P concentrations in surface water are frequently higher than the limit of level Ⅲ value of the Surface Water Environment Standards, leading the water fail to reach the level Ⅲ Standard, in which organic N should have largely contributed to the total N loadings;the sub-catchments are characterized by variation of assessed risks concerning soil erosion,geological hazards, anthropogenic contamination, drinking water source, water environment, water ecology,and water habitat. The results of this study have enhanced the precision of geologic survey in this typical riverlake-wetland systems, providing the scientific basis for ecology conservation and recovery as well as water resource management and, furthermore, supporting the ‘The Yangtze River Protection’ and ‘Yangtze River Economic Belt’ strategies.