涪陵页岩气开发区域地下水环境质量研究

STUDY ON THE GROUNDWATER ENVIRONMENT QUALITY IN FULING SHALE GAS FIELD

页岩气开发带来巨大的经济效益的同时,也带来了许多环境风险,如地下水污染等。为了准确评估页岩气开发对地下水的影响,有必要对页岩气开发前的水文地质情况、地下水地球化学特征及主要污染源进行调查,以及对页岩气开发前后的地下水环境质量进行监测。从调查结果来看,涪陵区块地下水与地表水转化频繁,地下水以HCO3·SO4-Ca水型为主,其p H为7.21~7.38,平均矿化度549.8 mg/L,平均硬度为383.8 mg/L;页岩气开发前地下水污染源主要为生活污染源、农业污染源;从监测结果来看除p H、硬度、硫酸盐含量、氯化物含量、高锰酸盐指数和氨氮指数等6个参数外,其余指标均在检出线内;从评价结果来看,单项组分评价法和综合评价法的评价结果表明页岩气开发对地下水环境质量有一定影响,但开发区的地下水水质均未超过III类水质标准,对地层地下水位影响也较小。

Shale gas development brings huge economic benefits,but it also brings a lot of environmental risks,such as the regional groundwater pollution. In order to accurately evaluated the groundwater environment quality of fuling shale gas field,it is necessary to know the conditions before shale gas developing, such as hydrogeological characteristics, geochemical characteristics of groundwater,main pollution sources. And then ground water quality is monitored during the process of shale gas development. According to investigation results,groundwater and surface water exchange frequently,and is dominated by HCO3·SO4-Ca type,its p H value is 7. 21 ~ 7. 38,average mineralization degree is 549. 8 mg/L,average hardness is383. 8 mg/L. Groundwater contamination comes from domestic pollution and agricultural pollution before shale gas development. The monitor results show that all indicators' value are below the assessment standard,except for p H value,water hardness, sulfate content, chloride content, permanganate index, ammonia nitrogen index. The groundwater environmental quality is used to evaluate by single factor assessment and multi-factors integrated evaluation. The evaluation results show the water quality has been influenced by shale gas development,but it belongs to class III water quality. It is also less impact on the formation of groundwater level.