摘要
再生水与天然地下水水质存在差异,利用再生水生态补给河道区可能会带来环境风险.引温济潮工程已运行10余年,为研究再生水长期河道入渗下不同位置地下水氮组分的演化特征与机制,收集近11年的地表水与地下水监测资料.采用聚类分析将地表水划分为不同区域后选择典型地下水监测点分析氮组分的演化差异,并利用Cl-计算混合比得出地下水中目标成分的计算浓度,初步推测地表水入渗后发生的氮转化,并选取DO、TOC、底泥、水文地质条件等环境指标分析证明.结果表明:①地表水明显分为3组,包括减河、土坝以北潮白河段、土坝以南潮白河段,各组间指标存在显著差异,影响水质差异的主要因素为再生水的氮、磷含量及水体流态.②再生水入渗过程中,包气带或黏土层较厚有利于氮的去除,减河和土坝以北潮白河段地表水中的NO_(3)^(-)-N流经包气带时通过反硝化与同化作用衰减,NH_(4)^(+)-N通过吸附与硝化作用得以去除,入渗后未引起地下水中的氮浓度明显增加.③而土坝以南潮白河段,河道补水后翌年地下水位抬升并趋于稳定,长期地表水入渗使底泥的氮和有机质含量升高,使得该断面于2013年后达到适宜的碳氮比而发生有机氮矿化作用,由于包气带较薄,生成的NH_(4)^(+)-N较少吸附于土壤介质中,易随水流入渗而引起地下水中ρ(NH4+-N)升高.研究显示,再生水入渗过程中,包气带或黏土层较厚可有效去除氮组分,但部分地区包气带较薄且发生有机氮矿化作用会增加地下水的氮污染风险.
The utilization of reclaimed water to replenish river area may pose environmental risks due to the difference between reclaimed water and groundwater.The water diversion project from the Wenyu River to the Chaobai River has been in operation for more than 10 years.To investigate the evolution characteristics and mechanisms of nitrogen components in groundwater at different locations under long-term river infiltration of reclaimed water,the monitoring data of surface water and groundwater in 11 years were collected.Meanwhile,cluster analysis was conducted to divide the surface water into different regions and typical groundwater monitoring points were selected to reveal the evolution difference of nitrogen components.Cl-was used to calculate the mixing ratio and get the calculated concentration of the target components in groundwater,which can infer the nitrogen transformation after surface water infiltrating into subsurface.The environmental indicators such as DO,TOC,sediment,and hydrogeological conditions were also used to support the abovementioned results.The results showed that:(1)The surface water could be divided into three groups,including the Jian River,Chaobai River section in the north and that in south of the earth-filled dam.There were significant differences among the indicators of these three groups.The water quality difference was mainly affected by the nitrogen,phosphorous and water flow pattern of reclaimed water.(2)During the infiltration process of reclaimed water,the thicker vadose zone or the clay layer was conducive to nitrogen removal,NO_(3)^(-)-N in the surface water of the Chaobai River section to the north of earth dam and the Jian River decayed through denitrification and assimilation in vadose zone,and NH_(4)^(+)-N was removed through nitrification and adsorption.The infiltration process did not cause an obvious increase in groundwater nitrogen concentration.(3)However,in the Chaobai River section to the south of the earth-filled dam,the groundwater level rose rapidly and tended to be stable after one year of river water replenishment.The long-term infiltration of surface water increased the content of nitrogen and organic matter in the sediment,which made the section reach a proper carbon-nitrogen ratio after 2013 and led to organic nitrogen mineralization.Due to the thin aeration zone,the generated NH_(4)^(+)-N was less adsorbed in the soil,and consequently,most of NH_(4)^(+)-N would infiltrate into groundwater and result in the increase ofρ(NH_(4)^(+)-N).The results of this study indicated that in the infiltration process of reclaimed water,a thick aeration zone or clay layer could effectively remove nitrogen components.However,in some areas,the aeration zone was thin and organic nitrogen mineralization occurred,which increased the risk of nitrogen pollution of groundwater.
作者
夏绮文
李炳华
何江涛
黄俊雄
郭敏丽
XIA Qiwen;LI Binghua;HE Jiangtao;HUANG Junxiong;GUO Minli(Key Laboratory of Water Resources and Environment Engineering,School of Water Resources and Environment,China University of Geosciences,Beijing 100083,China;Beijing Engineering Technique Research Center for Exploration and Utilization of Non-Conventional Water Resources and Water Use Efficiency,Beijing Water Science and Technology Institute,Beijing 100048,China)
出处
《环境科学研究》
EI
CAS
CSCD
北大核心
2021年第3期618-628,共11页
Research of Environmental Sciences
基金
国家水体污染控制与治理科技重大专项(No.2018ZX07109-004)
丹麦与格陵兰岛地质调查局(No.17-M08-GEU)
国家自然科学基金(No.41730749)。
