汉江下游河水-地下水交互带中地下水水化学和氮分布特征

Distribution of Nitrogen and Water Chemistry in River-groundwater Interaction Zone in the Lower Reaches of Han River

河水-地下水交互带被称为生物过滤器,对氮等污染物有截留净化功能。为研究汉江下游河水-地下水交互带氮的分布特征,本文设立了3个剖面和9口钻井,采集沉积物和地下水样品并进行测试。结果表明,在样品采集期间交互带剖面1河水补给地下水,剖面2地下水补给河水,剖面3河水和地下水水位持平。交互带地下水pH整体上呈中性,主要水化学类型为HCO_(3)-Ca型,处于缺氧或厌氧的还原环境,地下水硝态氮0.02~0.22 mg/L,亚硝态氮小于0.02 mg/L,小于Ⅰ或Ⅱ类地下水氮的浓度限值,位于农田的1-2井氨氮1.93 mg/L,符合Ⅴ类地下水氨氮浓度限值,而其它8口井氨氮0.01~0.32 mg/L,小于Ⅲ类地下水氨氮浓度限值。交互带沉积物pH呈中性偏弱碱性,1-2钻井不同深度沉积物氨氮0.05~2.45 mg/kg,其它钻井沉积物氨氮0.03~0.34 mg/kg。这些结果表明农业氮肥是导致交互带高氨氮的主因,但是影响范围比较有限。此外,交互带中氨氮主要以交换态铵氮存在,溶解态氨氮占比较少。

The river water-groundwater interaction zone is called as a biological filter,which has the function of intercepting and removing nitrogen and other pollutants. Hence,3 sections and 9 boreholes were set up in the lower reaches of the Han River to collect and analyze sediment and groundwater samples and to discover the distribution characteristics of nitrogen in the interaction zone between river water and groundwater. The results showed that the water level of the river and groundwater in profile 1 was recharged by river water,and profile 2 was opposite to profile 1,but in profile 3 river water and groundwater level was almost the same during the sampling period. The groundwater pH in the interaction zone was generally neutral,and its main water chemical type was HCO_(3)--Ca,,which was in anoxic or anaerobic reducing environment;nitrate-nitrogen was 0. 02-0. 22 mg/L,and nitrite-nitrogen was less than 0. 02 mg/L,which was less than the nitrogen concentration limits of the class I or II groundwater;The ammonia-nitrogen of the well 1-2 located in a farmland was 1. 93 mg/L,and it fitted the nitrogen concentration limit of the class V groundwater,while the ammonia-nitrogen of the other8 wells was 0. 01-0. 32 mg/L which was less than the nitrogen concentration limit of the Class III groundwater. The pH of the sediments in the interaction zone was neutral to slightly alkaline. The ammonia-nitrogen of the sediments at different depths in the drilling 1-2 was0. 05-2. 45 mg/kg,but the ammonia-nitrogen of other drilling sediments was 0. 03-0. 34 mg/kg. These results indicate that agricultural nitrogen fertilizer was the main cause of high ammonia in the interaction zone,but its influencing zone was relatively limited. In addition,the ammonia nitrogen in the interaction zone mainly exists as exchangeable ammonium-nitrogen,and the dissolved ammonia-nitrogen accounts for much less level.