AGW01 Long-term measurement of groundwater physical and chemical properties from wells on watershed N04D at Konza Prairie

In 1988 and 1990, the U.S.Geological Survey, Lawrence, KS, drilled 31 wells at 20 sites within the N04D watershed at the Konza Prairie Research Natural Area. The wells range in depth from about 2 to 13 meters, and are nested to include wells completed in alluvium/colluvium near the N04D drainage and in two Permian-aged limestone’s. In 1997, Konza LTER drilled an additional 4 wells at 3 sites, that range in depth from about 12 m to 37 m. The sites comprise four transects running approximately east-west across the drainage, and occupy the lower one-quarter of the surface area of the watershed. The geology of the area is characterized by patchy, near-stream alluvium/colluvium which overlies bedrock that is composed of thin (1-2 meter) limestones alternating with thicker (2-4 meter) shales. Beginning in 1990, water levels were measured and water samples collected quarterly. Since 1991, water levels have been measured and water samples for inorganic chemical analysis have been collected every four to six weeks; sample collection is by bailing wells after removing 1-2 well volumes of groundwater. The groundwater is then filtered through 0.45 micro; membrane filters by gravity feed or using a peristaltic pump. One 250-mL LDPE bottle is filled with 250 mL of sample and 5 mL of concentrated HNO3 for determination of major and minor cation concentrations. One 250-mL LDPE bottle is filled to the brim for anion determination by ion chromatography and alkalinity determination by titration with 0.02 N H2SO4. The bottles are stored on ice and later in a refrigerator.1988年与1990年，美国地质调查局（U.S. Geological Survey）堪萨斯州劳伦斯市分部在康扎草原自然研究区（Konza Prairie Research Natural Area）的N04D流域内的20个点位钻取了31口监测井。这些监测井的井深范围约为2至13米，采用嵌套式布设结构，涵盖了在N04D排水沟附近冲积层/坡积层中完钻的井，以及二叠纪灰岩地层中的两口井。1997年，康扎长期生态研究站点（Konza LTER）在3个点位额外钻取了4口井，井深范围约为12米至37米。这些点位包含四条大致沿东西向横跨该排水沟的样带，占据该流域地表面积的下游四分之一区域。该区域的地质特征为：溪流周边分布不均的冲积层/坡积层覆盖于基岩之上；基岩由厚度1~2米的灰岩与厚度2~4米的页岩互层构成。自1990年起，研究人员每季度开展一次水位测量并采集水样；1991年起，水位测量频率保持不变，而用于无机化学分析的水样采集频率调整为每4至6周一次，水样采集前需先抽排1至2倍井容的地下水，再通过舀取方式获取样品。随后，采集的地下水经重力过滤或使用蠕动泵通过0.45微米微孔滤膜进行过滤。取一只250毫升低密度聚乙烯（LDPE）瓶，装入250毫升水样与5毫升浓硝酸（HNO3），用于测定水体中主要与次要阳离子的浓度；另取一只250毫升LDPE瓶装满水样，用于通过离子色谱法测定阴离子浓度，以及通过0.02当量硫酸（H2SO4）滴定测定碱度。所有样品瓶均先置于冰上暂存，随后转移至冰箱冷藏保存。