Pollinator Health in Southern Crop Ecosystems Research Unit-United States, Department of Agriculture-Agricultural Research Service, Stoneville, MS, 38776, USA.
Department of Mechanical, Environmental and Civil Engineering, Tarleton State University, Stephenville, TX, 76402, USA.
Environ Monit Assess. 2022 Jul 8;194(8):574. doi: 10.1007/s10661-022-10209-2.
Excessive organic matter and nutrients can depress dissolved oxygen concentration (DOC) in streams. The aim of this study was to understand the depressed DOC of Kickapoo Creek in Texas, USA, which is an impaired stream; identify the possible sources causing the depressed DOC and elevated Escherichia coli levels; and identify possible remedial measures. Monthly grab water quality data was monitored for nine stations in the watershed. For three of the nine stations, 24-h DOC was also monitored for a comparison with the minimum and average DOC criteria. Correlational, graphical, spatial, and temporal analyses were carried out for DOC concentration with other water quality variables which have the potential to depress DOC in the stream. The correlational analyses show a weak to moderate correlation for DOC with nutrient and oxygen-demanding substance concentrations present in the stream. However, there are spatial and temporal trends in DOC data that can be attributed to the nutrient influx into the stream. A pattern of increasing nutrient concentrations from upstream to downstream partially explains the decreasing dissolved oxygen (DO) concentrations observed towards the lower reaches. Visual interpretations of riparian vegetation and sediment influx also support the spatial patterns in DO concentrations. The majority of the depressed DOC occurs in the summer months when streamflow is at a minimum. The depressed DOC during summer is partially explained by the increasing daily temperatures for the summer months as revealed by the trend analysis of the daily temperature data from 1981 to 2020 using the modified Mann-Kendall test, Pettitt test, and Sen's slope.
过量的有机物和营养物质会降低溪流中的溶解氧浓度（DOC）。本研究旨在了解美国德克萨斯州基卡普克里克（Kickapoo Creek）受损溪流中 DOC 降低的原因，确定导致 DOC 降低和大肠杆菌水平升高的可能来源，并确定可能的补救措施。对流域内 9 个站点的每月水质数据进行监测。对于其中的 3 个站点，还对 24 小时 DOC 进行了监测，以与最低和平均 DOC 标准进行比较。对与可能降低溪流中 DOC 的其他水质变量的相关性、图形、空间和时间分析进行了分析。相关分析表明，DOC 与溪流中存在的营养物和需氧物质浓度之间存在弱到中度的相关性。然而，DOC 数据存在空间和时间趋势，这可以归因于营养物流入溪流。从上游到下游的养分浓度增加模式部分解释了下游观察到的溶解氧（DO）浓度下降的情况。河岸植被和泥沙流入的直观解释也支持 DO 浓度的空间模式。大部分 DOC 降低发生在夏季，此时溪流流量最小。夏季的 DOC 降低部分可以通过趋势分析来解释，即 1981 年至 2020 年期间使用修正后的 Mann-Kendall 检验、Pettitt 检验和 Sen 斜率分析的夏季每日气温数据显示，夏季每日气温升高。
