RAPID - Evaluation of Soil Contamination due to Rio Grande Flooding July 2010

这项研究的主要目标是评估受最近德克萨斯州拉雷多附近格兰德河洪水影响的土壤中污染物的稳定性。格兰德河洪水在2010年7月8日达到顶峰，流量超过4,000立方米/S(410,000立方英尺)，水位为12.8米(42英尺)。高于平均流量水位。[请注意，主要洪水位被认为比平均洪水位高出9米(30英尺)。]农业、工业、采矿、航运和市政用地被洪水淹没，成为动员包括重金属和有机物在内的一系列污染物的来源。随着洪水退去，这些污染物被沉积到河流附近的土壤中。该项目将评估受洪水影响的格兰德河和土壤中重金属(全屏)和具有代表性的有机化合物(多溴二苯醚、三氯生、环丙沙星和阿特拉津)的保留和移动。从2010年5月开始，从六个地点采集了水样，在洪水期间进行了更频繁的采样，以更好地量化污染物沉积率，并将在整个项目期间继续进行。现场水质参数、流量、营养物质和感兴趣的化学物质(水和颗粒结合)将在每次采样中进行评估，以确定高流量(洪水)和平均流量条件下的污染程度。两个地点被选为样本-未开发的土地和那些用于河边的自然步行道。在每个地点建立三个样带，每个样带覆盖一半的泥沙淤积(1 mm-2厘米的泥沙淤积)和非冲击土壤。最初的样本是在洪水退去后2天内采集的，并将在6周、12周和24周再次采集。采集样本并按水平(表层/沉积物沉积、根部渗透深度和深层土壤)进行分段。每一种都将根据整体土壤条件和感兴趣的污染物进行评估。这项研究将使我们能够更好地评估由于进一步的自然和人为干扰而导致的这些化合物在根际的物理化学行为。对分水岭、泛滥平原和邻近土地的实地采样将有助于我们绘制该地区水和土壤中的污染物分布图。该项目将有助于对格兰德河下游农业区的实际污染物水平以及这些污染物对重要商业作物的潜在影响进行整个系统的评估。这一洪水事件将使我们能够更好地模拟根际环境中的污染物行为，同时对自然系统进行有限的操纵。与农民直接合作，这也将有助于我们更好地了解在格兰德河谷使用再生水灌溉对土壤健康和作物生产力的潜在影响。最终，这项研究将扩展到对微生物群落的检查，以支持在存在人为污染物的情况下营养动态和土壤质量的可持续性。

The primary goal of this research is to assess contaminant stability within soils impacted by recent flooding of the Rio Grande near Laredo, Texas. The Rio Grande flood peaked on 8 July 2010 with a flow exceeding 4,000 m3/s (410,000 cfs) at 12.8 m (42 ft.) above the average flow stage. [Note that major flood stage is considered to be 9 m (30 ft) above the average flow stage.] Agricultural, industrial, mining, shipping and municipal lands were flooded and served as sources which mobilized a suite of contaminants including heavy metals and organics. As flood waters receded, these contaminants were deposited into soils adjacent to the river. This project will assess the retention and movement of heavy metals (full panel), and representative organic compounds (PBDE, Triclosan, Ciprofloxacin, and Atrazine) within the Rio Grande and soils impacted by the flood. Water samples have been collected from six locations beginning in May 2010, with more frequent sampling during the flood to better quantify the contaminant deposition rate, and will continue throughout this project. In situ water quality parameters, flow rate, nutrients and the chemicals of interest (aqueous and particle bound) will be assessed for each sampling to determine the level of contamination during both high-flow (flood) conditions and average-flow conditions. Two sites were selected for sampling - undeveloped lands and those used for a nature walk adjacent to the river. Three transects were established at each site with half of each transect covering impacted (1 mm - 2 cm of sediment deposition) and non-impacted soils. Initial samples were collected within 2 days of the flood waters receding, and will be collected again at 6 weeks, 12 weeks and 24 weeks. Samples are collected and segmented by horizon (surface/sediment deposition, root penetration depth and deep soils). Each will be evaluated for overall soil conditions and the contaminants of interests. This research will allow us to better assess the physiochemical behavior of these compounds within the rhizosphere due to further natural and anthropogenic disturbances. Field sampling of the watershed floodplain and adjacent lands will help us to map contaminant distributions in both water and soil in the region. This project will contribute to a whole system assessment of actual contaminant levels in the lower Rio Grande agricultural region and the potential effects of these contaminants on commercially important crops. This flooding event will allow us to better model contaminant behavior within the rhizosphere with limited manipulations of the natural system. Working directly with farmers, this will also help us to better understand the potential impacts on soil health and crop productivity of using recycled water for irrigation in the Rio Grande Valley. Eventually this research will extend to the examination of the microbial community to support sustainability of nutrient dynamics and soil quality in the presence of anthropogenic contaminants.