RAPID: Investigation of Immediate Post-fire Hydro-geochemical Coupling and Contaminant Flux in an Urban-fringe Watershed in Southern California

车站火灾目前被认为是洛杉矶县历史上最大的火灾，也是加利福尼亚州历史上第10大火灾。被烧毁的地区紧邻洛杉矶盆地东侧人口稠密的城区。这些位于圣加布里埃尔山脉的城市-荒野地区现在将受到洪水增加、泥石流和泥沙携带的水流以及严重的水质问题的影响。众所周知，圣加布里埃尔山脉接收来自洛杉矶大都市区的高负荷大气污染物(干的和湿的)。来自这些山脉的径流通常会向下游的城市水道提供大量径流，然后被引导到渗透池或含水层补给区，或者进入输送渠道，将水通过人口稠密的城市地区输送到沿海海湾。这些城市边缘流域的火灾后径流现在可能会对下游城市系统造成重大的、潜在的有毒化学负荷，影响区域供水、生物群和生态系统功能。来自这笔快速赠款的资金将使人们能够立即和广泛地调查风暴导致的污染物通量(包括营养物质、金属、多环芳烃、沉积物和其他辅助参数)，该流域受到大量大气沉积的影响，并被完全烧毁。以前收集的关于研究流域的火灾前数据将使人们能够对燃烧前的行为进行独特和全面的比较，增进关于燃烧后水文-地球化学耦合和盆地质量负荷变化的知识，并为改进燃烧后系统的地球化学和水文模拟提供关键数据。拟议研究的首要目标是更好地了解控制灾难性野火后城市边缘流域化学和物理反应变化的机制。具体地说，我们建议解决以下科学问题：1)火灾后水文-地球化学耦合(行为)如何改变火灾前的条件？2)风暴变化如何影响火灾后径流行为和耦合污染物通量？3)燃烧对河岸土壤硝酸盐储存和溪水输出有什么影响？4)灾难性燃烧对下游城市系统的季节性污染物负荷有何影响？

The Station fire is currently noted as the largest fire in Los Angeles County history as well as the 10th largest fire in California history. The burned region is located immediately adjacent to dense urban areas on the east side of the Los Angeles basin. These urban-wildland regions, located in the San Gabriel Mountains, will now be impacted by increased flooding, debris and sediment-laden flows, and significant water quality issues. The San Gabriel Mountains are known to receive high loads of atmospheric pollutants (dry and wet)originating from the Los Angeles metropolitan region. Runoff from these mountains normally supplies significant runoff into downstream urban water ways, which is then directed to infiltration ponds or zones for aquifer recharge, or into conveyance channels that route water through dense urban areas to coastal bays. Postfire runoff in these urban-fringe watersheds may now contribute significant, and potentially toxic, chemical loads into downstream urban systems, affecting regional water supplies, biota and ecosystem function. Funds from this RAPID grant will allow an immediate and extensive investigation of storm-driven contaminant flux (including nutrients, metals, PAHs, sediments, and other ancillary parameters) in an urban fringe watershed affected by significant atmospheric deposition and that was burned in its entirety. Previously collected pre-fire data on the study watershed will allow a unique and comprehensive comparison to pre-burn behavior,advance knowledge on post-burn hydro-geochemical coupling and alterations in basin mass loading, and provide critical data to improve geochemical and hydrologic modeling in post-burn systems. The overarching goal of the proposed research is to better understand the mechanisms controlling alterations in the chemical and physical response of urban fringe watersheds after a catastrophic wildfire. Specifically, we propose to address the following science questions: 1) How does post-fire hydro-geochemical coupling (behavior) alter from pre-fire conditions? 2) How does storm variability influence post-fire runoff behavior and coupled contaminant flux? 3) What is the effect of burn on riparian nitrate soil storage and streamwater export? and 4) What is the impact of a catastrophic burn on seasonal pollutant loading to downstream urban systems?