PCBs in fish caught in Maryland from 1986 to 2021

Historical dataset collected to establish fish consumption advisories represents a valuable source of information on contamination levels in the waterbodies and changes over time. Of particular interest to environmental managers is the extent to which current and future levels of persistent chemicals in fish reflect the expected response to completed remediation projects. In this study, PCB concentrations measured across 323 monitoring stations in Maryland over 3 decades were curated and used to perform spatial and temporal analysis. Five watersheds out of 25 were identified as highly impacted by PCBs including the Upper Chesapeake Bay. Known areas of contamination were better predictors of PCBs in fish than generic land use or toxic release information, but PCB transport across watersheds may also explain PCB levels in watersheds with little or no known PCB sources. Impacted watersheds showed slow nationally consistent natural attenuation rates ranging from 2% to 6% yr-1, except the Gunpowder-Patapsco near Baltimore MD, where no temporal trend was observed since 1996. The overall study showed that PCB source mitigation implemented across Maryland and surrounding States helped recoveries, but more efforts are needed to fully control all PCB sources (legacy or ongoing) that are still impacting the rivers and fish.用于制定鱼类消费建议而收集的历史数据集，是了解水体污染物水平及其随时间变化的宝贵信息来源。环境管理人员尤为关注的是，鱼类体内当前及未来的持久性化学物质水平，在多大程度上能够反映已完成修复工程的预期响应效果。本研究对30余年来美国马里兰州323个监测站点测得的多氯联苯（Polychlorinated Biphenyls，PCB）浓度数据进行了整理，并用于开展时空分析。在25个流域中，有5个被认定为受PCB严重影响的流域，其中包括切萨皮克湾上游（Upper Chesapeake Bay）。相较于通用土地利用数据或有毒物质排放信息，已知污染区域能更好地预测鱼类体内的PCB水平，但跨流域的PCB迁移也能够解释那些几乎或完全无已知PCB污染源的流域内的PCB浓度情况。受影响流域整体呈现出全美范围内一致的缓慢自然衰减速率，范围为2%至6%每年，唯有马里兰州巴尔的摩附近的火药河-帕塔普斯科流域自1996年以来未观测到时间趋势。本研究整体结果表明，马里兰州及周边各州实施的PCB污染源减排措施已推动水体与鱼类质量有所恢复，但仍需加大工作力度，以全面管控所有仍在影响河流与鱼类的PCB污染源（包括遗留污染源与在排污染源）。