Numerous small public groundwater systems on coastal islands in Washington State (WA) that are susceptible to seawater intrusion have reported disproportionately high frequencies of regulatory exceedances for halogenated organic DBPs; especially brominated DBPs. Fifteen such systems spread across a ∼1000 km² study area were monitored quarterly over a year in a collaboration between the WA Department of Health and University of Washington to identify key drivers of these trends, and to develop operational and regulatory recommendations aimed at minimizing DBP formation in these and similar systems in WA and elsewhere. [Br⁻] alone was not observed to be a strong predictor of DBP formation potentials (DBP-FPs) or speciation for source waters across the study area, likely due to accompanying large variations in [DOC]. However, bromine substitution factors correlated relatively well with [Br⁻]/[DOC] ratios, highlighting the importance of both [Br⁻] and [DOC] in governing DBP formation and speciation in coastal groundwaters. Overall DBP-FPs correlated strongly with [DOC], UV absorbance at 254 nm (A₂₅₄), and selected size exclusion chromatography (SEC) and fluorescence metrics for each groundwater, with A₂₅₄ a particularly strong surrogate for DOC. This was consistent with high uniformity of DOM properties (confirmed from SUVA₂₅₄, fluorescence index, PARAFAC components, and SEC chromatograms) across the study area. Specific DBP-FPs (e.g., ∼72 μg_TTHM mg_C⁻¹) for the source waters were quite high compared to typical groundwaters, pointing to inherently high DOM reactivity as an additional factor in the frequent DBP regulatory exceedances observed for the investigated sites. Measurements also revealed seasonal trends (e.g., in [Br⁻] and [DOC]) correlated with DBP formation, but not captured by routine regulatory monitoring, as well as widespread inconsistencies in chlorination practices at the studied systems. While such factors and correlations are well established for surface waters, this work provides one of the few examinations incorporating both laboratory and full-scale observations to demonstrate their importance in small, coastal groundwater systems. Based on these findings, WA has adopted a number of changes in its design manual for new groundwater disinfection systems, and is evaluating changes in its disinfection monitoring and DBP programs that may also serve as models for wider implementation.

中文翻译：

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小型氯化沿海地下水系统中消毒副产物形成和形态形成的驱动因素：溴化物和有机物的相对作用，以及需要改进源水特性和监测的需求

华盛顿州（WA）沿海岛屿上的许多小型公共地下水系统容易受到海水入侵，据报道，卤化有机DBP的超标超标频率极高。特别是溴化DBP。在西澳州卫生部和华盛顿大学的合作下，在超过一年的季度中，每季度监测15个这样的系统，分布在约1000 km ^2的区域，以识别这些趋势的主要驱动因素，并制定旨在最小化DBP的操作和监管建议在西澳大利亚州和其他地方的这些系统和类似系统中形成。[BR ^-单独观察到]并不是研究区域整个源水的DBP形成潜力（DBP-FPs）或物种形成的有力预测指标，可能是由于[DOC]的变化很大。然而，溴取代的因素与相关相对较好[BR ^- ] / [DOC]比率，突出两者的重要性[BR ^-在管理在沿海地下水DBP的形成和形态和[DOC]。总体而言，DBP-FP与[DOC]，254 nm处的UV吸光度（A ₂₅₄）以及每种地下水的选定尺寸排阻色谱法（SEC）和荧光指标密切相关，其中A ₂₅₄是DOC的特别强替代物。这与DOM属性的高度一致性一致（由SUVA确认₂₅₄，荧光指数，PARAFAC组分和SEC色谱图）。特定DBP-FPS（例如，〜72微克_TTHM毫克_Ç ^-1）为源水就相当高相比典型地下水，指向固有的高反应性的DOM作为在所研究位点中观察到的频繁DBP监管超标一个附加因素。测量还显示季节性趋势（例如，在[BR ^-]和[DOC]）与DBP的形成有关，但未被常规的监管监测所捕获，并且在研究的系统中氯化实践中普遍存在不一致之处。尽管已经为地表水建立了这些因素和相关性，但这项工作提供了为数不多的结合实验室和全面观测的检查方法之一，以证明其在小型沿海地下水系统中的重要性。基于这些发现，西澳州在其新的地下水消毒系统的设计手册中采用了许多更改，并正在评估其消毒监控和DBP程序的更改，这些更改也可以作为更广泛实施的模型。