In the aftermath of the lead contamination crisis that plagued the water system in Flint, MI, more than 35,000 water samples were collected from the city's premises. The majority of these samples (>85%) were collected through a voluntary crowdsourced sampling campaign. The samples were analyzed for lead and copper concentrations by the Michigan Department of Environmental Quality (MDEQ). In this study, the crowdsourced sampling data was analyzed by means of spatial autocorrelation analysis to reveal the locations of statistically significant hotspot regions of high water lead levels (WLLs), and to track the spatiotemporal evolution of WLLs as the system recovered from lead contamination. The results showed that hotspot regions that experienced high WLLs were consistent with the areas where lead service line (LSL) density was the highest. Additionally, galvanized service lines and other lead-containing plumbing components could have also contributed to lead release in hotspot regions. The temporal trend exhibited by the crowdsourced sampling data did not reflect a consistent decrease in WLLs despite the interventions implemented by MDEQ and EPA. Instead, sampled WLLs remained high for several months after boosting the orthophosphate dose and launching a city-wide residential flushing campaign. The findings of this study suggest that this could be partially attributed to disproportionate sampling from premises in hotspot regions of high WLLs and LSL density.

中文翻译：

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众包水样显示，密歇根州弗林特市铅污染恢复的时空趋势。

铅污染危机困扰着密歇根州弗林特的供水系统，从该市房屋中收集了35,000多份水样。这些样本中的大多数（> 85％）是通过自愿的众包抽样活动收集的。密歇根州环境质量部（MDEQ）对样品中的铅和铜浓度进行了分析。在这项研究中，通过空间自相关分析对众包采样数据进行了分析，以揭示高水铅水平（WLLs）具有统计学意义的热点区域的位置，并随着系统从铅污染中恢复来追踪WLLs的时空演变。结果表明，经历高WLL的热点区域与铅服务线（LSL）密度最高的区域一致。此外，镀锌服务线和其他含铅管道组件也可能导致热点地区的铅释放。尽管由MDEQ和EPA进行了干预，但众包抽样数据显示的时间趋势并未反映出WLL的持续下降。取而代之的是，在增加正磷酸盐剂量并发起全市范围的住宅冲洗运动之后，采样的WLL保持了几个月高位。这项研究的结果表明，这可能部分归因于来自WLL和LSL密度高的热点区域的场所的不成比例的采样。尽管由MDEQ和EPA进行了干预，但众包抽样数据显示的时间趋势并未反映出WLL的持续下降。取而代之的是，在增加正磷酸盐剂量并发起全市范围的住宅冲洗运动之后，采样的WLL保持了几个月高位。这项研究的结果表明，这可能部分归因于来自WLL和LSL密度高的热点区域的场所的不成比例的采样。尽管由MDEQ和EPA进行了干预，但众包抽样数据显示的时间趋势并未反映出WLL的持续下降。取而代之的是，在增加正磷酸盐剂量并发起全市范围的住宅冲洗运动之后，采样的WLL保持了几个月高位。这项研究的结果表明，这可能部分归因于来自WLL和LSL密度高的热点区域的场所的不成比例的采样。