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. Author manuscript; available in PMC: 2019 May 1.
Published in final edited form as: Environ Pollut. 2018 May;236:505–513. doi: 10.1016/j.envpol.2018.01.066

Figure 4.

Figure 4

PFAS Occurrence Trend Using Quarterly Results for All Samples. Data from all UCMR3 samples with analysis of one or more PFAS were grouped by monitoring period (quarterly). The Mann-Kendall test was used to evaluate the trend in detection frequency for data from the first 12 quarters (2013–2015). Data from the last 4 quarters (2016) were not used due to the low number of samples per quarter (<2% of total). Circles are detection rates and correspond to the left y-axis; lines are the number of samples per quarter and correspond to the right y-axis.