|JEON, DONGJIN - Us Forest Service (FS)|
|HARRIGER, DANA - Wilson College|
|PICARD, RACHAEL - Wilson College|
|WELLS, EDWARD - Wilson College|
|HONG, EUNMI - Kangwon National University|
Submitted to: Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/11/2019
Publication Date: 11/1/2019
Citation: Jeon, D., Pachepsky, Y.A., Harriger, D., Picard, R., Coppock, C.R., Wells, E., Hong, E. 2019. Analysis of E. coli and enterococci concentrations patterns in a Pennsylvania creek using empirical orthogonal functions. Environmental Quality. 48(6): 1703-1710. https://doi.org/10.2134/jeq2019.05.0191.
Technical Abstract: Assessing microbial quality of irrigation waters is important to prevent foodborne illnesses caused by fresh produce contamination. Generic Escherichia coli (E. coli) and enterococci are used as indicators of the microbial water quality. The microbial concentrations undergo rapid change in time and space. There are one or more important factors which can create spatial patterns of the microbial concentrations. Understanding the factors facilitates effective monitoring strategies. The objective of this study was to see if temporally stable spatial patterns are present in time series of the indicator concentrations at the baseflow in the Conococheague creek, PA. Both microbial concentrations were measured at five water monitoring locations along the 20-km long creek reach weekly during three years. This continuous spatial and temporal monitoring dataset was analyzed using empirical orthogonal functions (EOFs) to detect temporally stable spatial patterns. In general, enterococci had higher average concentrations and larger seasonal variation compared with E. coli at all monitoring locations along the creek. In the rural area, there were larger differences in concentrations between warm and cold seasons compared to urban and forest areas. The highest concentrations were found in the urbanized area; the concentrations were relatively lower in the agricultural and sparsely urbanized area for all observation years. Based on the EOF analysis, the most significant spatial pattern of the both microbial concentrations possibly reflected differences in land use; 74.6% and 68.6% were explained by the first EOF for E. coli and enterococci. Much less variability (19.6 and 17%) was explained by the EOF that possibly reflected the presence of tributary and braided sections of the creek. We confirmed that EOF analysis can uncover the significant multiple temporally stable spatial patterns for the microbial concentrations along the creek in presence of multiple land use. Moreover, the uncovering temporally stable patterns is beneficial for establishing monitoring locations to characterize microbial water quality along streams.