Explaining differential sources of zoonotic pathogens in intensively-farmed catchments using kinematic waves

摘要

Surveys in streams draining intensively farmed catchments can, during flood events, indicatendifferential time-concentration patterns between a bacterial health-risk indicator (E. coli) and anmajor zoonotic pathogen that it seeks to indicate—Campylobacter. The indicator’s peaknconcentration at a monitoring station can arrive ahead of the flood peak (the pollutograph leadsnthe hydrograph), whereas the peak pathogen concentration arrives with the flood peak (thenpollutograph and hydrograph peaks coincide). In other cases the E. coli pollutograph can lag thenhydrograph. These observations have generated the hypothesis that such behaviour reflects threendifferent possible (predominant) sources of pathogens in the floodwater: (i) by sedimentnentrainment, (ii) via local land runoff, or (iii) from upstream releases (e.g., from dams, inflows,nor upstream floods). A general theory for contaminants in idealized stream floods has beenndeveloped, considering all three sources, based on kinematic wave theory. It can explain thenobserved differential time-concentration patterns. The calculation procedures and associatednresults are intended to inform public policy, by identifying predominant pathogen sources andntherefore helping to focus attention on the important delivery mechanisms. This will better informnquantitative health risk assessments for downstream water users (recreational uses, waternsupplies, food production and processing industries).