Microbial Quality of Irrigation Water used in the Production of Fresh Produce in Arizona.

Abstract

Environmental factors and produce practices influence the microbial quality of produce. The objective of this study was to determine the microbial quality of irrigation water used for the production of fresh produce in Arizona and factors, which may influence this water quality such as canal size, location and rainfall. A total of 117 samples were collected from irrigation canals in Yuma County between June 2001 and March 2003 and 263 water samples were collected in Maricopa County between May 2002 and February 2003. Parameters such as temperature, turbidity, conductivity and pH were recorded for all samples. Water samples were analyzed for microbial indicators which included total coliforms, Escherichia colt, Enterococcus , and Clostridium perfringens. Sampling sites were examined for the presence of Giardia spp., Cryptosporidium spp., Noroviruses, Salmonella spp. and Campylobacter spp. Samples collected in Yuma County showed that 4.3% of the samples were positive for Giardia spp., 19.6% were positive for Cryptosporidium spp., 17.4% were positive for Noroviruses, 20.7% were positive for Salmonella spp. and 55.2% were positive for Campylobacter spp. Overall, results from samples collected in Maricopa County showed that 2.3% of the samples were positive for Cryptosporidium spp, 18.2% were positive for Noroviruses, 28.9% were positive for Salmonella spp. and 68.7% were positive for Campylobacter spp. Giardia spp. were not detected in any samples. One-way ANOVA did not demonstrate any significant difference between microbial indicator concentrations in samples collected from Yuma and Maricopa Counties. Overall, E. colt concentrations correlated strongly with Enterococcus (r=0.858) in samples collected from Maricopa County. Rainfall within 7 days prior to sampling correlated strongly with overall averages for each indicator, the strongest correlation was seen with E. colt (r=0.726). Overall, the main canals tended to have lower microbial numbers than the lateral/drain canals. In Maricopa County, the sampling sites located furthest north and furthest south on each of the main canals tended to have the higher microbial numbers. The sampling points located furthest south tended to be ranked higher in terms of microbial loads. There appeared to be no positive correlation between the levels of microbial indicators and enteropathogens in this study.