Abstract
Evaluating the microbial quality of irrigation water is essential for the prevention of foodborne illnesses. Generic Escherichia coli (E. coli) is used as an indicator organism to estimate the microbial quality of irrigation water. Monitoring E. coli concentrations in irrigation water sources is commonly performed using water samples taken from a single depth. Vertical gradients of E. coli concentrations are typically not measured or are ignored; however, E. coli concentrations in water bodies can be expected to have horizontal and vertical gradients. The objective of this work was to research 3D distributions of E. coli concentrations in an irrigation pond in Maryland and to estimate the dynamics of E. coli concentrations at the water intake during the irrigation event using hydrodynamic modeling in silico. The study pond is about 22 m wide and 200 m long, with an average depth of 1.5 m. Three transects sampled at 50-cm depth intervals, along with intensive nearshore sampling, were used to develop the initial concentration distribution for the application of the environmental fluid dynamic code (EFDC) model. An eight-hour irrigation event was simulated using on-site data on the wind speed and direction. Substantial vertical and horizontal variations in E. coli concentrations translated into temporally varying concentrations at the intake. Additional simulations showed that the E. coli concentrations at the intake reflect the 3D distribution of E. coli in the limited pond section close to the intake. The 3D sampling revealed E. coli concentration hot spots at different depths across the pond. Measured and simulated 3D E. coli concentrations provide improved insights into the expected microbial water quality of irrigation water compared with 1D or 2D representations of the spatial variability of the indicator concentration.
Highlights
The microbial quality of irrigation water is a matter of public safety and concern
The boundaries between the sections were set at locations demonstrated that there was no significant difference between the average values of E. coli concentrations
E. coli concentrations were measured at depth increments of 0.5 m in the interior area and at the water surface along the bank of an irrigation pond
Summary
The microbial quality of irrigation water is a matter of public safety and concern. The WorldHealth Organization reported that an estimated 600 million people in the world suffer from diseases after eating contaminated food every year [1]. The microbial quality of irrigation water is a matter of public safety and concern. Health Organization reported that an estimated 600 million people in the world suffer from diseases after eating contaminated food every year [1]. The consumption of fresh produce has been increasingly. Water 2020, 12, 1708 viewed as a serious matter influencing food safety and health [2]. The microbial quality of irrigation water is recognized as a substantial factor affecting the contamination of produce, including fresh fruits and vegetables [3,4,5]. Generic Escherichia coli (E. coli) and enterococci are commonly used as fecal indicator microorganisms for the determination of the microbial quality of irrigation water [6,7,8].
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