Influence of Precipitation and Soil on Transport of Fecal Enterococci in Fractured Limestone Aquifers

Abstract

Limestone aquifers provide the main drinking water resources of southern Italy. The groundwater is often contaminated by fecal bacteria because of the interaction between rocks having high permeability and microbial pollutants introduced into the environment by grazing and/or manure spreading. The microbial contamination of springwater in picnic areas located in high mountains can cause gastrointestinal illness. This study was carried out in order to analyze the interaction between Enterococcus faecalis and the soil of a limestone aquifer and to verify the influence of this interaction on the time dependence of groundwater contamination. E. faecalis was chosen because, in the study area involved, it represents a better indicator than Escherichia coli. The research was carried out through field (springwater monitoring) and laboratory experiments (column tests with intact soil blocks). The transport of bacterial cells through soil samples was analyzed by simulating an infiltration event that was monitored in the study area. Comparison of laboratory results with data acquired in the field showed that discontinuous precipitation caused an intermittent migration of microorganisms through the soil and produced, together with dispersion in the fractured medium (unsaturated and saturated zones), an articulated breakthrough at the spring. The short distances of bacterial transport in the study area produced a significant daily variability of bacterial contamination at the field scale.

A high‐altitude temporary spring in a compartmentalized carbonate aquifer: the role of low‐permeability faults and karst conduits

“…Limestone lies below a pyroclastic soil (Celico et al, 2004b) that can be classified as Vitric Andosols (as defined by the FAO, 1988). The soil is characterized by a prevailing sandy loam texture (as defined by the US Department of Agriculture, 1979) and high organicmatter content (20-35%), and allows an easy and diffuse rainwater infiltration (Celico et al, 2004b. The Acqua dei Faggi carbonate aquifer is bounded by fault zones that act as barriers to groundwater flow and compartmentalize the aquifer system.…”

Removal of pathogenic bacteria from sewage-treated effluent and biosolids for agricultural purposes

“…Intermediate ratios indicate contamination from both man and animals (Young and Thackston 1999;Baudišová 2009). Enterococci are a more reliable indicator than faecal coliforms for the detection of microbial pollution as they are more resistant to the environment than faecal coliforms (Celico et al 2004). It has been frequently considered as reference microorganism for thermal treatments to be applied in pasteurized foods Ghazala et al 1991).…”

Influence of soil on groundwater geochemistry in a carbonate aquifer, southern Italy

“…Two intact soil block of Vitric Andosol (181.36 cm 2 by 11 cm deep) were collected from the test site according to described method (Celico et al, 2004). After collection, each soil sample was covered with plastic and transported to the laboratory where the experimental procedure was commenced immediately at room temperature.…”

“…Carbonates generally lie below a soil of pyroclastic origin (Celico et al, 2004) that can be classified as Vitric Andosol (as defined by FAO, 1988). The soil is characterized by (Naclerio et al, 2008) high organicmatter content (20% to 35%), fibrous structure, specific-gravity values ranging from 2.1 g/cm 3 to 2.4 g/cm 3 , uniformity coefficient ranging between 3 and 9, and a prevailing sandy loam texture (as defined by the US Department of Agriculture, 1979).…”