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Introduction: Groundwater is considered the best candidate for drinking water supply in the karst area. The groundwater water resources, however, are vulnerable to pathogenic microorganism contamination because of the typically thin soil layers overlying aquifers and the high permeability of the aquifer host rock, resulting in short residence times and low natural attenuation capacities. Until now, little attention has been paid to the critical environmental factors affecting the pathogenic microorganism contamination in soil-groundwater systems in the karst area. Methods: In the study, orthogonality column experiments with controlling ambient temperatures, pH values of inlet water, and soil porosities were carried out to investigate the transport and lifespan of pathogenic microorganisms in the leachate of agricultural soils in the karst area of Yunnan province, China. The pathogenic indicators, i.e., total bacteria count (TBC) and total coliforms count (TCC), and hydrochemical parameters, i.e., pH and permanganate index (CODMn) in the leaching water, were systematically monitored. Results and Discussion: The results showed that bacteria including coliforms can survive for prolonged periods of time in karst soils. The soils overlying the karst rocks were unable to impede the bacteria from seeping into the groundwater. The soils, in turn, likely served as both reservoirs and incubators for pathogenic bacteria. The ambient temperature was the most predominant influential factor affecting both TBC and TCC. The bacteria concentrations were proportional to the temperature in the leachate. Therefore, more attention should be paid to temperature variations in protecting the water supply, particularly in the high-temperature period, such as during the summer months. [ABSTRACT FROM AUTHOR]

As the focus of microbial degradation kinetics research, microbial activity detection is essential for the study of microbial degradation of contaminated groundwater. In this paper, luciferase assay was used to determine the microbial activity, and a rapid quantitative method for the determination of adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate (AMP) was developed. The experiment on microorganism of petroleum-contaminated groundwater was compared with ultraviolet and visible spectrophotometry (UV spectrophotometry) and plate count. Then, the practicability of the method for microbial degradation of petroleum-contaminated ground-water was verified. The results were as follows: the method had a detection range of 0.025–50 ppb, and each test took 10–15 s. The RSD of ATP, ADP, and AMP were 10.03, 2.84, and 6.57, respectively, and the R2 values of the standard curve were all >0.99, the method was accurate and precise; the correlation coefficients of UV spectrophotometry were all >0.99, and the correlation coefficients of plate count were all >0.98, the P-values were both <0.001. The results showed that the luciferase assay method developed in this study was convenient, fast, reliable, and economical. [ABSTRACT FROM AUTHOR]