Effects of UV intensity and water turbidity on microbial indicator Inactivation

The effects of UV intensity and turbidity on selected microbial indicator inactivation were investigated. Results showed that UV disinfection was effective in killing all the selected microbial indicators, the resistance order of the microorganisms was as follows： MS-2 coliphage 〉 Bacillus subtilis 〉 E. coil 〉 Staphylococcus aureus and Candida albicans. UV intensity had influence on the inactivation of all the microorganisms, high UV disinfection efficency was obtained with higher UV intensity. Turbidity had impact on the bacteria inactivation rate, but there was no evidence that turbidity had any negative contribution to MS-2 coliphage. Under the same UV dosage, higher UV intensity could overcome the negative influence of turbidity on UV performance, enhanced microorganism inactivation effect in turbidity water.

Effect of forest fire on soil microbial biomass and enzymatic activity in oak and pine forests of Uttarakhand Himalaya, India

Background:Forest fire incidences in the Himalayan region of Uttarakhand,India are very common in summers.Pine and oak are the principal and dominant species of Himalayan subtropical forest and Himalayan temperate forest,respectively.Forest vegetation influences the physicochemical and biological properties of soil and forest fire in pine and oak forests may have a different effect on the physicochemical and biological properties of soil.Therefore,the present study was carried out to assess the impact of forest fire on soil microbial properties,enzymatic activity,and their relationship with soil physicochemical properties in the advent of forest fire in the pine and oak forests of the Garhwal region of Uttarakhand Himalaya,India.Results:The soil microbial biomass carbon and nitrogen,soil basal respiration,and acid phosphatase activity decreased,whereas dehydrogenase activity increased at burnt sites of both forest types.The overall change in soil microbial biomass carbon was 63 and 40%at the burnt oak forest and burnt pine forest,respectively.Dehydrogenase activity and acid phosphatase activity showed a strong positive correlation with soil organic matter(r=0.8)and microbial indices,respectively.The ratio of soil microbial biomass carbon/nitrogen was reduced at burnt sites of both forest types.Factor analysis results showed that fire had a significant impact on soil characteristics.The soil basal respiration was linked with macro-and micronutrients at burnt sites,whereas at control sites,it was linked with physicochemical properties of soil along with nutrients.Conclusion:Forest fire had a significant impact on soil properties of both forest types.The impact of forest fire on soil microbial biomass carbon was stronger in the oak forest than in the pine forest.Forest type influenced soil enzymatic activity at burnt sites.The bacterial community was dominated over fungi in burnt sites of both forests.Soil microbial indices can be used as a selective measure to assess the impact of fire.Furthermore,forest type plays an important role in regulating the impact of forest fire on soil properties.

Winter survival of microbial contaminants in soil:An in situ verification

The aim of the research was to evaluate, at site scale, the influence of freezing and freeze/thaw cycles on the survival of faecal coliforms and faecal enterococci in soil, in a climate change perspective. Before the winter period and during grazing, viable cells of faecal coliforms and faecal enterococci were detected only in the first 10 cm below ground, while,after the winter period and before the new seasonal grazing, a lower number of viable cells of both faecal indicators was detected only in some of the investigated soil profiles, and within the first 5 cm. Taking into consideration the results of specific investigations, we hypothesise that the non-uniform spatial distribution of grass roots within the studied soil can play an important role in influencing this phenomenon, while several abiotic factors do not play any significant role. Taking into account the local trend in the increase of air temperature, a different distribution of microbial pollution over time is expected in spring waters, in future climate scenarios. The progressive increase in air temperature will cause a progressive decrease in freeze/thaw cycles at higher altitudes, minimising cold shocks on microbial cells, and causing spring water pollution also during winter.