Browsing by Author "Gunatilake, S.K."

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    Isolation of Fenobucarb Resistant Bacteria from Agricultural Soils in Belihuloya, Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2020) Randika, J.L.P.C.; Bandara, P.K.G.S.S.; Soysa, H.S.M.; Ruwandeepika, H.A.D.; Gunatilake, S.K.
    Pesticides are extensively used in controlling pests globally as well as in Sri Lanka, and many of these pesticidal compounds are nuisances of the natural ecosystem. But, some soil microbes immensely help in biodegrading the pesticide residues, enabling the pesticides to be less harmful. Fenobucarb is one of the extensively used carbamate insecticides in Sri Lanka. The objective of this study was to isolate resistant soil bacteria against Fenobucarb in agricultural soils. Three pooled soil samples were collected from three selected farming lands located in the Belihuloya area where Fenobucarb is used continuously in crop cycles. Each sample was grown on M9 minimal salt medium supplemented with 100 ppm Fenobucarb at 28 °C for 2-3 days. Seven well-grown single colonies were isolated and subcultured on the same medium supplemented with 100, 150, 200, 300 ppm Fenobucarb separately. Four out of the seven isolates were able to grow in all the concentrations of the pesticide. From the other three isolates, one was able to grow in 100 and 150 ppm while the other two showed their growth only in 100 ppm concentration of the pesticide. One out of four isolates that grew in all the pesticide concentrations didn't show any growth on control (M9 minimal salt medium without the pesticide). One out of two isolates that grew only in 100 ppm concentration also did not show any growth in control. However, the other five isolates exhibited very small colonies on control as well. These results support the fact that some soil bacteria can utilize pesticides as their sole carbon source. According to the above results, the study concludes that some isolated soil bacteria can resist up to the concentration of 300 ppm Fenobucarb being potential bioremediation agents for decontaminating the polluted sites. Keywords: Fenobucarb, Bioremediation, Soil Bacteria, M9 minimal salt medium
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    Seasonal Groundwater Quality Variation in Monaragala District of Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2019-02) Udeshani, W.A.C.; Gunatilake, S.K.
    Sri Lanka is divided into three climatic zones namely; ‘dry’, ‘intermediate’ and ‘wet’ based on the mean annual rainfall. Monaragala district in the Uva Province, lies within both dry and intermediate zones. Agriculture is the main livelihood of rural people in this area and paddy is the major crop. Paddy is cultivated in; “Maha” and “Yala” season which are associated with two monsoons i.e. “north-east monsoon” and “south-west monsoon”, respectively. Inorganic fertilizer is commonly applied by farmers to overcome the nutrient deficiency in permanent agricultural lands. However, excessive fertilizer application can cause severe environmental and health problems. Since groundwater is the main source for drinking water in this area, this study attempted to assess the seasonal variation of physico-chemical properties of groundwater. Samples were collected from 44 sampling points representing dug and tube wells which are closely located to the agricultural fields. A total of 88 groundwater samples were collected in both seasons. The collected samples were analyzed for pH, Electrical Conductivity, Total Dissolved Solids, Total Alkalinity, Total Hardness, HCO3-, Cl-, SO42-, NO3-, PO43- and F-. A student’s t-test was carried out to evaluate the seasonal effects on groundwater quality. The groundwater in both seasons is characterized by HCO3- > Cl- > SO42- > NO3- > F- > PO43- facies. As per the statistical analysis, only pH, NO3- and PO43- showed significant seasonal variation (p < 0.05). About 40.9% and 31.8% of groundwater samples are very hard, while 22.7% and 18% of are brackish in Maha and Yala seasons, respectively. Higher NO3- and PO43- levels in Maha season (the main cultivation season) potentially show the effect of fertilization on the groundwater quality. However, the proceeding of this assessment for several consecutive seasons would be more effective to identify the seasonal variation and agricultural effects (inorganic fertilization) on groundwater quality.