சுற்றுச்சூழல் & பகுப்பாய்வு நச்சுயியல்

A simple, accurate, and cost-effective procedure for separation and quantification of two pyrethroid insecticides residues on bean and cucumber plants was achieved using a Gas Chromatograph (GC) equipped with an electron capture detector (GC-ECD) and GC equipped with a Mass Selective Detector (MSD). Following spraying fruits and leaves were collected to determine insecticides dissipation constants and half-lives (T^1/2 values). Residues of the two pyrethroids revealed the presence of permethrin isomers at retention times of 26 and 26.6 min that correspond to the cis and trans-isomers, respectively. The GC also revealed the presence of four cypermethrin isomers at retention times of 30.3, 30.9, 31.3, and 31.5 min. The average initial deposits of permethrin were 2.7 and 0.2 on cucumber leaves and fruits surfaces, respectively. Whereas cypermethrin initial deposits were 5.1 and 2 μg g-1 on cucumber leaves and fruits, respectively indicating greater deposits on leaves than fruits. T^1/2 values of permethrin and cypermethrin residues on beans pods (7.2 and 9.5 d, respectively) and cucumber fruits (13 and 3.3 d, respectively) indicated that a waiting period of 10 and 15 d are required for consumption of cucumber fruits and bean pods sprayed with cypermethrin at the recommended spraying dosage to drop the residues to the Maximum Residue Limits.

Bioremediation employing the action of microbes alone has been shown to be inadequate. The aim of this study was to evaluate the efficacy of sewage sludge (SS) in enhancing bioremediation of diesel oil-polluted soil. Diesel oil was introduced into the soil at the concentration of 10 % (v/w) and mixed with 5%, 10% and 15% (w/w) of sewage sludge. The remediation of the oil was determined gravimetrically and spectrophotometrically using n-hexane as extractant. Effectiveness of the remediation strategy was assessed by the seed germination toxicity test At the end of forty-two days, 32.22 % oil loss was recorded in the unamended polluted soil while 58.33% oil loss was recorded in the soil amended with sewage sludge. Hydrocarbon- utilizing bacteria (HUB) counts were significantly high (P≤0.05) in the sewage sludge-amended options, ranging from 5.3 ±0.9 x 10⁶ to 12.3±0.75 × 10⁶CFU/g soil, as compared to the unamended control soil which gave 1.0 × 10⁶- 3.8 × 10⁶CFU/g of soil. The hydrocarbon- utilizing bacteria isolated from both the control and amended soils were identified tentatively as Bacillus cereus, Pseudomonas putida, Micrococcus varians, Corynebacterium spp and Staphylococcus spp based on their cultural, morphological and biochemical characteristics. The fungal counts in the SS-amendment options were also higher than was recorded in the control option ranging from 3.8 x 10⁵ ± 0.2 to 11.6 x 10⁵ ±0.25. Aerobic fungi isolated were Aspergillus niger, Aspergillus flavus, Fusarium sp, Cladosporium sp and Penicillium sp. The highest oil loss and germination indices were recorded in SS-amended options. There was a significant difference (P≤0.05) in oil loss and germination index between the unamended control soil and polluted soil amended with 15% SS.