Tannery effluents are one of the major sources of environmental pollution with various toxic parameters and the effluent generated during liming and pickling operations of leather processing are even more dangerous due to their high and low pH range, respectively. In the present work, liming and pickling streams generated during the production of chrome tanned cow hide shoe upper was treated at different ratios and optimized the pH range 6.5 - 7.5. The effluents were mixed at different ratios without adding any foreign chemicals and obtained the results 88% reduction of COD, 94% reduction of BOD and 97% removal of total solids. DOI: http://dx.doi.org/10.3329/jbas.v38i2.21348 Journal of Bangladesh Academy of Sciences, Vol. 38, No. 2, 235-239, 2014

Treatment of 2-Mercaptothiazoline, 2-Mercaptobenzimidazole, 2-Mercapto-1- methylimidazole with [M2(CO)10] (M = Re and Mn) at ambient temperature in presence of decarbonylating reagent Me3NO give the complexes [Mn2(?-?2-C3H4NS2)2(CO)6] (1), [Re2(?-?2-C3H4NS2)2(CO)6] (2), [Mn2(?-?2-C7H5SN2)2(CO)6] (3), [Re2(?-?2- C7H5SN2)2(CO)6] (4), [Re2(?-?2-C4H5N2S)2(CO)6] (5) and [Re2(?1-C4H5N2SH)(CO)9] (6) respectively. All the compounds have been characterized by IR, 1H NMR and mass spectral data. The heterocyclic ligands are expected to be coordinated to two or single metal atom through the nitrogen and sulfur atoms or via only sulfur atom.DOI: http://dx.doi.org/10.3329/jbcs.v25i1.11775 Journal of Bangladesh Chemical Society, Vol. 25(1), 62-70, 2012>

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The study was carried out to examine the Pb concentrations of water, sediment and soil of Shitalakhya River at Polash and Ghorashal areas in Bangladesh. The ranges of Pb in water, sediments, soils and vegetables like pumpkin leaves and alligator weeds were found 1. 87 -49.08, 8.49 -75.81, 19.68 -85.13, 1.08 -3.92 and 1.18 -4.22 mg/kg, respectively. The lead concentrations of surface water, sediment and soil samples were within the safe limit of different international standard except samples of the point source of urea fertilizer factory. The highest concentrations of Pb in alligator weeds and pumpkin vegetable leaves were recorded 3.92 and 4.224 mg/kg, respectively at the point source of urea fertilizer factory.

Sediment samples collected from the river Shitalakhya, Bangladesh, were analyzed using atomic absorption spectroscopy (AAS) to investigate site-to-site (spatial) and seasonal (i.e., dry, premonsoon, post-monsoon) variation of Cr, Mn, Ni, Cu and Zn. The mean concentrations of Cr, Mn, Ni, Cu and Zn were 22.37 ± 6.09, 612.59 ± 160.08, 54.11 ± 11.21, 50.36 ± 9.40 and 103.62 ± 62.74 mg/kg in the dry, 31.58 ± 5.22, 569.71 ± 112.16, 58.35 ± 7.82, 49.93 ± 17.36 and 110.88 ± 95.83 mg/kg in the pre-monsoon and 18.09± 6.32, 567.02 ± 115.55, 50.89 ± 6.58, 39.75 ± 4.56 and 55.22 ± 11.33 mg/kg in the post-monsoon, respectively. Based on the metals’ concentrations, no considerable difference was observed among the three seasons, but the concentrations were slightly elevated in the dry and pre-monsoon compared to that in the post-monsoon with respect to site-to-site variation. Among the metals examined, concentrations of Ni and Cu were elevated because of the use of oxides of these heavy metals as catalysts in the ammonia plant. The following statistical indices i.e., Pearson correlation matrix, geo-accumulation index (Igeo), contamination factor (Cf), degree of contamination (Cd), pollution load index (PLI) and ecological risk potential (RI) factors were taken into account to assess the heavy metals contamination of the sediments. According to the values of the statistical indices for Cr, Mn, Ni, Cu and Zn, it is concluded that the study area was with low contamination while concentrations of Ni and Cu were higher than the Threshold Effect Level (TEL) and Toxicity Reference Value (TRV) values suggesting unsafe to use the sediments for vegetation and other uses.