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Heavy metal pollution is associated with public health concerns. The study was conducted at the vicinity of the Tejgaon industrial area (8 km 2 ) adjacent to Dhaka City Corporation. To investigate the seasonal extent of soil-water ecosystems pollution with chromium discharged from the industries, municipality, and slums, and its transfer co-efficiency into plants or crops.Composite soil, plant and water were randomly collected from industrial sites by GPS guided sampling procedure during wet and dry seasons, processed, and analyzed. Soils were analyzed for particle size distribution (sand, silt and clay), pH, electrical conductivity (EC), total organic carbon,

The main focus of the study is Tejgaon industrial area which is located within the Dhaka City Corporation and about 5 km north of the city centre. The industries around the study area like battery, chemical manufacturing, electrical and electronic, metal finishing, mining, paint and dye, textiles, pharmaceuticals, pesticides, etc, discharge heavy metals like Ni with their effluents and wastes. At Tejgaon soil the minimum pH value was 5.3 and the maximum 7.6 (at 26 O C). High buffering capacity resulting from high soil organic matter content (4.87-11.55%) probably influenced soil pH. Electrical conductivity (EC) (25-551 µS/cm) and organic matter (OM) (4.87-11.55%) contents were also influenced by the industrial wastes and effluents of the factories. In the wet season, the average Ni concentration in different soil fractions was 1.69, 4.16, 13.21 and 93.12 mg kg -1 in water-soluble, NH 4 OAC extractable, DTPA extractable and total fractions respectively. Comparing wet season and dry season sampling data, total Ni concentrations in different locations were higher in the dry season and the mean concentration of total Ni was 223.89 mg kg -1 , which was more than 4 times higher than the tolerable limit.Concentrations of total Ni in different locations during wet season were found above the natural background level with few exceptions. Ni concentration in the group of tolerable level was 21% (>022-<50 mg kg -1 ) and 75% (>50 mg kg -1 ) soil samples were found in the group of in excess of tolerable level during wet season. During dry season, 11% of Ni (<50 mg kg -1 ) samples were in the normal range and 89% (>50 mg kg -1 ) soil samples were found in the group of in excess of tolerable level. Ni concentration during dry season samples in different extraction i.e in NH 4 OAC extractable, DTPA extractable and in total fraction was found to decrease with distance away from the disposal point source due to dilution of the effluent and water. The decreasing tendency with distance indicates the accumulation of metals by the industrial operations.

The Tejgaon industrial area is located within the Dhaka Municipality area and about 5 km north of the city centre. At Tejgaon soil pH was around neutrality (mean 6.73) although the minimum value was 5.3 and the maximum 7.6. High buffering capacity resulting from high soil organic matter content (4.87-11.55%) probably influenced soil pH to a neutral value. Electrical conductivity (EC) (25-551 μS), organic matter (OM) (4.87-11.55%) and nitrogen (N) contents were also influenced by the industrial wastes and effluents of the factories. The average Pb concentrations (mg/kg) in different soil fractions were 7.80, 21.85, 56.15 and 130.29 and 11.42, 20.27, 40.33 and 95.08 in water-soluble, NH4OAc extractable, DTPA ( Dietheline-Triamine-Penta-Acetic acid) extractable and total fractions during dry (January) and rainy seasons (September) respectively. Comparing 1st (rainy season) and 2nd (dry season) sampling data, Pb concentrations in different soil fractions were higher in the 2nd sampling data. Concentration of total Pb in soils during 1st sampling were found above the natural background level with few exceptions. Only 4% of total Pb (=20 mg kg-1) samples were in the normal range during wet season. Lead concentration in the group of tolerable level was 58% (>20-<=100 mg kg-1) and 38% (>=100 mg kg-1) were found in the group of in excess of tolerable level during 1st sampling. On the other hand 62.5% (>=100 mg kg-1) were found in the group of in excess of tolerable level (0.01 mg kg-1 Pb) during dry season. In case of water samples, total Pb concentration in the rainy season, all samples were found in the group of in excess of tolerable level during 1st sampling. Plant samples were found to contain untolerable total Pb (>20 mg kg-1) during rainy and dry seasons, respectively. Key words: Speciation; Tejgaon soil; Industrial area; Lead. DOI: http://dx.doi.org/10.3329/bjsir.v46i3.9032 BJSIR 2011; 46(3): 277-290