Abstract
A study was undertaken to evaluate the status of heavy metals in irrigation water and soils in the industrial areas, to examine the effects of heavy metals contamination on rice crop and to alleviate the toxic effect of heavy metals in soil through organic amendments. The first objective was achieved through survey and other objectives by the pot culture experiments. Eighty five each of irrigation water and soil samples from Hazaribug, Tongi and Gazipur areas were analyzed for heavy metal status along with other common parameters. The water sources were tanneries, pharmaceuticals, textiles, hand tubewells, deep tubewells, ponds and rivers. The industrial waste waters were found to be unsuitable for irrigation and followed the order of Tannery > Pharmaceutical > Textile (dying). Waste waters from weaving and spinning industries were uncontaminated. Heavy metals status of most of the agricultural soils was within the normal range. Pot culture experiments were conducted with terrace soil of Gazipur (AEZ 28) and floodplain soil of Narayanganj (AEZ 9) for consecutive two years taking Boro rice (cv. BRRI dhan29) as the test crop. The grain yield and nutrient content of rice decreased as the level of heavy metal increased. The concentration of heavy metal was much higher in straw than in grain. Among the heavy metals, chromium had the worst negative effect on crop followed by Ni. It appeared from the effluent experiment that at least 50% dilution of the effluents (tannery, pharmaceutical and textile) was necessary for irrigation use for normal crop growth in the terrace and floodplain soils. The organic amendment experiment indicated that addition of cowdung and poultry manure significantly increased the yield and nutrient content of rice which was possibly due to retention of toxic heavy metals by organic matter in addition to supply of plant nutrients. Between two sources of organic amendment, the effect of poultry manure was better than that of cowdung. There were some changes in soil properties after manure application. The soil pH remained almost unchanged and there was some improvement in N, P, K, & S status of soils. In every pot experiment, the grain yield was positively correlated with the number of tillers pot"', grains panicle1, 100-grain weight and straw yield. The nutrient and heavy metal uptake by plants followed mostly the pattern of rice yield due to different treatments. Overall study indicates that tannery effluent was the worst polluting source followed by pharmaceutical and textile effluents (dying).