HEAVY METALS STATUS OF EFFLUENTS AND SOILS: EFFECT OF Cu AND SOIL AMENDMENTS ON SWEET CORN GROWN IN HIGH Cu CONTAINING SOIL
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Date
1997
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AAU, Anand
Abstract
In the present investigation, a preliminary survey was carried out to monitor the status of heavy metals and pollutants in the effluents of the major industrial belt of the state. Besides, soils and plant samples were also analysed for heavy metals contamination. Based on the information available from the survey, a pothouse experiment was conducted during rabi, 1995 by growing sweet com in the Cu contaminated soil which was given treatments of high Cu levels (i.e. 50, 100 and 200 µg g-1) in the presence and absence of organic (FYM @ 5 t ha-1) and inorganic (gypsum @ 50 % GR) amendments to study their effects on the crop growth, uptake of heavy metals as well as soil properties. The effluents, water, soil and plant samples taken in the survey and pothouse experiment were analysed to determine the various contents and other parameters to assess their pollution status by using standard analytical procedures. The results of preliminary survey work indicated that amongst different effluents, the Khari river effluent was highly acidic and found to be the most toxic one. Besides, TSS, COD and BOD, this effluent contained very high levels of different harmful elements viz., Fe, Cu, Mn, Cd, Ni, Co and Cr above the standard permissible limits for irrigation purpose. Similarly, the effluents from Ankleshwar industrial area were also more toxic than those in Vadodara and Bharuch industrial belts. It was found that the practice of irrigating soils with sewage and industrial effluents for a long time has definitely resulted in accumulation of different polluting elements; but their levels were within the permissible limits except Cu which was nearer to toxic level in industrial effluent mixed sewage water irrigated soil for a long time in Pirana sewage farm at Behrampura near Ahmedabad. The contamination level in other soil was not alarming. However, the accumulation might rise to toxic level if the effluents are used continuously over the years without proper management practice in future. The study also revealed that inspite of their low levels in soils, the contents of certain polluting elements viz., Mn, Ni and Cu were found above toxic levels in brinjal, maize and jowar, respectively. Moreover, in general, the bioavailability of the elements cautioned for regular monitoring for their soil contents in case of Cu, Pb, Zn, Cd and Mn. Amongst the different soil properties soil organic carbon significantly affected the availability of the elements positively. Besides the soil OC, pH and EC were other important properties to affect the availability of these elements in the soil. In a pothouse experiment the reduction in maize dry matter yield was significant due to DTPA extractable Cu, Cd and Mn but the prediction level was just 55 per cent. Among the soil properties, pH showed significant positive correlation with dry matter yield and except organically bound Cu all other soil Cu fractions depressed dry matter yield. Among the different DTPA extractable trace elements, copper showed the highest predictability by 93 per cent with the inclusion of various soil properties. In general, the effect of FYM application was found to be beneficial in reducing the harmful effect. The antagonistic effect of high Cu contents was observed to cause Fe chlorosis in maize. The treatment was found to alter the availability of heavy metals and thereby their removal also. The predictability of Ni removal was the highest by 89 per cent followed by Cd. The application of Cu resulted in enrichment of all Cu fractions whereas, FYM enriched organically bound Cu at the cost of decrease in exchangeable Cu and other Cu fractions; and almost reverse trend was observed in case of gypsum application.
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