نوع مقاله : مقاله پژوهشی
نویسندگان
1 دانشجوی دکتری خاکشناسی دانشگاه شهید چمران اهواز
2 دانشیارگروه خاکشناسیدانشگاه شهید چمران اهواز
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
In recent years, use of sewage sludge as a fertilizer has become prevalent in agricultural lands, because of being cheap. Sewage sludge is a source of nutritional elements, however, it contains some heavy metals. A study was conducted to evaluate the effect of incubation time, sewage sludge, and Thiobacillus bacteria on the distribution of cadmium in a calcareous soil. For this purpose, an experiment with three levels of sewage sludge (0 , 50, and 100 t ha-1), two levels of bacteria (with and without), three incubation times (0 , 30, and 60 days) was carried out. The experiment was conducted in three replications in controlled conditions using factorial arrangement with a completely randomized design. The samples were incubated for two months at temperature of 25±2 °C and soil moisture condition close to field capacity. Distribution of Cd in fractions including soluble+ exchangeable, organically bound, carbonate-bound, and residual fractions was determined by a sequential extraction method. The results illustrated that residual and carbonate form of Cd were dominant and showed a significant change with sewage sludge treatment and time. Sewage sludge application increased the amount of fractions of cadmium significantly in the calcareous soil. The proportion of residual and carbonat-bound Cd was higher in soil with and without bacteria. In soil withThiobacillus thiooxidans bacteria, the percentage of Cd in the carbonate and organic fractions decreased and the percentage of Cd increased in other fractions. Carbonate fraction of Cd was significantly higher in 60 days than 0 and 30 days. The organic forms of Cd decreased significantly in the course of time. In general, based on the results, it may be concluded that sewage sludge, Thiobacillus thiooxidans bacteria, and time treatment play a key role in the distribution of Cd in different fractions of soils.
کلیدواژهها [English]