investigation of ammonium phosphate fertilizer influence on arsenic leaching in calcareous soils using soil columns

presence of arsenic, a heavy metal, in soil and water resources originating from geological formations of qorveh plain, which is considered as the main agricultural zone of kurdistan province in western iran, has put the agricultural products of this region at risk of pollution. since arsenate, as the most abundance form of arsenic in soil environment, competes against phosphate anion; application of ammonium phosphate fertilizer across farmlands in this region requires careful study. hence, four soil columns were made using a polluted soil sample obtained from the region. in the study, two control columns and two test columns were under weekly leaching process by pure and ammonium phosphate fertilizer containing distilled water, respectively, for six months. the results showed that there was no significant difference between the control and the test columns regarding amount of arsenic leached (p>0.05). after the six months of leaching; seven soil samples along every 10 cm of each soil column were taken and analyzed. according to the results, concentration of arsenic measured at the surface of the test columns was less than the control columns. moreover, arsenic concentrations significantly differed at various depths of both the control and the test columns (p<0.01). therefore, it could be concluded that the phosphate supplied to the test columns replaced arsenic at the soil surface encouraging arsenic to move into deeper layers where more root activities of cultivated plants are expected.