Investigation of heavy metals in soil samples before rice planting and after rice harvesting in Mazandaran province; Study of ecological risk potential and integrated pollution indexes

Soil contamination with heavy metals is a serious issue in all the world, and these heavy metals are released from both natural and human resources, especially agricultural activities in the environment. Therefore, in this study, the amount of heavy metals and the indicators of ecological risk potential and integrated pollution in soil samples before rice planting and after rice harvesting in Mazandaran province have been investigated. A mixture of nitric acid, hydrofluoric acid and perchloric acid was used for chemical digestion of soil samples and ICP-MS was used to measure the amount of heavy metals in soil samples. The results of comparing the levels of chromium, zinc, nickel and lead in the soil before rice planting and after rice harvesting with the national and international soil standard show that the levels of these metals in most stations are higher than Domestic and international standard limits were measured. Based on the results, the amount of ecological risk potential index in soil samples showed that in all studied stations ana sampling stages, the amount of this index was calculated in the range of low ecological risk (below 150). Also, the results of PI pollution index and integrated pollution index (IPI) for each studied station in soil samples before rice planting and after rice harvesting show the PI index for arsenic, chromium, cadmium, copper, nickel, zinc and mercury. In all stations in soil samples before rice planting and after rice harvesting in the range of low contamination was calculated, only the amount of this index for lead in all stations and sampling stages, in the range of moderate contamination was obtained. Also, the results of IPI for all studied stations in all stations and sampling stages, show that the level of this index was determined in the low pollution range. In general, the presence of heavy metals in the soil environment, followed by the accumulation of heavy metals in food, has detrimental and irreversible effects on human societies and food security, so more precautions are needed to reduce such effects.