Abstract

One of the most important effects of acidic rainfall is on the soil. It can affect other environments such as surface water and groundwater, plants and animals. In this study, to investigate the sensitivity of the runoff and sediment production of Gachsaran Gypsum Formation to acidic rainfalls and its density change, parts of Gypsum Mountain watershed the area in Izeh Township in Khuzestan province was selected with the area of 1202 ha. This investigation in order to determine the productivity of runoff and sediment in 8 points and with 3 replicates in Gachsaran Gypsum Formation in intensity 1 mm in a minute and the densities of distilled water, pH=4 and pH=5 in four slope aspects (northern, southern, eastern, western) with using of Kamphorst rainfall simulator, was done. In this investigation also, in order to determine the relationship between the sediment and runoff produced by rainfall simulator and some soil physic-chemical characteristics, like percent of gravel, sand, clay, silt, pH, EC, soil moisture, calcium carbonate, organic materials and sodium rate in slope, different aspects in Gachsaran Gypsum formations were done. To analyze data, SPSS and EXCEL packages was used. Summarily, in Gachsaran Gypsum Formation, soil chemical properties had the most important role in runoff production in precipitation with distilled water, soil physical properties had the most important role in sediment production in precipitation with distilled water; however, in acidic rainfall, soil chemical properties had the most important role.

Key words: Acidic rainfall, Gachsaran Gypsum Formation, soil erosion, Kamphorst rain simulator.