Anthropogenic and Natural Influences on Soil Organic Carbon Fractions: A Case Study on Soils of Meyghan Lake in Arak, Iran

Abstract

Monitoring and assessment of soil organic carbon (SOC) in the soils of arid areas are very important. The objectives of the study were to evaluate the responses of extractable and particulate organic matter in soils around Meyghan Lake in Arak (Iran) to surface water-inflows. Two layers (0-30 cm and 30-60 cm) of soils were sampled in the release sites of municipal wastewater and 3 rivers. Different fractions of SOC were measured and statistically analyzed. The soil sampled from the release sites of municipal wastewater had the highest total organic carbon (14.1 mg TOC g^-1 topsoil) and free particulate organic matter (8.07 mg FPOM g^-1 topsoil) due to better soil condition for plant growth. In contrast, the soil sampled from the release sites of wastewater of sodium sulfate plant had the lowest the total organic carbon (3.50 mg TOC g^-1 topsoil) and all of the fractions. The cold water extractable OC (CWEOC), occluded particulate organic matter (OPOM) and the heavy fraction (HF) as slow fractions responded to soil sampling time better than active fractions. They significantly increased in the soils sampled in fall. The means of CWEOC, hot water extractable OC (HWEOC) and OPOM were higher in the soils sampled from the eastern part of the lake with higher clay and moisture contents and lower elevation. They responded better to the soil properties controlling the biological activity and biodegradation. The best fraction for the study of short-term changes of SOM by anthropogenic and natural effects was FPOM in these non-agricultural lands.