Appraisal of the carbon to nitrogen (C/N) ratio in the bed sediment of the Betwa River, Peninsular India

Abstract

Bed sediment carbon to nitrogen (C/N) ratio is one of the essential variables reflecting sources of organic matter in river basins. In order to explore the spatial variability in sources of sediment C/N ratios, and the influence of land use and land cover (LULC) changes on the Betwa River basin in Peninsular India, 51 river bed sediment samples were collected in December 2016. The coefficient of variation (CV) was >35% indicating highly variable biogeochemical parameters. The sediment C/N ratio varied from 2.94 to 10.09, 3.21–56.40, and 6.50–76.97 in upstream, mid-stream, and downstream regions, respectively, indicating a progressive change in sources of organic matter and depositional environment. The positive correlation between total carbon (TC) and C/N ratio was increasing in the downstream direction [upstream (+0.560) < mid-stream (+0.603) < downstream (+0.838)], which is an indication of high deposition and slow decomposition of sedimentary terrigenous organic matter distant from the regions of urban pollution. The LULC change analysis done by remote sensing and Geographic Information System (GIS) methods revealed an adverse change for the forests and barren land and a positive change for the agricultural land and built-up areas. The sediment C/N ratio mapping showed the impact of LULC changes on the sediment quality. The spatial distribution of bed sediment C/N ratio in the Betwa River basin has important reference value for managing organic matter transport in the downstream Yamuna River and Ganga River basin.