Vertical distribution characteristics and source tracing of organic carbon in sediment of the Yellow River wetland, Sanmenxia, China

Abstract

To investigate the vertical distribution and sources of organic carbon in the Yellow River wetland, the carbon and nitrogen isotopic composition and hydrochemical characteristics of sediment were studied systematically. The contents of TON (0.01–0.02%) and TOC (0.07–0.2%) are low and exhibit no significant differences over the vertical distribution, illustrating the loess sediments are infertile in Yellow River wetland. NH4+ is the main form of dissolved inorganic nitrogen (DIN) in sediment, accounting for 68–98% of the total DIN. The sediment content of δ13C-TOC is − 25.17‰ ( ± 0.52‰) to − 23.90‰ ( ± 0.21‰), the poor correlation between δ13C-TOC and the C/N ratio indicates that the C/N ratio in the sediments is the result of a mixture of complex biochemical processes. The relationship between δ13C and δ15N shows that the sediment organic matter is a mixed phase of plants and suspended particulate matter (SPM). The simulation results of the three end-member mixing equations show that the sources of organic carbon in sediment are SPM, plants, and microphytobenthos, with contribution rates of 45.6% ( ± 5.80%), 27.90% ( ± 5.13%), and 26.2% ( ± 3.52%), respectively.