Abstract: Concerns over global change have fueled interest in the carbon cycle, which has impelled the research on the distribution of various forms of carbon in terrestrial ecosystems, and the estimation of carbon storage amounts in various reservoirs. Black carbon (BC) is an important componet of organic carbon (OC), and also an important component of the inert carbon pool involved in the global slow carbon cycle. Palaces of several dynaties were buried in the underground of Kaifeng city by flood sediments of the Yellow River. This has formed the
unique spectacle of overlapping cities, which provide excellent and rare samples to study carbon density and storage in the historical period. Four sedimentary cores with a length of 25m were drilled in April, 2012. Three of them were located in the urban area of Kaifeng city(ZKsz, ZKyz and ZKml), and another one was located at the western suburb of the city (ZKjm).Each core was split into 10 cm intervals mostly, for a total number of 861 sediment samples.Then the density and storage of OC and BC were analyzed based on their respective content determination and bulk density. The results show that OC and BC contents can demonstrate the consistent vertical distribution characteristics, and their high values are mainly concentrated within a range of 0-1 m in depth, followed by the historical cultural layers. The OC and BC contents are both significantly higher in urban strata (ZKsz, ZKyz and ZKml) than those in the suburb (ZKjm) of Kaifeng city. The BC density and storage in the 0-25 m layer are 24.67 kg/m2 and 11.30 Tg, accounting for 24.26% and 21.75% of the total organic carbon (TOC) density and storage, respectively. This indicates that the BC storage of the strata occupies a large proportion of the whole carbon pool, so that it should be taken into account when we calculate carbon density and storage in soils and sediments. Comparison of the storage ratio of BC/TOC respectively in the old urban area and new area of Kaifeng city in 0-25 m layer, show that the former is over 10% higher than that of the latter, mainly due to its stronger influence of human activities and more extensive use of coal. This study can provide a reference for finding"missing carbon" and further studying the cycle and balance of carbon.
Keywords: organic carbon; black carbon; carbon density; carbon storage; flood sediments of Kaifeng city
【source】 Geographical Research 2018 Vol. 37 (2)