Black carbon concentration and isotopic composition of surface sand from deserts and dune fields in Northern China

• We analyzed the stable carbon concentration and carbon isotopes of organic carbon (SOC%, δ13CSOC) and BC (BC%, δ13CBC) in surface sand from deserts and dune fields in Northern China.
• δ13СBC has positive correlation with δ13CSOC, and is controlled mainly by surface plants.
• SOC% and BC% are small, and BC/SOC is high.
• Exogenous BC from deserts has a limited impact on BC in the CLP.

Black carbon (BC) is a continuum of incomplete combustion products of vegetation and fossil fuels. It can be used as a proxy for wildfires and paleovegetation reconstruction. Nevertheless, BC can be transported by wind and water via atmospheric and fluvial transport. To research the characteristics of BC in deserts and dune fields that are directly connected with the Chinese Loess Plateau (CLP) in Northern China, and to evaluate the possibility that BC in deserts and dune fields occurs as exogenous BC in the CLP, we investigated surface sand from the Mu Us dune field, the Tengger Desert, and the Badain Jaran Desert, and analyzed the stable carbon concentration and carbon isotopes of organic carbon (SOC%, δ13CSOC) and BC (BC%, δ13CBC). The δ13CSOC, δ13CBC values ranged from − 27.4‰ to − 22.5‰, and − 28.2‰ to − 23.0‰, respectively, which mainly reflected δ13C changes in surface C3 grasses. A positive correlation was observed between δ13CBC and δ13CSOC, suggesting that local vegetation mainly controls δ13CBC. The difference between δ13CBC and δ13CSOC ranged from − 0.2‰ to + 3.5‰, and the difference is likely to be due to carbon isotope discrimination occurring during burning and SOC decomposition. The SOC% and BC% in these deserts and dune fields are very small (averaging 0.048% and 0.011%). The BC% of surface sand in these areas is about 5.5% of BC% in the CLP surface soils, and the Δ-δ13СBC value between surface sand in deserts and surface soils in CLP ranged from − 0.3‰ to − 6.3‰, so the change of δ13СBC in the CLP surface soils, deduced by exogenous BC from deserts, is less than 0.35‰. All these findings suggest that BC in deserts has a limited impact on BC in the CLP and is unlikely to affect interpretations of the BC record of wildfires and paleovegetation information in the CLP.