Organic Carbon Burial in the Aral Sea of Central Asia

Abstract

The burial of organic carbon in lake sediments plays an important role in the terrestrial carbon cycle. Clarifying the current status of carbon burial in the lakes of Central Asia is of great significance for the application of carbon balance assessments. With the analysis of the total organic carbon and nitrogen and the carbon isotope and organic carbon burial rate in the core sediment of the North Aral Sea, the status and influencing factors of organic carbon burial over the past 70 years can be revealed. The results showed that the main source of organic carbon was predominantly from lacustrine aquatic plants. However, the contribution of terrigenous organic carbon increased from the 1950s to the 1960s. The burial rate of organic carbon in North Aral Sea sediments was consistent with the overall change in the regional temperature. The burial rate of organic carbon showed an upward trend as a whole with an average of 28.78 g·m−2·a−1. Since 2010, the burial rate of organic carbon has stood at the highest level in nearly 70 years, with an average of 55.66 g·m−2·a−1. The protection of a lake by human beings can not only significantly improve the lake’s aquatic ecosystem but also help to increase the burial rate of the lake’s organic carbon.

Sediment Organic Carbon Sequestration of Balkhash Lake in Central Asia

“…On the one hand, the temperature directly affects the bacterial yield, which affects the rate of mineralization and the organic carbon burial efficiency [27]. The increase in temperature enhances the decomposition and transformation of organic carbon by microorganisms [59].…”

“…The higher the lake water temperature, the stronger the mineralization, and the less organic carbon burial [59]. On the other hand, temperature affects the biological primary productivity of the lake, which in turn affects the organic carbon storage [27,37]. As seen in Figure 4, the temperature in the Balkhash Lake area showed a significant increase over the past 100 years [35], indicating that the intensity of mineralization caused by temperature was far greater than the increase in primary productivity caused by temperature.…”

“…Detailed experimental procedures have been described in the literature [37,38]. The determination of TOC and total nitrogen (TN) was performed using a CE-440 elemental analyzer (EAI Company, Vienna, VA, USA), and the analytical error was below 5% [27,39]. δ 13 C values were analyzed using a Finnigan-MAT 251 isotope ratio mass spectrometer [39].…”

“…The analytical precision for δ 13 C of organic matter was 0.05‰. The calculation method for the organic carbon burial rate (OCBR) was based on the reference [27].…”

“…In the context of global warming, does the rate of carbon burial in lake sediments increase or decrease? Existing studies on the sediments of Small Aral Sea show that the organic carbon burial rate is increasing significantly [27]. The water area of Balkhash Lake is significantly larger than the Small Aral Sea, is there a similar change in Balkhash Lake?…”