New estimate of chemical weathering rate in Xijiang River Basin based on multi-model

Yong Zhang,Shi Yu,Pingan Sun,Peng Zeng,Xiao Li,Shiyi He,Fu Wu,Haiyan Zhu,Zhenyu Liu

doi:10.1038/s41598-021-84602-1

Yong Zhang, Shi Yu + Show 7 more

Open Access

https://doi.org/10.1038/s41598-021-84602-1

Copy DOI

Abstract

Hydrochemistry and Sr isotope compositions were measured in water samples collected during high- and low-water periods from the main stream and tributaries of the Xijiang River Basin in southern China. The primary weathering end-members were analyzed and calculated using the multi-model combination and classic hydrogeochemical method. During the high-water period, structural factors were found to be the main factors controlling chemical weathering in the basin, whereas anthropogenic activity and other random factors had a negligible influence. During the low-water period, both structural and random factors controlled chemical weathering. Through path-model and semi-variance analyses, we determined and quantified the relationship between the main weathering sources, whose results were stable; this is consistent with the inversion model. The total dissolved substances were mainly derived from carbonate weathering, which was approximately 76% (0–96%) while silicate weathering accounted for only 14% (5–19%). The inversion model results showed that the optimum silicate weathering rate was 7.264–35.551 × 103 mol/km2/year, where carbonic acid was the main factor that induces weathering. The CO2 flux consumed by rock weathering in the basin during the study period was 150.69 × 109 mol/year, while the CO2 flux consumed by carbonic acid weathering of carbonate (CCW) and silicate rocks (CSW) was 144.47 and 29.45 × 109 mol/year, respectively. The CO2 flux produced by H2SO4 weathered carbonate (SCW) was 23.23 × 109 mol/year.

Highlights

As a critical component of the global water cycle, rivers are the main channel that connect the land ecosystem and ocean, two major active carbon pools
The Fifth Intergovernmental Panel on Climate Change (IPCC) report confirmed that the inorganic carbon flux from the chemical weathering of carbonate rocks is a carbon sink on the century-to-millennium time scale[13,14,15]
The Xijiang River Basin is a region characterized by numerous agricultural activities from April–September, which may increase the N a+ and K + levels during the high-water period

Summary

Introduction

As a critical component of the global water cycle, rivers are the main channel that connect the land ecosystem and ocean, two major active carbon pools. Human activities are an important factor affecting rock weathering, especially the karst environment which is fragile[26,27] and prone to quick penetration from pollutants such as domestic sewage and agricultural fertilizers[28,29] This results in the high mobility of n itrogen[30], which directly leads to the action of ammonia nitrogen in the soil layer to control the hydrogeochemical process in the hydrochemical e volution[31,32]. For an in-depth study of the carbon sink due to rock weathering and its controlling mechanism, we must more accurately evaluate the contribution of each end-member, especially in rivers This places increased importance on the calculation method, assessment technique, and constructed model for the carbon sink effect. Assessing the total flux and proportion of each end-member is especially challenging

Methods

Results

Discussion

Conclusion