Carbon and mercury export from the Arctic rivers and response to permafrost degradation

Cuicui Mu; Feng Zhang; Xu Chen; Shemin Ge; Mei Mu; Lin Jia; Qingbai Wu; Tingjun Zhang

doi:10.1016/j.watres.2019.05.082

Carbon and mercury export from the Arctic rivers and response to permafrost degradation

Water Res. 2019 Sep 15:161:54-60. doi: 10.1016/j.watres.2019.05.082. Epub 2019 May 26.

Authors

Cuicui Mu¹, Feng Zhang², Xu Chen², Shemin Ge³, Mei Mu², Lin Jia², Qingbai Wu⁴, Tingjun Zhang⁵

Affiliations

¹ Key Laboratory of Western China's Environmental Systems (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou University, Lanzhou, 730000, China; State Key Laboratory of Cryospheric Science, Northwest Institute of the Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou, China; State Key Laboratory of Frozen Soil Engineering, Northwest Institute of Eco-Environment and Resource, Chinese Academy of Sciences, Lanzhou, Gansu, 730000, China. Electronic address: mucc@lzu.edu.cn.
² Key Laboratory of Western China's Environmental Systems (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou University, Lanzhou, 730000, China.
³ Department of Geological Sciences, University of Colorado Boulder, Boulder, CO, USA.
⁴ State Key Laboratory of Frozen Soil Engineering, Northwest Institute of Eco-Environment and Resource, Chinese Academy of Sciences, Lanzhou, Gansu, 730000, China.
⁵ Key Laboratory of Western China's Environmental Systems (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou University, Lanzhou, 730000, China; University Cooperation of Polar Research, Beijing, 100875, China. Electronic address: tjzhang@lzu.edu.cn.

PMID: 31176884
DOI: 10.1016/j.watres.2019.05.082

Abstract

Arctic rivers export a large amount of organic carbon (OC) and mercury (Hg) to Arctic oceans. Because there are only a few direct calculations of OC and Hg exports from these large rivers, very little is known about their response to changes in the active layer in northern permafrost-dominated areas. In this study, multiyear data sets from the Arctic Great Rivers Observatory (ArcticGRO) are used to estimate the export of dissolved organic carbon (DOC), particulate organic carbon (POC), total mercury (THg) and methylmercury (MeHg) from the six largest rivers (Yenisey, Lena, Ob, Mackenzie, Yukon and Kolyma) draining to the Arctic Ocean. From 2003 to 2017, annual DOC and POC export to the Arctic Ocean was approximately 21612 Gg and 2728 Gg, and the exports of Hg and MeHg to the Arctic Ocean were approximately 20090 kg and 110 kg (0.002% of the total Hg stored in the northern hemisphere active layer). There were great variations in seasonal OC and Hg concentrations and chemical characteristics, with higher fluxes in spring and lower fluxes in winter (baseline). DOC and Hg concentrations are significantly positively correlated to discharge, as discharge continues to increase in response to a deepening active layer thickness during recent past decades. This study shows that previous results likely underestimated DOC exports from rivers in the circum-Arctic regions, and both OC and Hg exports will increase under predicted climate warming scenarios.

Keywords: Active layer; Discharge; Mercury; Organic carbon; Riverine export.

MeSH terms

Arctic Regions
Carbon
Environmental Monitoring
Mercury*
Oceans and Seas
Permafrost*
Rivers
Water Pollutants, Chemical*
Yukon Territory

Substances

Water Pollutants, Chemical
Carbon
Mercury