Wastewater inputs reduce the CO2 uptake by coastal oceans

Yunxiao Li; Liang Xue; Xufeng Yang; Qinsheng Wei; Ming Xin; Ming Xue; Chenhua Han; Ping Han; Xiangyu Liu; Han Zang; Pengjin Yang; Xiangbin Ran; Lu Cao; Wei-Jun Cai; Longjun Zhang

doi:10.1016/j.scitotenv.2023.165700

Wastewater inputs reduce the CO₂ uptake by coastal oceans

Sci Total Environ. 2023 Nov 25:901:165700. doi: 10.1016/j.scitotenv.2023.165700. Epub 2023 Jul 24.

Authors

Yunxiao Li¹, Liang Xue², Xufeng Yang³, Qinsheng Wei⁴, Ming Xin⁴, Ming Xue⁵, Chenhua Han³, Ping Han⁶, Xiangyu Liu⁷, Han Zang⁸, Pengjin Yang⁹, Xiangbin Ran⁴, Lu Cao¹⁰, Wei-Jun Cai¹¹, Longjun Zhang⁷

Affiliations

¹ Environmental Science Laboratory, College of Resource and Environment, Shanxi Agricultural University, Taigu 030801, China.
² First Institute of Oceanography, and Key Laboratory of Marine Science and Numerical Modeling, Ministry of Natural Resources, Qingdao 266061, China. Electronic address: xueliang@fio.org.cn.
³ Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China.
⁴ First Institute of Oceanography, and Key Laboratory of Marine Science and Numerical Modeling, Ministry of Natural Resources, Qingdao 266061, China.
⁵ State Key Laboratory of Petroleum Pollution Control, CNPC Research Institute of Safety and Environmental Technology, Beijing 102206, China.
⁶ Department of Environmental Engineering, Shandong Urban Construction Vocational College, Jinan 250103, China.
⁷ College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China.
⁸ College of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
⁹ North China Sea Environmental Monitoring Center, State Oceanic Administration, Qingdao 266033, China.
¹⁰ Institute of Oceanographic Instrumentation, Qilu University of Technology (Shandong Academy of Sciences), Shandong Provincial Key Laboratory of Ocean Environmental Monitoring Techno1ogy, National Engineering and Technological Research Center of Marine Monitoring Equipment, Qingdao, China; R & D Center for Marine Instruments and Apparatuses, Qingdao Marine Science and Technology Center, Qingdao, China.
¹¹ School of Marine Science and Policy, University of Delaware, Newark, DE, USA.

PMID: 37495126
DOI: 10.1016/j.scitotenv.2023.165700

Abstract

Every year a large quantity of wastewater is generated worldwide, but its influence on the carbon dioxide (CO₂) uptake by coastal oceans is not well understood. Here, sea surface CO₂ partial pressure (pCO₂) and air-sea CO₂ flux were examined in the Jiaozhou Bay (JZB), a temperate coastal bay strongly disturbed by wastewater inputs. Monthly surveys from April 2014 through March 2015 showed that surface pCO₂ in the JZB substantially varied both temporally and spatially between 163 μatm and 1222 μatm, with an annual average of 573 μatm. During April-December, surface pCO₂ was oversaturated with respect to the atmosphere, with high values exceeding 1000 μatm in the northeastern part of the bay, where seawater salinity was low mainly due to the inputs of wastewater with salinity close to zero. During January-March, surface pCO₂ was undersaturated, with the lowest value of <200 μatm also mainly in the northeastern part because of low water temperature and strong biological production. Over an annual cycle, apparently sea surface temperature dominated the monthly variation of surface pCO₂ in this shallow bay, while wastewater inputs and related biological production/respiration dominated its spatial variability. Overall, the JZB was a net CO₂ source to the atmosphere, emitting 9.6 ± 10.8 mmol C m^-2 d^-1, unlike its adjacent western part of the Yellow Sea and most of the temperate coastal oceans which are a net CO₂ sink. This was possibly associated with wastewater inputs that cause high sea surface pCO₂ via direct inputs of CO₂ and degradation of organic matter. Thus, from this viewpoint reducing wastewater discharge or lowering CO₂ levels in discharged wastewater may be important paths to enhancing the CO₂ uptake by coastal oceans in the future.

Keywords: Air-sea CO(2) flux; Carbon dioxide; Coastal ocean; Jiaozhou Bay; Wastewater inputs.