Controlling mechanisms of surface partial pressure of CO2 in Jiaozhou Bay during summer and the influence of heavy rain

作者：Li Yunxiao; Yang Xufeng; Han Ping; Xue Liang; Zhang Longjun^*

来源：Journal of Marine Systems, 2017, 173: 49-59.

DOI：10.1016/jjmarsys.2017.04.006

• pCO(2)
• Heavy rain
• Sewage input
• Biological process
• Calcium carbonate precipitation
• Jiaozhou Bay

Due to the combined effects of natural processes and human activities, carbon source/sink processes and mechanisms in the coastal ocean are becoming more and more important in current ocean carbon cycle research. Based on differences in the ratio of total alkalinity (TA) to dissolved inorganic carbon (DIC) associated with terrestrial input, biological process (production and respiration), calcium carbonate (CaCO3) process (precipitation and dissolution) and CO2 evasion/invasion, we discuss the mechanisms controlling the surface partial pressure of CO2 (pCO(2)) in Jiaozhou Bay (JZB) during summer and the influence of heavy rain, via three cruises performed in mid-June, early July and late July of 2014. In mid-June and in early July, without heavy rain or obvious river input, sea surface pCO(2) ranged from 521 to 1080 atm and from 547 to 998 atm, respectively. The direct input of DIC from sewage and the intense respiration produced large DIC additions and the highest pCO(2) values in the northeast of the bay near the downtown of Qingdao. However, in the west of the bay, significant CaCO3 precipitation led to DIC removal but no obvious increase in pCO(2), which was just close to that in the central area. Due to the shallow depth and longer water residence time in this region, this pattern may be related to the sustained release of CO2 into the atmosphere. In late July, heavy rain promoted river input in the western and eastern portions of JZB. Strong primary production led to a significant decrease in pCO(2) in the western area, with the lowest pCO(2) value of 252 atm. However, in the northeastern area, the intense respiration remained, and the highest pCO(2) value was 1149 atm. The average air-sea CO2 flux in mid-June and early July was 20.23 mmol m(-2) d(-1) and 23.56 mmol m(-2) d-1, respectively. In contrast, in late July, sources became sinks for atmospheric CO2 in the western and central areas of the bay, halving the average air-sea CO2 flux to a value of 10.58 mmol m(-2) d(-1). Therefore, without considering the impact of heavy rains, the estimated air-sea CO2 flux is likely inaccurate in coastal waters. Our study implies that more studies in the coastal ocean are needed to determine the duration and intensity of the CO2 sink after the occurrence of heavy rain as well as the magnitudes of the CO2 sink associated with varying rainfall intensities.

• 出版日期2017-9
• 单位中国海洋大学; 国家海洋局第一海洋研究所