秋季长江口及邻近海域一氧化碳的分布、通量与微生物消耗速率

Distribution,Flux and Biological Consumption of Carbon Monoxide in the Changjiang River Estuary and Its Adjacent Area

2019年10月对长江口及邻近海域海水中一氧化碳(Carbon monoxide,CO)的浓度分布、海-气通量与微生物消耗速率进行了现场调查研究。秋季长江口及邻近海域大气中CO的体积分数处于142.6~482.7 ppbv之间,平均值为(271.6±80.1)ppbv。研究区域内表层海水中CO的浓度范围为0.11~3.27 nmol·L-1,平均值为(0.71±0.72)nmol·L-1。大气与海水中CO均呈现出近岸高、远岸低的分布趋势。CO浓度高值出现在表层海水中,且浓度随着深度增加而减少。表层海水中CO的浓度在中午时段表现出最大值,在凌晨前后出现最小值,具有明显的周日差异,表明了海水中CO的光化学产生这一来源特性。现场微生物消耗培养实验发现CO浓度随时间增长呈指数降低趋势,符合一级反应动力学,其微生物消耗速率常数(kbio)的范围为0.21~1.12 h^-1,平均值为(0.62±0.31)h^-1。此外,表层海水中CO浓度在绝大部分站位处于过饱和状态,过饱和系数在0.54~14.51之间,其海-气通量变化范围为-2.1~31.15 nmol·m^-2·h^-1,平均值为(4.84±7.54)nmol·m^-2·h^-1,显示长江口及邻近海域是大气中CO的源。

Distribution,sea-to-air flux and microbial consumption rate of carbon monoxide(CO)were studied in the Changjiang River Estuary and its adjacent area in October 2019.Atmospheric CO mixing ratios over the study area in autumn varied from 142.6 to 482.7 ppbv,with an average of(271.6±80.1)ppbv.The concentrations of CO in surface seawater in the study area ranged from 0.11 to 3.27 nmol·L^-1,with an average of(0.71±0.72)nmol·L^-1.Overall,the concentrations of atmospheric and seawater CO displayed a decreasing trend from inshore to offshore waters.The maximum value of CO concentration usually occurred in the surface seawater and decreased with increasing depth.The surface water CO concentration exhibited an obvious time variation,with maximal concentration at noon and minimal concentration at dawn.This phenomenon indicates that CO could be produced primarily via photochemistry.In situ incubation experiments of microbial consumption indicated that CO concentrations decreased exponentially with incubation time and the processes conformed to the first order reaction characteristics.The microbial CO consumption rate constants(kbio)in the surface water ranged from 0.21 to 1.12 h^-1,with an average of(0.62±0.31)h^-1.In addition,the surface CO concentrations at the most stations were oversaturated relative to the atmospheric concentrations.The saturation factors ranged from 0.54 to 14.51,with an average of(3.25±3.02).The sea-to-air fluxes of CO in the study area ranged from-2.1 to 31.15 nmol·m^-2·h^-1 with an average of(4.84±7.54)nmol·m^-2·h^-1,suggesting that the study area was a net source of atmospheric CO.