2011年长江口-东海P-PN断面碳酸盐体系参数的季节分布特征及影响因素

Seasonal distributions and influencing factors of seawater carbonate system parameters along the Changjiang(Yangtze River)Estuary-East China Sea P-PN transects in 2011

海水碳酸盐体系参数是反映碳循环调控机理和季节性酸化过程的重要海水化学参数。本文根据2011年3月、7月、11月和12月4个不同季节航次获取的长江口海域海水碳酸盐体系参数,探讨了长江口-东海P断面溶解无机碳(DIC)和总碱度(TA)的空间分布特征及其影响因素。结果表明:内陆架区,DIC和TA的平均值均表现为:夏季<秋季<冬季<春季;垂直分布上,夏季和秋季受长江冲淡水影响出现层化现象,春季和冬季均垂直混合较均匀。东海内陆架DIC与温度和DO呈显著负相关;TA则受温度和DO变化影响较小,与盐度呈正相关。结合2011年东海外陆架的PN断面数据分析,DIC和pH分别与表观耗氧量(AOU)呈显著正相关和负相关,东海外陆架的pH/AOU的斜率为-0.0027 pH/(μmol·kg^(-1));而内陆架区的pH/AOU的斜率为-0.0018 pH/(μmol·kg^(-1)),低于黑潮次表层水中pH/AOU的斜率。东海内陆架区由于存在季节性的通风作用以及较强的海水碳酸盐体系缓冲能力,底层水体中因有机质耗氧降解导致的季节性酸化信号在一定程度上得到了缓解。

The acquisition of seawater carbonate system parameters is essential to understand the carbon cycle in coastal ocean,the pattern of CO_(2) sources and sinks and assess the potential of carbon sinks.Based on the data obtained by 4 seasonal cruises conducted off Changjiang(Yangtze River)Estuary and adjacent East China Sea in March,July,November and December in 2011,we discuss the seasonal and spatial distributions of dissolved inorganic carbon(DIC)and total alkalinity(TA)and their influencing factors.The results showed that the averaged DIC and TA concentrations in inner shelf were increased from summer to autumn,then winter to spring;In cross-section distribution,DIC and TA in summer and autumn showed stratification pattern due to the influence of Changjiang Diluted Water,while in spring and winter,DIC and TA were vertically uniform due to mixing.In inner East China Sea shelf,transect DIC showed a significant negative correlation with temperature and dissolved oxygen,while TA was less regulated by temperature and dissolved oxygen changes,but positively correlated with salinity.DIC was significantly positively correlated with apparent oxygen consumption(AOU),while pH was significantly negatively correlated with AOU.The slope of pH/AOU in the outer East China Sea shelf was-0.0027 pH/(μmol·kg^(-1)),which was much higher compared with that of-0.0018 pH/(μmol·kg^(-1))in the inner shelf.The inner East China Sea shelf seawater(water depth is less than 200 meters)was affected by seasonal ventilation and had stronger carbonate system buffer capacity,which alleviated the seasonal acidification in the subsurface water induced by organic matter decomposition.