黄河口有机碳的时空输运特征及其影响因素分析

Spatial and temporal distribution of particulate and dissolved organic carbon in Yellow River estuary

通过2004年4月,2004年9月,2005年9月,2006年4月4个航次,结合2003年8月对河道感潮带的连续同步观测,对低流量下黄河口有机碳的输运特征进行了考察。结果发现:黄河输入至河口的悬浮物中颗粒有机碳(POC)含量约为0.51%,主要以陆源输入为主,几乎不受季节变化影响,由于大量POC含量低的陆源泥沙的稀释作用,浮游植物对总颗粒有机碳的贡献只有在悬浮物含量(TSS)<200 mg/L时才能显现出来;黄河口TSS超过455 mg/L时,有机碳入海以颗粒有机碳为主;反之,以溶解有机碳为主。黄河口悬浮物在低盐度区沉降作用前后的中值粒径降低,Φ>16μm的悬浮物的沉降作用比Φ<16μm的悬浮物更为剧烈,POC含量随悬浮物粒径的降低而升高,黄河携带的颗粒有机碳80%以上集中在Φ<16μm的TSS中;低流量下,黄河口最大混浊带对POC的过滤效率为65%,混浊带对POC的过滤效应能造成黄河口POC的有效通量被高估;由于受黄河口沉积物向水体解析DOC的影响,在盐度小于10时,DOC几乎不受海水稀释作用的影响,但在盐度大于10的区域DOC与盐度表现出良好的负相关关系,黄河口枯、丰水期淡水端溶解有机碳的有效浓度分别高于实测最高值20%和10%左右,从而造成黄河口DOC有效通量被低估。

The dissolved and particulate organic carbon（POC） at Yellow River estuary are studied by 4 cruises of April and September 2004, Septenber 2005 and April 2006, and simultaneously and consecutively measured in August 2003. The result indicates that POC in the total suspended sediment （TSS） is about 0.51% without variations from dry weather to wet one. With this uniformity, POC values are correlated well with the concentrations of the total suspended matter. Due to the terrestri- al TSS dilution, the contribution of autochthonous POC to total POC appears when TSS 〈 200 mg/L, Φ 〈 16 gm portion of TSS increases in the composite particles, which causes the decrease of median size-particles after precipitation of particles, and the percentage of POC increases with the decrease of the particles size. More than 80% POC concentrates on particles with Φ 〈 16 gin, and POC in particles with Φ〈 32 gm account for 95% flux from the Yellow River estuary to Bohai sea. 65% of the total POC will be settled with the precipitation of particles in the maximum turbidity zone （MTz）. When TSS = 455mg/L, the ratio of DOC/POC is 1. A linear distribution of DOC versus salinity are observed when S 〉 10 both in dry and wet weather, but the input of DOC in the sediments desorption process, when S 〈 10 range, will make DOC＇s effective concentration 10% and 20 % higher respectively than in situ freshwater in dry and wet weather.