长江口及其邻近海域营养盐与DSi余流通量的分布和季节变化

分别于夏季(2005年7月)、秋季(2005年11月)和春季(2006年4～5月)对长江口及毗邻海域进行观测,并根据水文数据、盐度与营养盐数据计算DSi余流通量.结果表明:三个季节SiO_3~(2-)平均浓度分别为54.31 μmol/L(秋季)、43.61 μmol/L(春季)和45.39 μmol/L(夏季).杭州湾区域PO_4~(3-)浓度一般比长江口高,与SiO_3~(2-)的分布情况不同,可能与悬浮物吸附与解吸附过程有关.调查区域内NO_2~- 和NH+4的浓度偏低.NO_3~-分布呈现出较好的保守性.NO_3~-占总氮的百分比平均为94.28%(夏季)、97.24%(秋季)、98.33%(春季).受陆源污染物排放的影响,在14号站位附近发现一个无机氮高于120 μmol/L的中心区.比较三个季节DSi余流通量东西分量和南北分量的绝对值,一般大潮大于小潮,表层大于底层.表层余流的方向一般向东,东南或南,底层流向主要是向西或西北.DSi的余流通量在近口门处站点较大,长江口前缘(SH1、SH2)和南缘(SH5)、杭州湾(ZJ1,ZJ2)的余流通量较大.

Distributions and seasonal variations of nutrients and DSi residual flux in Yangtze Estuary and adjacent area

Three cruises were carried out in the Yangtze Estuary and adjacent area,in summer (July,2005),autumn (Nov.2005) and spring (April to May,2006).The Residual fluxes of DSi were calculated using the data of flow rate,flow direction,salinity and concentration of nutrients.The results show that the concentration of SiO_3~(2-) in three seasons were 54.31 μmol/L (autumn),43.61 μmol/L (spring) and 45.39 μmol/L (summer),respectively.The concentration of PO_4~(3-) in Hangzhou Bay was higher than in Yangtze Estuary,which was related to the process of adsorption and desorption of suspension.The concentration of NO_2~- and NH+4 at some stations in research area were lower than the limit of detection.NO_3~- was conservative,and its percentages of total nitrogen in three seasons were 94.28% (summer),97.24% (autumn) and 98.33% (spring).Due to the impact of pollutant discharge,a center region of high concentration of DIN was detected around station 14.Compared with vector component of residual fluxes of DSi,values of vector components are higher during spring than neap tide,but values in surface are higher than in bottom.The residual fluxes in surface are generally eastward,southeastward or southward and those in bottom are generally westward.The fluxes of near estuary are higher than those in remote area.The higher values are usually detected at SH1,SH2,SH5,ZJ1 and ZJ2.