秋季东海水体Eh、pH分布特征及其影响因素

根据2016年9~10月在东海海域38个站位取得的114个水体样品的氧化还原电位（Eh）和酸碱度（pH）现场测试数据，结合同步获得的水文环境要素调查资料，分析了该区秋季Eh和pH的空间分布特征及主要影响因子。结果显示:秋季水体Eh值范围在337.2~588.3 mV，平均值为526.57 mV，空间上呈现不连续分布特征，内陆架为高Eh区，口门外为低Eh区；pH介于7.80~8.24之间，平均为8.04，呈现近岸低、离岸高、表层高、底层低的特点。针对实测Eh与Nernst理论值非耦合现象，认为非热力学平衡状态下海域高Eh值主要受控制于O_2（aq）/H₂O电对浓度，其次受海水层化现象阻滞海-气交换影响，水体有机物矿化分解及Fe（Ⅲ）还原的相对贡献量增加。此外，Eh与温度呈显著负相关，与盐度呈显著正相关，表明物理过程是影响氧化还原反应的重要因素。pH与温度、盐度均呈显著正相关，其中长江冲淡水输入、扩散及混合对近岸pH的影响最为显著。受浊度、叶绿素a浓度及Eh制约，现场浮游植物生产仅对表层pH变化产生作用。基于pH-T、S建立的一元线性回归模型扣除温盐效应，校正后口门外底层低pH的存在可能是水体层化与有机分解相互叠加的结果。

Distributions and influence factors of Eh and pH in the East China Sea in autumn

On the basis of in-situ measured data of Eh and pH from water body which has collected from 38 stations (a total of 114 samples) in the East China Sea during autumn season in 2016.With the combination simultaneous observations of environment hydrology, spatial distributions and influential factors of Eh and pH were discussed.The results illustrated that the values of Eh varies from 337.2 mV to 588.3 mV having average value 526.57 mV which is characterized by discontinuities.There is south and north "dual-core" structure in space having higher values of Eh in the inner shelf and lower in the estuary.The range of pH value is from 7.80 to 8.24 having an average value 8.04.While the values of pH in coastal areas and surface layers are higher than as compared to outer shelf and bottom layers, respectively.Comparison of two methods are involved to measured Eh with Pt electrode and calculated Eh from the Nernst equation, we can infer that high Eh in disequilibrium state is mainly controlled by the concentrations of O_2(aq)/H₂O couple and the contribution of organic mineralization and reduction of Fe(Ⅲ) relatively increased due to obvious stratification.Additionally, significant negative and positive correlations emerged between pH and temperature, and salinity, revealing that physical processes are also important factors for the oxidation-reduction reactions.Strong positive correlation between pH, temperature and salinity has been found which is indicating that the variation of pH in near-shore areas are affected by the input, diffusion and mixing of Yangtze Diluted Water.Restricted by turbidity, chlorophyll and Eh, the production of phytoplankton is only responsible for the variation of pH in surface water.On the basis of linear regression model established by pH-T and -S, the effects of temperature and salinity have been removed and the low values of pH performed in bottom water off the estuary may probably due to the stratification structure and the local decomposition of organic matter.