雨滴对水-气界面溶解氧与pH扩散影响的平面光极观测方法

水-气界面是一个重要的物质交换过程界面，对生态系统及生物地球化学循环过程有着重要影响。自然界的降雨可以改变水体表面平衡状态，提高气体在界面的通量交换速率，使得水体界面溶解氧和pH的水平、垂直方向浓度分布发生变化。本文利用平面传感膜具有高时空分辨率、可提供两维浓度分布信息的特点，开展了雨滴对水-气微界面层中的氧气扩散和pH值分布变化模拟实验，采用双参数平面光极同步测量获取低溶解气体在水-气界面的两维分布浓度变化。实验结果证明在受风速、温度影响较小区域，降雨过程对调节表层水体的溶解氧含量和pH值变化具有重要作用，雨滴可以打破水-气界面的微表层平衡机制，促进大气中氧气在表层水体的溶解，使得水面垂直方向23 mm内的溶解氧平均升高2.3 mg/L；降雨对水面12 mm之内表层水体pH值产生的影响较为明显，pH值平均降低了0.2~0.4个单位，表明降雨雨滴促进大气在水-气界面的迁移进程，溶解的CO₂使得表层水体向酸性方向转化。本文提出的基于平面光极两维观测方法为评估低风速、高降雨或低降雨区域的海岸带溶解氧和pH值的变化提供高空间分辨率的水-气界面实时观测新的技术支撑。

Planar optode observation method for the effect of raindrop on dissolved oxygen and pH diffusion of air-water interface

The air water interface is an important interface where material exchanges, it has important influence on ecosystem and biogeochemical cycle. The rain can change the balance of interface, improve the exchange rate of gas flux, and make the distribution of dissolved oxygen and pH of the interface change in horizontal and vertical direction. Based on planar sensing film with highly spatial and temporal resolution, which can provide the characteristics of two-dimensional distribution information, we carry out the simulation experiment of raindrops about oxygen and pH distribution in air-water interface by using double parameters planar optode. The results show that rainfall process plays an important role in adjusting dissolved oxygen and pH of the surface water, the raindrop can break the balance of micro surface of water-gas interface mechanism, and promote the dissolution of oxygen in the atmosphere in water to make a average increase of about 2.3 mg/L in vertical direction 23 mm. The impact of rainfall on pH of the water surface within 12 mm is relatively obvious, the pH value decreased by an average of 0.2-0.4 units, indicating that the raindrop promoted the migration of the atmosphere in the air-water interface, and the dissolved CO₂ caused the surface water acidification. This study provides a new technical method for understanding the influence of raindrops on the dissolved oxygen concentration and pH of the surface water in low wind impacting area and static water area.