Two short-term summer cruises were performed in the vicinity of Rizhao Port, western Yellow Sea, to investigate summer water stratification and the phenomenon of marine sediment acidification. Results show that water stratification has formed as early as in May. The chemoclines of dissolved oxygen (DO) and pH usually occur deeper than the thermocline. Sometimes the chemoclines of DO and pH occur synchronously at the same depths, but sometimes they do not synchronize. Above the chemocline DO fluctuates markedly and maintains at a high level or even oversaturation in daytime, suggesting the far-field impact of vessel propulsion. Below the chemocline it invariably remains at a low and stable level and slowly drops downward. The pH values of surface sediments vary in the range of 6.3–7.6. A conspicuous sediment acidification is observed along the navigation region. This phenomenon is chiefly attributed to the intermittent disruption of summer stratification by shipping activity along the shipping channel and waterways. Water stratification precludes the penetration of DO down to the bottom sediments on fair ocean status, and maintains anoxia below the sediment–water interface, whereas the abrupt DO increase driven by propeller agitating is nearly restricted in the navigation area. Therefore, the aeration effect accelerating oxidation of reducing substances and organic matter is primarily responsible for enhanced acid accumulation in surface sediments. In addition, the suspension effect is identified by the negative offsets of zero point on pH–mV diagram. Most of the measured points are scattered correspondingly on three distinct regression lines, with similar slopes but different negative offsets of pH 6.53, 6.87, and 6.99, respectively. Their geographical distribution suggests that this effect has a positive relationship with the intensity of anthropogenic disturbance. Although the suspension effect is caused by the adsorption of charged particles at the pH glass electrode interface (Yang et al. in Part Sci Technol 7:139–152, 1989), its various intensity observed in practice may also reflect the inherent distinction of depositional environments in physicochemical conditions.

中文翻译：

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黄海西部日照港附近曝气引起的海洋沉积物酸化

在黄海西部日照港附近进行了两次夏季短期航行，以调查夏季水层分层和海洋沉积物酸化现象。结果表明，早在5月份就形成了水分层。溶解氧 (DO) 和 pH 的趋化层通常比温跃层更深。有时 DO 和 pH 的趋化线在同一深度同步发生，但有时它们不同步。趋化层上方DO波动明显，白天维持在高水平甚至过饱和，表明船舶推进的远场影响。在趋化层之下，它总是保持在一个低而稳定的水平，然后慢慢下降。表层沉积物的 pH 值在 6.3-7.6 的范围内变化。沿航区观察到明显的沉积物酸化。这种现象主要归因于航道和水道沿岸的航运活动对夏季分层的间歇性破坏。水分层阻止了 DO 向下渗透到海洋状况良好的底部沉积物，并在沉积物 - 水界面以下保持缺氧，而由螺旋桨搅拌驱动的 DO 突然增加在航行区域几乎受到限制。因此，加速还原物质和有机物氧化的曝气效应是增加表层沉积物中酸积累的主要原因。此外，悬浮效应由 pH-mV 图上零点的负偏移量确定。大多数测量点相应地分散在三个不同的回归线上，具有相似的斜率，但负偏移量分别为 6.53、6.87 和 6.99。它们的地理分布表明这种影响与人为干扰的强度呈正相关。虽然悬浮效应是由带电粒子在 pH 玻璃电极界面的吸附引起的（Yang et al. in Part Sci Technol 7:139–152, 1989），但在实践中观察到的各种强度也可能反映了沉积物的固有区别。物理化学条件下的环境。它们的地理分布表明这种影响与人为干扰的强度呈正相关。虽然悬浮效应是由带电粒子在 pH 玻璃电极界面的吸附引起的（Yang et al. in Part Sci Technol 7:139–152, 1989），但在实践中观察到的各种强度也可能反映了沉积物的固有区别。物理化学条件下的环境。它们的地理分布表明这种影响与人为干扰的强度呈正相关。虽然悬浮效应是由带电粒子在 pH 玻璃电极界面的吸附引起的（Yang et al. in Part Sci Technol 7:139–152, 1989），但在实践中观察到的各种强度也可能反映了沉积物的固有区别。物理化学条件下的环境。