Roles of temperature and ventilation in oxygen consumption: A chemical kinetics view from the van't Hoff-based formulation.

In this study, we successfully estimated the apparent activation energy of a microbially driven oxygen-consuming reaction (microbial-driven) based on tracer data. The concept of the apparent chemical reaction rate constant was employed to estimate various thermodynamic parameters associated with the oxygen consumption rate in conjunction with Arrhenius/Eyring equations. Normal Ea values of 80-90 kJ mol-1 were found in the upper layers of the South China Sea and Sulu Sea, while higher Ea values (300-1000 kJ mol-1) were observed in the rapidly ventilated Mediterranean Sea, the Sea of Japan, and the Bering Sea with lower temperatures. We classified the characteristics of typical sea basins into four categories. The temperature-dependent oxygen consumption rate relationship in each marine region was systematically calculated to derive the respective thermodynamic characteristic values. This allowed us to parameterize the rate-temperature relationship into thermodynamic quantities, enabling more effective integration of distinct basin characteristics within different sea areas into the marine biochemical model. Parameterization facilitates relatively accurate prediction of changes such as temperature, oxygen consumption rate.

Tributary inflows enhance the microplastic load in the estuary: A case from the Qiantang River.

Microplastics (MPs) in the surface water of the Qiantang River and its tributaries were investigated in this study, to evaluate the contribution of riverine discharge on emerging pollution load in the Hangzhou Bay. The abundance of MPs (mean 1183 ± 269 particles/m3) showed spatially and temporally heterogeneous in the surface water. Polyamide, polyester, and polyethylene teraphalate were the major components, accounting for 77.4% of all polymer types. Fiber was the most common shape, indicating the potential anthropogenic sources of MPs. The MPs flux from the Qiantang River to the Hangzhou Bay was estimated to be 2831 tons/year, implying the importance of riverine discharge in an estuarine bay. The inputs from the complicated tributaries system led to a 20-fold increase of MPs flux, and would significantly improve their budget of downstream and estuary, so we suggested the control and management on plastic pollution should be strengthened in all aspects.