A Study on Transboundary Marine Governance of Floating Marine Debris—Taking Kinmen–Xiamen Waters between China and Taiwan as an Example

Mainland China’s economy has been developing rapidly. Unfortunately, it has led to an increase in municipal and industrial waste, including in Xiamen, in which is has greatly increased. Kinmen is located outside the estuary of the Jiulong River in Fujian, Mainland China, opposite to Xiamen Bay. Whenever there is heavy rainfall, the waste that flows along the Jiulong River is incredible. Kinmen unavoidably has to bear the invasion of floating marine debris due to the effect of ocean currents, tides and monsoons. It does not only pollute the Kinmen sea area, but it also affects the scenery of the beaches in Kinmen. Therefore, this study aimed to explore the data of Kinmen and Xiamen governments regarding the cleaning of floating marine debris, and the differences in distribution areas according to the monsoon, ocean current and tides. In-depth interviews, field investigation, and collection of expert opinions were applied in order to determine the research implication. The results of this study provide information on the marine issues encountered in the governance of the countries surrounding the sea. The study suggests that the transboundary marine governance mechanism should be established in order to effectively solve the problem of floating marine debris in Kinmen–Xiamen Waters. For the welfare of the people, it is expected that the governments of Mainland China and Taiwan will uphold the principle of “pragmatism and reciprocity” by working together to maintain the marine environment in Kinmen–Xiamen waters.

Mid-Level Riverine Outflow Matters: A Case of Microplastic Transport in the Jiulong River, China

Riverine outflow is one of the major pathways for microplastic transportation to coastal environments. Research on the output of microplastics in small- or medium-sized rivers will help accurately understand the status of their marine loads. In this study, we used both trawling and pumping methods to collect microplastics of different sizes in the Jiulong River Estuary and Xiamen Bay. We found that the abundance of small microplastics (44 μm–5.0 mm) was at least 20 times higher than the large particles (0.33–5.0 mm). The abundance of the large particles ranges from 4.96 to 16.3 particles/m3, and that of the small particles ranged from 82.8 to 918 particles/m3. Granule was the dominant shape (>60%), and polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET) were the most common components. The riverine flux of small microplastics (44 μm–5 mm, 472 ± 230 t/y) was at a medium level and was eight times greater than that of large particles (0.33–5.0 mm, 61.2 ± 2.6 t/y). The behavior of the large microplastics was relatively conservative, whose abundance had a significant correlation with salinity (R2 = 0.927) and was mainly influenced by physical factors. In contrast, results of statistical analysis revealed that more complicated factors influenced the small microplastics.

Identification and Regulation of Critical Source Areas of Non-Point Source Pollution in Medium and Small Watersheds Based on Source-Sink Theory

The identification and regulation of the critical source areas (CSAs) of non-point source (NPS) pollution have been proven as economical and effective ways to control such pollution in watersheds. However, the traditional models for the identification of CSAs have complex operation processes, and comprehensive systematic methods for the regulation of CSAs are still lacking. This study systematically developed a new methodological framework for the identification and regulation of CSAs in medium and small watersheds based on source-sink theory, which included the following: (1) a grid-based CSAs identification model involving the evaluation of the rationality of the source-sink landscape pattern and three geographical factors (landscape slope, relative elevation, and the distance from the river), and identifying CSAs by the calculation and division of the integrated grid pollution index (IGPI); (2) a comprehensive CSAs regulation strategy that was formulated based on three landscape levels/regulation intensities—including the optimization of the overall source-sink landscape pattern, the conversion of the landscape type or landscape combination, and local optimization for single source landscape—to meet various regulatory intensity requirements in watersheds. The Jiulong River watershed in Fujian Province of China was taken as a case study. The results indicate that: (1) the identified CSAs of the Jiulong River watershed covered 656.91 km2, equivalent to 4.44% of the watershed, and through adopting multiple-intensity regulation measures for 10 key control zones that had spatially concentrated high values of the IGPI among the CSAs, the watershed IGPIs were predicted to be generally reduced and the area of CSAs was predicted to decrease by 23.84% (31.43% in Zhangzhou, the major city in the watershed); (2) the identification model can identify the CSAs with easy data access and simple operation, and the utilization of neighborhood impact analysis makes the grid-based research more scientific in the evaluation of the rationality of the source-sink landscape pattern; (3) the application of multi-scale landscape planning framework and the principle of source-sink landscape pattern regulation make the CSAs regulation strategy systematic and cost-effective, and the provision of different intensity regulation strategies makes the regulation strategy easy to implement and relatively lower cost. The proposed methodological framework can provide technical support for governments to quickly and accurately identify the CSAs of NPS pollution and effectively control such CSAs in medium and small watersheds.