| dc.description.abstract | In the study of Taiwan Strait, a lagrangian particle tracking algorithms were applied to
characterize the transport of Plastic Marine Debris (PMD) which correspond to the seasonal
variability transportation in Taiwan Strait. The results of estimation probable trajectories could
be used to estimate the PMD amount at the sources. First, the estimation of PMD possible
sources could be obtained by simulating an ensemble average over 216 floating elements and
using the remote sensing surface ocean current data provided by TORI (Taiwan Ocean Research
Institute) High Frequency (HF) coastal radar network from 2015-2017. The Penghu Islands
were located in the middle of Taiwan Strait were chosen as PMD destination for example.
The results of first discussion are, ocean mixing and stokes drift that induced by wave
motion, were the main factors in uncertainty of applying HF coastal radar to simulate PMD
trajectories. The Dispersion Coefficient (K) was adopted to represent the horizontal mixing
efficiency. Based on the simulation results over 3 years, the average magnitude of K revealed
1.06 × 10−4 in spring, 3.66 × 10−5 in summer, 2.13 × 10−4 in fall, and 1.87 × 10−4 winter.
The periodic oscillation of dispersion coefficients could be identified, with an average period
of 4 days. It denoted that the surface wind speed plays important role in the PMD transport and
the HF data is capable to reflect these phenomena. Based on data, the simulation result error
using HR radar was known. The uncertainty of HF radar data for each PMD trajectories might
inaccurate, so we used probability viewpoint based on the results of ensemble average. Based
on simulation results for three years, the percentage of PMD transport patterns was East China
Sea (region I) 4.27%, Cross-Strait Mainland China (region II) 3.72%, South China Sea (region
III) 19.38%, Taiwan SW (region IV) 17.88%, Taiwan West (region V) 48.87%, and Taiwan
NW (region VI) 5.86%. Taiwan West (region V) has a higher possibility to produce PMD in
Penghu Islands, especially Yunlin Coast. The significant seasonal bias could be identified by
comparing the probability between region I (from East China Sea, higher probability in winter)
and III (from South China Sea, high probability in summer) due to prevailing southward China
Coastal Current (CCC) in winter and northward Taiwan Warm Current (TWC) in summer.
The second part of the results is the calculation of PMD amount. These trajectories
information could only be used if the PMD at source point was known already. The amount
could be calculated by multiplying the probability with the total amount of PMD at the sources.
ii
Monthly river discharge was applied to find the amount of PMD released from riverine using
Jambeck’s method (2015). PMD seasonal variability in the Penghu Islands were calculated
based on Yangtze River (into East China Sea), Mekong River (into South China Sea), and
Pahang River (into South China Sea). The results showed that Yangtze river produced the
highest PMD during summer to East China Sea, while Mekong and Pahang River released the
highest PMD during fall. This higher PMD was induced by higher riverine discharge which
was influenced by rainfall pattern during monsoon. | en_US |