304.
Dissolved and particulate
234Th activities in surface seawater were determined at 27 stations along the coastline of western Taiwan during 19–23 November
2004. Contrasting scavenging settings were observed between the northern and southern regimes of the nearshore water off western
Taiwan, separated by the Cho-Shui River. The northern regime is characterized by a large quantity of suspended load contributed
by northward transport of a suspension plume from the Cho-Shui River, while the southern regime, low in suspended load and
high in chlorophyll concentration, is a system controlled by biological activity. A scavenging model that takes account of
the physical transport was used to estimate the
234Th budget in order to estimate the scavenging and removal rates from the nearshore water. The scavenging and removal rates
ranged from 21 to 127 dpm m
−3d
−1 and from 36 to 525 dpm m
−3d
−1, for dissolved and particulate
234Th, respectively. The removal fluxes of particulate organic carbon (POC) and particulate organic nitrogen (PON) were estimated
by multiplying the particulate
234Th removal flux to the organic carbon/
234Th and nitrogen/
234Th ratios in suspended particles, which ranged from 4.5 to 275.2 mmol-C m
−2d
−1 and from 1.3 to 50.1 mmol-N m
−2d
−1, respectively. These fluxes resulted in residence times of 1∼20 days for the POC in the surface water of nearshore water
off western Taiwan.
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