Enhanced Sinks of Polycyclic Aromatic Hydrocarbons Due to Kuroshio Intrusion: Implications on Biogeochemical Processes in the Ocean-Dominated Marginal Seas

Abstract

The biogeochemical processes of polycyclic aromatic hydrocarbons (PAHs) in the South China Sea (SCS) are influenced by the exchanges of water masses, energies, and materials between this marginal sea and the Pacific Ocean. To investigate the impact of oceanic water intrusion on semivolatile compounds, we collected seawater samples in the Western Pacific, northern, and central SCS in 2017 and analyzed for dissolved PAHs. PAH concentrations in the water columns of the Pacific Ocean and SCS were 1.7–11 and 1.1–7.3 ng L–1, respectively, showing spatial distinctions in terms of the composition and source characteristics. A common depletion for three-ring PAHs was found in the northern SCS by comparing the modeling results of conservative mixing by Kuroshio intrusion. Kuroshio water increased the levels of temperature, dissolved oxygen, and nutrients when intruding into the northern SCS and was likely to enhance the bioavailability of PAHs and stimulate their biodegradation process. In the water column, the most effective layer under the Kuroshio intrusion impact is different for three- and four-ring PAHs, where the three-ring PAHs’ depletion was most significant at the surface; however, for four-ring PAHs, that was at the deep chlorophyll maximum layer. This study highlighted the effect of ocean currents on PAHs for their water-column processes both from physical and biogeochemical perspectives.

Particulate Export of PAHs Firstly Traced by 210Po/210Pb Disequilibrium: Implication on the “Shelf Sink Effect” in the Arctic Ocean

“…The highest concentration was observed at the surface water from BM07 on the Bering Shelf, while the lowest value was found at the surface water from R04 in the Chukchi Sea (Figure 2). Compared with other data reported in the literature, dissolved PAH concentrations observed in this study were within the same magnitude of the Japan Sea (Chizhova et al, 2018), Western Pacific Ocean (M. Liu, Zheng, et al, 2021), and Southern Ocean (Cai et al, 2016), but of larger magnitude than those in the Mediterranean Sea (Berrojalbiz et al, 2011), and North Atlantic Ocean (Lohmann et al, 2009). Details of the PAH ranges and comparison of literature values are listed in Table S4.…”

PAHs in the North Atlantic Ocean and the Arctic Ocean: Spatial Distribution and Water Mass Transport

“…Ant/(Ant + Phe) ratios, mostly more than 0.1, indicated the combustion source. It is worth noting that paired compounds usually have different reactivities to photodegradation and biodegradation, which may lead to a variance in the ratio value after long‐range transport (Liu, Zheng, et al., 2021; Yunker et al., 2002).…”

“…Oceanic transport of POPs is not only a physical mixing process, but also probably influences their biogeochemical processes, such as biodegradation and particulate settling, by changing temperature, dissolved oxygen, and seawater nutrients (Liu, Zheng, et al., 2021). The strong‐stratified Arctic Ocean undergoes complex inputs and outputs of PAHs from the neighboring oceans and continents.…”

The removal of atmospheric aerosols in a heavy industrial coastal city in China with frequent rainfall

“…This enables dimensionality reduction and ability to visualize the separation of classes or clusters (https://builtin.com/datascience/step-step-explanation-principal-component-analysis). The extracted PC with eigenvalue > 1.0 is retained for interpretation and the loading above 0.5 of each component is determined to be the major contribution to each of the PC scores (Gao et al, 2011;Zhang et al, 2011;Agarwal et al, 2020;Liu et al, 2021a;Liu et al, 2021b). In these studies, the determined component is regarded as tracer of certain source (Gao et al, 2011;Zhang et al, 2011;Agarwal et al, 2020;Liu et al, 2021a;Liu et al, 2021b).…”

“…The extracted PC with eigenvalue > 1.0 is retained for interpretation and the loading above 0.5 of each component is determined to be the major contribution to each of the PC scores (Gao et al, 2011;Zhang et al, 2011;Agarwal et al, 2020;Liu et al, 2021a;Liu et al, 2021b). In these studies, the determined component is regarded as tracer of certain source (Gao et al, 2011;Zhang et al, 2011;Agarwal et al, 2020;Liu et al, 2021a;Liu et al, 2021b). Similarly, the determined component can be used for tracing sources in the present study.…”