Effects of Organic Carbon Origin on Hydrophobic Organic Contaminant Fate in the Baltic Sea.

Inna Nybom,Naiara Berrojalbiz,Gisela Horlitz,Jannik Martens,Anna Sobek,Dorothea Gilbert,Hans Peter H Arp

doi:10.1021/acs.est.1c04601

Abstract

The transport and fate of hydrophobic organic contaminants (HOCs) in the marine environment are closely linked to organic carbon (OC) cycling processes. We investigated the influence of marine versus terrestrial OC origin on HOC fluxes at two Baltic Sea coastal sites with different relative contributions of terrestrial and marine OC. Stronger sorption of the more than four-ring polycyclic aromatic hydrocarbons and penta-heptachlorinated polychlorinated biphenyls (PCBs) was observed at the marine OC-dominated site. The site-specific partition coefficients between sediment OC and water were 0.2–1.0 log units higher at the marine OC site, with the freely dissolved concentrations in the sediment pore-water 2–10 times lower, when compared with the terrestrial OC site. The stronger sorption at the site characterized with marine OC was most evident for the most hydrophobic PCBs, leading to reduced fluxes of these compounds from sediment to water. According to these results, future changes in OC cycling because of climate change, leading to increased input of terrestrial OC to the marine system, can have consequences for the availability and mobility of HOCs in aquatic systems and thereby also for the capacity of sediments to store HOCs.

Highlights

Hydrophobic organic contaminants (HOCs) such as polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) are ubiquitously present in the aquatic environment.[1−3] The transport dynamics and ultimate fate of HOCs are dependent on compound properties and diverse environmental processes
Previous work demonstrated that the sorption of carbon tetrachloride and 1,2-dichlorobenzene to sediment organic carbon (OC) was a factor of 1.8 stronger than to soil OC,[14] and for PAHs, the effect was a factor of 1.6.15 on a local scale, primary production generates marine OC free of organic contaminants in comparison to the terrestrial OC that enters marine systems potentially loaded with organic contaminants from the catchment
Dissolved pore-water concentrations of more than four-ring PAHs and penta-heptachlorinated PCBs were higher at the terrestrial OC site compared to the marine OC site (Figure 2)

Summary

■ INTRODUCTION

Hydrophobic organic contaminants (HOCs) such as polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) are ubiquitously present in the aquatic environment.[1−3] The transport dynamics and ultimate fate of HOCs are dependent on compound properties and diverse environmental processes. Water column sampling was performed by mounting the LDPE samplers on the ropes with twist ties between the bottom weight and the surface buoy (terrestrial OC: 0.5, 5, and 10 m and marine OC: 0.5, 5, and 15 m) (Figure S3, Supporting Information). The time-averaged air concentrations (Ca) were calculated from the air samplers (CXAD), according to the study by Wania et al[32] (eq S12), by applying empirical sampling rates of the XAD resin with 122 days deployment time from Armitage et al.[56] For analytes for which published data on sampling rates were not available, the sampling rate was estimated from a regression analysis between sampling rates and log Kow[57,58] (regressions presented in Tables S4 and S5, Supporting Information). Sediment dating at 1967 (M-OC) and 1973 (T-OC) are indicated with a horizontal line

■ RESULTS AND DISCUSSION

■ ACKNOWLEDGMENTS

■ REFERENCES