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. 2023 Jul 16;1(3):191-202.
doi: 10.1021/envhealth.3c00059. eCollection 2023 Sep 15.

Organophosphate Esters in Air and Seawater of the South China Sea: Spatial Distribution, Transport, and Air-Sea Exchange

Lijie Mi  1   2 , Zhiyong Xie  1 , Lulu Zhang  3   4   5 , Joanna J Waniek  6 , Thomas Pohlmann  2 , Wenying Mi  7 , Weihai Xu  3   4
Affiliations

Organophosphate Esters in Air and Seawater of the South China Sea: Spatial Distribution, Transport, and Air-Sea Exchange

Lijie Mi et al. Environ Health (Wash). .

Abstract

Organophosphate esters (OPEs) have become one group of chemicals with emerging concern in the marine environment. In this work, we investigated OPEs in the air and seawater of the South China Sea in summer 2019. The concentrations of ∑10OPEs in the atmosphere ranged from 66 to 550 pg/m3, with TCIPP, TNBP, TPhP, and TEP predominating in the air. The total dissolved OPE concentrations (∑10OPEs without TEP) measured in high-volume water samples ranged from 300 to 3600 pg/L, with a mean concentration of 1180 ± 910 pg/L. TEP was measured with liquid-liquid extraction (LLE), and it showed the highest concentration (average 2000 ± 1450 pg/L) among the selected OPEs. Total suspended matter associated OPEs accounted for less than 4.7% of the sum of OPE concentrations in seawater. Fugacity fractions and air-sea exchange fluxes showed that TCEP, TCIPP, TIBP, TEHP, TPhP, and EHDPP were favored to volatilize, TEP dominated the deposition, while TPrP and TNBP varied between volatilization and deposition. Atmospheric particle deposition fluxes ranged from 5 to 71 ng/m2/day with an average of 17 ± 15 ng/m2/day. The input of ∑OPEs to the entire South China Sea via atmospheric particle deposition was estimated to be 22 ± 19 tons/year, while the net air-sea exchange fluxes of OPEs were volatilization from seawater to air with an average of 44 ± 33 tons/year. This work suggests that air-sea exchange and atmospheric particle deposition are significant processes interfering with the transport of OPEs in the marine environment.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
(A) Concentrations of OPEs in the atmosphere (ng/m3) over the South China Sea. (B) Box chart of OPEs. (C) Composition profile of OPEs. (D) Gas/particle partitioning of OPEs. Air masses originating from the Pacific Ocean and Southeast Asia dominated at the research area.
Figure 2
Figure 2
(A) Concentrations of OPEs (without TEP) in seawater of the South China Sea, measured with high-volume water samples. (B) Box chart of OPEs. (C) Distribution of TEP in seawater of the South China Sea, determined with 1 L water samples using liquid–liquid extraction. (D) Box chart of TEP.
Figure 3
Figure 3
(A) Heat map for the correlation analysis of OPEs and salinity. (B) Source appointment based on the gradient of the salinities of seawater samples.
Figure 4
Figure 4
Air–sea exchange fluxes of OPEs (ng/m2/day) calculated with two-film fugacity mode using paired air/seawater concentrations. Positive (+) values indicate water to air volatilization, and negative (−) values mean air to water deposition.
Figure 5
Figure 5
Dry deposition fluxes of particle-bound OPEs (ng/m2/day) to the South China Sea.
Figure 6
Figure 6
(A) Annual net dry deposition of particle-bound OPEs (tons/year). (B) Net air–sea deposition in the South China Sea (tons/year). TEP showed net deposition from air to water, while all other OPEs were dominated by water to air volatilization.
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