Seasonal variations and emissions of volatile organic compounds in the typical aquaculture areas

Based on field observations in the Yantai Sishili bay aquaculture area and its adjacent waters, the distribution characteristics, seasonal variations, and controlling factors of two representative volatile organic compounds (VOCs)—monocyclic aromatic hydrocarbons (BTEX) and short-chain non-methane hydrocarbons (NMHCs) were systematically investigated, to reveal the impacts of scallop farming on the productions and releases of VOCs. The analysis results showed that there were significant differences in VOCs between the different aquaculture periods, as well as between the aquaculture and non-aquaculture areas. The scallops' enrichment effect on BTEX significantly reduced the BTEX concentration in the seawater of the aquaculture area, with BTEX concentrations in the aquaculture area being 40% lower than that in the non-aquaculture area. The enrichment effect of scallops on BTEX in seawater varied at different stages of scallop aquaculture, with the strongest enrichment ability during the harvest period. In addition, there were differences in the enrichment effect of scallops on the components of BTEX, with a higher octanol-water partition coefficient (Kow) value corresponding to a greater reduction in concentration. In comparison, the mean concentration of NMHCs in the aquaculture area was approximately 12% higher than that in the non-aquaculture area, which could be attributed to the grazing of phytoplankton by scallops, which promoted the production and release of NMHCs in the aquaculture area. Scallop aquaculture results in a reduction of sea-air BTEX flux and an increase of sea-air NMHCs flux, ultimately leading to a 48% and 42% decrease in the contribution of VOCs emissions from this marine area to ozone and secondary organic aerosol formation potential, respectively.