|Other Abstract||Some historical-use pesticides (HUPs) and halogenated flame retardants (HFRs) are prohibited or strictly restricted for their bioaccumulative, toxic to organism, persistent in environment and potential for long-range atmospheric transport (LRAT) properties. With the elimination and phased out of traditional pesticides and flame retardants, some of their substitutes or alternatives, such as trifluralin, chlorothalonil, DBDPE and TBE, have been widely used globally. These current-use pesticides (CUPs) and novel halogenated flame retardants (NHFRs) have been detected in areas where they were using, such as the atmosphere and water in urban and rural areas. In addition, they were also found in remote areas like high mountains, polar regions, and pelagic zones. It indicates that they have the ability of long range transport and pollute the environment. Up to now, very limited data are available about the environmental fates of CUPs and NHFRs, especially in the Bohai Sea, North China.
CUPs (trifluralin, chlorothalonil, chlorpyrifos and dicofol) and HFRs (PBDEs, NBFRs and DPs) in the low atmosphere and surface seawater were taken during research cruises on the Bohai Sea in August and December 2016 and February 2017. Spatial distribution and seasonal variation in atmosphere and seawater were studied, and their sources are briefly explored.
Trifluralin, chlorothalonil, chlorpyrifos and dicofol are hydrophobic compounds, but they have high detection rates and concentrations in the gas and dissolved phases. Chlorpyrifos was the most abundant CUPs in the gas phase (59.06 ± 126.94 pg m-3) and dicofol had the highest concentration in dissolved phase in the seawater (115.94 ± 123.16 pg L-3). Seasonal variations of CUPs showed higher concentrations in spring and summer than those in winter. It is partially attributed to their using seasons, and partially to volatilization caused by high temperature. High levels were detected in the Bohai Bay (BB) and Laizhou Bay (LB). On the one hand, there are many factories along the two bays, which produce large amount of pesticides; on the other hand, the input from the rivers, such as the Yellow River and the Haihe River, aggravate the CUPs pollution in the LB and BB. Air-seawater exchange showed that atmospheric deposition was a significant input pathway of chlorothalonil into the Bohai Sea, whiles volatilization was the secondary source of trifluralin and chlorpyrifos from the seawater to the atmosphere.
BDE209 and DBDPE were the predominant compounds of PBDEs and NBFRs, respectively, and their showed significant correlation. As a substitute for BDE209, DBDPE was assumed to has common behaviors and sources with BDE 209 due to similar structure and physio-chemical properties. DPs were commonly detected in the atmosphere and surface water, with the mean values of 0.39 ± 0.62 pg m-3 and 1.29 ± 1.89 pg L-1, respectively. The ratio f(syn)=syn-DP/(syn-DP + anti-DP) can be used to identify the sources of DPs. As indicated by the results, f(syn) is close to industrial mixture in our study. The slightly lower ratio might attribute to the translation of syn-DP during the transport process. LB is the largest production area of BFRs in China. and the waste water, exhaust gas and residue produced in the process of manufacturing may enter the Bohai Sea through atmospheric transport and deposition, river discharge, and waste water pipeline, etc., and resulted in the high levels of HFRs in the LB. Seasonal variations of HFRs presents a higher values in winter than in summer. This is partially due to the increase of particulates and the decrease of temperature in winter. The pollutants are prone to be adsorbed in the particles. Another reason is that the northerly and north-westerly winds from land to south-easterly ocean in winter will bring pollutants to atmosphere above the Bohai Sea. Additionally, the scavenge effects of strong precipitation in summer is also an important factor in the reduction of particles and decrease of pollution concentrations.
In general, CUPs and HFRs belong to emerging persistent organic pollutants (POPs), and have obvious POPs attributes. Land-based pollution is the main source of POPs, atmosphere and ocean are the primary container of semi-volatile organic compounds (SVOCs). Bohai rim is the important source area of the two kinds of targets in our country. It is found that there are different detection rates of targets in the seawater and atmosphere in the Bohai Sea. CUPs are easily detected in the gas and dissolved phase, indicating that it is easy to transfer to the remote area with the airflow or ocean current. HFRs mainly exists in the particle phase, which indicates the deposition into soil or sediment during the process of migration, and the accumulation of pollutants. Therefore, our study about the spatial distribution and seasonal variation can provide reference for the behavior of emerging persistent organic pollutants, and guide environmental management and human health of the Bohai Rim.|