Qian Wang,Hanwen Xu,Jie Yin,Shengnan Du,Caicai Liu,Juan-ying Li
The Yangtze River protection strategies are expected to improve the water quality and ecological function of the Yangtze River Estuary (YRE). The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) and 6 heavy metals (HMs) in the YRE were measured and the riverine fluxes were calculated subsequently. In particular, the concentrations of low molecular weight PAHs (LMW-PAHs), arsenic (As) and mercury (Hg) in seawater decreased over time, while those of other studied pollutants did not change a lot. In sediments, the concentration changes for all the pollutants were insignificant. For the present pollutants, the river input is the dominant source, and the flux decreased after the protection. The contribution of the discharge from wastewater treatment plants (WWTPs) was quantified. Its influence cannot be ignored. The seafood quality remained stable and the risk via diet was insignificant. Long-term monitoring is necessary, and the positive impact of the Protection Strategy is gradually emerging.
Neonicotinoid and fipronil insecticides have been consumed worldwide, particularly in China. There is growing interest in the environmental research community about the occurrence, sources, and risks of neonicotinoids and fipronil. A new method based on high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) and disc solid phase extraction (SPE) techniques were developed for the determination of neonicotinoids and fipronil in seawater in this research. The effects of the styrene divinyl benzene-reverse phase sulfonated (SDB-RPS) membrane-based solid phase extraction optimization process and the HPLC separation parameters on the detection results of the target compounds were studied. Under the optimized conditions, the detection limit of this method for 12 target compounds ranged from 0.05 ng L−1 to 0.50 ng L−1 and absolute recovery was achieved from 58.9–106.5%. The results proved that this method can effectively detect neonicotinoid and fipronil pesticides in seawater. At the same time, dinotefuran, nitenpyram, thiamethoxam, imidacloprid, thiacloprid, fipronil and its metabolites were found in seawater samples from the Yangtze River Estuary and the adjacent sea area. Among them, the total concentration of neonicotinoid insecticides ranged from ND-12.45 ng L−1 and the average total concentration was 3.5 ng L−1; the total concentration of fipronil and its metabolites ranged from ND-2.45 ng L−1, and the average total concentration was 0.79 ng L−1. The results showed that there was contamination of neonicotinoids and fipronil in the Yangtze River Estuary and its adjacent area.
Methyl iodide (CH 3 I) is an important trace greenhouse gas in the atmosphere and an ozone-depleting substance. The influence of different environmental factors, such as the duration of illumination; the strength of illumination; the concentrations of humic acid, ferric ion (Fe 3+ ), and iodide ion (I − ); and pH, on the photochemical production of CH 3 I in artificial seawater (ASW) were tested by simulated solar irradiation. In addition, Yangtze River Estuary waters from inshore to offshore were used to explore the relationship between the photochemical production of CH 3 I and different sources of dissolved organic matter (DOM) in natural sea-water (NSW). The results revealed that higher concentrations of humic acid and I − , as well as higher strengths of illumination and longer illumination durations, promoted the photochemical formation of CH 3 I in ASW. The addition of Fe 3+ accelerated the photochemical production of CH 3 I, but high concentrations of Fe 3+ inhibited the formation of CH 3 I. Experiments on NSW obtained from the Yangtze River estuary spiked when concentrations of DOM were high, confirming that DOM plays an important role in facilitating the photochemical production of CH 3 I within the Yangtze River Estuary. The photochemical production of CH 3 I in the seawater was significantly higher under light conditions relative to dark conditions, indicating that illumination accelerated the production of CH 3 I.
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