Benzotriazole (BTA) is an emerging contaminant that also is a recalcitrant compound. Sequential and intimate coupling of UV-photolysis with biodegradation were investigated for their impacts on BTA removal and mineralization in aerobic batch experiments. Special attention was given to the role of its main photolytic products, which were aminophenol (AP), formic acid (FA), maleic acid (MA), and phenazine (PHZ). Experiments with sequential coupling showed that BTA biodegradation was accelerated by photolytic pretreatment up to 9 min, but BTA biodegradation was slowed with longer photolysis. FA and MA accelerated BTA biodegradation by being labile electron-donor substrates, but AP and PHZ slowed the rate because of inhibition due to their competition for intracellular electron donor. Because more AP and PHZ accumulated with increasing photolysis time, their inhibitory effects began to dominate with longer photolysis time. Intimately coupling photolysis with biodegradation relieved the inhibition effect, because AP and PHZ were quickly biodegraded and did not accumulate, which accentuated the beneficial effect of FA and MA.
Preharvest fruit-drop is a challenge to bayberry production. 2,4-D sodium as a commonly used anti-fruit-drop hormone on bayberry can reduce the yield loss caused by preharvest fruit-drop. The persistence and risk assessment of 2,4-D sodium after applying on bayberries were investigated. A method for determining 2,4-D sodium in bayberry was established based on LC-MS-MS. The average recoveries of 2,4-D sodium were at the range of 93.7–95.8% with relative standard deviations (RSDs) ranging from 0.9 to 2.8%. The dissipation rates of 2,4-D sodium were described using first-order kinetics, and its half-life ranged from 11.2 to 13.8 days. A bayberry consumption survey was carried out for Chinese adults for the first time. The safety assessments of 2,4-D sodium were conducted by using field trail data as well as monitoring data. Results showed that the chronic risk quotient and the acute risk quotient were calculated to be 0.23–0.59 and 0.02–0.05%, respectively, for Chinese adults, indicating low dietary risk for adults and children. In the end, the household cleaning steps were compared, and results showed that water rinsing for 1 min can remove 49.9% 2,4-D sodium residue, which provides pesticide removal suggestion for consumers.
The spatial and temporal distribution of polycyclic aromatic hydrocarbons (PAHs) has been investigated in Daya Bay, China. The total concentration of the 16 USEPA priority PAHs in surface sediments ranged from 42.5 to 158.2 ng/g dry weight with a mean concentration of 126.2 ng/g. The spatial distribution of PAHs was site-specific and combustion processes were the main source of PAHs in the surface sediments. Total 16 priority PAH concentration in the cores 8 and 10 ranged from 77.4 to 305.7 ng/g and from 118.1 to 319.9 ng/g respectively. The variation of the 16 PAH concentrations in both cores followed the economic development in China very well and was also influenced by input pathways. Some of the PAHs were petrogenic in core 8 while pyrolytic source was dominant in core 10. In addition, pyrolytic PAHs in both cores were mainly from the coal and/or grass and wood combustion. 相似文献
