Polycyclic aromatic hydrocarbons (PAHs), which are hard to degrade, are the main pollutants in the environment. Degradation of PAHs in the environment is becoming more necessary and urgent. In the current study, strain PL1 with degradation capability of pyrene (PYR) and benzo[a]pyrene (BaP) was isolated from soil and identified as Klebsiella pneumoniae by morphological and physiological characteristics as well as 16S rDNA sequence. With the presence of 20 mg L⁻¹ PYR and 10 mg L⁻¹ BaP in solution, the strain PL1 could degrade 63.4 % of PYR and 55.8 % of BaP in 10 days, respectively. The order of biodegradation of strain PL1 was pH 7.0 > pH 8.0 > pH 10.0 > pH 6.0 > pH 5.0. Strain PL1 degradation ability varied in different soil. The half-life of PYR in soil was respectively 16.9, 24.9, and 88.9 days in paddy soil, red soil, and fluvo-aquic soil by PL1 degradation; however, the half-lives of BaP were respectively 9.5, 9.5, and 34.0 days in paddy soil, red soil, and fluvo-aquic soil by PL1 degradation. The results demonstrate that the degradation capability on PYR and BaP by PL1 in paddy soil was relatively good, and K. pneumoniae PL1 was the new degradation bacterium of PYR and BaP. K. pneumoniae PL1 has potential application in PAH bioremediation.

A method was developed for the determination of cyantraniliprole (HGW86) and its metabolite J9Z38 in watermelon and soil by ultra-performance LC (UPLC)/MS/MS. Target compounds were extracted by acetonitrile-water, cleaned up on a silica gel column, and determined by UPLC/MS/MS. Average recoveries of cyantraniliprole and J9Z38 in watermelon and soil at three levels (0.01, 0.1, and 0.5 mg/kg) ranged from 85.71 to 105.74%, with RSDs of 0.90-6.34%. The LOQs for cyantraniliprole and J9Z38 were determined to be 0.00021, 0.00015, 0.0010, and 0.00090 mg/kg in watermelon and soil samples, respectively. This method was used to determine the cyantraniliprole and J9Z38 residues in watermelon and soil samples for studies on their dissipation. The trial results showed that the half-lives of cyantraniliprole obtained after treatments were 1.1 and 4.1 days in watermelon and soil in Zhejiang, and 2.7 and 2.6 days in watermelon and soil in Hunan, respectively. The average levels of cyantraniliprole and J9Z38 residues in watermelon and soil were all < 0.01 mg/kg within the 14-day interval after treatment.

Cyazofamid, as a fungicide of the novel cyanoimidazole chemical class, has been widely used to control tomato late blight. Understanding of cyazofamid residues in environment and crops is an essential prerequisite for its risk assessment. In this study, field investigations in four typical tomato-producing areas were conducted to explore the dissipation kinetics and residues of cyazofamid and its primary metabolite 4-chloro-5-p-tolylimidazole-2-carbonitrile (CCIM) in soil and tomato. A robust method using QuEChERS coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed for simultaneous analysis of cyazofamid and CCIM, with limits of quantification of 0.33 and 3.8 μg/kg, respectively. Field trials showed that the half-lives of cyazofamid were 3.6-6.9 days in soil and 12.2-18.3 days in tomato. The total residues of cyazofamid and CCIM in tomato collected at three time intervals were all below 0.5 mg/kg. Moreover, the potential risks of total residues via tomato intake to ten population subgroups were evaluated. We found that the risk quotient values were all generally low (0.13-1.3%), indicating that the recommended dose of cyazofamid on tomato will not result in a consumer exposure exceeding the toxicological reference value. Here, the results of field investigation provided important information for further understanding the behavior and risk of cyazofamid in the natural environment.

Polycyclic aromatic hydrocarbons (PAHs) are a class of persistent organic compounds derived from natural sources and anthropogenic processes, which have been recommended as priority pollutants. Degradation of PAHs in the environment is becoming more necessary and urgent. In the current study, strain PL2, which is capable of growing aerobically on pyrene (PYR) as the sole carbon source, was isolated from hydrocarbons-contaminated soil and then identified as Pseudomonas putida by morphological and physiological characteristics as well as 16S rDNA sequence. The strain PL2 was able to degrade 50.0% of the pyrene at 28°C within 6 days in the presence of 50 mg/L pyrene, while the strain PL2 degraded 50.0% of the pyrene within 2 days when a solution of 50 mg/L pyrene and 50 mg/L phenanthrene was used. In addition, phenanthrene was shown to increase the biodegradation efficiency of pyrene by the strain PL2. The order of degradation by the strain PL2 was pH 6.0 > pH 7.0 > pH 5.0 > pH 8.0. The degradation rate of PYR in the soil by the strain PL2 reached 70.0% at the 10 th day. The dynamics of PYR degradation in soil by PL2 was fit to the first order model and the strain PL2 was shown to efficiently degrade PYR in soil. The current study showed that P. putida PL2 was a novel bacterium that could degrade pyrene and holds great promise for use in PAHs bioremediation in soil.

No abstract