Screening of organophosphate esters in different indoor environments: Distribution, diffusion, and risk assessment.

ANALYSIS: of air conditioner (AC) filter dust can reveal the level of organophosphate ester (OPE) pollution in indoor environments, but comprehensive research on this topic remains lacking. This study combined non-targeted and targeted analysis to screen and analyze 101 samples of AC filter dust, settled dust, and air obtained in 6 indoor environments. Phosphorus-containing organic compounds account for a large proportion of the organic compounds found in indoor environments, and OPEs might be the main pollutants. Using toxicity data and traditional priority polycyclic aromatic hydrocarbons for toxicity prediction of OPEs, 11 OPEs were prioritized for further quantitative analysis. The concentration of OPEs in AC filter dust was highest, followed in descending order by that in settled dust and that in air. The concentration of OPEs in AC filter dust in the residence was two to seven times greater than that in the other indoor environments. More than 56% of the OPEs in AC filter dust showed significant correlation, while those in settled dust and air were weakly correlated, suggesting that large amounts of OPEs collected over long periods could have a common source. Fugacity results showed that OPEs were transferred easily from dust to air, and that dust was the main source of OPEs. The values of both the carcinogenic risk and the hazard index were lower than the corresponding theoretical risk thresholds, indicating low risk to residents through exposure to OPEs in indoor environments. However, it is necessary to remove AC filter dust in a timely manner to prevent it becoming a pollution sink of OPEs that could be rereleased and endanger human health. This study has important implications for comprehensive understanding of the distribution, toxicity, sources, and risks of OPEs in indoor environments.

The potential assessment of green alga Chlamydomonas reinhardtii CC-503 in the biodegradation of benz(a)anthracene and the related mechanism analysis.

Benz(a)anthracene (BaA) is a polycyclic aromatic hydrocarbons (PAHs), that belongs to a group of carcinogenic and mutagenic persistent organic pollutants found in a variety of ecological habitats. In this study, the efficient biodegradation of BaA by a green alga Chlamydomonas reinhardtii (C. reinhardtii) CC-503 was investigated. The results showed that the growth of C. reinhardtii was hardly affected with an initial concentration of 10 mg/L, but was inhibited significantly under higher concentrations of BaA (>30 mg/L) (p < 0.05). We demonstrated that the relatively high concentration of 10 mg/L BaA was degraded completely in 11 days, which indicated that C. reinhardtii had an efficient degradation system. During the degradation, the intermediate metabolites were determined to be isomeric phenanthrene or anthracene, 2,6-diisopropylnaphthalene, 1,3-diisopropylnaphthalene, 1,7-diisopropylnaphthalene, and cyclohexanol. The enzymes involved in the degradation included the homogentisate 1,2-dioxygenase (HGD), the carboxymethylenebutenolidase, the ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) and the ubiquinol oxidase. The respective genes encoding these proteins were significantly up-regulated ranging from 3.17 fold to 13.03 fold and the activity of enzymes, such as HGD and Rubisco, was significantly induced up to 4.53 and 1.46 fold (p < 0.05), during the BaA metabolism. This efficient degradation ability suggests that the green alga C. reinhardtii CC-503 may be a sustainable candidate for PAHs remediation.

[Effects of Mushroom Residue Application Rates on Net Greenhouse Gas Emissions in the Purple Paddy Soil].

China is the leading country for production of edible mushrooms and also outputs numerous mushroom residues. The recycling of mushroom residue can solve environmental pollution problems, provide nutrients for the farmland, and play an important role in reducing greenhouse gas emissions and increasing soil carbon sequestration capacity. In order to investigate the effects of mushroom residue amounts on net greenhouse gas emissions in purple paddy soil, potted experiments using static opaque chamber and gas chromatography methods were used to study the changes of greenhouse gases, soil carbon sequestration, and net greenhouse gas emissions (NGHGE) in the paddy soil with five treatments: no fertilizer (CK), conventional fertilization (NPK), 9 t·hm-2 mushroom residue+NPK (LM), 18 t·hm-2 mushroom residue+NPK (MM), and 36 t·hm2 mushroom residue+NPK (HM) from March 2017 to September 2017.The results showed that: ① The greenhouse gas emissions (including CH4, CO2, and N2O) increased with increasing additions of mushroom residue. The emissions of CH4 from highest to lowest followed: HM > MM > LM≈NPK > CK. The HM treatment significantly increased the CH4 emission flux (P<0.01) more than the other treatments and showed an obvious single peak curve, while the CH4 emission flux with the LM treatment showed a bimodal curve, and the MM treatment showed a multiple peak curve. The CO2 emission flux followed: MM > NPK≈LM > HM > CK; and the curves for the LM, MM, and HM treatments were a single peak curve, bimodal curve, and multiple peak curve, respectively. The N2O cumulative emission from the NPK treatment was significantly higher than with the other treatments. The N2O emission flux of the NPK treatment was a bimodal curve and that of the HM treatment was a single peak curve, while the N2O emission flux of treatments LM and MM showed multiple peak curves. ② The carbon sequestration capacity with the LM treatment was lower than that of the other treatments and that from the MM treatment was the highest. The carbon sequestration capacity of the MM treatment increased by 59.2% compared to that of the NPK treatment and increased by 87.79% and 65.65% compared to that of the LM and HM treatments. The LM treatment has the highest carbon sequestration capacity, which was higher than that of the NPK and MM treatments and about 2.1 times greater than the CK treatment and HM treatment. ③ The minimum NGHGE value was -490.29 kg·hm-2 for the whole rice production period, and 18 t·hm-2 mushroom residue applied to the soil was the best way to reduce net greenhouse gas emissions in purple paddy soil.