In vivo bioavailability and in vitro bioaccessibility of perfluorooctanoic acid (PFOA) in food matrices: correlation analysis and method development.

Food is a major source of human exposure to perfluorooctanoic acid (PFOA), however, PFOA bioavailability in food has not been studied. An in vivo mouse model and three in vitro methods (unified BARGE method, UBM; physiologically based extraction test, PBET; and in vitro digestion method, IVD) were used to determine the relative bioavailability and bioaccessibility of PFOA in the presence of 17 foods. PFOA was mixed with foods of different nutritional compositions and fed to mice over a 7-d period. PFOA relative bioavailability was determined by comparing PFOA accumulation in the liver following PFOA exposure via food to that in water. PFOA bioavailability relative to water ranged from 4.30 ± 0.80 to 69.0 ± 11.9% and was negatively correlated with lipid content (r = 0.76). This was possibly due to competitive sorption of free fatty acids with PFOA onto transporters on intestine epithelial cells. Besides, cations in the gastrointestinal tract, such as Ca(2+) and Mg(2+), are capable of complexing PFOA and partitioning to the lipid phase. On the other hand, when assessed using in vitro assays, PFOA bioaccessibility varied with methods, being 8.7-73% (UBM), 9.8-99% (PBET), and 21-114% (IVD). PFOA bioaccessibility was negatively correlated with lipid content when assessed using UBM (r = 0.82); however, a poor correlation with food composition was observed for PBET and IVD (r = 0.01-0.50). When in vivo and in vitro data were compared, a strong correlation was observed for UBM (r = 0.79), but poor relationships were observed for PBET and IVD (r = 0.11-0.22). This was probably because the higher lipolysis ability and presence of Ca(2+) and Mg(2+) in the gastrointestinal fluid of UBM resulted in a lower potential to form stable micelles compared to PBET and IVD. These results indicated that PFOA relative bioavailability was mainly affected by lipid content in foods, and UBM has the potential to determine PFOA bioaccessibility in food samples.

Application of particle swarm optimization algorithm in the heating system planning problem.

Based on the life cycle cost (LCC) approach, this paper presents an integral mathematical model and particle swarm optimization (PSO) algorithm for the heating system planning (HSP) problem. The proposed mathematical model minimizes the cost of heating system as the objective for a given life cycle time. For the particularity of HSP problem, the general particle swarm optimization algorithm was improved. An actual case study was calculated to check its feasibility in practical use. The results show that the improved particle swarm optimization (IPSO) algorithm can more preferably solve the HSP problem than PSO algorithm. Moreover, the results also present the potential to provide useful information when making decisions in the practical planning process. Therefore, it is believed that if this approach is applied correctly and in combination with other elements, it can become a powerful and effective optimization tool for HSP problem.

[Nontarget Screening and Ecological Risk Assessment of Polar Organic Pollutants in Surface Water on the West Bank of Taihu Lake].

Emerging pollutants occur in the environment, which has become a pressing issue for environmental research. In order to comprehensively screen potential polar organic pollutants in surface water of Wujin and Yixing in the Taihu Lake Basin, nontarget screening was carried out by high performance liquid chromatography(HPLC) and time of flight mass spectrometry(TOF-MS). Screened by accurate mass, isotope distribution, and MS/MS information, 162 organic compounds were identified, including 46 pesticides, 34 drugs, 8 personal care products, and 27 additives; 17 organic synthetic intermediates and 30 metabolites, 45 of which have been verified by reference standards. Through the quantitative analysis of 42 pollutants and ecological risk assessment of 3 trophic model species, it was found that 25 pollutants posed medium risk while 12 pollutants presented high risk. Nontarget screening can be used to identify potential pollutants with no prior information or standards. It is not only fast, accurate, and has high analytical flux, but also provides an important basis for subsequent ecological risk assessment.

[Pollution Characteristics and Risk Assessment of Nitro Polycyclic Aromatic Hydrocarbons in PM2.5 of Nanjing, China].

Nitro polycyclic aromatic hydrocarbons (NPAHs) are important pollutants with carcinogenic effects present in PM2.5. To analyze the pollution characteristics and sources of NPAHs, 14 samples of PM2.5 were collected in Nanjing from November 2017 to March 2018. The results showed that, 2,8-dinitrodibenzothiophene (743 pg·m-3), 2, 7-dinitrofluorene (331 pg·m-3), 9-nitroanthracene (326 pg·m-3), 3-nitrofluoranthene (217 pg·m-3), and 1,8-dinitropyrene (193 pg·m-3) were dominant, and the detection concentrations notably varied between seasons; the highest concentrations occurred in winter (3082 pg·m-3) followed by autumn (1553 pg·m-3) and spring (1218 pg·m-3). The ratio of nitrofluoranthene and 1-nitropyrene concentrations, and 9-nitroanthracene and 1-nitropyrene concentrations, indicated that the main sources of NPAHs in the PM2.5 of Nanjing were photooxidation of polycyclic aromatic hydrocarbons and biomass burning. NPAHs were more typically associated with smaller particles, which further indicated that secondary formation is an important source. The current carcinogenic risk of NPAHs in PM2.5 in Nanjing is controllable, and dinitro-polycyclic aromatic hydrocarbons represent the highest level of risk. The data presented in this study provide important baseline information that can inform the management of risks associated with NPAHs in PM2.5 in Nanjing.

Photodegradation of carbon dots cause cytotoxicity.

Carbon dots (CDs) are photoluminescent nanomaterials with wide-ranging applications. Despite their photoactivity, it remains unknown whether CDs degrade under illumination and whether such photodegradation poses any cytotoxic effects. Here, we show laboratory-synthesized CDs irradiated with light degrade into molecules that are toxic to both normal (HEK-293) and cancerous (HeLa and HepG2) human cells. Eight days of irradiation photolyzes 28.6-59.8% of the CDs to <3 kilo Dalton molecules, 1431 of which are detected by high-throughput, non-target high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry. Molecular network and community analysis further reveal 499 cytotoxicity-related molecules, 212 of which contain polyethylene glycol, glucose, or benzene-related structures. Photo-induced production of hydroxyl and alkyl radicals play important roles in CD degradation as affected by temperature, pH, light intensity and wavelength. Commercial CDs show similar photodegraded products and cytotoxicity profiles, demonstrating that photodegradation-induced cytotoxicity is likely common to CDs regardless of their chemical composition. Our results highlight the importance of light in cytocompatibility studies of CDs.

[Contamination Levels and Ecological Risk Assessment of Phthalate Esters (PAEs) in the Aquatic Environment of Key Areas of Taihu Lake].

To better understand phthalate esters (PAEs) pollution in key areas of Taihu Lake, water and sediment samples were collected for content analysis. The concentrations of ∑PAEs in water samples from wet, dry, and normal seasons ranged 1.6-11.2 µg·L-1 (mean:3.68 µg·L-1), nd-6.21 µg·L-1 (mean:1.3 µg·L-1), and nd-1.72 µg·L-1 (mean:0.48 µg·L-1), respectively. No differences were found between upstream and downstream samples. DEHP was the predominant component in water samples, whereas DBP exceeded the national surface water environmental quality standards. The total PAE concentration in the sediment ranged between 0.74 and 6.90 µg·g-1 (mean:2.64 µg·g-1), with DBP and DEHP the predominant PAEs. The risk quotient (RQ) results showed that DBP and DEHP contributed the most potentially adverse effects to the aquatic environment in the key areas. The contents of PAEs in sediment were all less than the ERLs, thus posing no significant threat to aquatic organisms. The overall level of PAEs in the study area was moderate compared to those in other areas, including rivers, lakes, and estuaries from cities worldwide. Industrial pollution and urban activities are the major sources of PAEs in the aquatic environment of key areas of Taihu Lake.

In situ measurement of perfluoroalkyl substances in aquatic systems using diffusive gradients in thin-films technique.

To better understand the environmental impact of ubiquitous perfluoroalkyl substances (PFASs) in waters, reliable and robust measurement techniques are needed. As one of the most widely used passive sampling approaches, diffusive gradients in thin-films (DGT) is not only easy to handle but also provides time-weighted analyte concentrations. Based on DGT with XAD18 as a binding agent, we developed a new methodology to measure two frequently detected PFASs in surface waters and wastewaters, i.e. perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). Their diffusion coefficients in the diffusive gel, measured using an independent diffusion cell, were 4.37 × 10-6 and 5.08 × 10-6 cm2 s-1 at 25 °C, respectively. DGT had a high capacity for PFOA and PFOS at 196 and 246 µg per gel disk, suggesting the DGT sampler was suitable for deployment of several weeks. Time-integrated concentrations of PFOA and PFOS in a natural lake and river, and a municipal wastewater treatment plant effluent using DGT samplers deployed in situ for 12-33 d were comparable to those measured by a solid-phase extraction method coupled with high-frequency grab sampling. This study demonstrates that DGT is an effective tool for in situ monitoring of PFASs in natural waters and wastewaters.