Characteristics, source apportionment and health risk assessment of heavy metals in urban road dust of the Pearl River Delta, South China.

To investigate the characteristics of heavy metals (As, Cd, Cr, Cu, Pb, Hg, Ni and Zn) in urban road dust from different cities and functional areas in the Pearl River Delta (PRD), South China, a total of 294 dust samples were analyzed. The contamination characteristics and health risk of heavy metals in the dust were assessed, their chemical speciation were distinguished, and their sources were identified by the correlations, cluster and principal component analysis (PCA). The mean concentrations of As (15.89 mg/kg), Cd (1.59 mg/kg), Cr (143.75 mg/kg), Cu (184.42 mg/kg), Pb (114.82 mg/kg), Hg (0.11 mg/kg), Ni (41.53 mg/kg) and Zn (645.94 mg/kg) in urban road dust were in high or moderate levels compare with other previous researches. In this case, the contamination of Cr, Cu, Ni and Zn in the industrial area (IA) and the contamination of Cd and Hg in the commercial area (CA) were significantly higher relative to other functional areas (P < 0.05), and the contamination of heavy metals in Foshan City was significantly higher than other cities (P < 0.01). The order of mobility of the heavy metals with higher concentration in urban road dust of the Pearl River Delta declined in the following order: Zn, Ni, Cu, Pb and Cr. Statistical analysis result showed the contaminated heavy metals in urban road dust were mainly contributed by industrial activities, traffic activities and building pollution. There were no significant carcinogenic and noncarcinogenic risks for adults, children however showed significant noncarcinogenic effect caused by As and Cr in partial points, albeit with low contamination level of the two metals. The ingestion was a principal pathway for heavy metals via urban road dust to exposure population. More protection measures should be considered to reduce children's exposure to the dust, especially in the CA and IA.

The enrichment and purification of hexabromocyclododecanes and its effects on thyroid in zebrafish.

Hexabromocyclododecanes (HBCDs) are the third most highly produced brominated flame retardants (BFRs) all over the world. Based on the current research status of HBCDs, zebrafish were exposed to three dietary concentrations of HBCDs (0, 10, 100, 400 ng/g) for 56 days, and followed by clean food for 28 days. In order to investigate the enrichment and purification of HBCDs in zebrafish, HBCD enantiomers in zebrafish were determined using ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). To investigate the effects of long-term exposure of HBCDs on thyroid dysfunction and oxidative stress in zebrafish, the concentrations of thyroid hormone (T3, T4, FT3 and FT4) and the activities of malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT) and reduced glutathione (GSH) were measured. RT-PCR was used to reveal the molecular mechanism of HBCDs' influence on thyroid hormone in zebrafish. The result of UPLC-MS/MS showed that there were three main reasons for the existence of α-HBCD as the major isomer in the organism. HBCDs had significant inhibitory effect on T3 and T4 in liver of adult zebrafish after 56 days' exposure. Compared with the control group, the ratio of T3 and T4was significantly higher in the medium and high concentration group. The content of FT3 and FT4 in the liver tissue of zebrafish increased first and then decreased with the increase of exposure concentration. With the increase of exposure concentration, the content of MDA in zebrafish liver decreased firstly and then increased. The activity of SOD and CAT in zebrafish liver showed the opposite trend with MDA. And the concentration of GSH in liver decreased gradually, which showed a significant dose-effect relationship. HBCDs exposure has an inhibitory effect on thyroid hormone receptor gene (TRß) and adrenocorticotropin-releasing hormone gene (Crh) in zebrafish.

Radon exhalation from cement-based materials under accelerated carbonation.

Cement-based materials manufactured from rocks and soils will release radon which is a carcinogen and affects indoor air quality. The alkaline cement-based material neutralizes with the acidic gas carbon dioxide in the air, reducing its pH value, known as carbonation. Carbonation of cement-based materials is an important environmental factor that can change the pore structure and effect radon release. In this study, test blocks of concrete, fly ash concrete, cement mortar, and cement paste were subjected to carbonation at 20 vol% CO2, 70% relative humidity, and a temperature of 20 ± 2 ℃ for 28 days to explore the effect of material characteristics and carbonation age on the radon exhalation rate. Carbonation had a significant influence on the radon exhalation rate, but this effect showed positive (promoting/increasing) and negative (inhibiting/decreasing) fluctuations with carbonation age. Among the material characteristics, aggregate content had the most significant influence, followed by fly ash and cement variety. The radon exhalation rate was ordered as cement mortar > concrete > cement paste before carbonation, but was concrete > cement mortar > cement paste after carbonation. The radon exhalation rate of cement paste blocks without aggregate was ~ 1 mBq/(m2·s) lower than that of cement mortar. The inhibition of radon emission by concrete was mainly observed in the early carbonation period (< 7 days), while that by fly ash concrete was observed after 7 days. The content of fly ash did not have a significant influence on the radon exhalation rate of materials. Radon inhibition by composite Portland cement concrete was mainly observed in the middle stage of carbonation (~ 14 days), while inhibition by ordinary Portland cement concrete was mainly observed in the early (3-7 days) and late (i.e., ~ 28 days) stages. The water/binder ratio did not significantly affect the radon exhalation; concrete with a low water/binder ratio showed weak radon inhibition only when the carbonation age was long. These results will help to evaluate radon pollution in indoor or underground environments under long-term use.

[Accumulation Characteristics and Health Risk Assessment of Heavy Metals in Wild Fish Species from Diaojiang River, Guangxi].

To explore the accumulation characteristics and health risk assessment of heavy metals in wild fish species, the concentrations of heavy metals (Pb, Cd, Cr, As and Hg) in the muscle samples of eight wild fish species collected from Diaojiang River, Guangxi were analyzed. The degree of pollution, food safety and health risk of heavy metals in wild fish species were evaluated using the average pollution index and the target hazard quotient methods. The results showed that the concentrations of Pb, Cd, Cr, As and Hg in wild fish species ranged from 0.041 to 1.160, 0.0001 to 0.066, 0.173 to 0.789, 0.010 to 2.420 and 0.0007 to 0.077mg·kg-1, respectively. The concentrations of Pb and As in wild fish species exceeded the limit values of the Maximum Levels of Contaminants in Foods (GB 2762-2012), and the over-standard rates were 5.06% and 64.56% respectively. The concentrations of Cd, Cr and Hg did not exceed the standard. The average pollution index results showed that Acheilognathus tonkinensis and Acheilognathus barbatus were seriously polluted by heavy metals. The Oreochromis niloticus were moderately polluted. The Siniperca kneri Garman, Carassius auratus, Pseudohemiculter dispar, Ctenopharyngodon idellus, Hemiculter leucisculus were slightly polluted. Higher bioaccumulation factors of Pb, Cr and Hg were found in wild fish species from Diaojiang River. The concentrations of heavy metals in carnivorous fish and omnivorous fish were higher than those in herbivorous fish. Potential health risk assessment showed that the total target hazard quotients (TTHQ) of Acheilognathus tonkinensis and Acheilognathus barbatus were higher than 1. It indicated that the local residents posed higher human health risk due to the long-term consumption of Acheilognathus tonkinensis and Acheilognathus barbatus. Among all the TTHQ in wild fish species (except Pseudohemiculter dispar and Hemiculter leucisculus), the contribution rate of As was the highest, and the average contribution rate reached 76.63%, which indicated that As was the main risk factor.