Surface soil (0-20 cm) samples from nine representative vegetable fields located in Guangzhou, Shenzhen, Zengcheng and Huadu within the Pearl River Delta, South China were collected and analyzed for 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs) using gas chromatography coupled to mass spectrometry (GC-MS). Total concentrations of 16 PAHs (Sigma(PAHs)) ranged from 160 to 3700 microg kg(-1). Large variations were observed also between concentrations of individual PAHs from different vegetable fields and within the site as well. Acenapthylene, benzo[b]fluoranthene, fluoranthene, benzo[a]pyrene and benzo[k]fluoranthene were consistently the most prevalent individual PAHs. The values of PAH isomer ratios [anthracene/(anthracene+phenanthrene) and fluoranthene/(fluoranthene+pyrene)] indicate that combustion processes are the major sources of PAHs. Concentrations of PAHs were poorly correlated with organic carbon concentrations of soils, suggesting different sources and also indicating that the PAH pollution of this area is recent. The same outcome is confirmed by the predominance of PAHs with fewer rings (相似文献
Responses of understory plant diversity to nitrogen (N) additions were investigated in reforested forests of contrasting disturbance regimes in southern China from 2003 to 2008: disturbed forest (with harvesting of understory vegetation and litter) and rehabilitated forest (without harvesting). Experimental additions of N were administered as the following treatments: Control, 50 kg N ha−1 yr−1, and 100 kg N ha−1 yr−1. Nitrogen additions did not significantly affect understory plant richness, density, and cover in the disturbed forest. Similarly, no significant response was found for canopy closure in this forest. In the rehabilitated forest, species richness and density showed no significant response to N additions; however, understory cover decreased significantly in the N-treated plots, largely a function of a significant increase in canopy closure. Our results suggest that responses of plant diversity to N deposition may vary with different land-use history, and rehabilitated forests may be more sensitive to N deposition. 相似文献
Environmental Geochemistry and Health - Microplastic pollution has been considered as a global environmental issue that potentially threatens human health. However, research about microplastic... 相似文献
In present study, atmospheric particles from Shanghai, the biggest city and the most important industrial base in China, were analyzed for polybrominated diphenyl ethers (PBDEs) and Dechlorane Plus (DP). Concentrations of ∑(20)PBDEs and DP both exhibited the changing trend of industrial area > urban areas. Jiading District had the highest levels of particulate PBDEs and DP with values of 744 ± 152 pg/m(3) and 5.48 ± 1.28 pg/m(3), respectively. Compared with similar data in other areas of the world, PBDEs in Shanghai were at medium pollution level, while DP was at lower level, which reflected their different production and use in Shanghai. The results from multiple linear regression analysis suggested that deca-BDE mixture was the most important contributor of particulate PBDEs in Shanghai. The fractions of anti-DP showed no significant differences to those of the technical mixtures (p > 0.05), which suggested that no obviously stereoselective process occurred in ambient air around Shanghai. 相似文献
Two series of activated carbons modified by Fe (II) and Fe (III) (denoted as AC/N-FeII and AC/N-FeIII), respectively, were used as adsorbents for the removal of phosphate in aqueous solutions.
Method
The synthesized adsorbent materials were investigated by different experimental analysis means. The adsorption of phosphate on activated carbons has been studied in kinetic and equilibrium conditions taking into account the adsorbate concentration, temperature, and solution pH as major influential factors.
Results
Maximum removals of phosphate are obtained in the pH range of 3.78?C6.84 for both adsorbents. Langmuir isotherm adsorption equation well describes the experimental adsorption isotherms. Kinetic studies revealed that the adsorption process followed a pseudo-second order kinetic model. Results suggest that the main phase formed in AC/N-FeII and AC/N-FeIII is goethite and akaganeite, respectively; the presence of iron oxides significantly affected the surface area and the pore structure of the activated carbon.
Conclusions
Studies revealed that iron-doped activated carbons were effective in removing phosphate. AC/N-FeII has a higher phosphate removal capacity than AC/N-FeIII, which could be attributed to its better intra-particle diffusion and higher binding energy. The activation energy for adsorption was calculated to be 22.23 and 10.89 kJ mol?1 for AC/N-FeII and AC/N-FeIII, respectively. The adsorption process was complex; both surface adsorption and intra-particle diffusion were simultaneously occurring during the process and contribute to the adsorption mechanism. 相似文献
Using molasses wastewater as partial acidifying agent, a new Fenton-like catalyst (ACRMsm) was prepared through a simple process of acidification and calcination using red mud as main material. With molasses wastewater, both the free alkali and the chemically bonded alkali in red mud were effectively removed under the action of H2SO4 and molasses wastewater, and the prepared ACRMsm was a near-neutral catalyst. The ACRMsm preparation conditions were as follows: for 3 g of red mud, 9 mL of 0.7 mol/L H2SO4 plus 2 g of molasses wastewater as the acidifying agent, calcination temperature 573 K, and calcination time 1 h. Iron phase of ACRMsm was mainly α-Fe2O3 and trace amount of carbon existed in ACRMsm. The addition of molasses wastewater not only effectively reduced the consumption of H2SO4 in acidification of red mud but also resulted in the generation of carbon and significantly improved the distribution of macropore in prepared ACRMsm. It was found that near-neutral pH of catalyst, generated carbon, and wide distribution of macropore were the main reasons for the high catalytic activity of ACRMsm. The generated carbon and wide distribution of macropore were entirely due to the molasses wastewater added. In degradation of orange II, ACRMsm retained most of its catalytic stability and activity after five recycling times, indicating ACRMsm had an excellent long-term stability in the Fenton-like process. Furthermore, the performance test of settling showed ACRMsm had an excellent settleability. ACRMsm was a safe and green catalytic material used in Fenton-like oxidation for wastewater treatment.