Micro-distribution of arsenic and polycyclic aromatic hydrocarbons and their interaction in Pteris vittata L.

Interactive effects of inorganic arsenic (As) species and polycyclic aromatic hydrocarbons (PAHs) on their uptake, accumulation and translocation in the hyperaccumulator Pteris vittata L. (P. vittata) were studied hydroponically. The presence of PAHs hindered As uptake and acropetal translocation by P. vittata, decreasing As concentrations by 29.8%-54.5% in pinnae, regardless of the initial As speciation. The inhibitive effect of PAHs was 1.6-8.7 times greater for arsenite [As(III)] than for arsenate [As(V)]. Similarly, inorganic As inhibited the uptake of fluorene (FLU) and benzo[a]pyrene (BaP) by P. vittata roots by 0.4%-21.7% and by 33.1%-69.7%, respectively. Interestingly, coexposure to As and PAHs slightly enhanced the translocation of PAHs by P. vittata with their concentrations increased 0.3 to 0.8 times in shoots, except for the As(III)+BaP treatment. The antagonistic interaction between As and PAHs uptake is likely caused by competitive inhibition or oxidative stress injury. By using synchrotron radiation micro X-ray fluorescence imaging, high concentrations of As were found distributed throughout the microstructures far from main vein of the pinnae when coexposed with PAHs, the opposite of what was observed with exposure to As only. PAHs could also significantly inhibit the accumulation and distribution of As in vascular bundles in rachis treated with As(III). The results of two-photon laser scanning confocal microscopy revealed that PAHs were mainly distributed in the vascular cylinder, epidermal cells, vascular bundles, epidermis and vein tissues, and this was independent of As speciation and treatment. This work offers new positive evidence for the interaction between As and PAHs in P. vittata, presents new information on the underlying mechanisms for interactions of As and PAHs affecting their uptake and translocation within P. vittata L., and provides direction for future research on the mechanisms of PAHs uptake by plants.

[Occurrence Characteristics and Health Risks of PAHs on the Surface of Buildings and Devices in the Coking Plant].

The occurrence characteristics of polycyclic aromatic hydrocarbons (PAHs) on the surfaces of buildings and devices in a typical coking plant were analyzed with the samples from different functional zones and materials. The health risk of PAHs was also evaluated. The results showed that PAHs concentrations ranged from 8.00×10-2-1.98×102 µg·dm-2, and 22.0% wiping samples exceeded the World Trade Center Task Group(WTCTG)standard (1.45 µg·dm-2), the highest rate beyond the standard in the samples was 135. The functional zones with the high PAHs concentration were mainly located in the coking and refinery zone. The PAHs concentration on the surfaces of buildings in the coking zone was 12.1 µg·dm-2, which was the highest in all functional zones. Among the surface materials, the antirust paint contained the highest concentrations of PAHs and were over the standard rate, whereas the glass had the lowest adsorption ability for PAHs. The US Superfund Risk Assessment Method was used to evaluate the health risk of PAHs. The evaluation results showed that PAHs in the coking and refinery zones were a risk for carcinogenicity, the total carcinogenic risk value to the exposed population (3.78×10-6-1.32×10-5) was higher than the lower limit of the US EPA standard (10-6). The results could provide the scientific basis for environmental management and remediation of contaminated sites.

[Persulfate Oxidation Effect of Soil Organic Pollutants by Natural Organic Matters].

This study explored the degradation effect and mechanism of persulfate oxidation activated by different macromolecular substances (polysaccharides, humic acid, and citric acid), combined with ferrous ions and different kinds of carbohydrate (monosaccharide, disaccharide, and polysaccharide). The results showed that the oxidation effects of total petroleum hydrocarbons (TPHs) and polycyclic aromatic hydrocarbons (PAHs) by different activation treatments were in the order:humic acid combined with ferrous ion > polysaccharide > citric acid chelated with iron > polysaccharide combined with ferrous ion > disaccharides > monosaccharide > CK. Among them, humic acid combined with ferrous ion-activated persulfate achieved the highest removal rates (up to 79.21% and 79.89%, respectively), and also showed the weakest pollutant content rebound phenomenon. For oxidation of high-ring PAHs, humic acid combined with ferrous ion treatment and polysaccharide activation showed great advantages, with degradation rates being 77.96% and 84.37%, much higher than other treatments. Humic acid combined with ferrous ion-activated persulfate result in the highest Eh of soil (up to 618-676 mV), and polysaccharide treatment was secondary, indicating that macromolecular materials exhibited great oxidation ability and can degrade soil organic pollutants efficiently.

[Influence of Arsenate and Phenanthrene on Carbon-groups of Pteris vittata L. Roots].

To ascertain absorption of arsenate and phenanthrene as well as their influence on carbon groups in excised roots of Pteris vittata L., the chemical structure of the carbon groups in excised roots was characterized by solid state13C-Nuclear Magnetic Resonance (13C-NMR). The results showed that the excised roots could effectively absorb As and PHE without transpiration, and PHE promoted As accumulation in the roots. Similarly, arsenate increased the adsorption of PHE by the excised roots, the concentration of PHE was increased by 15%-53% compared with CK. The carbon groups of the excised roots were dominated by O-alkyl C, the percentage of carboxyl C was the lowest, mainly composed of carboxylic acids, esters and amides. With the addition of As and PHE, the percentage of carboxyl C increased significantly. The more stable and complex aromatic organic matter was formed to improve the resistance and adaptability in excised roots of Pteris vittata L. under As and PHE stress.

[Occurrence Characteristics of Pyrene and Arsenate and Their Interaction in Pteris vittata L].

Pteris vittata L. can absorb and accumulate high arsenic levels in soil. To clarify the occurrence characteristics of pyrene (PYR) and arsenate (As) as well as their interaction in P. vittata L., the hosting and distribution rules of PYR were determined via two-photon laser scanning confocal microscopy (TPLSCM). The results showed that PYR addition resulted in obviously lower concentrations of total As in various parts of P. vittata, with a largest decrease of about 35% in the leaves and stem, and 20. 5% in the roots. PYR addition could also decrease the proportion of trivalent arsenic and increased that of pentavalent arsenate in different parts of P. vittata. The concentrations of trivalent and pentavalent arsenic in the leaves of P. vittata showed the largest decrement, which were 42.2% and 32.49%, respectively. Arsenate addition increased the accumulation of PYR in the root and stem of P. vittata by 9.8 µg and 139 ng per plant, respectively, while no obvious influence was found on the PYR in the leaves. Pyrene mainly attached to the cell membrane and other membrane structure such as nuclear membrane and organelle membrane, and there was less pyrene in the cytoplasm. There was little PYR in the phloem and cortex in the stem as well as palisade tissue and spongy tissue in leaves.