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.

[Spectral Distribution and Pollution Characteristics of Polybrominated Diphenyl Ethers in the Air of an Office Building Clustered Area].

To evaluate the pollution level, congener distribution, and human exposure of polybrominated diphenyl ethers (PBDEs) in the atmosphere of Beijing's office buildings, outdoor air samples (particles+gas) were collected from a typical scientific area and PBDEs concentrations were quantified using GC-MS. The results showed that the mass concentrations of PBDEs in the gas phase, PM2.5, and PM10 were 2.3-78.6 pg·m-3, 14.4-335.3 pg·m-3, and 11.6-431.7 pg·m-3, respectively, and the annual average mass concentrations were 21.7 pg·m-3, 96.9 pg·m-3, and 149.3 pg·m-3, respectively. BDE-209 was the predominant congener in particulates, accounting for 50% of the total concentration. The mass concentration of PBDEs in the particles decreased in the following order:autumn > winter > summer > spring, with an obvious change in winter and stability in summer. Tri-BDEs mainly existed in the gas phase, and the proportion of PBDEs in the particle phase increased with bromine number. Source analysis indicated that BDE-209 degradation was an important source of other PBDEs in the air. Exposure risk analysis showed that the respiratory intake of children and adults was 18.6 pg·(kg·d)-1 and 7.1 pg·(kg·d)-1, respectively, which is far below the recommended lowest observed adverse effect level of 1 mg·(kg·d)-1. Similarly, the carcinogenic risk values of BDE-209 for children and adults were 2.3×10-9 and 3.7×10-9, respectively, which were much smaller than the carcinogenic risk limit of 10-6, indicating that there was no health hazard from PBDEs in the atmosphere.

[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.

[Effects of Soil Moisture on Phytoremediation of As-Containinated Soils Using As-Hyperaccumulator Pteris vittata L].

A pot experiment was carried out to study the effects of soil moisture on the growth and arsenic uptake of As-hyperaccumulator Pteris vittata L. The results showed that the remediation efficiency of As was the highest when the soil moisture was between 35%-45%. P. vittata grew best under 45% water content, and its aboveground and underground plant dry weights were 2.95 g x plant(-1) and 11.95 g x plant(-1), respectively; the arsenic concentration in aboveground and roots was the highest under 35% water content, and 40% content was the best for accumulation of arsenic in P. vittata. Moreover, controlling the soil moisture to 35%-45% enhanced the conversion of As(V) to As(III) in aboveground plant, and promoted arsenic detoxification in P. vittata. These above results showed that soil moisture played an important role in the absorption and transport of arsenic by P. vittata. The results of this study can provide important guidance for the large-scale planting of P. vittata and the moisture management measures in engineering application.

[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.

[Discussion on several key points of decision support system for remediation of contaminated sites].

The problem of site contamination has become a focus in the environment protection field in the recent years. Decision support system (DSS) for remediation of contaminated sites is used for selecting the optimal remediation technologies and formulating economic and efficient remediation plans based on site investigation and risk assessment. This paper reviewed and analyzed the key steps in the decision-making process, including frames, models and methods. In addition, the modules and functions of more than 40 types of decision-making software in the world were evaluated and summarized. Aimed at the demand of site contamination in our country, a skeleton frame and feature were proposed in the paper, where the international experience in developed countries has been absorbed and learned.

[Effect of thermal enhanced soil vapor extraction on benzene removal in different soil textures].

Experiments were carried out to investigate the effect of thermal enhanced soil vapor extraction (SVE) on benzene removal from sand, loam and clay and the mechanism. Compared to the routine control treatment, the benzene removal rates were improved by 13. 1% and 12. 3% and the remediation periods were reduced by 75% and 14%, from sand and loam respectively using thermal enhanced SVE. Thermal enhancement decreased the moisture content and increased the soil permeability of clay. On the surface of clay particles, absorption peaks of carboxyl and ethyl disappeared and the content of soil organic substances decreased significantly. Compared to the conventional SVE, the benzene removal rate was improved by 34% in clay soil treated by thermal enhanced SVE. For sand and loam, thermal enhancement could increase the removal rate by promoting the diffusion of benzene in the soil and achieve substantial removal of pollutants in a relatively short period of time. For clay, it could enhance the effect of SVE by reducing the absorption capacity between soil particle surface and contaminant and improving the performance of the gas diffusion in soil by decreasing the moisture content and increasing the soil permeability.

Environmental risk presented by arsenic contamination of building and facility surfaces in a coking plant.

Arsenic contamination on the surface of buildings and facilities at a coking plant and associated health risk were studied. A total of 94 wipe samples from 56 buildings and facilities were collected, and As concentrations were found to range from 0.01 to 23.90 µg/100 cm(2). 20.2% of the samples exceeded the As level calculated to present health risk: 4.02 µg/100 cm(2). Arsenic mean concentration was found to be highest on the surface of bricks, and coking zone showing the highest As risk. The findings of this study may provide clues to As pollution control and risk evaluation in coking plants.

[Urban industrial contaminated sites: a new issue in the field of environmental remediation in China].

Contamination of urban industrial lands is a new environmental problem in China during the process of upgrade of industrial structure and adjustment of urban layout. It restricts the safe re-use of urban land resources, and threatens the health of surrounding inhabitants. In the paper, the market potential of contaminated-site remediation was known through analysis of spatial distribution of urban industrial sites in China. Remediation technologies in the Occident which were suitable for urban industrial contaminated sites were discussed and compared to evaluate their superiority and inferiority. And then, some advices of remediation technologies for urban industrial contaminated sites in China were proposed.

[Pb pollution on surfaces in a typical coking plant and health risk assessment].

Pb pollution on the surfaces of buildings and devices at a coking plant was studied. The objectives of this study were to determine the Pb content and its spatial variation on the surfaces, and to assess the potential health risk from this Pb. Ninety-four wipe samples were collected from 56 buildings and devices at the coking plant, and their Pb contents were determined. Surface Pb concentrations ranged from 0-538 micro x g/dm2, and concentrations in 78.7% of the samples exceeded the US Department of Housing and Urban Development (HUD) standard (2.69 microg/dm2). By area, the proportion of samples with concentrations greater than the US HUD standard were 78.9% in the office and living zone, 75.0% in the refining zone, 73.7% in the coking zone and 78.6% in the coke-gas zone. Among the various types of surfaces, the coke pusher had the highest average surface concentration of Pb. The average surface concentrations of Ph on common coking plant surface materials followed the order paints > brick > cement > glass, and the concentrations in 94.4% of the wipe samples taken from paint surfaces exceeded the US HUD standard.

[Chemical oxidants for remediation of soils contaminated with polycyclic aromatic hydrocarbons at a coking site].

Different oxidants were evaluated for removal of polycyclic aromatic hydrocarbons (PAHs) from contaminated soils at industrial coking sites with the use of simulating device, and the fate of pollutants during the treatment was investigated. Permanganate showed the highest PAHs removal rate (96.2%) of the oxidants studied. Most of the PAHs were oxidized and only < 1% of PAHs volatilized and transferred to the solvent. The removal of PAHs by activated persulfate reached 92%. Modified Fenton reagent could remove 80% of PAHs, and < 2% of PAHs volatilized and transferred to the solvent after treatment with activated persulfate and modified Fenton reagent. The efficiencies of hydrogen dioxide and Fenton reagent for removal of PAHs were both < 60% ,and up to 6% of PAHs volatilized and transferred to the solvent. In summary, permanganate and activated persulfate are the most effective and environment-friendly oxidants for removing PAHs from contaminated soils. The chemical oxidants could easily remove ANY, ANT, BaP, DahA, BghiP and IcdP, but FLE, CHR and Fla were relatively resistant to chemical oxidation.

[Comparative study on determinations of BTEX in soils from industrial contaminated sites].

In order to ascertain BTEX measurements of soils from industrial contaminated sites, static headspace, purge-and-trap and solid phase microextraction (SPME) combined gas chromatography were selected to determine BTEX in the soils. This method of SPME could not be used to analyze BTEX isomers in soils from highly contaminated sites because the high concentration of organic contaminants eroded the SPME probe head. The recoveries for added standard ranged from 95.2% - 98.2% for static headspace-GC and 99.2% - 101.3% for purge-and-trap-GC. When the soil samples contained low concentrations of BTEX (< 60 mg/kg), the concentration determined by purge-and-trap-GC was 12.6% - 37.6% higher than the value from static headspace-GC. For soil samples containing high concentrations of BTEX, the static headspace-GC result was higher than that from purge-and-trap-GC. The correlation trend lines of individual BTEX isomers to total BTEX were similar for both static headspace-GC and purge-and-trap-GC results.

[Chemical oxidants for remediation of BTEX-contaminated soils at coking sites].

An enclosed reactor was used to evaluate Fenton reagent, modified Fenton reagent, potassium permanganate and activated persulfate for removal of benzene, toluene, ethyl benzene, and xylene (BTEX) from soil at contaminated industrial coking sites. The results showed that Fenton reagent and modified Fenton reagent were the optimum oxidants for removing BTEX, and these oxidants decreased the concentration of BTEX in soils by 83% and 73%, respectively. The proportion of BTEX volatilized from the soil was < 4% in both cases, and the rates of BTEX removal from the whole system were 80% and 71%. More than 65% of xylene was removed after treatment with Fenton reagent and modified Fenton reagent. In contrast, benzene, toluene were more resistant to oxidation, and ethyl benzene was the most resistant of these compounds. The concentration of BTEX decreased to some extent when permanganate and activated persulfate were used as oxidants. However, the proportions of volatilized BTEX were 83% and 77% for permanganate and activated persulfate, respectively. This indicates that they could stimulate the desorption and volatilization of BTEX, while they were ineffective for removing BTEX from the environment.

[Accumulation of soil arsenic by Panax notoginseng and its associated health risk].

Panax notoginseng is a valued traditional Chinese medical herb. In this study, the arsenic (As) contamination of soil in P. notoginseng plantation area in Wenshan (Yunnan, China) was investigated; the absorption and accumulation of soil As by the P. notoginseng was revealed; and the associated health risk was evaluated. The results revealed that the soil As concentrations ranged between 6.9-242.0 mg x kg(-1). Arsenic concentrations in 48% of the total soil samples were > 40 mg x kg(-1). The As concentrations in 24% of main root samples, 81% of fibrous root samples, 14% of stem samples, 57% of leaf samples, and 44% of flower/fruit samples were greater than the regulation concentration of 2.0 mg x kg(-1). Arsenic accumulation in the main root increased with the soil As concentration at soil As concentrations < 100 mg x kg(-1), but sharply decreased with the soil As concentration at soil As concentrations > 100 mg x kg(-1). With increasing soil As concentration, the total biomass of P. notoginseng and the main root biomass decreased. Calculating with the As concentration in different parts of Sanqi P. notoginseng plants, percent of the average ingestion rates of As with ADI regulated by FAO/WHO showed fibrous root > leave > flower/fruit > main root > stem. Based on the As concentration in the main root, the daily As intake accounted for a mean fraction of 12.83% (maximum 45.87%) of the acceptable daily intake specified by FAO/WHO,and the ratio increased with the increasing of soil As concentration. Arsenic contamination of soil and P. notoginseng at the plantation area of Wenshan should not be neglected, and effective strategies should be adopt to reduce As accumulation in the plant and human health risk.

[Enhancement of As-accumulation by Pteris vittata L. affected by microorganisms].

A pot experiment was carried out to study the root character and As accumulation of Pteris vittata L. affected by actinomycete PSQ, shf2 and bacteria Ts37, C13. The results indicated that growth of the fern was improved by the microorganisms. The biomass, root activity and root volume of shf2 treatment were 11.5 g/pot, 2.01 microg/(g x h), 38.3 mL, which were higher than those of other microorganisms treatments. Arsenic concentrations in the plants treated by the microorganisms were higher than that of the control treatment. The As concentration of leaves in Ts37 treatment was up to 837 mg/kg, 206% more than that of the control. The As concentration of root treated by shf2 is 427 mg/kg, 88% more than that of the control. The arsenic accumulation by the plant in microorganism treatments was higher than that of the control, especially shf2 treatment up to 5804 microg/pot, 136% more than that of the control. The phytoremediation efficiency of the fern in greenhouse experiment after 45d was from 8.9% to 11.3%. The ability of As-accumulation of Pteris vittata is greatly enhanced by application of microorganism, and actinomycete shf2 is proved as the perfect one.

The arsenic hyperaccumulator fern Pteris vittata L.

Arsenic (As) contaminated soils and waters are becoming major global environmental and human health risks. The identification of natural hyperaccumulators of As opens the door for phytoremediation of the arsenic contaminant. Pteris vittata is the first identified naturally evolving As hyperaccumulator. More than a decade after its discovery, we have made great progress in understanding the uptake, transport, and detoxification of As in the fern. The molecular mechanisms controlling As accumulation in P. vittata are now beginning to be recognized. In this review, we will try to summarize what we have learned about this As accumulator, with particular emphasis on the current knowledge of the physiological and molecular mechanisms of arsenic phytoremediation. We also discuss the potential strategies to further enhance phytoextraction abilities of P. vittata.

Leaching potential of arsenic from Pteris vittata L. under field conditions.

Foliar leaching might be an important process in the biogeochemical cycle of elements, but the leaching behaviors of As remain unclear. This study examined As leaching from foliage of an As-hyperaccumulator, Pteris vittata L. in the field. Results indicated that substantial amounts of As can be leached from the foliage by precipitation. Arsenic concentrations in the foliar leachate ranged from 4.06 to 519 microgL(-1), and the percentages of As(III) with respect to total As in leachate ranged from 5% to 10%. A positive linear relationship existed between As concentrations of the foliar leachate and the amounts of As accumulated in the plant. The rate of As leaching from the leaves was accelerated by an increase of rainfall and time in a simulated precipitation experiment. Water-soluble As distributed within the cuticle and apoplast of the plant was speculated as the main source of the leached As. The As leaching is an important process of within-ecosystem As cycling in phytoremediation and it deserves further investigation.

Arsenic transformation and volatilization during incineration of the hyperaccumulator Pteris vittata L.

Safe incineration of harvested hyperaccumulators containing high content of heavy metals to avoid secondary environmental pollution is a problem for popularizing phytoremediation technology. The As volatilization behavior and its mechanism during incineration of Pteris vittata, an As-hyperaccumulator, was investigated. Incineration results reveal that 24% of total As accumulated by P. vittata (H-As) containing high As content (1170 mg/kg) is emitted at 800 degrees C, of which 62.5% of the total emitted As is volatilized below 400 degrees C. A study of the extended X-ray absorption fine structure (EXAFS) shows that part of As(III) was identified in the thermal decomposition residue of dried P. vittata (H-As), As2O5 + P. vittata (L-As) containing low As content (14.7 mg/kg), and As2O5 + charcoal (C) at 200 degrees C, suggesting that carbon originating from biomass incineration might catalyze As(V) reduction. This speculation was tested through thermogravimetric experiments, in which either C or P. vittata (L-As) markedly catalyzed the volatilization of pure As2O5 at low temperature. Therefore, the reduction of As(V) to As(III) is responsible for As volatilization during incineration of P. vittata below 400 degrees C. This study provides important insights into As behavior during incineration of As-hyperaccumulators, which is helpful to safely dispose harvested biomass with high As content.