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ABSTRACT: The effects of interactions between genetic materials and polycyclic aromatic hydrocarbons (PAHs) on gene expression in the extracellular environment remain to be elucidated and little information is currently available on the effect of ionic strength on the transformation of plasmid DNA exposed to PAHs. Phenanthrene and pyrene were used as representative PAHs to evaluate the transformation of plasmid DNA after PAH exposure and to determine the role of Ca2+ during the transformation. Plasmid DNA exposed to the test PAHs demonstrated low transformation efficiency. In the absence of PAHs, the transformation efficiency was 4.7 log units; however, the efficiency decreased to 3.72-3.14 log units with phenanthrene/pyrene exposures of 50 µg·L-1. The addition of Ca2+ enhanced the low transformation efficiency of DNA exposed to PAHs. Based on the co-sorption of Ca2+ and phenanthrene/pyrene by DNA, we employed Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and mass spectrometry (MS) to determine the mechanisms involved in PAH-induced DNA transformation. The observed low transformation efficiency of DNA exposed to either phenanthrene or pyrene can be attributed to a broken hydrogen bond in the double helix caused by planar PAHs. Added Ca2+ formed strong electrovalent bonds with "-POO--" groups in the DNA, weakening the interaction between PAHs and DNA based on weak molecular forces. This decreased the damage of PAHs to hydrogen bonds in double-stranded DNA by isolating DNA molecules from PAHs and consequently enhanced the transformation efficiency of DNA exposed to PAH contaminants. The findings provide insight into the effects of anthropogenic trace PAHs on DNA transfer in natural environments.
PLoS ONE 01/2013; 8(3):e58238. · 4.09 Impact Factor
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ABSTRACT: There is an increasing need to describe the growth characteristics of cyanobacteria exposed to polycyclic aromatic hydrocarbons (PAHs) because the presence of PAHs in lakes is known to affect the growth of this kind of microorganisms. In this work, the effects of low concentrations of PAHs on Microcystis aeruginosa (M. aeruginosa) were investigated. M. aeruginosa were cultivated in the medium with a mixture of PAHs (0.486mgL(-1) naphthalene, 0.049mgL(-1) phenanthrene, and 0.0015mgL(-1) pyrene) and different concentrations of nitrogen and phosphorus. During 31d of incubation, profiles of cell number and chlorophyll-a content were determined. The results indicated that when the concentration of an individual PAH was below its no observed effect concentration (NOEC), the exposure of M. aeruginosa to a mixture of PAHs markedly promoted cell density after 7d of culture. Low concentrations of nutrients in the medium improved the growth of M. aeruginosa in the presence of PAHs. When concentrations of both phosphorus and nitrogen were 50% lower than those of the control, the specific growth rate of M. aeruginosa increased by 100% when exposed to PAHs, and the generation time decreased from 10.5 to 5.3d. The chlorophyll-a content in medium also increased from 2.23 to 3.18μgmL(-1), which was attributed to an increase in cell numbers.
Journal of hazardous materials 08/2012; 237-238:371-5. · 4.14 Impact Factor
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ABSTRACT: PurposeThe soil contamination by hydrophobic organic contaminants (HOCs), such as polycyclic aromatic hydrocarbons (PAHs), poses
great threats to human health and ecological security and attracts worldwide concerns. The total HOC concentrations overestimate
its available fraction to the soil biota. Increased understanding of the availabilities of PAHs in soil environment will have
considerable benefits for their risk assessment and be very instructive to food safety and remediation strategies in contaminated
sites. However, the availability of PAHs in aging soils and particularly the correlations of the availabilities with their
forms in soils have yet to be elucidated. In this work, the availabilities of PAHs in aging soils were evaluated using a sequential
mild extraction technique.
Materials and methodsFour typical zonal soils in China previously free of PAHs were collected from A (0–20cm) horizon, air-dried, and sieved.
Soils were spiked with a solution of phenanthrene and pyrene as representative PAHs in acetone. After the acetone evaporated
off, the treated soils were progressively diluted with unspiked soils and sieved again several times to homogenize the soil
samples. The forms of PAHs in soils were experimented using microcosms that are similar to those reported in literature. Various
treated soils were packed into amber glass microcosms (each with 25g soil). Three replications were given for each treatment.
NaN3 solution (0.5%) was added to some microcosms in order to get the microbe-inhibited treatments. The soil water contents were
adjusted to be 20% of soil water-holding capacity. After incubation for 0, 2, 4, 8, 12, and 16weeks in microcosms with a
temperature of 25°C, the soils were sampled. PAHs were then extracted by a sequential mild extraction technique, and their
forms and availabilities were determined.
Results and discussionThe available residual concentrations of phenanthrene and pyrene generally decreased with aging time, and the PAHs were more
readily available at the start of the incubation, but their availabilities decreased rapidly with increasing the soil-PAH
contact time. In addition, the degradation efficiency of the available PAHs in soils was generally higher for PAHs with low
molecular weight. The available residues of PAHs in soils were fractionated into desorbing and non-desorbing fractions. The
desorbing fractions were the largest portion of the available PAHs in soils. In addition, the desorbing fractions were the
main portion to be readily biodegradable. The non-desorbing fractions of PAHs were less bioavailable and with less possibility
to be biodegraded in soils. The dissipation of the desorbing PAH fractions accounted for the dominant contribution to the
dissipation of the available fractions of tested PAHs. The formation of bound PAH residues was observed in soils. However,
the concentrations of the bound residual PAHs were very low. Comparing with the microbial biodegradation, the transformation
of PAHs from available fractions to bound residues was a negligible contribution to the dissipation of available fractions
of tested PAHs in soils.
ConclusionsA mild extraction technique was utilized for the evaluation of the availabilities of phenanthrene and pyrene in aging soils.
We found that the available residues of tested PAHs generally decreased with time resulting dominantly from microbial biodegradation.
The desorbing fractions were the largest portion of the available fractions of PAHs. The dissipation of the desorbing PAH
fractions accounted for the dominant contribution to dissipation of the available fractions of tested PAHs, and in contrast,
the transformation of PAHs from available fractions to their bound residues contributed little to the dissipation of their
available residues in soils. In this work, the correlations of the availability of PAHs with their forms in soils were elucidated,
and a useful method on this subject was provided, which would be very instructive to other HOCs in soil environment.
KeywordsAging soil-Availability-Bound residue-Form-Mild extraction-Polycyclic aromatic hydrocarbons (PAHs)
Journal of Soils and Sediments 04/2012; 10(5):799-807. · 1.86 Impact Factor
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ABSTRACT: In this study, we evaluated (1) the plant uptake of polycyclic aromatic hydrocarbons (PAHs) from soil and water and (2) the applicability of the partition-limited model on the prediction of plant concentrations with respect to PAH contents in soils and other associated parameters. To accomplish these goals, the plant uptake of PAHs from culture solution and soils were extensively experimented. A steady state was shown for ryegrass kinetic uptake of phenanthrene and pyrene from water after about 48h. As to the ryegrass uptake from soils, root and shoot concentrations of PAHs generally increased, while root concentration factors (RCFs) and shoot concentration factors (SCFs) tended to decrease with the increasing PAH concentrations in soils after 45days. One note of interest is that root concentrations and RCFs of phenanthrene and pyrene for ryegrass uptake were larger than shoot concentrations and SCFs, irrespective of soil–plant and water–plant systems. However, root and shoot concentrations, or RCFs and SCFs, for ryegrass uptake from culture solution were always much higher than those for ryegrass uptake from soils at the same PAH concentrations in water or soil interstitial water, indicating that PAHs in culture solution would be more available and susceptible than those in soil interstitial water for uptake by plants. In addition, the partition-limited model showed a high level of model performance on prediction of plant uptake of phenanthrene and pyrene from soils, with the overall differences of the modeled and experimented concentrations in ryegrass roots or shoots less than 187%. This suggests that the partition-limited model might be a potentially useful instrument for vegetation-contamination assessment.
Biology and Fertility of Soils 04/2012; 42(5):387-394. · 2.32 Impact Factor
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ABSTRACT: The influence of dissolved organic matter (DOM) on the sorption of atrazine (2-chloro-4-ethylamino-6-isopylamino-1,3,5-triazine) by ten soils was investigated. Batch sorption isotherm techniques were used to evaluate the important physiochemical properties of soil determining the sorption of atrazine in the presence of DOM. The sorption of atrazine as a representative of nonionic organic contaminants (NOCs) by soil with and without DOM could be well described by the Linear and Freundlich models. The n values of the Freundlich model were generally near to 1, indicating that linear partitioning was the major mechanism of atrazine sorption by soil samples. The apparent distribution coefficient, K*dK^{*}_{d} value, for atrazine sorption in the presence of DOM initially increased and decreased thereafter as the DOM concentration increased in the equilibrium solution. DOM at relatively lower concentrations significantly enhanced the sorption of atrazine by soil, while it inhibited the atrazine sorption at higher concentrations. For all the soil samples, the maximum of K*dK^{*}_{d} was 1.1~3.1 times higher than its corresponding K
d value for the control (without DOM). The maximum enhancement of the distribution coefficient (Dk*d\Delta k^{*}_{d}) in the presence of DOM was negatively correlated with the content of soil organic carbon (SOC) and positively correlated with the clay content. The critical concentration of DOM, below which DOM would enhance atrazine sorption, was negatively correlated with SOC. The influence of DOM on atrazine sorption could be approximately considered as the net effect of the cumulative sorption and association of atrazine with DOM in solution. Results of this study provide an insight into the retention and mobility of a NOC in the soil environment.
Biology and Fertility of Soils 04/2012; 42(5):418-425. · 2.32 Impact Factor
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ABSTRACT: Plant contamination by polycyclic aromatic hydrocarbons (PAHs) is crucial to food safety and human health. Enzyme inhibitors are commonly utilized in agriculture to control plant metabolism of organic components. This study revealed that the enzyme inhibitor ascorbic acid (AA) significantly reduced the activities of peroxidase (POD) and polyphenol oxidase (PPO), thus enhancing the potential risks of PAH contamination in tall fescue (Festuca arundinacea Schreb.). POD and PPO enzymes in vitro effectively decomposed naphthalene (NAP), phenanthrene (PHE) and anthracene (ANT). The presence of AA reduced POD and PPO activities in plants, and thus was likely responsible for enhanced PAH accumulation in tall fescue. This conclusion is supported by the significantly enhanced uptake of PHE in plants in the presence of AA, and the positive correlation between enzyme inhibition efficiencies and the rates of metabolism of PHE in tall fescue roots. This study provides a new perspective, that the common application of enzyme inhibitors in agricultural production could increase the accumulation of organic contaminants in plants, hence enhancing risks to food safety and quality.
PLoS ONE 01/2012; 7(11):e50467. · 4.09 Impact Factor
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ABSTRACT: Some plants can tolerate and even detoxify soils contaminated with heavy metals. This detoxification ability may depend on what chemical forms of metals are taken up by plants and how the plants distribute the toxins in their tissues. This, in turn, may have an important impact on phytoremediation. We investigated the impact of arbuscular mycorrhizal (AM) fungus, Glomus intraradices, on the subcellular distribution and chemical forms of cadmium (Cd) in alfalfa (Medicago sativa L.) that were grown in Cd-added soils. The fungus significantly colonized alfalfa roots by day 25 after planting. Colonization of alfalfa by G. intraradices in soils contaminated with Cd ranged from 17% to 69% after 25-60 days and then decreased to 43%. The biomass of plant shoots with AM fungi showed significant 1.7-fold increases compared to no AM fungi addition under the treatment of 20 mg·kg(-1) Cd. Concentrations of Cd in the shoots of alfalfa under 0.5, 5, and 20 mg·kg(-1) Cd without AM fungal inoculation are 1.87, 2.92, and 2.38 times higher, respectively, than those of fungi-inoculated plants. Fungal inoculation increased Cd (37.2-80.5%) in the cell walls of roots and shoots and decreased in membranes after 80 days of incubation compared to untreated plants. The proportion of the inactive forms of Cd in roots was higher in fungi-treated plants than in controls. Furthermore, although fungi-treated plants had less overall Cd in subcellular fragments in shoots, they had more inactive Cd in shoots than did control plants. These results provide a basis for further research on plant-microbe symbioses in soils contaminated with heavy metals, which may potentially help us develop management regimes for phytoremediation.
PLoS ONE 01/2012; 7(11):e48669. · 4.09 Impact Factor
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ABSTRACT: Soybean [Glycine max (L.) Merr.] stalk-based biochar was prepared using oxygen-limited pyrolysis. We evaluated phenanthrene (PHE) and Hg(II) sorption, from single and binary component solutions, onto prepared biochar. We found that the prepared biochar efficiently removed PHE and Hg(II) from aqueous solutions. The isotherms for PHE and Hg(II) sorption could be described using linear and Tóth models, respectively, both with high regression coefficients (R(2) > 0.995). When PHE and Hg(II) coexisted in an aqueous solution, we observed direct competitive sorption, each one suppressing another. Our results provide insight into the recycling of agricultural residues, and also a new application for removal of polycyclic aromatic hydrocarbons and heavy metals from contaminated water utilizing biochar from agricultural residue.
Journal of Agricultural and Food Chemistry 11/2011; 59(22):12116-23. · 2.82 Impact Factor
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ABSTRACT: A rapid inhibitory effect of polycyclic aromatic hydrocarbons (PAHs) on DNA degradation was examined by conventional spectral analysis and microtitration. The purpose was to determine whether PAHs inhibited free DNA degradation by the enzyme DNase I. The results showed that model PAHs phenanthrene and pyrene combined with free DNA to decelerate DNA degradation by DNase I. Phenanthrene-induced inhibition was stronger than that of pyrene. Trace level of PAHs did not induce DNase I deactivation. The DNase I enzyme exhibited only slight shifts in IR absorption bands related to amide II and III upon PAH exposure, and no change was observed with other bands. The decelerating degradation of DNA is attributed to the changes in structure, backbone composition, and guanine constituents of DNA induced by PAHs inserted into double strands, and to the imidazole-like derivates from the combination of imidazole rings with pyrene.
Environmental Science & Technology 11/2010; 44(23):8891-6. · 4.80 Impact Factor
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ABSTRACT: An available remediation technique--arbuscular mycorrhizal phytoremediation (AMPR)--is further proposed for soils contaminated with phenanthrene and pyrene as representative polycyclic aromatic hydrocarbons (PAHs) utilizing a greenhouse pot experiment. The initial concentrations of phenanthrene and/or pyrene in soils were 103 mg kg(-1) and 74 mg kg(-1), respectively. The host plant was alfalfa (Medicago sativa L.), and the experimental arbuscular mycorrhizal fungi (AMF) were Glomus mosseae and G. etunicatum. More than 98.6% and 88.1% of phenanthrene and pyrene were degraded after 70 days in soils with AMPR. Use of multiple mycorrhizal species significantly promoted degradation of PAHs in soils. The co-contaminant (pyrene) present clearly inhibited the degradation of a single PAH (phenanthrene) in soil. Mycorrhizal colonization caused increased accumulation of PAHs in plant roots but a decrease in shoot. However, plant uptake contributed negligibly to PAH dissipation in AMPR, and plant accumulated PAHs amounted to less than 3.24% of total PAH degradation in mycorrhizal soils. In contrast, the optimized microbiota in mycorrhizal association was responsible for PAH degradation in AMPR. The high rate of PAH dissipation in mycorrhizal soils, the evident promotion of PAH degradation by AM colonization, and the healthy plant growth suggest encouraging opportunities for AMPR of PAH-contaminated soils.
Journal of hazardous materials 10/2010; 185(2-3):703-9. · 4.14 Impact Factor
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ABSTRACT: The arbuscular mycorrhizal (AM) hyphae-mediated uptake of polycyclic aromatic hydrocarbons (PAHs) by the roots of ryegrass (Lolium multiflorum Lam.) was investigated using three-compartment systems. Glomus mosseae and Glomus etunicatum were chosen, and fluorene and phenanthrene were used as representative PAHs. When roots were grown in un-spiked soils, AM hyphae extended into PAH-spiked soil and clearly absorbed and transported PAHs to roots, resulting in high concentrations of fluorene and phenanthrene in roots. This was further confirmed by the batch equilibration experiment, which revealed that the partition coefficients (K(d)) of tested PAHs by mycorrhizal hyphae were 270-356% greater than those by roots, suggesting the great potential of hyphae to absorb PAHs. Because of fluorene's lower molecular weight and higher water solubility, its translocation by hyphae was greater than that of phenanthrene. These results provide new perspectives on the AM hyphae-mediated uptake by plants of organic contaminants from soil.
Bioresource technology 09/2010; 101(18):6895-901. · 4.25 Impact Factor
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ABSTRACT: A batch experiment was conducted to evaluate the impact of root exudates on the desorption of phenanthrene and pyrene in soils. Rhizosphere model systems where soils are given artificial root exudates (AREs) have been utilized. ARE addition markedly influenced the desorption of phenanthrene and pyrene in soils, and the effects depended on ARE concentration, aging time, and soil properties. The desorption of phenanthrene and pyrene increased with ARE concentration of 0-1000 mmol/L. Soils with higher soil organic matter content (f(oc)) had lower desorption than soils with lower f(oc) values, at the same ARE concentration. The aging of phenanthrene and pyrene in soils markedly reduced the desorption of both compounds. The increment of phenanthrene and pyrene desorption was always higher with the addition of citric and oxalic acid than with the same concentration of AREs, indicating that the effects of AREs on desorption may be dominantly due to the organic acids.
Bioresource technology 02/2010; 101(4):1159-65. · 4.25 Impact Factor
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ABSTRACT: Because of the increasing quantity and high toxicity to humans of polycyclic aromatic hydrocarbons (PAHs) in the environment, several bioremediation mechanisms and protocols have been investigated to restore PAH-contaminated sites. The transport of organic contaminants among plant cells via tissues and their partition in roots, stalks, and leaves resulting from transpiration and lipid content have been extensively investigated. However, information about PAH distributions in intracellular tissues is lacking, thus limiting the further development of a mechanism-based phytoremediation strategy to improve treatment efficiency.
Pyrene exhibited higher uptake and was more recalcitrant to metabolism in ryegrass roots than was phenanthrene. The kinetic processes of uptake from ryegrass culture medium revealed that these two PAHs were first adsorbed onto root cell walls, and they then penetrated cell membranes and were distributed in intracellular organelle fractions. At the beginning of uptake (< 50 h), adsorption to cell walls dominated the subcellular partitioning of the PAHs. After 96 h of uptake, the subcellular partition of PAHs approached a stable state in the plant water system, with the proportion of PAH distributed in subcellular fractions being controlled by the lipid contents of each component. Phenanthrene and pyrene primarily accumulated in plant root cell walls and organelles, with about 45% of PAHs in each of these two fractions, and the remainder was retained in the dissolved fraction of the cells. Because of its higher lipophilicity, pyrene displayed greater accumulation factors in subcellular walls and organelle fractions than did phenanthrene.
Transpiration and the lipid content of root cell fractions are the main drivers of the subcellular partition of PAHs in roots. Initially, PAHs adsorb to plant cell walls, and they then gradually diffuse into subcellular fractions of tissues. The lipid content of intracellular components determines the accumulation of lipophilic compounds, and the diffusion rate is related to the concentration gradient established between cell walls and cell organelles. Our results offer insights into the transport mechanisms of PAHs in ryegrass roots and their diffusion in root cells.
BMC Plant Biology 01/2010; 10:210. · 3.45 Impact Factor
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ABSTRACT: An understanding of the primary pathways of plant uptake of organic pollutants is important to enable the risks from crops grown on contaminated soils to be assessed. A series of experiments were undertaken to quantify the importance of the pathways of contamination and the subsequent transport within the plant using white clover plants grown in solution culture. Root uptake was primarily an absorption process, but a component of the contamination was a result of the transpiration flux to the shoot for higher solubility compounds. The root contamination can be easily predicted using a simple relationship with K(OW), although if a composition model was used based on lipid content, a significant under prediction of the contamination was observed. Shoot uptake was driven by the transpiration stream flux which was related to the solubility of the individual PAH rather than the K(OW). However, the experiment was over a short duration, 6 days, and models based on K(OW) may be better for crops grown in the field where the vegetation will approach equilibrium and transpiration cannot easily be measured. A significant fraction of the shoot contamination resulted from aerial deposition derived from volatilized PAH. This pathway was more significant for compounds approaching log K(OA) > 9 and log K(AW) < -3. The shoot uptake pathways need further investigation to enable them to be modeled separately. There was no evidence of significant systemic transport of the PAH, so transfer outside the transpiration stream is likely to be limited.
Environmental Science and Technology 08/2009; 43(16):6190-5. · 5.23 Impact Factor
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ABSTRACT: Understanding the forms and availabilities of polycylic aromatic hydrocarbons (PAHs) would have considerable benefits for their risk assessment, and is of crucial importance for food security and remediation strategies in contaminated sites. In this work, the forms of six PAHs (fluorene, phenanthrene, fluoranthene, pyrene, benzo[a]anthracene, and benzo[a]pyrene) in soils were separated into three fractions including a desorbing fraction, a non-desorbing fraction, and a bound residual fraction using a sequential extraction mass balance approach. The desorbing and non-desorbing fractions were extracted with hydroxypropyl-beta-cyclodextrin (HPCD) and dichloromethane:acetone (1:1, vol/vol), respectively. The desorbing and non-desorbing fractions always dominated the total PAH content in soils. The proportion of bound PAH residue in nonsterilized soils was small (<16%), and even smaller (4.5%) in sterilized soils. The concentrations of the desorbing fraction of PAHs as well as the percentage of this fraction to the total PAH content in soils clearly decreased in 0-16 weeks, which may be due to microbial biodegradation and its transfer to other fractions in soils. The concentrations of the non-desorbing PAH fractions increased in sterilized soils, while remaining nearly constant or decreasing to some extent in nonsterilized soils after 16 weeks. The proportion of non-desorbing PAH fractions significantly increased in 16 week-incubation, and this proportion was positively correlated with the molecular weights of the PAHs tested, indicating that larger PAHs are more likely to be present in non-desorbing fractions. The bound PAH residue tended to increase at first and decrease thereafter over the 0-16-week period, and microbes played an important role in the formation of bound residue.
Journal of hazardous materials 07/2009; 172(2-3):897-903. · 4.14 Impact Factor
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ABSTRACT: A greenhouse study examined plant uptake of phenanthrene and pyrene, as representatives of polycyclic aromatic hydrocarbons (PAHs), from an aqueous solution containing a nonionic surfactant Tween 80. The uptake was conducted with 1.0 mg l(-1) phenanthrene and 0.12 mg l(-1) pyrene under a wide range of Tween 80 concentrations (0-105.6 mg l(-1)). Tween 80 at the test concentrations did not show any apparent phytotoxity toward the growth of red clover (Trifolium pretense L.). At concentrations generally lower than 13.2 mg l(-1), Tween 80 enhanced the plant uptake based on the concentrations and PCFs (plant concentration factors) of these two PAHs. When present at higher concentrations, Tween 80 inhibited the uptake of both PAH compounds by the tested plant. The maximal plant uptake was observed at 6.6 mg l(-1) Tween 80, in which PAH concentrations and PCFs were 18-115% higher than those in Tween 80-free controls. The total mass removal (off-take) of phenanthrene and pyrene by root or shoot increased initially and decreased thereafter with the increase in Tween 80 concentrations. Although shoot biomass was evidently larger than root, the off-take was much higher in root than shoot because of the larger root concentrations of these chemicals. Results from this study show promises for the potential efficacy of enhanced phytoremediation in PAH contaminated sites using surfactant amendment.
Chemosphere 07/2008; 72(4):636-43. · 3.21 Impact Factor
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ABSTRACT: Partition of phenanthrene between water and roots was determined for 13 plant species using a batch equilibration technique.
Partition coefficients (K
rt) from 734 to 2,564L/kg were measured. A simple model to estimate the partition of organic contaminants between roots and
water was developed based on the composition of plant roots and the 1-octanol/water partitioning coefficient. The estimates
were close to the observed results, with differences of < 14%. The partition coefficients of phenanthrene by root cell walls
were 13–84% greater than sorption by the corresponding roots. The cell wall fraction—the dominant fraction of root organic
components—was identified as the primary domain for partition of phenanthrene. The measured hydroponic uptake of phenanthrene
into roots was always less than phenanthrene partition by plant roots. A modified sorption model containing a quasi-equilibrium
factor (αpt) could reasonably predict hydroponic uptake by plant roots. The results obtained from this study provide insights into partition
of highly lipophilic organic chemicals in roots, and provide convenient methods to estimate this partition as well as uptake
of such chemicals in root–water systems.
Plant and Soil 01/2008; 311(1):201-209. · 2.73 Impact Factor
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ABSTRACT: The impacts of exotic and inherent dissolved organic matter (DOM) on phenanthrene sorption by six zonal soils of China, chosen so as to have different soil organic carbon (SOC) contents, were investigated using a batch technique. The exotic DOM was extracted from straw waste. In all cases, the sorption of phenanthrene by soils could be well described by the linear equation. The presence of inherent DOM in soils was found to impede phenanthrene sorption, since the apparent distribution coefficients (K(d)(*)) for phenanthrene sorption by deionized water-eluted soils were 3.13-21.5% larger than the distribution coefficients (K(d)) by control soils. Moreover, the enhanced sorption of phenanthrene by eluted versus control soils was in positive correlation with SOC contents. On the other hand, it was observed that the influence of exotic DOM on phenanthrene sorption was related to DOM concentrations. The K(d)(*) values for sorption of phenanthrene in the presence of exotic DOM increased first and decreased thereafter with increasing the added DOM concentrations (0-106mgDOC/L). The K(d)(*) values at a low exotic DOM concentration (< or =28mgDOC/L) were 14.7-48.4% larger than their control K(d) values. In contrast, higher concentrations (> or =52mgDOC/L) of added exotic DOM clearly impeded the distribution of phenanthrene between soil and water. The effects of exotic and inherent DOM on phenanthrene sorption by soils may primarily be described as 'cumulative sorption', association of phenanthene with DOM in solution, and modified surface nature of soil solids due to DOM binding.
Journal of Hazardous Materials 02/2007; 140(1-2):138-44. · 4.17 Impact Factor
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ABSTRACT: The fate of polycyclic aromatic hydrocarbons (PAHs) in soils with co-contaminants of heavy metals has yet to be elucidated. This study examined sorption of phenanthrene as a representative of PAHs by three soils contaminated with Pb, Zn or Cu. Phenanthrene sorption was clearly higher after the addition of heavy metals. The distribution coefficient (K(d)) and the organic carbon-normalized distribution coefficient (K(oc)) for phenanthrene sorption by soils spiked with Pb, Zn or Cu (0-1000 mg kg(-1)) were approximately 24% larger than those by unspiked ones, and the higher contents of heavy metals added into soils resulted in the larger K(d) and K(oc) values. The enhanced sorption of phenanthrene in the case of heavy metal-contaminated soils could be ascribed to the decreased dissolved organic matter (DOM) in solution and increased soil organic matter (SOM) as a consequence of DOM sorption onto soil solids. Concentrations of DOM in equilibrium solution for phenanthrene sorption were lower in the case of the heavy metal-spiked than unspiked soils. However, the decreased DOM in solution contributed little to the enhanced sorption of phenanthrene in the presence of metals. On the other hand, the sorbed DOM on soil solids after the addition of heavy metals in soils was found to be much more reactive and have far stronger capacity of phenanthrene uptake than the inherent SOM. The distribution coefficients of phenanthrene between water and the sorbed DOM on soil solids (K(ph/soc)) were about 2-3 magnitude larger than K(d) between water and inherent SOM, which may be the dominant mechanism of the enhanced sorption of phenanthrene by soils with the addition of heavy metals.
Chemosphere 12/2006; 65(8):1355-61. · 3.21 Impact Factor
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ABSTRACT: Arbuscular mycorrhiza (AM), the symbiont of arbuscular mycorrhizal fungi (AMF) and host plant root, has been proved to be able to improve soil structure and enhance the plant resistance to environmental stress. There are more than 170 kinds of AMF worldwide. Recently, the promoted degradation of organic pollutants in soils in the presence of AM was observed, and AM bioremediation (AMB) is becoming a promising and perspective remediation technique for organic pollutants-contaminated soils. This paper reviewed the research progress on the AMB of soils contaminated by typical organic pollutants such as polycyclic aromatic hydrocarbons, PAEs, petroleum, and pesticides. The mechanisms of AMB mainly include the metabolism of organic pollutants by AM fungi, the degradation of these pollutants by the enzymes derived from AM exudation and by the enhanced root exudation and rhizospheric microbial activity in the presence of AM, and the removal of the pollutants by plant uptake and accumulation. As a new approach for the remediation of contaminated soils, some aspects involved in AMB, e.g., the screening of high efficient AM fungi, efficacy of co-existing AM fungi, soil ageing, and plant uptake of organic pollutants from soils in the presence of AM, still need to be further investigated.
Ying yong sheng tai xue bao = The journal of applied ecology / Zhongguo sheng tai xue xue hui, Zhongguo ke xue yuan Shenyang ying yong sheng tai yan jiu suo zhu ban 12/2006; 17(11):2217-21.
