Potential of Five Plant Species for Phytoremediation of Metal-PAH-Pesticide Contaminated Soil

Contaminated soils are a global environmental concern requiring the development of low cost and sustainable remediation techniques. Often soils are contaminated by more than one class of contaminants (mixed contamination) which further complicates remediation efforts. Phytoremediation of contaminated soils has gained great attention as a low-cost and environmentally friendly remedial option. Given these desired advantages, there is not as much information available on plant species suitable for phytoremediation of mixed contaminated soil compared to single class soil contamination. This research evaluates the potential of established phytoremediation plants: alfalfa, oat, ryegrass, indian mustard, sunflower, tall fescue and switch grass to remediate a ternary mixed contaminated soil through greenhouse experiment in pots. Mixed contaminated soil was prepared by spiking soil with Copper (Cu) and Lead (Pb), pyrene and DDT as model compounds for common organic and inorganic contaminants found in mixed contaminated sites; metals, petroleum based hydrocarbon and pesticides. A phytotoxicity test was conducted prior to pot experiment to determine preliminary toxicity of mixed contamination on plants. Results eliminated tall fescue and switch grass from further consideration. Alfalfa, oat, ryegrass, indian mustard and sunflower were grown in triplicates for 72days in pots containing clean and mixed contaminated soils. In addition, unplanted mixed contaminated soils were maintained alongside for the same duration. Results demonstrate that sunflower and indian mustard were the most tolerant plants to the studied contaminant mixtures and concentration. However, only sunflower had the potential to simultaneously remove metals, PAH and pesticide from contaminated soil. Oat was identified as unsuitable for phytoremediation of metal-PAH-pesticide contaminated soil due to its ability to increase exchangeable Cu compared to unplanted soils. In soils planted with ryegrass, exchangeable Cu in soil was redistributed to a less mobile organic fraction while a reduction was observed for exchangeable Pb. The presence of alfalfa in mixed contaminated soils improved the degradation pyrene and DDT only with no metal reduction or changes in metal fractions. Overall the work supports the use of phytoremediation as a potential remedial option for mixed contaminated soils

Linking bioavailability and toxicity changes of complex chemicals mixture to support decision making for remediation endpoint of contaminated soils

A six-month laboratory scale study was carried out to investigate the effect of biochar and compost amendments on complex chemical mixtures of tar, heavy metals and metalloids in two genuine contaminated soils. An integrated approach, where organic and inorganic contaminants bioavailability and distribution changes, along with a range of microbiological indicators and ecotoxicological bioassays, was used to provide multiple lines of evidence to support the risk characterisation and assess the remediation end-point. Both compost and biochar amendment (p = 0.005) as well as incubation time (p = 0.001) significantly affected the total and bioavailable concentrations of the total petroleum hydrocarbons (TPH) in the two soils. Specifically, TPH concentration decreased by 46% and 30% in Soil 1 and Soil 2 amended with compost. These decreases were accompanied by a reduction of 78% (Soil 1) and 6% (Soil 2) of the bioavailable hydrocarbons and the most significant decrease was observed for the medium to long chain aliphatic compounds (EC16–35) and medium molecular weight aromatic compounds (EC16–21). Compost amendment enhanced the degradation of both the aliphatic and aromatic fractions in the two soils, while biochar contributed to lock the hydrocarbons in the contaminated soils. Neither compost nor biochar affected the distribution and behaviour of the heavy metals (HM) and metalloids in the different soil phases, suggesting that the co-presence of heavy metals and metalloids posed a low risk. Strong negative correlations were observed between the bioavailable hydrocarbon fractions and the ecotoxicological assays suggesting that when bioavailable concentrations decreased, the toxicity also decreased. This study showed that adopting a combined diagnostic approach can significantly help to identify optimal remediation strategies and contribute to change the over-conservative nature of the current risk assessments thus reducing the costs associated with remediation endpoint

The use of plants, including trees, to remediate oil-contaminated soils : a review and empirical study

Soil contamination can result in soil degradation, bring great loss to agricultural production and pose threat to human health. Many of the soil contaminants are petroleum hydrocarbons (PHCs) derived from crude oil or refined petroleum products. Phytoremediation which relies on plants and their associated microorganisms to remove contaminants is cost-effective and applicable to treat a wide variety of soil contaminants. Besides trees, herbaceous plants are widely and effectively used in the remediation of PHC contaminated soils. Greenhouse studies have found that Galega orientalis co-inoculated with Rhizobium galegae and plant growth promoting bacteria (PGPB) benefiting soil with nitrogen fixation is able to remediate PHC contaminated soils. The FP7 ‘‘Legume-Futures’’ remediation field experiment was established at Viikki experimental farm, University of Helsinki in 2009 in order to test the practical applicability of the greenhouse results in a field scale. In a split-plot design, crop (Galega orientalis, Bromus inermis, Galega orientalis + Bromus inermis, bare soil control) treatments were designated the main factor, oil (±) and PGPB (±) the sub-factors in factorial combination with four replicates. Soil samples were taken at four time points from July 2009 to May 2011. Soil total solvent extractable material (TSEM) was extracted and measured by the gravimetrical method as a direct indicator of oil content. Physiochemical properties (pH, EC, total C and N and C/N ratio) of soil samples (taken in July 2009 and Nov. 2010) were determined. The losses of total C and TSEM between July 2009 and Nov. 2010 were calculated to estimate the differences crops and PGPB brought in oil treated plots. Crop dry matter yields were determined. The changes of soil microbial population, bacterial diversity and community structures were studied by the 16S rRNA gene based community fingerprinting method LH-PCR. Bioremediation and physical removal were the main processes of oil removal in our experiment. Climate factors (e.g. temperature and precipitation) had an overriding influence on the removal of oil in our study. Soil condition with a neutral pH and C/N ratio in our field was optimal for biodegradation of hydrocarbons. The changes in soil microbial total DNA, diversity and community structure were sensitive indicators of soil contamination and recovery. Crop (Galega orientalis and Bromus inermis) and PGPB treatment had no significant effect on soil physiochemical and microbiological properties nor on the removal of oil in our experiment, which largely differed from our hypothesis. Resource competition between crops and microorganisms might have resulted in the better oil remediation in bare soils than in vegetated soils. Nevertheless, crops were found to have a high tolerance to oil contamination and surprisingly, the oil contamination seemed to increase the growth of both crop species. Bromus in mixture plots (without commercial nitrogen fertilization) had better yield than in pure plots (with commercial nitrogen fertilization) as a result of biological nitrogen fixation of Galega orientalis and Rhizobium galegae. Therefore the mixture of galega and bromus can be suggested to be applied in future phytoremediation projects

Gentle Remediation Options (GRO): A Literature Review (Part 1/2)

Soils are a non-renewable resource and comprise a key component of the world\u27s stock of natural capital. Due to industrialisation, urbanisation and other patterns of unsustainable development, widespread land degradation in the form of contamination, soil sealing, compaction, etc. has impaired the capacity of soils to perform their essential functions and provide humans with vital ecosystem services. Brownfields are typically urban or peri-urban sites that have been affected by the former uses of the site, are or are perceived to be contaminated, and require intervention to bring them back to beneficial use. They also constitute an important and underutilised land and soil resource to provide ecosystem services in urban areas as an element of green infrastructure through the use of nature-based solutions such as gentle remediation options (GRO). Within the scope of the Ph.D. project " Enhancing ecosystem services by innovative remediation using gentle remediation options (ECO-GRO)", an in-depth but inexhaustive literature review has been carried out to build a theoretical understanding of GRO for the overall research project. This literature review report (part 1 of 2) will present a compilation of the main findings by beginning with A) core concepts of GRO including the background of their usage and development as well as key physiological mechanisms and processes; then B) mechanisms for the gentle remediation of organic (i.e. degradation and volatilisation) and inorganic contaminants (i.e. extraction and stabilisation) are reviewed, including the various strategies for implementation, practical aspects, key limitations, the possibilities to enhance effectiveness by combining with soil amendments and compilations of field studies demonstrating successful application. GRO mechanisms that are more specific in use like rhizofiltration and phytohydraulics are also briefly discussed as well as other remediation techniques included under the GRO umbrella such as bioremediation, mycoremediation and vermiremediation; C) the development in the field towards applying GRO to both manage risks and provide wider economic, social and environmental benefits, i.e. phytomanagement, is discussed at some length while considering its broader implications; and finally D) suitable plants for the various GRO mechanisms are discussed throughout the report but a specific section is set aside to discuss methods for selecting the most suitable plants as well as summarising the most applied plants

The remediation of industrially contaminated soil

PhD ThesisThe remediation of two contaminated soils in the Tyne and Wear Metropolitan district was examined. These were a sediment dredged from the river bed at Dunston Coal Staiths on the River Tyne (downstream from Derwenthaugh coke work site) and coke work-contaminated soil from the Derwenthaugh site, Blaydon, Nr. Newcastle-upon-Tyne. The river Tyne dredgings were of a very fine material (70% silt; 24% clay) with high water retention capacity. Levels of (EDTA available) Zn (490mg/kg), total Cd (7.5mg/kg) and total Pb (510mg/kg) were above the Department of Environment's (1987) threshold values for soil contaminants. Barley (Hordeuin vulgare L. cv Kym) sown in the drcdgings in ten outdoor plots (Irn x 0.5m), grew very poorly (yield = 2.4g dry wt. /plant, compared with that on an uncontaminatedc. ontrol soil (7.4g dry wt./ plant). The barley exhibited all the classic signs of metal phytotoxicity despite the addition of fcrtiliscr and organic waste (straw and spent mushroom compost). When lime was added to raise the pH of the dredgings in the plots to over pH 7.1, the growth rate and the yield of barley improved significantly (yield = 6.8g dry wt. /plant). Levels of available Zn, Cd, Pb and Cu in the limed dredgings were now lower than in the unlimed dredgings. Copper and zinc levels in leaves of barley raised on the limed material were lower than levels in barley grown on unlimed dredgings. There was no significant difference in yield or growth rate between the different plots of dredgings in which organic supplementation parameters were varied. In conclusion, pH was the dominant factor in the remediation of the heavy metal phytotoxicity in the dredged material. Gas chromatography/mass spectrophotometry analysis showed the principal contaminants of the coke works soil to be organic. The soil was heavily contaminated with coal tars (19.0%) consisting of a complex mixture of aliphatic, polycyclic and aromatic compounds including phenols (160mg/kg). Viable counts of the soil microflora, on selective media, showed the presence of bacteria capable of degrading phenol and several of its alkylated homologues and thiocyanate, which was converted to ammonia and used as aN source. The coke works soil was treated on a laboratory scale using microbially based clean-up methods. Soil was incubated in glass jars under laboratory conditions. Nu trients (yeast extract) and microbial biomass (a mixed culture, previously isolated and enriched by growth on cresol and thiocyanate, but capable of oxidising a wide range of alkylated phenols), were inoculated into the contaminated soil. The addition of such biomass (106 organisms /g soil) led to a marked improvement in the rate of phenolic degradation in the soil (26% loss in'22 weeks, compared with 9% in the untreated control. ). Degradation rates decreased after 14 days but a repeated application of biomass (106 organisms/g soil) caused further phenolic loss (47% total loss). Cresol (100mg/kg) subsequently added to the bacterial ly-amended soil disappeared within 7 days, showing that the biomass amendment was still biochemically very active. These findings demonstrate the importance and the effectiveness of two different treatment methods in the rcmediation of contaminated soil.Science and Engineering Research Council

Plant-Microbe Interaction: Prospects and Applications in Sustainable Environmental Management

Plant-microbe interaction is mostly mutualistic although sometimes it can be negative. These interactions contribute to improving the environmental quality and health of all organisms. One significant aspect to this is application in sustainable environmental management. Plants are known to be involved in remediation of polluted environments through a mechanism known as phytoremediation and this process is usually more effective in collaboration with microorganism resident within the plant environment. These plants and microbes possess attributes that makes them great candidates for sustainable remediation of impacted environments. Different organic pollutants have been decontaminated from the environment using the phytoremediation approach. The plant-associated microbes possess certain traits that exert selective effect on the growth of plants which consequently perform the decontamination process through different mechanisms. Also, these microorganisms’ harbour requisite genes charged with the responsibility of mineralization of different organic and inorganic compounds through several pathways to produce innocuous by-products. The limitations associated with this approach that prevents full-scale application such as contaminant-induced stress frequently leads to low/slow rates of seed germination, plant development and decreases in plant biomass have been solved by using plant growth promoting rhizobacteria. Phytoremediation is an emerging, cost-effective, eco-friendly and operational technology for the cleanup of polluted environment

Plant-Associated Bacterial Degradation of Toxic Organic Compounds in Soil

A number of toxic synthetic organic compounds can contaminate environmental soil through either local (e.g., industrial) or diffuse (e.g., agricultural) contamination. Increased levels of these toxic organic compounds in the environment have been associated with human health risks including cancer. Plant-associated bacteria, such as endophytic bacteria (non-pathogenic bacteria that occur naturally in plants) and rhizospheric bacteria (bacteria that live on and near the roots of plants), have been shown to contribute to biodegradation of toxic organic compounds in contaminated soil and could have potential for improving phytoremediation. Endophytic and rhizospheric bacterial degradation of toxic organic compounds (either naturally occurring or genetically enhanced) in contaminated soil in the environment could have positive implications for human health worldwide and is the subject of this review

Comprehensive Perspectives in Bioremediation of Crude Oil Contaminated Environments

Diverse components of crude oil and petroleum such as polycyclic aromatic hydrocarbons (PAHs) have been found in waterways as a result of pollution from industrial effluents and petrochemical products (Beckles, et al., 1998). Petroleum hydrocarbon pollution of the environment may arise from oil well drilling production operations, transportation and storage in the upstream industry, and refining, transportation, and marketing in the downstream industry. Petroleum hydrocarbon pollution could also be from anthropogenic sources (Oberdorster and Cheek, 2000). Some non combusted hydrocarbons escape into the environment during the process of gas flaring. Until recently, the bulk of the associated gas produced during drilling in Nigeria, was flared. Sources of petroleum and its products in the environment will also include accidental spills and from ruptured oil pipelines. Today the international oil and gas-pipelines span several million kilometers and this is growing yearly due to inter-regional trade in petroleum products. Just like any other technical appliance, pipelines are subject to ââtear and wearââ, thus can fail with time (Beller, et al., 1996). Spilled petroleum hydrocarbons in the environment are usually drawn into the soil due to gravity until an impervious horizon is met, for example bedrock, watertight clay or an aquifer

Development of analytical, phyto- and myco-remediation techniques to manage petroleum-contaminated soils

Practical solutions to soil pollution by the petroleum industry are still to be fully realised. With new, unresolved and recurring cases, remediation options that are readily available, cost effective and environmentally friendly are required. Analytical methods for quick and easy monitoring are also crucial. To find appropriate solutions to petroleum-contaminated soils particularly for the Niger Delta, Nigeria; options, which satisfy the above principles, were investigated. Thus, the aims of this research were to identify readily available and sustainable techniques for remediation of petroleum-contaminated soils; evaluate ways to overcoming associated limitations, thereby enhancing these techniques; and investigate for readily available methods of monitoring the petroleum-contaminated and remediated soils. After a systematic and critical literature review, phyto- and myco-remediation were identified as viable options for this research, their limitations were evaluated. The actual study involved sampling of petroleum contaminated soils, treatment with phyto- and myco-remediation agents and investigation of methods for analysis and monitoring of the soils. Agents used for the remediation (evaluated in terms of reduction in Total Petroleum Hydrocarbons-TPHs in the soil samples) were: 3 species of sunflowers (Helianthus annus-pacino gold, Helianthus sunsation & Helianthus annus-sunny dwarf), the fern-Dryopteris affinis, fermented palm wine (from 2 species of palm trees -Elaeis guineensis & Raffia africana), and oyster mushroom (Pleurotus ostreatus). Supplementing the agents with Tween 80 and the use of alternative substrates and methods for application of P. ostreatus enabled the investigation of possible enhancement of their remediation efficiency. The investigation revealed up to 525 g of TPHs per Kg dry weight of soils. The remediation treatments produced as much as 69% reduction in TPHs by the sunflower species, 70% by fermented palm wine, 74% by D. affinis and 85% by P. ostreatus; with up to 100% enhancement on the addition of Tween-80. It was also found that substrates type and method of application has a significant effect on the remediation efficiency of P. ostreatus. The study further revealed that available nitrate, electrical conductivity, standardised crude oil and the biomarkers dodecane and benzene-1,3-bis(1,1-dimethylethyl) can be used to broadly monitor the concentration of TPHs and remediation progress in soils. This research thus demonstrated that, phyto-and myco-remediation can provide readily available and sustainable techniques for remediation of TPHs in soils. Further studies are required to evaluate the application of these techniques for individual petroleum contaminant components such as the polycyclic aromatic hydrocarbon compounds and Asphaltenes