Use of a forensic geochemical technique and a hydrogeological assessment to determine the source of petroleum hydrocarbon contamination at a foreshore site in Korea

Investigations undertaken in 2013 at a foreshore site that was historically used for ship repairs in Korea indicated that soil and groundwater were contaminated with petroleum hydrocarbons over an area of 10,000 m². Groundwater investigations and modelling were undertaken to determine the characteristics of aquifers beneath the site, including the direction and rate of groundwater flow and the extent of dispersion of total petroleum hydrocarbon contamination. To identify petroleum products residing in contaminated soils, the hump of an unresolved complex mixture on the baseline found in the data of gas chromatography was used as a new method. Based on objective facts obtained from basic investigation, the current state of contamination, and discrimination of oil species, the polluter as specified in the Korean Soil Environment Conservation Act was identified.     

Dynamics of diesel fuel degradation in contaminated soil using organic wastes

Bioremediation is an effective measure in dealing with such contamination, particularly those from petroleum hydrocarbon sources. The effect of soil amendments on diesel fuel degradation in soil was studied. Diesel fuel was introduced into the soil at the concentration of 5 % (w/w) and mixed with three different organic wastes tea leaf, soy cake, and potato skin, for a period of 3 months. Within 84 days, 35 % oil loss was recorded in the unamended polluted soil while 88, 81 and 75 % oil loss were recorded in the soil amended with soy cake, potato skin and tea leaf, respectively. Diesel fuel utilizing bacteria counts were significantly high in all organic wastes amended treatments, ranging from 111 × 106 to 152 × 106 colony forming unit/gram of soil, as compared to the unamended control soil which gave 31 × 106 CFU/g. The diesel fuel utilizing bacteria isolated from the oil-contaminated soil belongs to Bacillus licheniformis, Ochrobactrum tritici and Staphylococcus sp. Oil-polluted soil amended with soy cake recorded the highest oil biodegradation with a net loss of 53 %, as compared to the other treatments. Dehydrogenase enzyme activity, which was assessed by 2,3,5-triphenyltetrazolium chloride technique, correlated significantly with the total petroleum hydrocarbons degradation and accumulation of CO₂. First-order kinetic model revealed that soy cake was the best of the three organic wastes used, with biodegradation rate constant of 0.148 day^?1 and half life of 4.68 days. The results showed there is potential for soy cake, potato skin and tea leaf to enhance biodegradation of diesel in oil-contaminated soil.     

Evaluation of petroleum hydrocarbon biodegradation in shallow groundwater by hydrogeochemical indicators and C, S-isotopes

Biodegradation is one of the main natural attenuation processes in groundwater contaminated with petroleum hydrocarbons. In this work, preliminary studies have been carried out by analyzing the concentrations of total petroleum hydrocarbons (TPH), dissolved inorganic carbon (DIC), dominant terminal electron accepters or donors, as well as δ ¹³C_DIC and δ ³⁴S_SO4, to reveal the biodegradation mechanism of petroleum hydrocarbons in a contaminated site. The results show that along groundwater flow in the central line of the plume, the concentrations of electron acceptors, pH, and E _h increased but TPH and DIC decreased. The δ ¹³C_DIC values of the contaminated groundwater were in the range of ?14.02 to ?22.28 ‰_PDB and ?7.71 to 8.36 ‰_PDB, which reflected a significant depletion and enrichment of ¹³C, respectively. The increase of DIC is believed to result from the non-methanogenic and methanogenic biodegradation of petroleum hydrocarbon in groundwater. Meanwhile, from the contaminated source to the downgradient of the plume, the ³⁴S in the contaminated groundwater became more depleted. The Rayleigh model calculation confirmed the occurrence of bacterial sulfate reduction as a biodegradation pathway of the petroleum hydrocarbon in the contaminated aquifers. It was concluded that stable isotope measurements, combined with other biogeochemical measurements, can be a useful tool to prove the occurrence of the biodegradation process and to identify the dominant terminal electron-accepting process in contaminated aquifers.     

Characterization of fresh and weathered petroleum for potential impacts to soil fertility

In many petroleum-producing regions, there are not adequate controls to prevent pipeline breaks and spills, and thus soil is frequently contaminated with petroleum hydrocarbons. Different petroleum oil compounds may produce negative impacts on soil fertility. In this study, four fresh crudes, a weathered petroleum, and oils from bioremediated and burned sites were investigated (specific gravities 0.83–1.27). Fourier transform infrared spectroscopy revealed three predominant polar functional groups to be more plentiful in the heavier crudes. The relative abundance of these groups was used to calculate an index that was directly correlated with specific gravity (R ² = 0.9960) and the percent of asphaltene plus (polars + resins) fractions in the oil (R ² = 0.9643). This index correlated exponentially to the water repellency caused by petroleum in an alluvial soil (R ² = 0.9928). Furthermore, extra-heavy oil at a concentration of 10,000 ppm, the maximum allowable oil concentration in the soil that is within regulatory norms in many US states and other countries, and with a specific gravity >1.002, showed severe water repellency. This study presents an alternative for determining soil remediation criteria based on the API gravity of the oil rather than the C-range of the hydrocarbon mixtures, simplifying analytical methods and systematically studying the interaction between the kinds of petroleum mixtures and potential impacts to soil fertility.     

Field-scale evaluation of the chemical–biological stabilization process for the remediation of hydrocarbon-contaminated soil

Developing countries face the challenge of growing their economy while reducing the negative environmental impacts of industry, thus requiring treatment technologies that are economical and effective. One recent technology developed in the tropical part of Mexico for the remediation of petroleum-contaminated soil was tested in this scale-up project at an industrial level, whereas previously it had only been tested at laboratory scale; 150 m³ of bentonitic mud, contaminated with weathered hydrocarbons (3.4°API) at ~50,000 ppm, was treated with 4 % Ca(OH)₂, 4 % organic amendment, and a fine-root tropical grass. Hydrocarbons in soil and in leachates, as well as pH, and acute toxicity (Microtox) were monitored for 28.8 months. At the end of the study, basal respiration, root density, and earthworm toxicity were also measured. The hydrocarbon concentration in soil was reduced to 45 %, and toxicity was eliminated. Hydrocarbons in leachates were reduced to ~1 mg/l, safe for human consumption. The pH adjustment depended on low soil moisture and was stabilized at 7.1. Intense revegetation resulted in good root density, within 90 % of nearby uncontaminated soil under pasture. Basal respiration was increased to levels comparable to uncontaminated tropical soils with agricultural use, pasture and gallery forest. At an industrial scale, strict moisture control was necessary for good pH stabilization. By controlling these conditions and applying this novel treatment process, it was possible to transform a heavily contaminated geological material into a non-toxic, fertile, soil-like substrate capable of maintaining a complete vegetative cover and microbial activity comparable to similar soils in a tropical environment.     

Deterioration of groundwater quality in the vicinity of an active open-tipping site in West Malaysia

There is an urgent need for characterization of leachate arising from waste disposal to ensure a corresponding effective leachate management policy. Field and laboratory studies have been carried out to investigate the impact of municipal landfill leachate on the underlying groundwater at a site in West Malaysia. The solid waste was disposed of directly onto an unprotected natural soil formation. This situation was made worse by the shallow water table. The hydrochemical composition of groundwater in the vicinity of the site (background) is a dilute mixed cation, bicarbonate water. The high ionic balance error of ~13.5% reveals that the groundwater body underneath the site was a highly contaminated leachate rather than contaminated groundwater. Elevated concentration of chloride (355.48 mg/L), nitrate (10.40 mg/L as NO₃), nitrite (14.59 mg/L), ammoniacal-N (11.61 mg/L), sodium (227.56 mg/L), iron (0.97 mg/L), and lead (0.32 mg/L) measured downgradient indicate that the contamination plume has migrated further away from the site. In most cases, the concentration of these contamination indicators, together with the ranges of sodium percentage (66.3–89.9%) and sodium adsorption ratio (10.1–19.7%), were found to be considerably higher than the limit values of safe water for both domestic and irrigation purposes, respectively.     

Environmental impact and geochemical behavior of soil contaminants from an industrial waste landfill in Southern Brazil

Industrial waste landfills produce great impacts on soil and groundwater. There are many industrial waste landfills in Vale dos Sinos, Southern Brazil, which were inadequately planned and maintained since the industry started in the first half of the twentieth century. The largest industrial landfill in the Valley, which causes the most severe impacts on soil and groundwater, is the subject of this paper, which studies the environmental impacts and behavior of contaminants in soil. The landfill was carefully mapped on a scale of 1:1,000; 88 samples were collected from soil probes; the leachate of three samples was comprehensively analyzed; and soils mineralogy and chemistry were studied. Few studies have been made on this landfill. This study shows widespread contamination of soil in the surrounding areas of the landfill. Chromium, chloride and ammonium have the highest contamination levels, reflecting their high contents in landfill leachate. Contamination by petroleum hydrocarbons, cyanide and mercury is registered in more than 65% of soil samples with low concentrations. Lead, copper and barium show low contamination restricted to a few soil samples. Soil contamination occurs mainly in the unsaturated zone of the aquifer at the convergence points of stormwater, showing that the preferential transport of contaminants occurs on surface flow followed by soil infiltration. The results of leaching tests indicate high metal sorption capacity of soil. The remediation of contaminated soil must contain at least the following actions: sealing the top of the landfill, installation of geochemical barriers, removal of the liquid waste basins without sealing the base and collection and treatment of the rainwater drainage.     

Water lily (<Emphasis Type="Italic">Nymphaea</Emphasis> sp.): an alternative organic amendment for treatment of hydrocarbon-contaminated soil by chemical–biological stabilization

The chemical–biological stabilization technology has been employed in several successful studies using sugarcane cachasse as the organic amendment. However, in some petroleum-producing areas, there are no sugar mills nearby (which is the source of this material), and the cost of transport to the contaminated site is prohibitive. Therefore, water lily, which is considered a weedy plant in many tropical and subtropical areas, was evaluated as an alternative. In 3-month experiment, water lily was compared (with and without addition of molasses) with cachasse for the treatment of clayey sediment contaminated with > 6% extra-heavy crude oil. All treatments resulted in a reduction in the hydrocarbon concentration of 15–23%, without significant differences (P > 0.05). During this process, the pH was reduced to the 7–7.5 range and water repellency (molarity ethanol drop) to 3.5–3.6 M. Also, field capacity increased to 36.3–38.5% humidity, establishing adequate conditions for the development of vegetation at this site. Likewise, toxicity was reduced to practically null (Vibrio fischeri bioassay), and hydrocarbons in leachates were reduced to 3.4–4.3 mg/l, conditions adequate for the protection of groundwater and human health in rural areas. This study confirms that water lily is an adequate substitute for the application of this treatment method for hydrocarbon-contaminated sites that are far from sugar production areas.     

Diffusion of municipal waste contaminants in compacted lateritic soil treated with bagasse ash

Compacted clay can minimize infiltration of liquid into waste or control the release of contaminated liquids to the surrounding soils and groundwater. Compacted lateritic soil treated with up to 12 % bagasse ash and municipal solid waste (MSW) leachate sourced from a domestic waste land fill were used in diffusion test studies to access the diffusion characteristics of some inorganic species present in the municipal solid waste leachate. Diffusion set-up were prepared containing 0, 4, 8 and 12 % bagasse ash—soil mixes compacted at 2 % wet of optimum using the modified proctor effort. The set up was saturated with water for 30 days before the introduction of MSW leachate and initiation of diffusion test for another 90 days. After diffusion testing, water content within the soil column showed a decrease with depth. Diffusion test results generally showed that diffusion is an active means of transport of chemical species even at very low flow rates in the compacted soil-bagasse ash mixes, and the effective diffusion coefficient is affected by bagasse ash. The pore fluid concentration profile for the various chemical species tested showed that the compacted soil-bagasse ash mix has the capacity to attenuate Ca²⁺, Pb²⁺ and Cr³⁺ ions.     

Laboratory-scale analysis of transportation and natural attenuation of diesel fuel in aquifer

Processes that control the distribution and natural attenuation (NA) of petroleum hydrocarbons dissolved from the released diesel fuel in a bench-scale model aquifer were evaluated. The experimental results obtained in two-dimensional aqueous-phase petroleum hydrocarbon concentrations indicated that the total petroleum hydrocarbon (TPH) in the aquifer migrated in longitudinal and lateral directions. The TPH plume of 2 mg L^?1 spread to the entire area of the aquifer, and the maximum concentration at the center of the plume was 44.15 mg L^?1 after 90 days of release. After diesel fuel release, the NA of TPH was evaluated and quantified. Experimental data indicated that the NA of TPH was immediately implemented to prevent migration of the plume into the downgradient of the aquifer, but controlling the TPH plumes using NA mechanisms requires a long time.     

Biodegradation of petroleum by <Emphasis Type="Italic">Klebsiella pneumoniae</Emphasis> isolated from drilling fluid

The removal of petroleum and petroleum-based products from the environment is of great importance. The objectives of this study were to investigate the most suitable physiological conditions and the effects of additional carbon, nitrogen and surfactant sources on petroleum biodegradation by Klebsiella pneumoniae ATCC13883 isolated from drilling fluid and to evaluate petroleum biodegradation with detailed hydrocarbon analysis by GC–MS. The results indicated that the highest biodegradation rate of 66.5% for K. pneumoniae was obtained under the conditions of pH 7, petroleum concentration 1% (v/v) and 7-day incubation at 150 rpm and 25 °C, proving to be the most effective physical conditions for petroleum biodegradation in this present study. Additional sources such as Triton X: 100, glucose and yeast extract significantly enhanced the petroleum biodegradation of K. pneumoniae to 68, 71 and 72.5%, respectively. In the last stage of this study, biodegradation rates were above 90% for hydrocarbons ranging from C₁₀ and C₂₀, above 70% for hydrocarbons ranging from C₂₁ and C₂₂ and above 40% for hydrocarbons ranging from C₃₁ and C₃₂. In conclusion, oil field adapted K. pneumoniae could efficiently degrade short-, medium- and long-chain alkanes in petroleum and thus is a potential source for advanced petroleum treatment.     

Characterization of the hydrogeologic environment at a petroleum hydrocarbon contaminated site in Korea

The hydrogeologic environment of a petroleum hydrocarbon contaminated site in Korea is characterized by hydrogeologic field work and chemical analyses of groundwater. Quaternary alluvium is the main aquifer contaminated by petroleum hydrocarbons, mainly TEX (toluene, ethylbenzene and xylenes). Contamination at this site was derived from the leaking of petroleum storage tanks. The aquifer is highly permeable, but vertically heterogeneous. Water-table fluctuations reach up to 2 m during heavy rains. Contaminants migrated to the northwest along the main groundwater-flow direction. The concentration of hydrocarbons in groundwater is particularly high downgradient from the source area. The ubiquitous distribution of TEX was caused by the heterogeneity of the aquifer material and the significant fluctuation of the water-table. Chemical properties of the contaminated groundwater and field parameters indicate that intrinsic biodegradation, including aerobic respiration, nitrate reduction, iron reduction, manganese reduction, and sulfate reduction, occurs at this site. The dilution and mixing due to new groundwater recharge from rainfall is also identified as one of the major attenuation processes of TEX.     

Hydrocarbon biodegradation and soil microbial community response to repeated oil exposure

Bioremediation strategies continue to be developed to mitigate the environmental impact of petroleum hydrocarbon contamination. This study investigated the ability of soil microbiota, adapted by prior exposure, to biodegrade petroleum. Soils from Barrow Is. (W. Australia), a class A nature reserve and home to Australia’s largest onshore oil field, were exposed to Barrow production oil (50 ml/kg soil) and incubated (25 °C) for successive phases of 61 and 100 days. Controls in which oil was not added at Phase I or II were concurrently studied and all treatments were amended with the same levels of additional nutrient and water to promote microbial activity. Prior exposure resulted in accelerated biodegradation of most, but not all, hydrocarbon constituents in the production oil. Molecular biodegradation parameters measured using gas chromatography–mass spectrometry (GC–MS) showed that several aromatic constituents were degraded more slowly with increased oil history. The unique structural response of the soil microbial community was reflected by the response of different phospholipid fatty acid (PLFA) sub-classes (e.g. branched saturated fatty acids of odd or even carbon number) measured using a ratio termed Barrow PLFA ratio (B-PLFAr). The corresponding values of a previously proposed hydrocarbon degrading alteration index showed a negative correlation with hydrocarbon exposure, highlighting the site specificity of PLFA-based ratios and microbial community dynamics. B-PLFAr values increased with each Phase I and II addition of production oil. The different hydrocarbon biodegradation rates and responses of PLFA subclasses to the Barrow production oil probably relate to the relative bioavailability of production oil hydrocarbons. These different effects suggest preferred structural and functional microbial responses to anticipated contaminants may potentially be engineered by controlled pre-exposure to the same or closely related substrates. The bioremediation of soils freshly contaminated with petroleum could benefit from the addition of exhaustively bioremediated soils rich in biota primed for the impacting hydrocarbons.     

Effect of oil pollution on fresh groundwater in Kuwait

Massive oil fires in Kuwait were the aftermath of the Gulf War. This resulted in the pollution of air, water, and soil, the magnitude of which is unparalleled in the history of mankind. Oil fires damaged several oil well heads, resulting in the flow of oil, forming large oil lakes. Products of combustion from oil well fires deposited over large areas. Infiltrating rainwater, leaching out contaminants from oil lakes and products of combustion at ground surface, can reach the water table and contaminate the groundwater. Field investigations, supported by laboratory studies and mathematical models, show that infiltration of oil from oil lakes will be limited to a depth of about 2 m from ground surface. Preliminary mathematical models showed that contaminated rainwater can infiltrate and reach the water table within a period of three to four days, particularly at the Raudhatain and Umm Al-Aish regions. These are the only regions in Kuwait where fresh groundwater exists. After reaching the water table, the lateral movement of contaminants is expected to be very slow under prevailing hydraulic gradients. Groundwater monitoring at the above regions during 1992 showed minor levels of vanadium, nickel, and total hydrocarbons at certain wells. Since average annual rainfall in the region is only 120 mm/yr, groundwater contamination due to the infiltration of contaminated rainwater is expected to be a long-term one.     

Protection of groundwater from oil pollution in the vicinity of airports

Airports are potential, and quite frequently also actual, sources of serious groundwater pollution. This is due to the large amounts of liquid fuel being handled all the time, to the physicochemical properties of oil hydrocarbons, and often to technical errors in the transport and storage of fuels. The environment is further affected by liquid and gaseous emissions escaping during the take-off and landing of aircraft Snow in the vicinity of runways has been found to contain oil hydrocarbons in concentrations of tenths to units of milligrams per liter Moreover, soil tends to accumulate carcinogenous benzopyrenes. In rock formations, oil hydrocarbons spread as a separate layer as well as in solution in porous permeable formations, pollution by a free product affects areas on the order of tens of meters, while hydrocarbons in solution penetrate to distances of hundreds of meters or even kilometers. More complex conditions for the spreading of oil-based substances arise in fissured rocks. Aviation kerosene as a separate phase was found to migrate over 700 meters within 5 months through fissure systems in sandstones Prevention is the most efficient way of protecting groundwater from oil pollution. Preventive surveys are based on the drilling of observation wells at suitable points of the potentially endangered areas. Monitoring of these wells provides timely detection of possible leaks of oil products into the aquifer In the case of an emergency, it is necessary to remove, as soon as possible, the oil substances from the surface or to remove the contaminated soil. When the contaminant has penetrated into the aquifer, the reparatory measures are usually based on hydraulic protection which consists of a system of boreholes. The respective hydrocarbon product is removed from the formation by pumping, the process being speeded up by the change in groundwater flow caused by the creation of depression cones The example of Prague Airport is suitable for describing a successful, although complex and expensive, purification of a Chalk aquiter polluted among other things by a leak amounting to 300 m³ of aviation kerosene. Vapex filters have proven very satisfactory for purifying the contaminated water Preventive protection of groundwater and mineral waters using monitoring devices is being carried out at Karlovy Vary Airport No groundwater pollution has so far been observed in this instance. However, a seasonal variation in the content of hydrocarbons dissolved in groundwater has been established. The highest content occurs in the spring months. Observation wells situated in the tectonic zone can also be utilized for reparative pumping     

Effect of simulated acid rain on soil acidification and rare earth elements leaching loss in soils of rare earth mining area in southern Jiangxi Province of China

Acid rain has long been a great concern because of environmental and ecological problems; however, the effect of acid rain on soil acidification, loss of rare earth elements (REEs) via the leaching process, and transformation are rarely reported in rare earth mining areas. Through a simulated acid rain leaching experience, the effect of acid rain was studied on soil acidification and REEs leaching loss. The results showed that the tested soil had certain buffering capacity against nearly neutral rainwater. However, simulated acid rain of low and very low pH (pH ≤ 3.5) had a greater impact on soil acidification. After eluviating by simulated acid rain of pH 3.5 for 36 h, the pH of tailings, garden soil, paddy soil, and alluvial soil decreased by 20.41, 32.03, 13.60, 16.88, and 15.83 %, respectively, from the original values. For simulated acid rain of pH 2.5, it was 31.89, 44.76, 31.26, 29.87, and 29.15 %, respectively. After simulated acid rain eluviations of low and very low pH (pH ≤ 3.5), the order of the leaching rate of REEs in the tested soil was as follows: garden soil > tailings > paddy soil > alluvial soil. For nearly neutral rainwater (pH 4.5 simulated acid rain and pH 5.6 deionized water), the order was tailings > garden soil > paddy soil > alluvial soil. For simulated acid rain of the same pH, the leaching amounts of REEs in tailings and garden soil were higher than those in paddy soil and alluvial soil. After leaching by low and very low pH-simulated acid rain (pH ≤ 3.5), the peak value of the leaching amount of REEs in all tested soil appeared at 2 h, and then gradually reduced and reached a stable leaching state 20 h after leaching. On leaching by simulated acid rain of pH 2.5, the maximum REEs contents of leachate in tailings, garden soil, paddy soil, and alluvial soil were 156.35, 145.82, 99.88, and 85.97 mg/L, respectively. For pH 3.5 of simulated acid rain, it was 130.49, 110.49, 80.57, and 62.73 mg/L, respectively. On leaching by simulated acid rain of pH 4.5, the maximum contents of REEs in the leachate were 53.46 and 29.82 mg/L, respectively, which were observed after leaching for 6 h in tailings and garden soil that became stable 12 h after leaching. The contents of leached REEs in paddy soil and alluvial soil were always in a lower and stable state. After eluviations with deionized water of pH 5.6, the contents of leached REEs in other soils were lower, except for the slight fluctuations in tailings. The maximum content in the leachate of REEs was in the water-soluble and exchangeable fraction. When bound to carbonate fractions, REEs were not detected in the leachate. REEs bound to iron-manganese (Fe–Mn) oxides fraction and to organic matter fraction in the leachate possibly came from the tested soil or from the REEs transformation during the migration process. The content of residual fraction REEs in the leachate was very low.     

Induced degradation of crude oil mediated by microbial augmentation and bulking agents

Different bacterial and fungal strains, isolated from petroleum hydrocarbon-contaminated soil, were tested, in isolation as well as in combination, for their ability to degrade total petroleum hydrocarbon (TPH) in soil samples spiked with crude oil (2, 5 or 10 %, w/w) for 30 days. The selected combination of bacterial and fungal isolates, i.e., Pseudomonas stutzeri BP10 and Aspergillus niger PS9, exhibited the highest efficiency of TPH degradation (46.7 %) in soil spiked with 2 % crude oil under control condition. Further, when this combination was applied under natural condition in soil spiked with 2 % (w/w) crude oil along with inorganic fertilizers (NPK) and different bulking agents such as rice husk, sugarcane, vermicompost or coconut coir, the percent degradation of TPH was found to be maximum (82.3 %) due to the presence of inorganic fertilizers and rice husk as bulking agent. Further, results showed that the presence of NPK and bulking agents induced the activity of degradative enzymes, such as catalase (0.718 m mol H₂O₂ g^?1), laccase (0.77 µmol g^?1), dehydrogenase (37.5 µg g^?1 h^?1), catechol 1, 2 dioxygenase (276.11 µ mol g^?1) and catechol 2, 3 dioxygenase (15.15 µ mol g^?1) as compared to control (without bioaugmentation). It was inferred that the selected combination microbes along with biostimulants could accentuate the crude oil degradation as evident from the biostimulant-induced enhanced activity of degradative enzymes.     

Investigation on potential groundwater impacts and influence of local hydrogeology on natural attenuation of leachate at a municipal landfill

The influence of local hydrogeology on natural attenuation of contaminants from landfill leachates in shallow aquifer underlying the active Olusosun landfill base in Lagos was investigated. In addition, the level of groundwater contamination in the vicinity of the landfill and of leachate migration pattern in groundwater down gradient of the landfill base was equally assessed. Landfill leachate and groundwater samples were collected and analyzed and characterized. Physico-chemical analyses of sampled water followed standard analytical methods. Analytical results showed a measurable impact of leachate outflows on groundwater quality. Elevated levels of anions: nitrate, chloride and sulphate in the groundwater body and heavy metals: Cr₃. Cd and Cu, were detected at measurable levels in groundwater down gradient of the landfill location without any particular attenuation pattern. The migration pattern and dispersion of leachates down gradient, 750 m away from the landfill location are irregular and difficult to predict as depicted by levels of contaminants present in groundwater. The study highlighted the importance of soil stratigraphy beneath the landfill base as an important factor in the natural attenuation of leachate constituents in the groundwater body.     

Risk Assessment on Organic Contamination of Shallow Groundwater of an Oilfield in Northeast China

With the oil contaminated site of an oil field in northeast as the research area, based on the site geological and hydrogeological conditions, and by virtue of the methods of assessment on current situation of organic contamination and environmental impact assessment as well as leaching mobility assessment on organics, the internal and external risk assessments on organic contamination of shallow groundwater in the research area are conducted respectively. According to the results, about 30 kinds of organic components, including chlorinated hydrocarbons, mononuclear aromatics, heteroaromatic compound, polycyclic aromatic hydrocarbon and n-alkanes, are detected in the shallow groundwater in the research area. The current situation contamination of dichloromethane is the most serious, and all well points are of contamination at medium or above level. Compared with dichloromethane, contamination of trichloromethane and benzene is lighter, but several seriously contaminated well points occur in these two groups. The leaching mobility of dichloromethane, trichloromethane and benzene is extremely high, posing the greatest contamination risks against groundwater.     

Phytoremediation of soil contaminated by heavy oil with plants colonized by mycorrhizal fungi

The purpose of this study was to investigate the effect of phytoremediation on soils contaminated with heavy crude oil using plants infected by mycorrhizal fungi. Five plant species, Vetiveria zizanioides, Bidens pilosa, Chloris barbata, Eleusine indica, and Imperata cylindrica, infected with the species of mycorrhizal fungi Glomus mosseae, were selected for this study. The degradation of total petroleum hydrocarbons in soils and several physiological parameters of plants such as shoot length and biomass were analyzed. Out of the 5 plant species tested, only V. zizanioides, B. pilosa, and E. indica could take up the G. mosseae. Out of these three, V. zizanioides showed the greatest growth (biomass) in soils with 100,000 mg kg^?1 total petroleum hydrocarbons. In addition, B. pilosa infected with G. mosseae was found to be able to increase degradation by 9 % under an initial total petroleum hydrocarbons concentration of 30,000 mg kg^?1 in soils after 64 days. We conclude that plants infected with mycorrhizal fungi can enhance the phytoremediation efficiency of soils contaminated with high concentrations of heavy oil.