Polynuclear Aromatic Hydrocarbons In Soil Research Articles

CHARACTERIZATION AND DISTRIBUTION OF POLYNUCLEAR AROMATIC HYDROCARBONS IN WET PRECIPITATIONS, SURFACE WATERS AND SOILS FROM SOUTH-EASTERN NIGERIA

Polynuclear aromatic hydrocarbons (PAHs), are known as persistent organic pollutants (POP) which exist in different media as contaminants in parts of the environment’s atmosphere, seawater, sediments, soils, and vegetation. PAHs have been known for their mutagenic, carcinogenic, and toxic properties to humans through the food chain. This study is aimed to characterize and investigate the distribution of PAHs in wet precipitations, surface waters, and soils from Ikot Abasi, Ibeno, and Eastern Obolo Local Government Areas of Akwa Ibom State, Nigeria. PAHs were determined in the environmental components by gas chromatography-mass spectrometry technique. Two soil and two surface water samples were taken from selected locations and wet precipitation samples were harvested on event basis from the study areas .The results reveal the presence of the following priority PAHs at different concentrations: naphthalene, (0.02-0.09 mg/L);benzo[k]fluoranthrene (0.001 -0.09 mg/L); benzo[e]pyrene (0.001-0.08 mg/L); benzo[a]pyrene (0.001 -0.09 mg/L) ; 3-methylcholanthrene (1.27-7.21 mg/L) during the rainy and dry seasons in Ikot Abasi. The concentrations of naphthalene ranges (0.02-0.06 mg/L), 3-methylcholanthrene ranges (2.40-3.65 mg/L), while other PAHs levels were below detection limits in rainwater from Ibeno in both seasons. The concentrations of naphthalene ranges (0.02-0.05 mg/L); 3-methylcholanthrene (2.30 – 5.65 mg/L), while other PAHs levels were below detection limits in rainwater from Eastern Obolo in both seasons The PAHs levels indicated were higher than the World Health Organization (WHO) acceptable limit of PAHs (0.0007 mg/L) in drinking water. The PAHs detected in the surface waters were in the order: Ikot Abasi (11.09 ±0.02 mg/L) > Eastern Obolo (3.87± 0.002 mg/L) > Ibeno (1.94 ± 0.004 mg/L), during the rainy season, while the PAHs detected in the surface waters were in the order: Ikot Abasi (13.79 ± 0.03 mg/L) > Eastern Obolo (3.95± 0.008 mg/L) > Ibeno (2.45±0.011 mg/L), during the dry season. The PAHs obtained for the soils in the three study areas during the rainy season were in the order: Eastern Obolo (776 ± 5.92 ug/kg) > Ibeno (732 ± 8.33 ug/kg) > Ikot Abasi (8 ± 0.07 ug/kg), while, during the dry season, the results were in the order: Ibeno (872±11.05 ug/kg) > Eastern Obolo (105±9.03 ug/kg) > Ikot Abasi (20 ± 1.95 ug/kg). Soils from Eastern Obolo and Ibeno have PAHs levels greater than 700 ug/kg, which is categorized as slightly polluted, with toxic equivalent concentrations (TEQ) higher than permissible limit (33 ug/kg).This may cause ecological risk and raises public health concern that should attract more attention. Molecular diagnostic ratio analyses show that the sources of PAHs in the three study area are mainly pyrogenic.

Simple analysis of polynuclear aromatic hydrocarbons in soil

Simple analysis of polynuclear aromatic hydrocarbons in soil

Polynuclear aromatic hydrocarbons (PAHs) mediate cadmium toxicity to an emergent wetland species

Growth and pollutant removal by emergent wetland plants may be influenced by interactions among mixed pollutants in constructed wetlands. A glasshouse experiment was conducted to investigate interactive effects of cadmium (Cd) × polynuclear aromatic hydrocarbons (PAHs) × plant treatments on growth of Juncus subsecundus, Cd and PAH removal from soil and the total number of microorganisms in soil. Growth and biomass of J. subsecundus were significantly influenced by interaction of Cd and PAHs, significantly decreasing with either Cd or PAH additions, but with the effect of Cd on plant growth being stronger than that of PAHs. The mixture of low Cd and low PAH lessened Cd toxicity to plants, resulting in improved plant growth and increased Cd accumulation in plant tissues, thus enhancing Cd removal by plants. The dissipation of PAHs in soils was significantly influenced by interactions of Cd, PAH and plant presence or absence. The total number of microorganisms in soils was significantly increased by the PAH additions. The interactive effect of Cd and PAHs on plant growth may be linked to the changes in the abundance of microorganisms in the rhizosphere, probably via a positive effect of PAH metabolites and/or phytohormones produced by microorganisms on plant growth.

Polynuclear aromatic hydrocarbons (PAHs) in global background soils

The levels and distribution of polynuclear aromatic hydrocarbons (PAHs) were investigated in global background soil samples. Total PAH concentrations (sum of 15 compounds) ranged over 5 orders of magnitude, from <1 to 7,840 (mean 328) ng g(-1) dry weight. The order was generally Europe > North America > Asia > Oceania > Africa > South America. Proximity to long-term emissions sources and locations susceptible to high atmospheric depositional inputs tended to have higher concentrations. A broad positive correlation was obtained between population density and soil PAH concentrations (i.e. source-related factors). However, concentrations were also influenced by the holding capacity of the soils (i.e. sink-related factors) with statistically significant correlations observed between PAHs and soil organic matter (SOM), and black carbon (BC).

PAHs in background soils from Western Europe: Influence of atmospheric deposition and soil organic matter

The levels and distribution of polynuclear aromatic hydrocarbons (PAHs) were determined in soil samples from background locations in the UK and Norway, to investigate their spatial distribution and the controlling environmental factors. Concentrations ranged between 42 and 11 200 μg kg −1 (geometric mean 640 μg kg −1) and 8.6 and 1050 μg kg −1 (150 μg kg −1) dry weight in the UK and Norwegian soil, respectively. Proximity to sources and locations susceptible to high atmospheric depositional inputs resulted in higher concentrations. Statistically significant relationships were observed between PAH and total organic carbon (TOC) in the Norwegian samples. High molecular weight PAHs correlated with black carbon (BC) in UK-woodland soil. These observations support the hypothesis that TOC plays an important role in the retention of PAHs in soil and that PAHs are often combined with BC during combustion emissions. PAHs with 4 and more rings comprised ∼90% of total PAHs in the UK soil, but only 50% in the Norwegian soil. The mixture of PAHs implied that fractionation occurred during long-range atmospheric transport and deposition. The lighter PAHs with lower K ow values more readily reached the most remote sites. The heavier PAHs with higher K ow values remained in closer proximity to sources.

Decreased Release of PAHs from Soils as a Result of Field Bioremediation

In this study, the relationship between the release characteristics of contaminants from soil and the biodegradability of the contaminants was evaluated. The soils used were from a large-scale field site. A batch rate of release procedure was used to quantify the release of polynuclear aromatic hydrocarbons (PAHs) from manufactured gas plant site soils before and during bioremediation in a field land treatment unit (LTU). This evaluation assessed the performance of the field-scale LTU with respect to changes in the soil PAH concentrations and to changes in chemical release parameters. The practical implications of the evaluation are discussed. During 147 days of LTU operations, the concentrations of specific PAHs were reduced 39–93%. ROR studies were conducted on LTU soil samples obtained at Days 0, 58, 72, and 147 of treatment. As a result of 147 days of treatment in the LTU, the fraction of a PAH released rapidly (F) had decreased for 8 of 10 PAHs, and the value of k2 (the first-order rate constant describing slow release) had decreased for 5 of 10 PAHs. There were no increases in F or k2 for any of the PAHs as a result of treatment in the field LTU. The results indicated that (1) only a fraction of the total concentration of the individual PAHs in the LTU samples was readily available to be released from the soil; (2) the remainder was released at a much slower rate; and (3) the mass of PAH released from the LTU soils to the aqueous phase decreased considerably. In addition, the fraction of the chemical released rapidly (F) for the Day 0 soil sample provided a reasonable prediction of the extent of PAH loss during 147 days of biological treatment in the field LTU.

Potential of Phytoremediation for Treatment of PAHs in Soil at MGP Sites

Phytoremediation is a natural, aesthetically pleasing, low-cost technology that employs plant-influenced microbial, chemical, and physical processes to remediate contaminated soils and waters. The Institute of Gas Technology (IGT) conducted a laboratory study to determine the potential of phytoremediation to remediate soils contaminated with polynuclear aromatic hydrocarbons (PAHs). The soils used for the study were collected from a former manufactured gas plant (MGP) site in Newark, NJ. Phytoremediation was assessed both as a primary remediation technology and as a final polishing step for soil treatment. The following three plant species were used for the 6-month laboratory study: alfalfa (Medicago sativa), switch grass (Panicum virgatum), and little bluestem grass (Schizachyrium scoparium). Using both alfalfa and switch grass for primary treatment of PAH-contaminated soil, a 57% reduction in total PAH concentration was observed after 6-months of treatment. Final polishing of that soil using alfalfa further reduced the total PAH concentration in that soil by 15%. Research is in progress with the objective of improving both the efficiency and the economics of phytoremediation for the cleanup of contaminated soils to environmentally acceptable endpoints at MGP sites.

Mass transfer limitation in PAH-contaminated soil remediation

Batch experiments were conducted to determine the effects of Triton X-100, a nonionic phenolic ethoxylate surfactant, on the biodegradation of soil-bound naphthalene and phenanthrene. Two different types of soils, one contaminated with polynuclear aromatic hydrocarbons (PAHs) for different lengths of time, 2 days to 10 months, in the laboratory and the other, a field-contaminated soil from a manufactured gas plant (MGP) site, were used. Biodegradation of PAHs was measured by monitoring the 14CO2 production for the artificially contaminated soils and the residual PAHs in soil phase for the MGP soil. Without adding surfactant, the mineralization rate of phenanthrene was significantly smaller in the 1 0-month contaminated soil compared to that in the 2-day contaminated soil. Presumably, mineralization was mass-transfer limited in the soil with longer contamination period. Triton X-100 significantly enhanced mineralization in the 10 month-old soil but none in the 2-day old soil. The MGP soil, weathered over 2-3 decades, exhibited even greater enhancement of mineralization. Mineralization of PAHs in aged soils appears to be controlled by mass transfer rather than the rate of biodegradation. Surfactants increase the rate of release of soil-bound contaminant and thus help promote biodegradation.

Multi-phase partitioning and co-solvent effects for polynuclear aromatic hydrocarbons (pah) in authentic petroleum- and creosote-contaminated soils

The residual oil phase, present at substantial levels in hydrocarbon-contaminated soils, was found to be the principal medium for retention of polynuclear aromatic hydrocarbons (PAH). Using authentic petroleum and creosote-contaminated soils containing 2–6% w/w solvent extractable matter, individual PAH were shown to exist in the oil phase at values between 84 and 95% w/w of the total mass of each compound in the system, with the exception of naphthalene (70% w/w). Evaluation of the phase partitioning of PAH in creosote-contaminated soil confirmed that PAH were predominantly in the creosote oil phase, with substantially lower proportions associated with soil organic matter and soil water. In the aqueous phase, solubility enhancement was observed for PAH with the degree of enhancement more evident for the hydrophobic PAH. A normalised solubility enhancement factor (ESF’) was derived to illustrate the combined effect of increased PAH solubility in the aqueous phase. Values of log ESF’ varied from −4.97 (naphthalene) to 0.09 (benzo[ghi]perylene). The findings suggest limitations exist for successful remediation of PAH contamination in the soils evaluated and indicate that the focus of remediation must be on the residual oil phase if total PAH are to be removed.

Field-portable determination of polychlorinated biphenyls and polynuclear aromatic hydrocarbons in soil using supercritical fluid extraction

A single SFE method for field extraction of PCBs and PAHs in soils was developed for use in combination with capillary GC-ECD or FID without the need for cleanup steps after extraction. The method involves 20-min extractions using pure CO 2 at 150°C and 400 bar. GC analysis was performed with 15-min (PCBs) or 22-min (PAHs) temperature programs. The final analytical method was demonstrated in field experiments (with the use of portable power sources) at different waste sites and was shown to give results in excellent agreement with conventional laboratory Soxhlet extraction. The practical determination limits of the method (as concentrations of the 5-g soil samples) without any concentration or cleanup of the SFE extracts was 2≈200 ppb of individual PAHs and 2≈10 ppb of individual PCBs (2≈100 ppb of total PCB as Aroclor 1260) Since the SFE collection solvent was acetone, the extracts were compatible with enzyme-linked immuno-sorbent assay (ELISA). ELISA and GC-ECD determinations of PCBs as total Aroclors agreed within 2≈50% when ELISA was performed in the laboratory. However, ELISA failed to yield useable results when performed outdoors under field conditions.

PAHs in soils: contemporary UK data and evidence for potential contamination problems caused by exposure of samples to laboratory air

Archived (1951–1974) and contemporary (1993) surface soil samples collected from the same 46 locations widely distributed over the UK have been analyzed for 12 polynuclear aromatic hydrocarbons (PAHs). Contemporary soils were analyzed wet, ensuring that contamination, losses or alteration of PAHs in the samples was minimal. Archived soils had been air-dried prior to storage. The ΣPAH concentration of the contemporary and archived soils range from approx. 20 μg kg −1 to 7.4 mg kg −1 (mean = 1.1 mg kg −1) and from approx. 160 μg kg −1 to 7.1 mg kg −1 (mean = 2.1 mg kg −1), respectively. Comparison of the concentrations of PAHs in the archived and contempcrary soils revealed no significant trends for compounds heavier than benzanthracene. For some of the lighter molecular weight compounds the concentrations were notably higher in the archived soils than in the contemporary soils. Two soils of contrasting PAH content (0.08 and 9.8 mg kg −1) were used in an experiment to compare the effects of air-drying on soils with relatively low and high PAH concentrations. Subsamples of soil (10 g) were placed into foil trays and exposed to laboratory air for up to 64 days. A clear increase in theiconcentration of the lighter molecular weight compounds (acenaphthene, fluorene, phenanthrene) occurred in both soils. No marked changes were observed for the heavier molecular weight PAH compounds. This experiment suggests that the higher concentrations of the lower molecular weight compounds measured in the archived soil samples is due to contamination during air drying.

Assessing the fate of polynuclear aromatic hydrocarbons from oily waste land spreading by modelling

The organic wastes produced by petroleum refineries are often treated by spreading them on land sites, allowing hydrocarbons to degrade naturally. In such conditions, mathematical models representing the transport of organics in the soil are useful for predicting the quantities of hydrocarbons, like polynuclear aromatic hydrocarbons (PAHs), that could reach the water table in the short and long term. The pesticide root zone model (PRZM) simulates the fate of pesticides in the soil. Because of the analogy between the agricultural use of pesticides and the land spreading of petroleum residues containing hydrocarbons, and the similar physicochemical characteristics of these two types of potential organic contaminants, this model was applied to a land-spreading site in southern Quebec. The simulation results indicate that the studied PAHs may not migrate to depths of more than 40 cm. The predicted concentrations may be several hundred times lower when the degradation rate doubles. Natural variations in the local hydrodynamic conditions caused by soil texture do not greatly affect the concentrations of a relatively mobile PAH in soil or in water. In contrast to the texture, the soil organic matter content greatly influences the distribution of PAHs between the liquid and solid phases and, consequently, their migration through the soil. Key words: PAH, phenanthrene, pyrene, refinery, land treatment, mobility, degradation, simulation, PRZM.

A study of interactions between soil fractions and PAH compounds in thermal desorption of contaminated soils

AbstractThe interactions between three polynuclear aromatic hydrocarbons (PAHs), namely fluorene, naphthalene and anthracene, and three fractions of a soil, namely fulvic acid (FA), humic acid (HA) and humin/inorganic fractions, were studied experimentally. Prepared PAH + soil fraction binary mixtures, with PAH concentrations ranging over 0.8–7 mass%, were tested using a differential scanning calorimeter (DSC) over a temperature range of 20−390°C. The DSC thermograms for the PAH + HA mixtures showed distinctly different characteristics compared to mixtures with the other two soil fractions, where the endothermic peak for the vaporization of the PAH was absent. With the aid of vapour‐liquid flash calculations, the lack of the boiling point peak is interpreted to be due to the liquid‐phase miscibility of the PAHs and the HA fraction. Implications of the DSC results on the design and performance of the thermal desorption process are discussed.

Mini-round-robin study of a supercritical fluid extraction method for polynuclear aromatic hydrocarbons in soils with dichloromethane as a static modifier

A mini-round-robin study of a supercritical fluid extraction (SFE) method for polynuclear aromatic hydrocarbons (PAHS) from soil samples was conducted. Three laboratories participated in the study, and each laboratory extracted three real-world samples in triplicate. The cryogenically milled samples were extracted at 350 atm (1 atm = 101 325 Pa) and 90°C for 20 min in the dynamic mode using supercritical carbon dioxide at a flow-rate of 1 to 1.5 ml/min and the extracted material was collected in 10 ml dichloromethane, which was then subjected to silica chromatography. The SFE method accuracy (percent recovery) was determined relative to the sonication extraction since the true levels of PAHs in these samples are not known. The PAHs were recovered quantitatively (recovery ⪢ 80%) by SFE when present at concentrations of 1 mg/kg or higher. The interlaboratory method precisions (overall R.S.D.s) appear to be concentration-dependent; at concentrations above 1 mg/kg, they were 27% or lower; at concentrations below 1 mg/kg, they ranged from 19 to 80%. From these results, we concluded that the method appears quite rugged, and the interlaboratory data compare well with other SFE interlaboratory studies.

PAH RIS® Soil Test—A Rapid, On-Site Screening Test for Polynuclear Aromatic Hydrocarbons in Soil

Abstract Polynuclear aromatic hydrocarbons (PAHs) are chemicals of concern when they contaminate the environment. Current detection methods (gas chromatography and liquid chromatography) are laborious, time consuming, and expensive. As an alternative, we developed a competitive enzyme-linked immunosorbent assay kit that can be used on site for the detection of PAHs at 1 ppm in soil. The immunoassay kit includes all the components necessary to conduct the analysis in the field. The test consists of 3 major steps: (1) sample treatment; (2) immunoassay, in which the target compound is bound by a specific antibody followed by the development of an indicator color; and (3) interpretation of results. A sample that develops less color than the standard is interpreted as positive (soil sample contaminated with PAHs at ≥1 ppm). Validation studies demonstrated that the assay is sensitive and specific. The assay detects PAH contamination in soil at 1 ppm or greater and specifically detects the 3- and 4-ringed aromatics and most of the 5-and 6-ringed aromatics. PAH-free soil samples gave negative results in the assay at a confidence level of &amp;gt;95%. Matrix effects, interperson, and interlot variations were minimal. The test requires &amp;lt;25 min to complete. The test kit is field compatible and provides a cost effective method for screening soils at risk for PAH contamination.

The significance of polynuclear aromatic hydrocarbons applied to agricultural soils in sewage sludges in the U.K.

The ubiquity of polynuclear aromatic hydrocarbons (PAHs) in sewage sludges is now well documented. Since PAHs exhibit carcinogenic/mutagenic behaviour concern has been expressed over their fate following sludge application to agricultural soils. This paper presents a resume of the behaviour of sludge applied PAHs in soils and their propensity to transfer from the soil into plant tissues. This information is used to assess the environmental significance of PAHs in sludge amended soils. Sludge PAH inputs to the U.K. environment are compared with other known sources, such as waste disposal and atmospheric deposition and the possible impact of sludge application on human exposure is considered. It is concluded that at present there is no necessity to specifically regulate PAH inputs to agricultural soils in sewage sludge.

The Significance of Polynuclear Aromatic Hydrocarbons Applied To Agricultural Soils in Sewage Sludges in the U.K

The ubiquity of polynuclear aromatic hydrocarbons (PAHs) in sewage sludges is now well documented. Since PAHs exhibit carcinogenic/mutagenic behaviour concern has been expressed over their fate following sludge application to agricultural soils. This paper presents a resume of the behaviour of sludge applied PAHs in soils and their propensity to transfer from the soil into plant tissues. This information is used to assess the environmental significance of PAHs in sludge amended soils. Sludge PAH inputs to the U.K. environment are compared with other known sources, such as waste disposal and atmospheric deposition and the possible impact of sludge application on human exposure is considered. It is concluded that at present there is no necessity to specifically regulate PAH inputs to agricultural soils in sewage sludge.

Considerations of SFE for GC/MS Determination of Polynuclear Aromatic Hydrocarbons in Soils and Sediments

Considerations of SFE for GC/MS Determination of Polynuclear Aromatic Hydrocarbons in Soils and Sediments

PAH loss during bioremediation of manufactured gas plant site soils

This research investigated loss of polynuclear aromatic hydrocarbons (PAH) while attempting to bioremediate soils from a manufactured gas plant (MGP) site. Laboratory microcosms using site soils were used to evaluate how environmental factors, such as temperature, pH and nutrients affected PAH loss. Results indicated that: (a) PAH in the MGP site soil resisted mineralization by microorganisms; (b) test soils were non-toxic before and after testing; (c) significant populations of bacteria were present in the microcosms during the degradation studies; (d) addition of free naphthalene and phenanthrene to the soils resulted in rapid loss of the added chemicals while the concentrations of indigenous chemicals were unchanged; (e) PAH were not soluble in a water extract of these soils; and (f) the PAH in these soils were unavailable for microbial degradation.

Polynuclear Aromatic Hydrocarbon Uptake by Carrots Grown in Sludge‐Amended Soil

AbstractThe uptake of polynuclear aromatic hydrocarbons (PAHs) from sewage sludge‐amended soils by carrots (Daucus carota) was investigated. Carrots were grown in control soils and soils amended with three sludge application rates, 15, 55, and 180 t/ha. Applied sludge contained 17.2 mg ΣPAH/kg, a concentration typical for a sludge derived from a rural area. Carrot foliage, root peels and root cores were analyzed for 15 PAH compounds. Carrots foliage PAH concentrations were unaffected by sludge applications (PAH loadings), but root peel PAH concentrations increased to a plateau concentration with increasing soil PAH levels. Low molecular weight PAH compounds dominated individual components of the ΣPAH load in the root tissues. The PAH concentrations detected in the root peels were all significantly lower than in the foliage, which receives PAH inputs from the atmosphere. Carrot core ΣPAR concentrations were unaffected by sludge application, implying little or no transfer of PAHs from the peels to the core. About 70% of the PAH burden found in carrots was associated with the peels. Fresh weight carrot core concentrations were all &lt;4.2 µg/kg. Overall, this investigation suggests that the risks posed to human health by PAHs applied in sewage sludge to arable soils are minimal.