Polycyclic Aromatic Hydrocarbons,Heavy Metals,and Genotoxicity of the Suburban Soils from Guangzhou,China

During the past few decades, urban and suburban developments have grown at unprecedented rates and extents with unknown consequences for ecosystem function. The problem of soil pollution as a result of the accelerating development of Guangzhou in China is becoming great concerns. In the present study, gas chromatograph coupled mass spectrometry (GC-MS), inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma atomic emission spectrometry (ICP-AES) were employed to determine the 16 US Environmental Protection Agency (EPA) priority polycyclic aromatic hydrocarbons (PAHs) and the heavy metals (As, Cr, Cu, Pb, Cd, Hg, and Se) of soils collected from suburban areas of Guangzhou. The genotoxicity of these soils was screened with micronucleus (MN) assay in Vicia faba root cells. The concentrations of the pollutants in the soils were (dried weight): ΣPAHs (230.6–1263 ng·g^?1), As (2282.6–36064 μg·kg^?1), Cr (7109–64699 μg·kg^?1), Cu (7047–56388 μg·kg^?1), Pb (9675.9–93739 μg·kg^?1), Cd (68.5–847.3 μg·kg^?1), Hg (85.4–549.2 μg·kg^?1), and Se (219.2–968 μg·kg^?1), which fell in the moderately polluted range. However, six out of nine soil-exposed groups had a significant increases of MN frequencies observed in the V. faba root cells compared with the negative group (P < 0.05, P < 0.01), indicating that they had potential genotoxic risks. Bringing together the chemical analyses with the biological effects observed in this study, the genotoxic response could at a certain degree be explained by both the soil PAHs and heavy metals. Our results suggested that apart from chemical analysis, bioassays like the MN assay of V. faba root cells should also be included in a battery of tests to assess the eco-environmental risks of urban and/or urbanization in the developing areas on the soils.     

The Effect of Polycyclic Aromatic Hydrocarbons on the Structure of Organotrophic Bacteria and Dehydrogenase Activity in Soil

The objective of this article was to determine the structure of microbial communities and the activity of dehydrogenases in soil samples contaminated with four polycyclic aromatic hydrocarbons (PAHs), i.e., naphthalene, phenanthrene, anthracene, and pyrene, in the amount of 0, 1000, 2000, and 4000 mg kg^?1soil DM. Organic substances—cellulose, sucrose, and compost—were added to the samples in the amount of 0 and 9 g kg^?1soil DM. The experiment was performed in a laboratory on samples of loamy sand. Indices of colony development (CD) and eco-physiological diversity (EP) of organotrophic bacteria, soil resistance (RS), and soil resilience (RL) were calculated. Soil contamination with PAHs differentiated the structure of organotrophic bacteria, and the lowest CD and EP values were noted in soil samples containing pyrene. PAHs inhibited the activity of dehydrogenases, and pyrene exerted the most inhibitory effect on enzyme activity. Dehydrogenase activity was determined mainly by the applied PAH dose, the date of analysis and the type of organic substance added to soil. Low RL values indicate that exposure to PAHs induces long-term changes in dehydrogenase activity.     

Occurrence and Source Apportionment of Polycyclic Aromatic Hydrocarbons in Urban Residential Soils from National Capital Region,Uttar Pradesh,India

This study aims to investigate the level of priority polycyclic aromatic hydrocarbons (PAHs) and identification of their potential sources in residential soils. During the study, a total 36 soil samples collected from twelve residential locations at Sahibabad-Ghaziabad area of western Uttar Pradesh, India, a constituted part of the National Capital Region of India. Samples extracted using ultrasonication, cleaned with silica and analyzed by diode array detector–high-performance liquid chromatography using acetonitrile/water as mobile phase. The 25th and 75th percentile concentration of ∑PAHs was 264 μg kg^?1 and 584 μg kg^?1, respectively, with mean and median of 445 μg kg^?1 and 421 μg kg^?1. The detection frequency of PAHs in all samples was lower for low molecular weight PAHs (19%) than high molecular weight PAHs (81%). The concentration of seven probable carcinogenic PAHs accounted for 67% of the ∑PAHs. PAHs toxicity potential as benzo(a)pyrene toxicity equivalent ranged between 2.52–253 μg BaP_TEQ kg^?1. Composition profile of PAHs with different aromatic rings and selected diagnostic molecular ratios suggested the local pyrogenic sources of PAHs from vehicular emissions, diesel engines, biomass combustion, gasoline, and coal combustions.     

Application of marble powder as a potential green adsorbent for miniaturized solid phase extraction of polycyclic aromatic hydrocarbons from water samples

ABSTRACT

In this study, marble powder was evaluated as a cheap, easy to prepare and efficient green sorbent for miniaturized solid phase extraction of polycyclic aromatic hydrocarbons (PAHs) and determination by high performance liquid chromatography with UV detection. Under the optimized experimental conditions, wide linear dynamic ranges were achieved in the range of 0.1–200 μg L^?1, with correlation coefficient higher than 0.996. The limits of detection and quantification for target analytes could reach 16.3–120.2 and 54.3–398 ng L^?1, respectively. The method precision based on obtained RSD values in the range of 4.9–7.9% (n = 8) was very satisfactory.     

Source Allocation of Aliphatic and Polycyclic Aromatic Hydrocarbons in Particulate-Phase (PM10) in the City of Valdivia,Chile

The concentration and signature of n-alkanes (n-C₁₀ to n-C₃₃) and 18 PAHs were determined in air filters across a year period (2010) in an urban area of the city of Valdivia, Chile. Filter samples were extracted using sohxlet apparatus and analyzed by GC-MS techniques. Concentrations of total hydrocarbons ranged from 45–352 ng.m^?3 and total PAHs ranged from 2.93–78.01 ng.m^?3. Concentrations of hydrocarbons during the summer were high (288–352 ng.m^-3) and reduced when the autumn began (45–79 ng.m^?3) to then increase almost linearly to the next summer. The drop in concentration was attributed in part to the significant reduction of traffic when summer ends as tourists leave the city (about 9–15% of the total cars circulating). Results from the chemometric technique of Polytopic Vector Analysis (PVA) indicated three main sources for the alkanes: biogenic (terrestrial plants), signatures of oil combustion, and an unconfirmed source which is thought to come from non specific organic matter degradation. Total PAHs correlated well with total particulate matter with a R² = 0.94. Levels of PAHs in the atmosphere were higher during the winter (6.85–78.01 ng.m^?3) period than the rest of the year (2.93–36.30 ng.m^?3). PVA results indicate three key sources of PAHs and two of those sources derived from oil combustion and biomass burning.     

Determination of Polycyclic Aromatic Hydrocarbons in Water- and Gin-Based Tea Infusions of Selected Tea Brands in Nigeria

The concentrations of the 16 priority polycyclic aromatic hydrocarbons (PAHs) in tea infusions made of water and local gin (alcohol) were investigated with a view to providing information on the profiles and health hazards associated with these two common Nigerian methods for tea consumption. The water-based tea infusion was prepared by submerging 4 g of tea in boiling water and allowing it to stand for 15 min, while the gin-based infusion was simply prepared by submerging 4 g of tea in gin at room temperature and allowing it to stand for 15 min. The concentrations of the ∑16 PAHs in the infusions were measured by using gas chromatography equipped with a flame ionization detector (GC-FID) after ultrasound-assisted extraction and clean-up. The concentrations of the ∑16 PAHs ranged from 24.9–623.4 μg kg^?1 with a mean value of 177 μg kg^?1 and 36.8–438.3 μg kg^?1 with a mean of 189 μg kg^?1 for water- and local gin-based infusions, respectively. The concentration of the ∑16 PAHs in the water- and local gin-based infusions of these teas were high when compared with levels reported in the literature for tea infusions. The local gin-based infusions had a higher mean level of the ∑16 PAHs than the water-based infusions. Four- and five-ring PAH compounds were dominant in these tea infusions.     

Urban Stream Vulnerability Toward PAHs and n-Alkanes and Their Source Identification

Monjolinho River is an important water body located in the central urban region of São Paulo State in southeast Brazil. The present work reports a 4-year study related to spatio-temporal distribution and source identification of polycyclic aromatic hydrocarbons (PAHs) and n-alkanes in surface water and sediment samples of Monjolinho River. A total of 25 sampling campaigns for water, and 10 sampling campaigns for sediment collection, were performed from 2011 to 2014. In sediment samples, total PAHs were found in the range of 2.25 µg kg^?1–26,253.87 µg kg^?1, while n-alkane concentrations ranged from 0.01 to 165.64 µg kg^?1. Total PAHs' concentration in surface water was in the range of 0.17–1,348.35 ng L^?1, while n-alkanes were detected in the range of 6.17–316.15 µg L^?1. Principal component analysis was used as a statistical tool for summarizing and interpreting a huge quantity of data. It was observed that concentrations of contaminants increased along the river course in urban zone. Distribution indexes were calculated to identify possible sources of carbon pool that pointed towards petrogenic, pyrogenic, and biogenic sources. The overall concentrations of PAHs and n-alkanes were low compared to many previous studies done elsewhere and were mostly below the threshold effects level except in very few occasional cases, while probable effect level was violated in 1 sample during 4 years. Although adverse impacts are unexpected due to overall low contaminant concentrations, unexpected industrial, and sewage discharges make it risky for safer use as a drinking water resource, especially in dry conditions.     

Polycyclic Aromatic Hydrocarbons in Residential Soils from an Indian City near Power Plants Area and Assessment of Health Risk for Human Population

This article deals with the distribution, composition profiles, and possible sources of sixteen priority polycyclic aromatic hydrocarbons (PAHs) in residential soils from Korba district in Chhattisgarh State, India. Sixteen priority PAHs in soils were analyzed after ultrasonic extraction, silica gel column chromatographic cleanup, and quantitation was performed using HPLC-DAD. The concentrations of ∑16PAHs were within acceptable limits of soil quality guidelines and the study area got classified as weakly contaminated. The concentration of probable human carcinogenic PAHs in soils accounted for 10% of ∑16PAHs. The concentration of Benzo(a)Pyrene (BaP) accounted 1% to total PAHs. Benzo(a)pyrene Toxicity Equivalency (BaP_TEQ) for 16 PAHs was 30 ± 12 μg BaP_TEQ kg^?1. The composition profiles and molecular ratios of PAHs suggested mixed pyrogenic sources of PAHs from combustion of coal, wood, and vehicular exhaust emissions. Human health risk was assessed by calculating the lifetime average daily dose (LADD) and incremental life time cancer risk (ILCR) for human adults and children. Estimated ILCR was within safe limit (10^?6?10^?5), indicating low risk to human population. Potential risk to contaminated ground water from leaching of carcinogenic PAHs was assessed by estimating the Index of Additive Cancer Risk (IACR).     

Equilibrium and dynamic studies of the removal of As(III) and As(V) from contaminated aqueous systems using a functionalized biopolymer

BACKGROUND: A study of the removal of arsenic from a sample of actual groundwater using crosslinked xanthated chitosan is described. RESULTS: Removal of As(III) and As(V) was studied at pH 7.5 under equilibrium and dynamic conditions. The equilibrium data were fitted to Langmuir and Freundlich adsorption models and the various model parameters evaluated. The monolayer adsorption capacity from the Langmuir model for xanthated chitosan flakes (XCF) (As(V) 20.0 ± 0.56 mg g^?1; As(III) 33.0 ± 0.32 mg g^?1) were lower than obtained for xanthated chitosan granules (XCB) (As(V) 36.0 ± 0.52 mg g^?1; As(III) 48.0 ± 0.45 mg g^?1). Adsorption of As (V) was unaffected by the presence of other anions while in the case of As(III) the presence of sulfate and silicate caused a 26.5–50.9% decrease in adsorption. A sample (940 bed volumes) of a groundwater spiked with 200 µg L^?1 As(V) treated with XCF in column experiments reduced the arsenic concentration to < 10 µg L^?1. The adsorbent was also successfully applied for the removal of total inorganic arsenic down to < 10 µg L^?1 from real samples of arsenic‐contaminated groundwater. CONCLUSION: Xanthated chitosan was an efficient adsorbent for the removal of both forms of arsenic from groundwater under near neutral conditions. The presence of sulfur and the amino groups resulted in increased adsorption capacity of the sorbent. Copyright © 2012 Society of Chemical Industry     

Factorial Design Optimization of Solid-Phase Microextraction for High-Performance Liquid Chromatography−Ultraviolet Spectrometry Analysis of Polycyclic Aromatic Hydrocarbons in Cigarette Filter Tar

A simple and rapid procedure for the determination of polycyclic aromatic hydrocarbons (PAHs) in cigarette filter tar using solid-phase microextraction (SPME) was developed. The analysis was carried out using high-performance liquid chromatography equipped with an ultraviolet detector. The effects of the SPME experimental parameters on the extraction recovery were studied simultaneously using a central composite design (CCD) after a 2^6?2 fractional factorial experimental design. The SPME variables of interest were the extraction temperature, the extraction time, and the stirring speed, as well as the pH and the concentrations of NaCl (%, w/v) and acetonitrile (ACN). The optimal SPME conditions were as follows: an extraction temperature of 65°C, an extraction time of 50 min, a stirring speed of 800 rpm, 0% NaCl (w/v), 10% ACN in the sample, and a source pH of 8.0. The extraction calibration plots were linear over the range of 0.25?20 ng mL^?1 (r² > 0.9912) and the limits of detection (LODs) for the 6 PAHs studied were from 0.17–5.02 ng cigarette^?1. The relative standard deviation (RSD) ranged from 7.1–13.5% for intra-day variation and from 8.5–18.4% for inter-day variation. The performance of the proposed method was evaluated for extraction and determination PAHs in real samples (various brands of cigarettes). The total amounts of all of the studied PAHs found in the filter tar of the three brands of cigarettes were 320.2, 17.9, and 66.7 ng cigarette^?1, respectively.     

EQUILIBRIUM AND KINETIC STUDIES FOR THE ADSORPTION OF MN(II) AND CO(II) FROM AQUEOUS MEDIUM USING AGAR–AGAR AS SORBENT

An extensive increase in industrial activities and environmental accidents in recent years have greatly contributed to increasing metal pollution in water resources, thereby causing threats to terrestrial as well as aquatic life. The toxicity of metal pollution is slow and long lasting, as these metal ions are nonbiodegradable. The most appropriate solution for controlling the biogeochemistry of metal contaminants to produce high-quality treated effluents from polluted wastewaters is sorption technique. Agar–agar, a readily available seaweed, was used as sorbent for the removal of Mn(II) and Co(II) from aqueous media. Batch experiments were performed to study adsorption as a function of process parameters: sorption time, initial pH, concentration of sorbate and sorbent. The Freundlich model fitted best with the experimental equilibrium data between the two adsorption isotherm models tested. The kinetic data correlated well with the Lagergren pseudo-second-order kinetic model for the sorption of both Mn(II) and Co(II) using agar–agar. Adsorbed metal ions were quantitatively recovered from the spent adsorbent using 5.0 mol L^?1 HCl. The efficiency of agar–agar for decontaminating Mn(II) and Co(II) from electroplating effluent has also been evaluated. The results proved agar–agar to be a favorable adsorbent to remove and recover Mn(II) and Co(II) from waste effluent for further use in diversified industrial applications.     

Levels of Some Persistent Organic Pollutants (PCBs and PAHs) in Jordanian Oil Shale Ash after Direct Heating at Different Temperature Ranges

The levels of 13 polycyclic aromatic hydrocarbons (PAHs) and 12 polychlorinated biphenyls (PCBs) were studied in oil shale ash samples gathered after heating oil shale samples collected from major deposit sites in Jordan. All analyses were carried out using GC/MS instrument. The results showed that the total concentration of the studied polycyclic aromatic hydrocarbon (PAHs) was the highest (75.99–317.53 μg /kg) at the lowest temperature range (200–400°C) and it decreased as the temperature increased. For the heating temperature range 400–600°C the concentrations were all decreased to below the limit of quantification while none of the samples contained any of the studied PAHs at the highest temperature range 600–800°C. While all the analyzed samples did not contain any of the studied 13 compounds of PCBs at different temperature ranges.

Recoveries of PAHs and PCBs were found between 82–106% and 91–114%, respectively. Precision of the analytical method for both PAHs and PCBs, calculated as relative standard deviation (RSD), ranged from 0.95–7.08% and 0.78–9.03%, respectively. The limit of detection values for PAHs and PCBs were between 0.006–0.070 μg/kg and 0.149–0.330 μg/kg, respectively.

The total estimated cancer risks of exposure to PAHs in the soil samples were ranged from 9.13 × 10^?7 to 2.15 × 10^?6. By multiplying these numbers of cancer risks of exposure to oil shale ash sample-PAHs by 10⁶, it is possible to determine the maximum theoretical number of cancer cases per million of people. The maximum estimated cancer risks cases determined in this study (2 out of 1 million) are well within the acceptable range of excess cancer risk specified by the US Environmental Protection Agency.     

Reductions in cod and acute toxicity of wastewater generated from refined cotton production using activated carbon fibre (ACF)

Activated carbon fibre is investigated for adsorption of organic pollutants from wastewater generated from refined cotton production. UV–Vis spectroscopy and FTIR are used to evaluate the chemical changes. Results indicate that the main organic components of refined cotton production wastewater are guaiacyl (G‐) and hydroxyphenyl (H‐) lignin. It is found that 85% of COD can be removed at 40°C with ACF dosage of 90 g L^?1. The adsorption process is described by the Redlich–Peterson isotherm model. The kinetic data follows a pseudo‐second‐order equation. Over 99% of acute toxicity for Refined Cotton Production (RCP) wastewater has been reduced after adsorption using ACF. © 2012 Canadian Society for Chemical Engineering     

Kinetic and Statistical Studies of Adsorptive Desulfurization of Diesel Fuel on Commercial Activated Carbons

Diesel fuel desulfurization by different commercial activated carbons was studied in a batch adsorber. Experiments, carried out to determine the sulfur adsorption dependency on time, were used to perform kinetic characterization and to screen the best performing activated carbon. The equilibrium characterization of the adsorption process was also performed. The statistical study of the process was undertaken by way of a two‐level one‐half fractional factorial experimental design with five process parameters. Individual parameters and their interaction effects on sulfur adsorption were determined and a statistical model of the process was developed. Chemviron Carbon SOLCARBTM C3 was found to be the most efficient adsorbent. The kinetic pseudo‐second order model and Freundlich isotherm are shown to exhibit the best fits of experimental data. The lowest achieved sulfur concentration in treated diesel fuel was 9.1 mg kg^–1.     

Removal of sulfide ions from aqueous solutions using carbon- and silicon-containing sorbents

Sulfide ions are among the most common pollutants in natural waters. Sulfide sorption methods are widely used in the waste water treatment practice. The most promising sorbents for removing sulfide ions are porous carbon materials. In the present study we researched sorption capacity of the carbon- and silicon-containing samples of rice and buckwheat processing wastes, as well as the activated carbon, carbon fiber, chitosan and natural silicates toward the sulfide ions in aqueous solutions. It was found that the most effective sorbent from the studied ones is the carbon fiber Aktilen B (99%) and from plant wastes – carbonaceous sorbents obtained from rice straw (77–98%) and buckwheat (94%). We studied the physico-chemical and structural properties of the carbonaceous sorbent based on rice straw and it was found that this sample is amorphous and has a predominant microporous structure. At the concentration of sulfide ions ranging from 140 to 800?µg?l^?1, the studied sorbent reduces the amount of sulfide ions to 0.4–1.4 of the maximum permissible concentration and can be used for treating natural and post-treating waste waters.     

LONG TERM MONITORING OF POLYCYCLIC AROMATIC HYDROCARBONS (PAHS) IN BLUE MUSSELS (Mytilus edulis) FROM A REMOTE SCOTTISH LOCATION

Farmed mussels have been collected on a monthly basis since 1999 from a remote site on the west coast of Scotland for polycyclic aromatic hydrocarbon (PAHs) analysis with the aim of establishing background concentrations as a benchmark against which to assess any environmental incident. Total PAH (2- to 6-ring parent and alkylated) concentrations ranged from 12.5 to 151.2 μg kg^?1 wet weight. Seasonal trends were evident with concentrations being significantly higher for samples collected between November and March compared to those collected between April and October. By taking the median of medians for each of these time periods two background concentrations are suggested for the total PAH concentrations (2- to 6-ring PAHs parent and alkylated); for April to October: 31.2 μg kg^?1 wet weight and for November to March: 62.9 μg kg^?1 wet weight. Individual PAH concentrations were mainly below the OSPAR Background Assessment Concentrations (BACs), where they are specified, and were only exceeded for the heavier 4- and 5-ring PAHs (fluoranthene, pyrene, benz[a]anthracene and benzo[a]pyrene) in samples collected between November and March. Differences were also seen in the PAH profiles with season. Mussels collected between November and March had a higher proportion of the heavier PAHs compared to mussels collected in the summer and autumn.     

Aerobic biodegradation and inhibition kinetics of poly‐aromatic hydrocarbons (PAHs) in a petrochemical industry wastewater in the presence of biosurfactants

BACKROUND: In Izmir, Turkey, wastewaters from the petrochemical industry are treated using conventional activated sludge systems. A significant proportion of poly‐aromatic hydrocarbons (PAHs) with high‐molecular weights remains in this treatment system and inhibits the biological activity. Biosurfactants increase PAHs degradation by enhancing the solubility of the petroleum components. The aerobic inhibition kinetics of PAHs has not previously been investigated in the presence of biosurfactants for a real petrochemical industry wastewater. RESULTS: Among the kinetic models used (Monod‐type, zero, first‐order and second‐order) it was found that the Monod kinetic was effective for describing the biodegradation of PAHs in petrochemcal industry wastewater in the presence of three biosurfactants, namely Rhamnolipid (RD), Surfactine (SR) and Emulsan (EM) in an aerobic activated sludge reactor (AASR). The maximum PAH removal rate (R_max) and specific growth rate of PAH degrading bacteria (µ_max) increased, while the half saturation concentration of PAH (K_s) decreased at 15 mg L^?1 RD concentration compared with the control without biosurfactant at a sludge retention time (SRT) of 25 days. CONCLUSION: PAH oxidation is typified by competitive inhibition at RD concentrations > 15 mg L^?1 resulting in increases in K_s values with PAH accumulation. Low inhibition constant (K_ID) values reflect difficulties in the metabolizability of PAHs. Metabolite production decreased at RD = 25 mg L^?1 in the PAHs indeno (1,2,3‐cd) pyrene (IcdP), flourene (FLN), phenanthrene (PHE) and benzo(a)pyrene (BaP). Copyright © 2011 Society of Chemical Industry     

Kinetics of polycyclic aromatic hydrocarbons removal using hyper-cross-linked polymeric sorbents Macronet Hypersol MN200

The search for suitable sorbents for polycyclic aromatic hydrocarbons (PAHs) removal from aqueous solutions prompted the evaluation of polymeric resins incorporating new properties that solve many of the existing problems when using granulated-activated carbon. A new type of non-functionalized macroporous hyper cross-linked resin, Hypersol Macronet (MN200) has been evaluated. Analyses of the respective batch rate data, for a family of six PAHs, with two kinetic models, the homogenous diffusion model (HDM) and the shell progressive model (SPM) were carried out. The process is controlled by the rate of diffusion of the solutes (PAHs) penetrating the reacted layer at PAH concentrations for the range 0.1–10 mg L⁻¹. Effective particle-diffusion coefficients (D_eff) were determined from the rate data proposed by both models. The D_eff values from both HMD and SPM equations varied from 5 × 10⁻¹³–4 × 10⁻¹⁵ m² s⁻¹. Pore diffusion is considered to be the predominant intraparticle transport mechanism inside the cross-linked polymer. The simplest model, the pore diffusion model, was applied first for data analysis. Close fitting of the data using this model requires that the apparent diffusivities are in the same order than the Brownian diffusivity reported in the literature. As a next step, the model of the next level of complexity, the surface diffusion model, was applied for data analysis. This model can explain the data, and the apparent surface diffusivities are the same order of magnitude as the literature values for similar resins.     

Vehicular Tire as Potential Adsorbent for the Removal of Polycyclic Aromatic Hydrocarbons

ABSTRACT

Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants, entering into various water and wastewater systems through various natural and anthropogenic activities. The aim of the work is to convert vehicular tires, a highly available waste material, into potential adsorbent for the removal of PAHs from aqueous solutions. The BET surface area of the prepared vehicular tire activated carbon is 643.86 m²/g. Removal of PAHs using activated carbons and the effect of various parameters such as contact time, adsorbent dose, temperature, and pH on the adsorption have been evaluated. The data were fitted to Freundlich and Langmuir isotherms and values of various constants were evaluated. In all the cases, Freundlich model was found to be better fitted. The equilibrium time for adsorption of PAHs was 120 min. The values of thermodynamic parameters, such as Gibb's free energy change ΔG°, enthalpy change ΔH°, and entropy change ΔS°, were calculated using adsorption equilibrium constants obtained from Langmuir isotherm. The thermodynamic data for adsorption of PAHs revealed spontaneity and endothermic nature of the adsorption process. The samples were analyzed using a UV–vis spectrophotometer for PAH determination. Mixture of sodium hydroxide and ethanol in different proportions was tried for desorption of PAHs and 50% ethanolic NaOH solution was most effective. The developed activated carbon demonstrates good adsorption and desorption capabilities for PAHs, indicating towards its suitability for use in the treatment processes of various industrial effluents or water streams containing PAHs.     

焦化厂土壤中PAHs的累积、垂向分布特征及来源分析

引言多环芳烃(polycyclic aromatic hydrocarbons,PAHs)在环境中普遍存在,由于具有强烈的诱变、致癌和致畸作用而受到越来越多的关注。以煤为主要原料的焦化行业,是环境中人类活动产生PAHs的主要来源之一,其各个生产车间内化石燃料的不完全燃烧及焦油、煤气等化工产品的加工过程都可能导致PAHs的排放。土壤是PAHs累积和迁移的重要介质,环境中的PAHs可由大气