Evaluation of drum bioreactor performance used for decontamination of soil polluted with polycyclic aromatic hydrocarbons

A laboratory‐scale drum bioreactor system was used to study engineering aspects of soil bioremediation. Polycyclic aromatic hydrocarbons (PAHs) were chosen as contaminants in soil. In the operation of the reactor, different mixing strategies were applied according to the size of soil without separate washing of sand. The effect of the water content of the soil mixture on solid mixing time and phenanthrene degradation rate was of particular interest. At 20% water content, which was below the saturation level, the mixing efficiency of soil and the degradation rate of phenanthrene was lower than those at 30% or 40% water content. Optimal water content was variable according to the soil texture. The drum bioreactor was operated under optimal water content and PAH concentration (fluorene, phenanthrene, anthracene, pyrene) and microbial numbers were measured in each soil phase (sediment and suspension). Over 95% of PAHs with three or four rings (fluorene, phenanthrene, anthracene, pyrene) were degraded at 270 mg kg⁻¹ soil within 20 days. The degradation rate of PAHs in the suspension phase was higher than that in sediment phase. © 1999 Society of Chemical Industry     

Bioactivity of POPs and their effects in mosquitofish in Sydney Olympic Park, Australia

The site of the 2000 Olympic Games (Sydney Olympic Park (SOP), Sydney, Australia) was contaminated by persistent organic pollutants (POPs) prior to remediation in the 1990s. This study investigates the bioactivity of POPs in the sediment and water of wetlands across SOP by in vitro 2,3,7,8-TCDD equivalence (TCDDeq) measurement (H4IIE cell line bioassay). Further, it examines whether disturbance of these sediments is likely to mobilise ligands for this receptor into the water column. Exposure to aryl hydrocarbon receptor (AhR) ligands was measured in vivo using hepatic cytochrome P4501A (CYP1A) induction (EROD) in the mosquitofish (Gambusia holbrooki). Aqueous TCDDeq ranged from 0.013 to 0.057 pM in SOP wetlands which was significantly (p < 0.05) less that in urban reference sites. These concentrations were not correlated to physical or chemical characteristics of the wetlands. In the sediments, TCDDeq ranged from 0.0016 to 7.06 µg/kg and these were not significantly (p ≥ 0.05) different to that measured in urban reference sites. Simulated disturbance of small quantities of sediment in water samples significantly (p < 0.05) increased the levels of TCDDeq measured in the water. Sediment TCDDeq was correlated to sediment ΣPAH concentration in 2006 and sediment ΣPCB, ΣDDT concentrations and fine sediment grain size in 2005. While fish at one SOP wetland had hepatic EROD activity elevated above the estimated basal level for this species, these were at the lower end of the range measured in urban impacted, non-remediated wetlands. EROD activity was positively correlated with both the sediment ΣPCB load and aqueous TCDDeq. Increased catchment size was correlated with increased EROD activity suggesting an even spread of POPs throughout the residential areas of the Sydney metropolitan area. The concentration of bioactive POPs in the wetlands of SOP is therefore low relative to urban reference sites demonstrating the ongoing success of the remediation program.     

Removal of naphthalene from aqueous solution on chemically modified activated carbons

The aim of this work was to correlate the textural and chemical features of carbonaceous adsorbents with the adsorption capacity of naphthalene from aqueous phase, at the concentration in which this compound is usually found in wastewater from coke ovens. The study reveals that the adsorption capacity in different carbon materials depends not only on the textural characteristics of the material but also on the functionalities of the activated carbons. The micropores of the adsorbents, particularly those of narrower diameter, were found to be active sites for the retention of naphthalene. In contrast, the modification of the surface chemistry of the carbon materials led to a decrease in the adsorption capacities. Dispersive forces play an important role, and adsorbents with a higher non-polar character have proven to be more efficient for the naphthalene adsorption. This behaviour has been linked to the presence of specific interactions between the basal planes and the polyaromatic structure of the naphthalene molecule.     

Bioremediation of polycyclic aromatic hydrocarbons (PAH) in an aged coal-tar-contaminated soil using different in-vessel composting approaches

The biodegradation of 16 USEPA-listed PAHs (SigmaPAHs) during simulated in-vessel composting-bioremediation of an aged coal-tar-contaminated soil amended with fresh green waste compost (FGWC) collected from two landfill sites in the United Kingdom (UK) were studied over 56 days. The experimental design compared three constant temperature profiles (TC=38, 55 and 70 degrees C) with one variable temperature profile including treatment at 70 degrees C to comply with regulatory requirements (TP1). The highest disappearance of SigmaPAHs was observed in the soil amended with FGWC (53.2% and 48.1% SigmaPAHs disappearance in soil amended with FGWC-Site 1 and FGWC-Site 2, respectively) containing lower initial organic mater (TOM) (Initial TOM(FGWC-Site 1)=25.6+/-0.6%PAHs occurred when the same coal-tar soil was amended with fresh green waste (56.0% SigmaPAHs disappearance in soil amended with fresh green waste) instead of FGWC. Using a constant TC1=38 degrees C resulted in a higher disappearance of SigmaPAHs when compared to other temperature treatments. However, using a variable temperature profile TP1 during in-vessel composting of a soil amended with fresh green waste is required to promote contaminant degradation and pathogen control.     

The effect of coal size on PM2.5 and PM-bound polycyclic aromatic hydrocarbon (PAH) emissions from a domestic natural cross-draft stove

Residential coal combustion has played an important role in the domestic energy supply of Northern China for many decades and will do so for the foreseeable future, although it is also an important contributor to severe air pollution. Meeting the daily cooking and spacing-heating demands of rural residents in an eco-friendly manner necessitates cleaner-burning technologies for residential coal combustion. Several reports have suggested that appropriately sized coal be beneficial for optimizing the performance of domestic coal-fired stoves. The effects of coal size (<1.6 cm, 1.6–2.0 cm, 2.0–2.5 cm and >2.5 cm) on fine particulate matter (PM_2.5) and sixteen U.S. Environmental Protection Agency (EPA) priority polycyclic aromatic hydrocarbons (16-PAHs) emissions from a natural cross-draft stove, operating in different phases (ignition, high power heating, low power heating, ramping up and high power cooking) were analyzed in this study. Results indicated that decreasing the coal size enhanced thermal efficiency and reduced pollutant emissions. When the coal size decreased from >2.5 cm to <1.6 cm, the average emission factor (EF) of PM_2.5 over a complete combustion sequence decreased from 3.12 to 1.42 mg/MJ_net, and the EF of PM-bound total PAHs decreased from 44.9 to 10.9 μg/MJ_net. The corresponding toxic equivalent quantity (TEQ) decreased from 1.25 to 0.38 μg/MJ_net. Emissions and energy efficiencies varied markedly between the various combustion phases, adequate air supply during the high power heating and cooking phases reduced the EFs of PM_2.5 and PAHs, while the low power heating phase produced relatively more pollutants due to a fuel-rich condition.     

Vapour-phase and particulate-bound PAHs profile generated by a (SI/HCCI) engine from a winter grade commercial gasoline fuel

The vapour-phase and particulate-bound Aromatic Hydrocarbons, PAHs, generated by a V6 gasoline engine working in spark-ignition (SI) and homogeneous charge compression ignition (HCCI) modes were collected and analysed. All data were obtained during steady-state, fully warmed-up operation at different engine power levels (low and medium loads and mid-speed), and two different engine operation modes (SI and HCCI). The fuel used in this study was winter grade commercial gasoline fuel.The vapour-phase exhaust gases were passed through stainless-steel cartridges containing XAD-2 resin to capture PAHs. The PAHs were extracted from the resin with dichloromethane in an ultrasonic bath, the obtained extracts were later analysed qualitatively and quantitatively by GC-MS. The vapour-phase PAHs compounds observed from HCCI mode operated in low load were Naphthalene, Acenaphthylene and Acenaphthene only, while that obtained from SI mode under low load were Naphthalene, Acenaphthylene, Acenaphthene, Fluorene, Anthracene, Phenanthrene, Fluoranthene and Pyrene.The PAHs bound to particulates were trapped by using a complex of dilution tunnels with filter papers. The soluble organic fractions (SOF) of the trapped particulates were separated from the insoluble fraction (ISF) with the help of ultrasonic elution, and analysed by GC-MS method. The most abundant PAHs detected under selected operation condition for HCCI mode was Benzo[a]anthracene, followed by Chrysene, then Pyrene and pursued by Benzo[b]fluoranthene, in SI mode under same operation condition the highest PAH detected was Benzo[a]anthracene followed by Pyrene, Benzo[b]fluoranthene and Chrysene. Probable mechanisms for the production of some of the pyrosynthetic PAH were discussed.     

Levels of Polycyclic Aromatic Hydrocarbons (PAHs) in Atmospheric Environment of Urban Areas in Latin America

Polycyclic aromatic hydrocarbons (PAHs) are chemical compounds considered as pollutants of high priority due to their carcinogenic potential. PAH can appear in water, soil or in the atmosphere as adsorbed on particulate material or in gas phase. An increased number of studies on atmospheric PAH in urban areas have been published in the last decade, especially in the last years. Anthropogenic sources are frequently mentioned to be responsible for the increased concentration of PAHs in the atmosphere of urban areas, which at the same time seems to depend on meteorological parameters. This research is focused on compiling information on PAH levels in Latin America and their relationship with typical meteorological variables from seasonal and tropical countries. Brazil is the country with the most number of bibliographies about this topic, followed by Argentina, Chile and Mexico. Scarce information was found for Colombia and Venezuela and none for the rest of Latin American countries. The majority of studies checked have evaluated the climatological parameters in relationship with the PAH concentration and their distribution, finding that it affects meaningfully their levels. The monitor campaigns in Brazil have been developed mainly in the southern cities, where PAHs are strongly influenced by the seasons and their proximity to the South Pole. Tropical countries such as Venezuela and Colombia showed moderate variation of PAH concentration through months. The main influential parameters are precipitation and direction/speed winds.     

Effect-directed analysis of Ah receptor-mediated activities caused by PAHs in suspended particulate matter sampled in flood events

Suspended particulate matter (SPM) sampled during a flood event in the year 2004 at the rivers Neckar and Rhine (Southwest Germany) was assessed for aryl hydrocarbon receptor (AhR)-mediated activities using EROD induction in the rainbow trout liver cell line RTL-W1. All EROD inductions were normalized to the positive control TCDD and given as bio-TEQ values. Since all samples indicated elevated AhR-mediated toxicities, an effect-directed analysis (EDA) was applied to identify substances causing the effects. In three primary fractions (F1 to F3) non-polar aliphatics, non-polar aromatic substances and more polar substances were separated. Fraction F2, co-eluting with non-polar polyaromatic substances (PACs) including polycyclic aromatic hydrocarbons (PAHs) gave highest AhR-agonistic effects and, thus, were sub-fractionated into seven secondary fractions (F2-1 to F2-7). Fraction F2-1, co-eluting with PCBs and PCDD/Fs, did not cause AhR-agonist activities. F2-2 to F2-4 containing PACs of less than 16 aromatic C-atoms produced minor activities. Highest inductions were detected with fraction F2-5 to F2-7, containing substances of more than 16 aromatic C-atoms (bio-TEQs up to approximately 4500 pg/g).Concentrations and relative potencies (REPs) of priority EPA-PAHs allowed the calculation of chemical toxicity equivalent concentrations (chem-TEQ values). Based on the chem-TEQs, EPA-PAHs explained between 5 and 58% of crude extract bio-TEQs from both rivers. Whereas fractions F2-1 to F2-4 indicated no biological activities, EPA-PAHs in fraction F2-5 to F2-7 accounted for 2 to 137% of AhR-related activities.