nitro-PAHs Research Articles

PAHs (polycyclic aromatic hydrocarbons), nitro-PAHs, and hopane and sterane biomarkers in sediments of southern Lake Michigan, USA

PAHs in the Great Lakes basin are of concern due to their toxicity and persistence in bottom sediments. Their nitro derivatives, nitro-PAHs (NPAHs), which can have stronger carcinogenic and mutagenic activity than parent PAHs, may follow similar transport routes and also are accumulated in sediments. Limited information exists regarding the current distribution, trends and loadings of these compounds, especially NPAHs, in Lake Michigan sediments. This study characterizes PAHs, NPAHs, and biomarkers steranes and hopanes in surface sediments collected at 24 offshore sites in southern Lake Michigan. The ΣPAH14 (sum of 14 compounds) ranged from 213 to 1291ng/g dry weight (dw) across the sites, levels that are 2 to 10 times lower than those reported 20 to 30years earlier. Compared to consensus-based sediment quality guidelines, PAH concentrations suggest very low risk to benthic organisms. The ΣNPAH5 concentration ranged from 2.9 to 18.6ng/g dw, and included carcinogenic compounds 1-nitropyrene and 6-nitrochrysene. ΣSterane6 and ΣHopane5 concentrations ranged from 6.2 to 36 and 98 to 355ng/g dw, respectively. Based on these concentrations, Lake Michigan is approximately receiving 11, 0.16, 0.25 and 3.6metrictons per year (t/yr) of ΣPAH14, ΣNPAH5, ΣSterane6 and ΣHopane5, respectively. Maps of OC-adjusted concentrations display that concentrations decline with increasing off-shore distance. The major sources of PAHs and NPAHs are pyrogenic in nature, based on diagnostic ratios. Using chemical mass balance models, sources were apportioned to emissions from diesel engines (56±18%), coal power plants (27±14%), coal-tar pavement sealants (16±11%), and coke ovens (7±12%). The biomarkers identify a combination of petrogenic and biogenic sources, with the southern end of the lake more impacted by petroleum. This first report of NPAH levels in sediments of Lake Michigan reveals several carcinogenic compounds at modest concentrations, and a need for further work to assess potential risks to aquatic organisms.

Composition and Integrity of PAHs, Nitro-PAHs, Hopanes, and Steranes in Diesel Exhaust Particulate Matter

Diesel exhaust particulate matter contains many semivolatile organic compounds (SVOCs) of environmental and health significance. This study investigates the composition, emission rates, and integrity of 25 SVOCs, including polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs (NPAHs), and diesel biomarkers hopanes and steranes. Diesel engine particulate matter (PM), generated using an engine test bench, three engine conditions, and ultra-low sulfur diesel (ULSD), was collected on borosilicate glass fiber filters. Under high engine load, the PM emission rate was 0.102 g/kWh, and emission rate of ΣPAHs (10 compounds), ΣNPAHs (6 compounds), Σhopanes (2 compounds), and Σsteranes (2 compounds) were 2.52, 0.351, 0.02 ~ 2 and 1μg/kWh, respectively. Storage losses were evaluated for three cases: conditioning filters in clean air at 25 °C and 33% relative humidity (RH) for 24 h; storing filter samples (without extraction) wrapped in aluminum foil at 4 °C for up to one month; and storing filter extracts in glass vials capped with Teflon crimp seals at 4 °C for up to six months. After conditioning filters for 24 h, 30% of the more volatile PAHs were lost, but lower volatility NPAHs, hopanes and steranes showed negligible changes. Storing wrapped filters and extracts at 4 °C for up to one month did not lead to significant losses, but storing extracts for five months led to significant losses of PAHs and NPAHs; hopanes and steranes demonstrated greater integrity. These results suggest that even relatively brief filter conditioning periods, needed for gravimetric measurements of PM mass, and extended storage of filter extracts can lead to underestimates of SVOC concentrations. Thus, SVOC sampling and analysis protocols should utilize stringent criteria and performance checks to identify and limit possible biases occurring during filter and extract processing.

Evaluation of Potential Molecular Markers for Urban Stormwater Runoff

Source specificity and persistence of several sulfur-polycyclic aromatic hydrocarbons (S-PAHs), nitro-PAHs (N-PAHs), and triphenylene were examined via analyses of stormwater runoff and wastewater effluent samples and spiked samples upon exposure to sunlight. Samples were collected during the 1997/1998 wet weather season from two major storm channels and four major wastewater treatment plants in southern California. Among the target compounds examined, 2-(4-morpholinyl)benzothiazole, dibenzothiophene, and triphenylene/chrysene were detected in storm runoff only. However, 2-(4-morpholinyl)benzothiazole appeared to degrade rapidly in seawater and sediment after sunlight exposure, which might impede its use as a runoff indicator. Dibenzothiophene and triphenylene also degraded quickly in sunlight-exposed seawater samples, but remained fairly abundant in sediments after six months of exposure to sunlight. They are by far the most promising candidates of urban runoff markers based on the criteria of abundance, source specificity, and persistence, although more research efforts are needed to ensure that no other sources would also contribute significantly to their presence in the aquatic environment.

Mutagenic nitroarenes, diesel emissions, particulate-induced mutations and cancer: an essay on cancer-causation by a moving target

Initial analyses of the lung tumors seen in rats exposed for their lifetime to elevated levels of the emissions of diesel engines suggested that they were due to powerful mutagens and carcinogens (PAHs, nitro PAHS) adsorbed onto the diesel particles. However, further studies showed that carcinogenicity occurred only under conditions that resulted in impaired lung clearance (‘overloading’) leading to inflammatory reactions and other pathologic sequelae. These observations together with the findings that carbon black, a model for diesel particles devoid of organic mutagens and carcinogens, also induced lung cancers under conditions of overloading led to the suggestion that the cancers resulted from a non-genotoxic mechanism. However, the further finding that inert particulate carcinogens devoid of organics, induced mutations has led to a re-evaluation of the role of mutations in lung carcinogenesis caused by particles and the relevance of the rat model to humans. This is especially timely as epidemiological studies suggest that humans may develop lung cancers following occupational exposure to diesel emissions by a mechanism unlikely to involve lung overloading. Finally, the recent recognition that environmental PM-10 (respiratory size particles) may be responsible for a significant portion of human morbidity and mortality, ensures that the health effect of diesel emissions will continue to receive scrutiny as they contribute to the PM-10 load.

Modeling of nitro-polycyclic aromatic hydrocarbon formation and decay in the atmosphere

A reaction mechanism of polycyclic aromatic hydrocarbons (PAH) and nitro-PAH (NPAH) in the gas and particle phase in the atmosphere has been further evaluated and modified using outdoor smog chamber experimental results. Diesel exhaust emissions were added to a 190 m 3 outdoor smog chamber and permitted to age under conditions of daylight and darkness. A sampling train consisting of an annular denuder, filter, and polyurethane foam (PUF) or XAD resin was used for the collection of gas and particle phase PAH and NPAH. On the basis of the results, the current denuder design has sufficient flow (20 ℓ min −1) and adsorption characteristics for collection of PAH and NPAH in the chamber studies. Outdoor smog chamber experiments with dilute diesel soot were conducted under different initial photochemical conditions. Ozone (0 3), nitrogen oxides (NO x ), and volatile hydrocarbons in the gas phase were monitored. Simulations for fluoranthene (FL) and pyrene (PY) in the gas phase were close to chamber observations, but those for the particle behavior of FL and PY were not as good. This may occur because PAH and NPAH inside of the particle are not available for reaction in sunlight. Mono-nitro-pyrenes (NPYs) and nitro-fluoranthenes (NFLs) were almost exclusively found in particle associated extracts. This implied that no or non-detectable 2nitro-FL (2NF) or 2nitro-PY (2NP) distributed in the gas phase and that they deposited on particles immediately after formation in the gas phase by the photochemical processes. Formation of 2NF was observed in the chamber, but 2NP degraded rapidly under photochemical conditions. Reasonable simulation results were obtained for 2NP and 2NF. The addition of NO 2 to the gas phase adduct of FL + OH or PY + OH was the main reaction for NPAH formation. Photodecomposition was the main loss pathway for NPAH in the atmosphere.

Simultaneous determination of polycyclic aromatic hydrocarbons and their nitrated derivatives in airborne particulates by HPLC with fluorescence/chemiluminescence detection.

A simultaneous determination method for polycyclic aromatic hydrocarbons (PAHs)and nitro-PAHs (NPAHs) in airborne particulates was developed. Airborne particulates were extracted with benzene/ethanol, cleaned up by liquid-liquid partition, refluxed in the presence of NaSH and then the resultant solution was injected into an HPLC system. The system was hybridized into two systems with different optimum conditions for PAHsand NPAHs by introducing a switching valve and a mini separation column. Mobil ephases were acetonitrile/water (75 : 25) for PAHs, and acetonitrile/imidazole HClO4 buffer (1:1) for NPAHs and the postcolumn reagent solution for NPAHs was an acetonitrile solution containing bis(2, 4, 6-trichlorophenyl)oxalate and H2O2. By this method, four NPAHs (1, 3-, 1, 6-, 1, 8-dinitropyrenes and 1-nitropyrene) and eight PAHs (fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a] pyrene and coronene) in sub-milligram quantities of airborne particulates were de-termined chemilumigenically and fluorogenically, respectively using 2-fluoro-7-nitrofluorene as an internal standard within sixty minutes.

Artefacts during the sampling of nitro PAHs of diesel exhaust

Artefacts during the sampling of nitro PAHs of diesel exhaust