Ronald A. Hites

The global distribution of polycyclic aromatic hydrocarbons in recent sediments

Abstract Polycyclic aromatic hydrocarbons (PAH) and their alkyl homologs are distributed in sediments throughout the world. The qualitative PAH pattern is remarkably constant for most of the locations studied, and the quantitative PAH abundance increases with proximity to urban centers. These findings are consistent with anthropogenic combustions being the major source of these compounds. Two non-combustion sources of PAH have also been noted: retene coming from abietic acid and perylene probably coming from various extended quinone pigments.

Fluxes of polycyclic aromatic hydrocarbons to marine and lacustrine sediments in the northeastern United States

Polycyclic aromatic hydrocarbons (PAH) were measured in dated sediment cores from several sites in the northeastern United States (Lake Superior, Isle Royale, Somes Sound, Hadlock Lower Pond. Coburn Mountain Pond, and outer Boston Harbor). Fluxes of ten PAH were measured for each site for the periods roughly corresponding to the present, 1950, and 1900. Remote sites consistently demonstrated present-day deliveries of individual PAH near 1 ng cm−2 yr−1, probably reflecting the atmospheric fallout of these combustion-derived pollutants. Sites located nearer to urban centers showed much greater current inputs (average of 35 ng cm−2 yr−1 for most individual PAH), presumably caused by greater fallout of PAH-laden particles nearer their urban origins, augmented by runoff delivery of PAH-contaminated sediments. Differences in the relative abundances of individual PAH at remote-versus-urban locations support suggestions of different delivery mechanisms. The sedimentary historical records of PAH inputs confirm the previous finding that anthropogenic activities began introducing large quantities of PAH into the environment about 80–100 years ago.

Organic Pollutant Accumulation in Vegetation

Recent advances in the study of organic pollutant accumulation in vegetation are reviewed. Major areas include (a) the mechanism of uptake by vegetation, (b) the use of vegetation to indicate contamination levels, and (c) the importance of vegetation as a pollutant sink. The mechanism of vegetation uptake of organic pollutants is governed by the chemical and physical properties of the pollutant, environmental conditions, and the plant species. We recommend that additional field studies be done on the uptake of industrial pollutants by native plants and that empirical models and controlled exposure experiments be validated under field conditions. Vegetation can be used to qualitatively indicate organic pollutant atmospheric contamination levels as long as the mechanism of accumulation is considered. Vegetation has been used to identify point sources of pollutants and to determine regional and global contamination patterns. Plant pollutant concentrations should be normalized to the plant lipid concentration or surface area, especially when directly comparing different species. Although vegetation has a great potential to accumulate organic pollutants, little is known about the quantitative importance of vegetation as a pollutant sink. Overall recommendations for future research are presented.

Vegetation-atmosphere partitioning of polycyclic aromatic hydrocarbons

The partitioning of polycyclic aromatic hydrocarbons (PAH) between vegetation and the atmosphere was studied throughout the growing season and under natural conditions. A vegetation-atmosphere partition coefficient (K[sub v]) was derived by analogy to partition coefficients for gas-particle partitioning and fish-water partitioning. K[sub v] is temperature dependent, and from this functional relationship we calculated PAH-vegetation binding energies. These energies were highly correlated with heats of vaporization. The PAH-vegetation partitioning process is primarily dependent upon the atmospheric gas-phase PAH concentration and ambient temperature. At low ambient temperatures (spring and fall) gas-phase PAH partition into vegetation, and at high ambient temperatures (summer), some PAH volatilize and return to the atmosphere. This study provides further evidence that atmospheric semivolatile organic compounds undergo an annual partitioning cycle with the surface of the earth. 39 refs., 3 figs., 1 tab.

Atmospheric deposition of polycyclic aromatic hydrocarbons to water surfaces: a mass balance approach

A mass balance model was developed to explain the movement of polycyclic aromatic hydrocarbons (PAH) into and out of Siskiwit Lake, which is located on a wilderness island in northern Lake Superior. Because of its location, the PAH found in this lake must have originated exclusively from atmospheric sources. Using gas Chromatographie mass spectrometry, 11 PAH were quantified in rain, snow, air, lake water, sediment core and sediment trap samples. From the dry deposition fluxes, an aerosol deposition velocity of 0.99 ± 0.15 cm s−1 was calculated for indeno[1,2,3-cd]pyrene and benzo[ghi]perylene, two high molecular weight PAH which are not found in the gas phase. The dry aerosol deposition was found to dominate the wet removal mechanism by an average ratio of 9:1. The dry gas flux was negative, indicating that surface volatilization was taking place; it accounted for 10–80 % of the total output flux depending on the volatility of the PAH. The remaining PAH were lost to sedimentation. From the dry gas flux, an overall mass transfer coefficient for PAH was calculated to be 0.18 ± 0.06 m d−1. In this case, the overall mass transfer is dominated by the liquid phase resistance.

Sedimentary polycyclic aromatic hydrocarbons: the historical record.

Polycyclic aromatic hydrocarbons in three sections of a dated sediment core from Buzzards Bay, Massachusetts, have been analyzed by gas chromatographic spectrometry. This historical information suggests that sedimentary polycyclic aromatic hydrocarbons, at least at this location, result primarily from the anthropogenic combustion of fossil fuels.

Environmental fate of combustion-generated polychlorinated dioxins and furans

Polychlorinated dioxins and furans were found in sediments from the Saginaw River and Bay and from Lake Huron. The congener distributions of the dioxins and furans indicate that combustion may be the major source of these compounds. The depth vs. concentration profiles in dated sediment cores shows that emission of dioxins and furans has increased greatly since 1940. This historical increase is similar to trends for the production, use, and disposal of chlorinated organic compounds and suggests that chlorinated precursors of dioxins and furans, present in incinerator combustion fuels, may be the main source of the dioxins and furans found in these sediments.

Polycyclic aromatic hydrocarbons in an anoxic sediment core from the Pettaquamscutt River (Rhode Island, U.S.A.)

Abstract Fifteen sections from an anoxic sediment core were analyzed for polycyclic aromatic hydrocarbons (PAH). Two types of PAH were observed: (a) those from combustion sources such as pyrene and chrysene and (b) those from natural sources such as retene and perylene. The combustion PAH levels in core sections dated between 1900 and 1970 were much higher than in earlier sections; this indicated an anthropogenic origin of these PAH at this location. The perylene and retene core profiles show significant anomalies during the period 1850–1880. Organic carbon does not fluctuate markedly but δC-13 of organic carbon shows several unexplained excursions; one of which correlates with the perylene and retene anomalies.

Airborne dioxins and dibenzofurans: sources and fates

Polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) were found in urban air particulates and Great Lakes sediments. In all samples, octachlorodibenzo-p-dioxin predominated. Combustion of municipal and chemical wastes was the most likely source of these compounds. When these data were compared with dioxins and dibenzofurans found in combustion sources, evidence was found that the most likely source of PCDD and PCDF to a western Lake Ontario site was pentachlorophenol production. Historical fluxes of dioxins and dibenzofurans to sediment cores from Lake Erie and Siskiwit Lake (Isle Royale) suggest that the incineration of chloro aromatics has been an important source of dioxins and dibenzofurans. 24 references, 6 figures, 1 table.

Hydroxylated metabolites of polybrominated diphenyl ethers in human blood samples from the United States.

Background A previous study from our laboratory showed that polybrominated diphenyl ethers (PBDEs) were metabolized to hydroxylated PBDEs (HO-PBDEs) in mice and that para-HO-PBDEs were the most abundant and, potentially, the most toxic metabolites. Objective The goal of this study was to determine the concentrations of HO-PBDEs in blood from pregnant women, who had not been intentionally or occupationally exposed to these flame retardants, and from their newborn babies. Methods Twenty human blood samples were obtained from a hospital in Indianapolis, Indiana, and analyzed for both PBDEs and HO-PBDEs using electron-capture negative-ionization gas chromatographic mass spectrometry. Results The metabolite pattern of HO-PBDEs in human blood was quite different from that found in mice; 5-HO-BDE-47 and 6-HO-BDE-47 were the most abundant metabolites of BDE-47, and 5′-HO-BDE-99 and 6′-HO-BDE-99 were the most abundant metabolites of BDE-99. The relative concentrations between precursor and corresponding metabolites indicated that BDE-99 was more likely to be metabolized than BDE-47 and BDE-100. In addition, three bromophenols were also detected as products of the cleavage of the diphenyl ether bond. The ratio of total hydroxylated metabolites relative to their PBDE precursors ranged from 0.10 to 2.8, indicating that hydroxylated metabolites of PBDEs were accumulated in human blood. Conclusions The quite different PBDE metabolite pattern observed in humans versus mice indicates that different enzymes might be involved in the metabolic process. Although the levels of HO-PBDE metabolites found in human blood were low, these metabolites seemed to be accumulating.