Evaluation of a solid phase microextraction method for community-based monitoring of 1,3-butadiene and benzene in Houston, Texas

The Houston region is home to arguably the largest petrochemical and refining complex anywhere. The effluent of this complex includes many potentially hazardous compounds. Study of some of these compounds has led to recognition that a number of known and probable carcinogens are at elevated levels in ambient air. Two of these, benzene and 1,3-butadiene, have been found in concentrations which may pose health risk for residents of Houston.^ Recent popular journalism and publications by local research institutions has increased the interest of the public in Houston's air quality. Much of the literature has been critical of local regulatory agencies' oversight of industrial pollution. A number of citizens in the region have begun to volunteer with air quality advocacy groups in the testing of community air. Inexpensive methods exist for monitoring of ozone, particulate matter and airborne toxic ambient concentrations. This study is an evaluation of a technique that has been successfully applied to airborne toxics.^ This technique, solid phase microextraction (SPME), has been used to measure airborne volatile organic hydrocarbons at community-level concentrations. It is has yielded accurate and rapid concentration estimates at a relatively low cost per sample. Examples of its application to measurement of airborne benzene exist in the literature. None have been found for airborne 1,3-butadiene. These compounds were selected for an evaluation of SPME as a community-deployed technique, to replicate previous application to benzene, to expand application to 1,3-butadiene and due to the salience of these compounds in this community. ^ This study demonstrates that SPME is a useful technique for quantification of 1,3-butadiene at concentrations observed in Houston. Laboratory background levels precluded recommendation of the technique for benzene. One type of SPME fiber, 85 μm Carboxen/PDMS, was found to be a sensitive sampling device for 1,3-butadiene under temperature and humidity conditions common in Houston. This study indicates that these variables affect instrument response. This suggests the necessity of calibration within specific conditions of these variables. While deployment of this technique was less expensive than other methods of quantification of 1,3-butadiene, the complexity of calibration may exclude an SPME method from broad deployment by community groups.^

Changes of dissolved organic matter compositions in artifical and natural seawater during Pseudovibrio growth experiment

To study the consumption of dissolved organic matter (DOM) by bacteria living in untra-oligotrophic artificial or natural seawater, we analyzed the composition of DOM before (timepoint t0, directly after inoculation) and after (timepoint t2, 3 weeks of incubation) growth of the bacteria using Fourier transform ion cyclotron mass spectrometry (ESI FT-ICR-MS). The oligotrophic natural seawater used originates from the South Pacific Gyre. Our data show that the bacteria were able to utilize a variety of different organic compounds. These compounds belong to different chemical compound groups and likely fuel the bacterial energy, carbon and nitrogen requirements under the ultra-oligotrophic conditions.

Halocarbons in surface water from SWEDARP97/98

A number of parameters of biogeochemical interest were monitored along a north-southerly transect (S 43-S 63°) in the Atlantic Sector of the Southern Ocean from the 8th to the 20th of December 1997. Changes in total dissolved inorganic carbon (CT) and total alkalinity (AT) were mostly dependent on temperature and salinity until the ice edge was reached. After this point only a weak correlation was seen between these. Highest mean values of CT and AT were observed in the Winter Ice Edge (WIE) (2195 and 2319 µmol/kg, respectively). Lowest mean AT (2277 µmol/kg) was observed in the Sub-Antarctic Front (SAF), whereas lowest mean CT concentration (2068 µmol/kg) was associated with the Sub-Tropical Front (STF). The pH in situ varied between 8.060 and 8.156 where the highest values were observed in the southern part of the Antarctic Polar Front (APF) and in the Summer Ice Edge (SIE) Region . These peaks were associated with areas of high chlorophyll a (chl a) and tribromomethane values. In the other areas the pH in situ was mainly dependent on hydrography. Bacterial abundance decreased more than one order of magnitude when going from north to south. The decrease appeared to be strongly related to water temperature and there were no elevated abundances at frontal zones. Microphytoplankton dominated in the SAF and APF, whereas the nano- and picoplankton dominated outside these regions. Volatile halogenated compounds were found to vary both with regions, and with daylight. For the iodinated compounds, the highest concentrations were found north of the STF. Brominated hydrocarbons had high concentrations in the STF, but elevated concentrations were also found in the APF and SIE regions. No obvious correlation could be found between the occurrence of individual halocarbons and chl a. On some occasions trichloroethene and tribromomethane related to the presence of nano- and microplankton, respectively.

Organic-geochemical and petrographical composition of sediments from ODP Leg 164 sites

Sediments from Holes 994C, 995A, 997A, and 997B have been investigated for "combined" gases (adsorbed gas and that portion of free gas that has not escaped from the pore volume during core recovery and sample collection and storage), solvent-extractable organic compounds, and microscopically identifiable organic matter. The soluble materials mainly consist of polar compounds. The saturated hydrocarbons are dominated by n-alkanes with a pronounced odd-even predominance pattern that is derived from higher plant remains. Unsaturated triterpenoids and 17ß, 21ß-pentacyclic triterpenoids are characteristic for a low maturity stage of the organic matter. The low maturity is confirmed by vitrinite reflectance values of 0.3%. The proportion of terrestrial remains (vitrinite) increases with sub-bottom depth. Within the liptinite fraction, marine algae plays a major role in the sections below 180 mbsf, whereas above this depth sporinites and pollen from conifers are dominant. These facies changes are confirmed by the downhole variations of isoprenoid and triterpenoid ratios in the soluble organic matter. The combined gases contain methane, ethane, and propane, which is a mixture of microbial methane and thermal hydrocarbon gases. The variations in the gas ratios C1/(C2+C3) reflect the depth range of the hydrate stability zone. The carbon isotopic contents of ethane and propane indicate an origin from marine organic matter that is in the maturity stage of the oil window.

Geochemistry and petrography of organic matter at DSDP Hole 77-535

Organic geochemical and organic petrographic methods were used to study three Lower to middle Cretaceous sediment samples from Hole 535 in the southeastern Gulf of Mexico for organic matter contents and origin and level of maturation. All three samples contain mixed kerogen Type II/III organic matter with a maturity corresponding to about 0.4% vitrinite reflectance. The marine component increases with stratigraphic age, and microbial reworking of the organic matter is significant in each age. The lower two samples of Hauterivian to Valanginian age appear to be impregnated (or contaminated) with soluble polar organic compounds, but there is only a weak indication for the presence of more mature, nonindigenous hydrocarbons.

Seasonal changes in labile organic matter composition on the continental shelf and bathyal sediments of the Cretan Sea

Bacterial abundance, biomass and cell size were studied in the oligotrophic sediments of the Cretan Sea (Eastern Mediterranean), in order to investigate their response to the seasonal varying organic matter (OM) inputs. Sediment samples were collected on a seasonal basis along a transect of seven stations (ranging from 40 to 1570 m depth) using a multiple-corer. Bacterial parameters were related to changes in chloroplastic pigment equivalents (CPE), the biochemical composition (proteins, lipids, carbohydrates) of the sedimentary organic matter and the OM flux measured at a fixed station over the deep basin (1570 m depth). The sediments of the Cretan Sea represent a nutrient depleted ecosystem characterised by a poor quality organic matter. All sedimentary organic compounds were found to vary seasonally, and changes were more evident on the continental shelf than in deeper sediments. Bacterial abundance and biomass in the sediments of the Cretan Sea (ranging from 1.02 to 4.59 * 10**8 cells/g equivalent to 8.7 and 38.7 µgC/g) were quite high and their distribution appeared to be closely related to the input of fresh organic material. Bacterial abundance and biomass were sensitive to changes in nutrient availability, which also controls the average cell size and the frequency of dividing cells. Bacterial abundance increased up to 3-fold between August '94 and February '95 in response to the increased amount of sedimentary proteins and CPE, indicating that benthic bacteria were constrained more by changes in quality rather than the quantity of the sedimentary organic material. Bacterial responses to the food inputs were clearly detectable down to 10 cm depth. The distribution of labile organic compounds in the sediments appeared to influence the vertical patterns of bacterial abundance and biomass. Cell size decreased significantly with water depth. Bacterial abundance and biomass were characterised by clear seasonal changes in response to seasonal OM pulses. The strong coupling between protein flux and bacterial biomass together with the strong bacterial dominance over the total biomass suggest that the major part of the carbon flow was channelled through the bacteria and the benthic microbial loop.

Organic geochemistry of interstitial waters at DSDP Holes 64-474 and 64-479

Studies of the nature and amount of dissolved organic matter (DOM) in pore-water solutions have been confined mostly to recent sediments (Henrichs and Farrington, 1979; Krom and Sholkovitz, 1977; Nissenbaum et al., 1972). The analyses of organic constituents in interstitial waters have not been extended to sediment depths of more than 15 meters (Starikova, 1970). Large fluctuations in organic contents of near-bottom interstitial fluids suggest that organic compounds may provide insight into the chemical and biological processes occurring in the sedimentary column. Gradients in inorganic ion concentrations have been used as indicators of diagenesis of organic matter in deep sediments and interstitial waters. Shishkina (1978) attributed the occurrence of iodine and Cl/Br ratios that deviated from the value of seawater to the breakdown of organic matter and the liberation of bromide during mineralization. Sulfate depletion and maxima in ammonia concentrations were interpreted to be a consequence of sulfate reduction reactions in pore fluids, even at depths of more than 400 meters (Miller et al., 1979; Manheim and Schug, 1978).The purpose of this chapter is to study organic carbon compounds dissolved in interstitial waters of deep sediments at Sites 474 and 479.

Organic chemistry of sediments of the Peru margin

Organic-carbon-rich anoxic sediments from the continental shelf (Site 680) and the lower continental slope (Site 688) off Peru were studied to determine factors controlling the accumulation of reduced sulfur. High concentrations of organic matter in diatomaceous muds, its thermal immaturity, and the presence of abundant hydrogen-containing organic compounds lead to the conclusion that organic matter is not limiting for reduced sulfur formation. Rather, high degrees of iron pyritization at Site 680 limit pyrite accumulation in sediments from this shelf site. The low degree of iron pyritization and nearly complete reduction of dissolved sulfate at Site 688 suggest that a lack of interstitial sulfate is limiting pyrite formation there. Although factors that limit the formation of sedimentary iron sulfide are different at each site, the resulting average reduced-sulfur concentrations are remarkably similar (0.85 wt.% at Site 680 and 0.86 wt.% at Site 688). Carbon to sulfur (C/S) ratios are higher in samples containing in excess of 3 wt.% organic carbon than the average of 2.8 in normal marine sediments and have been primarily influenced by variations in organic matter concentrations.

Halocarbon and pigment profiles in the waters of the Amundsen and Ross Seas, Antarctica

Little is known regarding the distribution of volatile halogenated organic compounds (halocarbons) in Antarctic waters, and their relation to biophysical variables. During the austral summer (December to January) in 2007-08 halocarbon and pigment concentrations were measured in the Amundsen (100-130ºW) and Ross Sea (158ºW- 160ºE). In addition, halocarbons were determined in air, snow and sea ice. The distribution of halocarbons was influenced to a large extent by sea ice, and to a much lesser extent by pelagic biota. Concentrations of naturally produced halocarbons were elevated in the surface mixed layer in ice covered areas compared to open waters in polynyas and in the bottom waters of the Ross Sea. Higher concentrations of halocarbons were also found in sea ice brine compared to the surface waters. Incubations of snow revealed an additional source of halocarbons. The distribution of halocarbons also varied considerably between the Amundsen and Ross Seas, mainly due to the different oceanographic settings. For iodinated compounds, weak correlations were found with the presence of pigments indicative of Phaeocystis, mainly in the Ross Sea. Saturation anomalies for the surface water and brine (in sea ice) were determined for the two indicator halocarbons bromoform and chloriodomethane. For bromoform, the surface water anomalies varied between -83 and 11%, whereas chloroiodomethane anomalies varied between -6 and 1,200%. The saturation anomalies for brine varied between -56 to 120% for bromoform and 91 to 22,000% for chloroiodomethane, indicating that sea ice could be a possible source both to the atmosphere and the surface waters. Polar waters can have a substantial impact on global halocarbon budgets and need to be included in large-scale assessments.