Immunoassay monitoring of polychlorinated biphenyls (PCBs) in the Great Lakes

Although polychlorinated biphenyls (PCBs) are no longer manufactured, they are still entering the environment. In some compartments of the environment, PCB concentrations are a serious concern. This is especially true in compartments which accumulate PCBs, and in food items consumed by humans and wildlife. Also, there are situations in which management decisions require rapid, sensitive, accurate measurements, which can be made in real time under field conditions. Methods to use an enzyme-linked immunosorbent assay (ELISA) for PCBs were developed and applied to sediments and fish muscle homogenates collected from the Great Lakes. The extraction methods developed can be applied in the field with non-hazardous solvents, in the absence of sophisticated laboratory equipment. The method detection limit for PCBs in dimethyl sulfoxide (DMSO) extracts of sediment was 0.9 mg/kg. For PCBs in isopropanol extracts of fish tissue, the method detection limit was 0.6 mg/kg. The resolution of the ELISA was 0.83 mg/kg at 1.1 mg/kg and 1.6 mg/kg at 1.7 mg/kg, for sediment and fish tissue, respectively.     

Aerially guided leak detection and repair: A pilot field study for evaluating the potential of methane emission detection and cost-effectiveness

Novel aerial methane (CH₄) detection technologies were used in this study to identify anomalously high-emitting oil and gas (O&G) facilities and to guide ground-based “leak detection and repair” (LDAR) teams. This approach has the potential to enable a rapid and effective inspection of O&G facilities under voluntary or regulatory LDAR programs to identify and mitigate anomalously large CH₄ emissions from a disproportionately small number of facilities. This is the first study of which the authors are aware to deploy, evaluate, and compare the CH₄ detection volumes and cost-effectiveness of aerially guided and purely ground-based LDAR techniques. Two aerial methods, the Kairos Aerospace infrared CH₄ column imaging and the Scientific Aviation in situ aircraft CH₄ mole fraction measurements, were tested during a 2-week period in the Fayetteville Shale region contemporaneously with conventional ground-based LDAR. We show that aerially guided LDAR can be at least as cost-effective as ground-based LDAR, but several variable parameters were identified that strongly affect cost-effectiveness and which require field research and improvements beyond this pilot study. These parameters include (i) CH₄ minimum dectectable limit of aerial technologies, (ii) emission rate size distributions of sources, (iii) remote distinction of fixable versus nonfixable CH₄ sources (“leaks” vs. CH₄ emissions occurring by design), and (iv) the fraction of fixable sources to total CH₄ emissions. Suggestions for future study design are provided.

Implications: Mitigation of methane leaks from existing oil and gas operations currently relies on on-site inspections of all applicable facilities at a prescribed frequency. This approach is labor- and cost-intensive, especially because a majority of oil and gas–related methane emissions originate from a disproportionately small number of facilities and components. We show for the first time in real-world conditions how aerial methane measurements can identify anomalously high-emitting facilities to enable a rapid, focused, and directed ground inspection of these facilities. The aerially guided approach can be more cost-effective than current practices, especially when implementing the aircraft deployment improvements discussed here.     

Changes in enantiomeric fraction as evidence of natural attenuation of mecoprop in a limestone aquifer

Natural attenuation of the chiral pesticide mecoprop [2-(2-methyl-4-chlorophenoxy)propionic acid] has been studied by determining changes in its enantiomeric fraction in different redox environments down gradient of a landfill in the Lincolnshire Limestone. Previous studies have shown that mecoprop degrades predominantly aerobically and that differences in the biological behaviour of the two enantiomers will change their relative proportions during biodegradation. Originally deposited as a racemic mixture, there has been no change in the enantiomeric fraction in the most polluted part of the landfill plume where conditions are sulphate reducing/methanogenic. In the nitrate-reducing zone, the proportion of (S)-mecoprop increases, suggesting preferential degradation of (R)-mecoprop; while in the aerobic zone, the proportion of (R)-mecoprop increases, suggesting faster degradation of (S)-mecoprop. Mecoprop persistence in the confined Lincolnshire Limestone further downdip is explained by inhibition of degradation in sulphate-reducing conditions, which develop naturally. Laboratory microcosm experiments using up to 10 mg l(-1) of mecoprop confirm these inferences and show that under aerobic conditions, (S)-mecoprop and (R)-mecoprop degrade with zero-order kinetics at rates of 1.90 and 1.32 mg l(-1) day(-1), respectively. Under nitrate-reducing conditions (S)-mecoprop does not degrade, but (R)-mecoprop degrades with zero-order kinetics at 0.65 mg l(-1) day(-1) to produce a stoichiometric equivalent amount of 4-chloro-2-methylphenol. This metabolite only degrades when the (R)-mecoprop has disappeared. The addition of nitrate to a dormant iron-reducing microcosm devoid of nitrate stimulated anaerobic degradation of (R)-mecoprop after a lag period of 21 days. There was no evidence for enantiomeric inversion. The study demonstrates the sensitivity of changes in enantiomeric fraction for detecting natural attenuation, and reveals subtle differences in mecoprop degradation in different redox environments within the Lincolnshire Limestone aquifer.     

A mathematical model of PCB bioaccumulation in plankton

In batch experiments exposing individual plankton constituents to Aroclor 1254 PCB, the rate at which the organism approaches partitioning equilibrium appears to be partly size-dependent while the extent of PCB accumulation is species-specific. The sorptive desorptive kinetics of PCB in these experiments can be described mathematically by a first-order expression. Employing this expression in a model plankton food web permits examination of the role of feeding and sorptive processes in determining PCB body burden under various environmental conditions. When ingestion rates exceed desorption and excretion rates, a consuming organism accumulates PCB above levels predicted by equilibrium partitioning relationships. Feeding-induced oscillations in PCB body burden could thus obscure the reduction of soluble PCB concentration which determine a “baseline” PCB body burden. Unless referenced to a specific set of biological and environmental conditions, the importance of direct partitioning from water vs. food uptake appears to be a moot topic.     

Risk perception, risk communication, and stakeholder involvement for biosolids management and research

An individual's perception of risk develops from his or her values, beliefs, and experiences. Social scientists have identified factors that affect perceptions of risk, such as whether the risk is knowable (uncertainty), voluntary (can the individual control exposure?), and equitable (how fairly is the risk distributed?). There are measurable differences in how technical experts and citizen stakeholders define and assess risk. Citizen knowledge and technical expertise are both relevant to assessing risk; thus, the 2002 National Research Council panel on biosolids recommended stakeholder involvement in biosolids risk assessments. A survey in 2002 identified some of the factors that influence an individual's perception of the risks involved in a neighbor's use of biosolids. Risk communication was developed to address the gap between experts and the public in knowledge of technical topics. Biosolids management and research may benefit from applications of current risk communication theory that emphasizes (i) two-way communications (dialogue); (ii) that the public has useful knowledge and concerns that need to be acknowledged; and (iii) that what may matter most is the credibility of the purveyor of information and the levels of trustworthiness, fairness, and respect that he or she (or the organization) demonstrates, which can require cultural change. Initial experiences in applying the dialogue and cultural change stages of risk communication theory--as well as consensus-building and joint fact-finding--to biosolids research suggest that future research outcomes can be made more useful to decision-makers and more credible to the broader public. Sharing control of the research process with diverse stakeholders can make research more focused, relevant, and widely understood.     

Effects of elevated temperature on larval settlement and post-settlement survival in scleractinian corals, <Emphasis Type="Italic">Acropora solitaryensis</Emphasis> and <Emphasis Type="Italic">Favites chinensis</Emphasis>

We examined the effects of elevated temperature under different exposure periods on larval settlement and post-settlement survival in scleractinian corals, Acropora solitaryensis and Favites chinensis. In the first experiment with the subtropical coral, A. solitaryensis, the numbers of larvae settling and those dead were examined daily for 5 days at 20, 23 (ambient), 26 and 29°C conditions. Larval settlement of A. solitaryensis was initially greater at higher temperature conditions, but the peak in number of settled larvae shifted from 29 to 26°C by day 5, due to ca. 90% post-settlement mortality at 29°C condition. In order to determine the effects under short-term exposure, larvae of F. chinensis were exposed to 27 (ambient), 31 or 34°C only for one hour in the second experiment. The number of larvae settling for 24 h after the exposure and their survivorship over subsequent week was monitored in the ambient temperature condition. Larvae of F. chinensis exhibited greater settlement at higher temperature treatments and constantly low post-settlement mortalities (< ca. 17%) in all temperature treatments, resulting in the highest number of settled larvae at 34°C treatment. These results suggested two different effects of elevated temperature on the early stages of recruitment process of scleractinian corals; (1) the positive effect on larval settlement and (2) the negative effect on post-settlement survival under prolonged exposure.     

Sinking rate response to depletion of nitrate,phosphate and silicate in four marine diatoms

The effect of nutrient (N, P, and Si) depletion on sinking rates was studied for two small (Skeletonema costatum (Grev.) Cleve and Chaetoceros gracile Schütt) and two large [Ditylum brightwellii (West) Grun and Coscinodiscus wailesii (Gran et Angst)] centric diatoms obtained from stock cultures. Each diatom was examined under conditions of (1) nutrient repletion (=log growth phase), (2) nutrient depletion (48 h without a given substrate), and (3) recovery (24h after addition of limiting substrate to nutrient-deplete populations). All nutrient-replete cultures displayed low sinking rates despite large differences in cell size. In nutrient-deplete populations, sinking rate was related to the kind of nutrient depleted and varied among species. Silicate depletion elicited by far the greatest increase in sinking rates in all 4 species, indicating that biochemical aspects of silicon metabolism are more important to buoyancy regulation than density-related variations in the amount of silicon per cell. Since N- and P-depletion caused lower sinking rates in 3 of the species, this observation calls for re-evaluation of the axiom that nutrient depletion necessarily causes increased sinking rates. The exception was Coscinodiscus wailesii, which sank faster under all types of nutrient limitation. In most cases, sinking rates typical of log-phase cultures were not regained within 24 h after the addition of limiting nutrient to nutrient-depleted populations. Ultimately, the length of the recovery period may be useful in identifying the metabolic processes responsible for buoyancy regulation in actively growing cells.     

Inhibition of the growth of micro-algae and bacteria by extracts of eelgrass (Zostera marina) leaves

The effects of the water-soluble fraction of dead leaves of the eelgrass Zostera marina L. on the growth of 8 species of micro-algae (pennate and centric diatoms, dinoflagellates, and a green flagellate) and a bacterium were studied on agar plates and in liquid culture. The extracts of leaves which had been dead from a few days to 2 wk inhibited growth and often killed cells in all test organisms. Extracts were lethal even at concentrations equivalent to as little as 0.25 mg dry leaf ml^-1, but inhibition decreased when extracts were prepared from leaves aged in the laboratory for 35 d (loss of anti-bacterial activity) or 90 d (loss of anti-algal activity). Extracts of leaves which had aged and dried several months in the field had no effect, except at very high concentrations (13 mg dry leaf ml^-1) when the lag phase of growth was prolonged several days in a culture of the chlorophyte Platymonas sp. The active fraction in eelgrass leaves may be important in controlling initial growth of micro-organisms on eelgrass detritus, and it could determine the composition and activity of the epiphytic community on living leaves.     

Marine diatoms grown in chemostats under silicate or ammonium limitation. I. Cellular chemical composition and steady-state growth kinetics of Skeletonema costatum

Skeletonema costatum was grown in chemostats under ammonium or silicate limitation to examine its growth kinetics and changes in cellular chemical composition at different steady-state growth rates. When the relationship between the effluent limiting substrate concentration and steady-state growth rates was examined, deviations from the simple hyperbolic form of the Monod growth equation were noted at low and high dilution rates. The data from the plot of growth rate and substrate concentration were divided into 4 regions and the relationship of these region to cell quota is discussed. Two physiological states were identified. All populations grown at D<0.05 h^-1, regardless of the size of the cells or the magnitude of Q, exhibited a maximal growth rate of approximately 0.05 h^-1, while populations grown at higher dilution rates (D>0.06 h^-1 to 0.14 h^-1). The maximal value of growth rate is obtained only in cultures grown at very high dilution rates where nutrient shift-up appears to occur, the cell quota approaches a maximum and the heterogeneous cell population becomes more homogeneous.Contribution No. 881 from the Department of Oceanography, University of Washington, Seattle, Washington 98195, USA. This paper represents a portion of two dissertations submitted by P.J.H. and H.L.C. to the Department of Oceanography, University of Washington, Seattle, in partial fulfillment of the requirements for the Ph.D. degree.     

Sources and processes affecting concentrations of PM10 and PM2.5 particulate matter in Birmingham (U.K.)

Hourly average concentrations of PM₁₀ and PM_2.5 have been measured simultaneously at a site within Birmingham U.K. between October 1994 and October 1995. Comparison of PM₁₀ and NO_x data with two other sites in the same city shows comparable summer and winter mean concentrations and highly significant inter-site correlations for both hourly and daily mean data. Over a four-month period samples were also collected for chemical analysis of sulphate, nitrate, chloride, ammonium and elemental and organic carbon. Analysis of the data indicates a marked difference between summer and winter periods. In the winter months PM_2.5 comprises about 80% of PM₁₀ and is strongly correlated with NO_x indicating the importance of road traffic as a source. In the summer months, coarse particles (PM₁₀−PM_2.5) account for almost 50% of PM₁₀ and the influence of resuspended surface dusts and soils and of secondary particulate matter is evident. The chemical analysis data are also consistent with three sources dominating the PM₁₀ composition: vehicle exhaust emissions, secondary ammonium salts and resuspended surface dusts. Coarse particles from resuspension showed a positive dependence on windspeed, whilst elemental carbon derived from road traffic exhibited a negative dependence.