Sediment Contamination Study of Casco Bay part 4, Ramboll Environ PowerPoint 2016

https://digitalcommons.usm.maine.edu/cbep-presentations/1003/thumbnail.jp

Sediment Contamination Study of Casco Bay part 2, Ramboll Environ PowerPoint 2016

https://digitalcommons.usm.maine.edu/cbep-presentations/1001/thumbnail.jp

Sediment Contamination Study of Casco Bay part 5, Ramboll Environ PowerPoint 2016

https://digitalcommons.usm.maine.edu/cbep-presentations/1004/thumbnail.jp

Sediment Contamination Study of Casco Bay part 3, Ramboll Environ PowerPoint 2016

https://digitalcommons.usm.maine.edu/cbep-presentations/1002/thumbnail.jp

Sediment Contamination Study of Casco Bay part 1, Ramboll Environ PowerPoint 2016

https://digitalcommons.usm.maine.edu/cbep-presentations/1000/thumbnail.jp

Casco Bay Sediment Assessment (Fact Sheet)

Since 1991, Casco Bay Estuary Partnership (CBEP) has sponsored a monitoring program to track the concentrations of certain pollutants in sediments throughout Casco Bay to answer the following questions: What are the concentrations of chemicals in Casco Bay sediments? Are chemical concentrations in sediment high enough to harm marine life? How have chemical concentrations in sediment in the Bay changed over time? This fact sheet presents and interprets the results from sediment monitoring conducted from 1991 through 2011, the most recent year for which data are available. The sediment data show that concentrations for legacy pollutants tend to be declining throughout the Bay.https://digitalcommons.usm.maine.edu/cbep-toxic-pollution/1000/thumbnail.jp

Casco Bay Sediment Assessment 1991 – 2011

The Casco Bay Estuary Partnership (CBEP) has funded three comprehensive sediment quality assessments throughout Casco Bay since 1991, at roughly ten-year intervals. Chemicals analyzed include metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), organochlorine pesticides, dioxins and furans, and organotins. This report summarizes the results from the most recent sediment sampling program conducted in 2010-2011 and describes how concentrations of chemicals in sediment have changed over the 20-year period since samples were originally collected.https://digitalcommons.usm.maine.edu/cbep-toxic-pollution/1001/thumbnail.jp

Coordination Environments of Highly Charged Cations (Ti, Cr, and Light REE's) in Borosilicate Glass/Melts to 1120C

The local environments around Ti, Cr, and several light rare-earth elements (La, Ce, and Nd) were investigated by in-situ XANES spectroscopy in a number of complex borosilicate glasses and melts (to 1120 C) that are used for nuclear waste storage. Examination of the high-resolution XANES spectra at the Ti K-edge shows that the average coordination of Ti changes from {approx}5 to {approx}4.5. Cr is dominantly trivalent in the melts studied. However, its average coordination is probably lower in the melt (tetrahedral ?) as revealed by the more intense Cr-K pre-edge feature. Ce also changes its average valence from dominantly +4 to +3.5 upon glass melting. These changes are reversible at T{sub g}, the glass transition temperature ({approx}500-550 C for these glasses). In contrast, the local environments of Nd, Pr, and La are unaffected by melting. Therefore, structural reorganization of these borosilicate glass/melts above T{sub g} is variable, not only in terms of valence (as for Ce) but also speciation (Ti and Cr). Both the ability of B to adopt various coordination geometries (triangular and tetrahedral) and the chemical complexity of the glass/melts explain these changes

Between-airport heterogeneity in air toxics emissions associated with individual cancer risk thresholds and population risks

Abstract Background Airports represent a complex source type of increasing importance contributing to air toxics risks. Comprehensive atmospheric dispersion models are beyond the scope of many applications, so it would be valuable to rapidly but accurately characterize the risk-relevant exposure implications of emissions at an airport. Methods In this study, we apply a high resolution atmospheric dispersion model (AERMOD) to 32 airports across the United States, focusing on benzene, 1,3-butadiene, and benzo [a]pyrene. We estimate the emission rates required at these airports to exceed a 10-6 lifetime cancer risk for the maximally exposed individual (emission thresholds) and estimate the total population risk at these emission rates. Results The emission thresholds vary by two orders of magnitude across airports, with variability predicted by proximity of populations to the airport and mixing height (R2 = 0.74–0.75 across pollutants). At these emission thresholds, the population risk within 50 km of the airport varies by two orders of magnitude across airports, driven by substantial heterogeneity in total population exposure per unit emissions that is related to population density and uncorrelated with emission thresholds. Conclusion Our findings indicate that site characteristics can be used to accurately predict maximum individual risk and total population risk at a given level of emissions, but that optimizing on one endpoint will be non-optimal for the other.</p

Adsorption and Precipitation of Aqueous Zn(II) on Hematite Nano- and Microparticles

As part of a study of the effect of particle size on reactivity of hematite to aqueous metal ions, the sorption of Zn(II) on hematite nanoparticles and microparticles was examined over a wide range of Zn(II) concentrations using Zn K-edge EXAFS. When reacted with nanoparticles at pH 5.5 and low Zn(II) sorption densities (0.04 {le} {Lambda} &lt; 2.76 imol/m{sup 2}), Zn(II) formed five-coordinated or a mixture of four- and six-coordinated surface complexes with an average Zn-O distance of 2.04({+-}0.02){angstrom}. At pH 5.5 and high Zn(II) sorption densities (2.76 {ge} {Lambda} {le} 3.70 mol/m{sup 2}), formation of surface precipitates is suggested based on the presence of second-shell Zn and multiple scattering features in the Fourier transform (FT) of the EXAFS spectra. EXAFS fitting of these high {Lambda} samples yielded an average first-shell Zn-O distance of 2.10({+-}0.02){angstrom}, with second-shell Zn-Fe and Zn-Zn distances of 3.23({+-}0.03){angstrom} and 3.31({+-}0.03){angstrom}, respectively. Qualitative comparison between the EXAFS spectra of these sorption samples and that of amorphous zinc hydroxide and Zn-bearing hydrotalcite indicates the development of surface precipitates with increasing {Lambda}. EXAFS spectra of Zn(II) sorbed on hematite microparticles under similar experimental conditions showed no evidence for surface precipitates even at the highest Zn surface coverage ({Lambda} = 4 {micro}mol/m{sup 2}). These results indicate that reactivities of hematite nanoparticles and macroparticles differ with respect to Zn(II)aq, depending on Zn(II) sorption density. We suggest that the degree of hematite crystallinity affects the reactivity of hematite surfaces toward Zn(II)aq and the formation of the Zn(II) surface complexes