Mary M. Lynam

Using thermal analysis coupled to isotope dilution cold vapor ICP-MS in the quantification of atmospheric particulate phase mercury

An analytical method combining thermal analysis with isotope dilution cold vapor inductively coupled plasma mass spectrometry, ID-CV-ICP-MS, was developed to study mercury in particulate matter samples collected in urban Detroit, MI. We used this method to quantify mercury in NIST 1633b “mercury in fly ash standard” and determined an average concentration of 0.139 ± 0.009 μg g−1 (RSD 6%), which was within the certified range of 0.141 ± 0.019 μg g−1 determined by the National Institute of Standards and Technology using cold vapor atomic absorption spectrometry. The method detection limit for each 3 second integration window was approximately 20 fg of mercury. When we compared results from thermal analysis coupled to ID-CV-ICP-MS to a well-established analysis method that combines microwave assisted nitric acid digestion with cold vapor atomic fluorescence spectroscopy, mercury concentrations were found to be in good agreement with each other indicating that the former is a suitable technique for quantitative release and analysis of mercury from aerosol matrices. Using this method mercury concentrations in denuded and undenuded fine particulate samples collected in Detroit, MI were quantified. Undenuded filters collected more particulate mercury compared to filters that were denuded using a KCl-coated denuder in 60% of samples. Thermal profiles for samples revealed complex patterns and differences in amounts and release patterns of mercury likely due to temporal differences in meteorology and air shed properties that were evident during sampling. Night time samples that were undenuded revealed the most complexity and may be a reflection of increased partitioning of reactive gaseous mercury to the particle phase with decreasing overnight temperatures and reduced height of the boundary layer. These profiles suggest that binding sites of varying physical and chemical characteristics in particulate matter are available for sorption and/or condensation of reactive gaseous mercury.

Structure-Biodegradability Relationships for Chlorinated Dibenzo-p-Dioxins and Dibenzofurans

Biotransformation and biodegradation of chemical compounds are the major processes which determine the fate of organic compounds in aquatic and terrestrial environments. The susceptibility of a chemical compound to undergo decomposition by the action of indigenous microorganisms is a very important property which must be considered to estimate the safety of the compound for biota and the environment. In addition, an understanding of biodegradation mechanisms and identification of those factors which limit the biodegradation rates is desirable for the development of bioremediation technologies suitable for cleanup of contaminated soil and water.

Polychlorinated Dibenzo-p-Dioxins in Anaerobic Soils and Sediments

Significant differences have been observed in the 2,3,7,8-substituted residue patterns of polychlorinated dibenzo-p-dioxins (PCDD) in freshwater, estuarine and marine sediments. Whereas these patterns can, to some degree, be explained by source identification, PCDD at environmental concentrations were recently found to be dechlorinated via microbial and chemical processes. Both peri- (1,4,6,9-substituted chlorines) and lateral (2,3,7,8-substituted chlorines) dechlorination patterns, as well as differences in extent of dechlorination were found to be correlated to specific abiotic and biotic catalytic activities. Qualitative relationships were based on isomer-specific analysis and the appearance of selective congeners under different conditions. The relevance of these processes to sediment biogeochemistry indicates that microbial dechlorination contributes significantly to the natural weathering of these types of pollutants. Whereas the lack of knowledge on the catalytic nature of the dechlorination reaction precludes the establishment of QSARs, characterization of microbial activities in combination with geochemical indicators may eventually present a means to describe the potential for microbial PCDD dechlorination in a given sediment environment and allow for a scientifically justified interpretation of patterns observed.

Effects of Airborne Particulate Matter on Respiratory Health in a Community near a Cement Factory in Chilanga, Zambia: Results from a Panel Study

We conducted a panel study to investigate seasonal variations in concentrations of airborne PM2.5 and PM10 and the effects on respiratory health in a community near a cement factory; in Chilanga; Zambia. A panel of 63 and 55 participants aged 21 to 59 years from a community located at the edge of the factory within 1 km and a control community located 18 km from the factory respectively; were followed up for three climatic seasons July 2015 to February 2016. Symptom diary questionnaires were completed and lung function measurements taken daily for 14 days in each of the three climatic seasons. Simultaneously, PM2.5 and PM10 concentrations in ambient air were monitored at a fixed site for each community. Mean seasonal concentrations of PM2.5 and PM10 ranged from 2.39–24.93 μg/m3 and 7.03–68.28 μg/m3 respectively in the exposed compared to the control community 1.69–6.03 μg/m3 and 2.26–8.86 μg/m3. The incident rates of reported respiratory symptoms were higher in the exposed compared to the control community: 46.3 vs. 13.8 for cough; 41.2 vs. 9.6 for phlegm; 49.0 vs.12.5 for nose; and 13.9 vs. 3.9 for wheeze per 100 person-days. There was a lower performance on all lung indices in the exposed community compared to the control; overall the mean FEV1 (forced expiratory volume in one second) and FVC (forced vital capacity) predicted percentage for the exposed was six and four percentage points lower than the control. Restriction of industrial emissions coupled with on-going monitoring and regulatory enforcement are needed to ensure that PM (airborne particulate matter) levels in the ambient air are kept within recommended levels to safeguard the respiratory health of nearby community residents.