Integration of field chemical data in initial risk assessment of forest fire smoke

Occupational exposure of firefighters to hazardous pollutants during prescribed fires in Portugal

Firefighters perform high-risk activities and during the course of their functions are highly exposed to a wide range of occupational hazards, including air pollution. Thus, this study aimed to assess the exposure of firefighters in prescribed wildland fires and their occupational exposure, as well as to identify and chemically characterise the particles collected during wildland firefighting and inside fire stations. Exposure to wildfire smoke was evaluated in 7 prescribed fires in Portugal, 2 in the north and 5 in the south of Viseu district. The concentrations of PM2.5, NO2, SO2, CO and VOCs were monitored and exceedances to occupational exposure limit values were identified. Moreover, the chemical composition of PM2.5 was analysed. The results showed that firefighters were exposed to high concentrations of these pollutants during prescribed fires and that, in some cases, exceeded occupational exposure limits, both for time-weighted average concentrations for an 8-h working day (a time-weighted average, TWA) of PM2.5, and for short-term exposure values (STEL) of NO2 and SO2. Despite being exposed to very high concentrations of CO, no exceedances to the occupational exposure values were observed. FT-IR and SEM-EDS allowed to chemically characterise the composition of the particles collected inside the fire stations and also during wildland fires, identifying mainly quartz, aluminium and magnesium silicates, characteristic of earth's crust constituents. and also, fibres that have undergone combustion. Concluding, firefighters' exposure to high concentrations of harmful pollutants, can lead to the degradation of their respiratory health. It is therefore extremely important to increase existing knowledge and conduct further studies, especially longitudinal ones, that can assess their lung function. This will allow an understanding of the impacts of smoke on firefighters' health and develop effective strategies to protect them during wildland firefighting operations.

Development of a conceptual framework for risk assessment of elevated internal temperatures in landfills

Subsurface elevated temperatures (SETs) often occur in landfills and pose great threats to their structural and environmental integrity. Current landfill gas monitoring practices only recommend maintaining certain soil gases percentages, with no integrated strategy for predicting subsurface temperature. As a solution, this paper proposes a comprehensive risk assessment framework specific to SET mitigation. The risk model (R_SET) was constructed by incorporating independent gas variables (methane, carbon dioxide, oxygen, residual nitrogen, and temperature) identified in the existing literature as SET indicators, and analyzing gas-well data from the Bridgeton Landfill. Upon identifying these gas indictors and their safety thresholds, we found a significant association (p-value < 0.05) between safe-unsafe ranges of gas variables and subsurface temperature. Temperatures above 80 °C were found to be associated with 100%, 92.3%, and only 4% of the unsafe ranges of methane, residual nitrogen, and oxygen, respectively. As the correlation between gases and temperature seemed to vary for different gas combinations, we developed the R_SET by incorporating into these correlation coefficients event intensities specific to certain gas combinations, and then normalizing the R_SET scale over a 0-10 range. Over the study period, we identified 22.29% of cases as medium risk at the Bridgeton Landfill and 17.7% as high risk. SETs are governed by different combinations of safe-unsafe ranges of parameters rather than any individual parameters alone. Subsequently, we used a decision tree algorithm to assess the risk types associated with R_SET values. The proposed R_SET can serve as a monitoring and decision-making tool for landfill authorities for managing and preventing SET incidents.

Contributions of Kansas rangeland burning to ambient O3: Analysis of data from 2001 to 2016

Prescribed range/pasture burning is a common practice in Kansas to enhance the nutritional value of native grasses and control invading weeds, trees, and brush. A major concern associated with the burning is the contribution of smoke to elevated ground level ambient ozone (O₃). The objective of this study is to estimate contributions of Kansas rangeland burning to ambient O₃ mixing ratios through regression analysis (1) between observed O₃ data and available satellite burn activity data from 2001 to 2016; and (2) between observed O₃ data and the smoke contributions to PM_2.5 which were resolved from receptor modeling. Positive correlations were observed between ambient O₃ levels and the acres burned each year estimated from satellite imagery. When burned acres in April were larger than or equal to 1.9 million, O₃>70ppb occurred at least at one of the ten monitoring sites in Kansas. Statistical regression models of daily maximum 8-hour O₃ mixing ratios were developed at each of the ten monitoring sites using meteorological predictors. The O₃ model residuals that were not explained by the meteorological effect models were affected by PM_2.5 contributors including sulfate/industrial sources and emissions that generated secondary organic particles, such as rangeland burning, which were derived from receptor modeling. The average O₃ model residual on the high O₃ days in April was 21±9ppb, which was likely associated with smoke emissions from burning. Research will continue to obtain daily satellite burn activity data and to correlate burn data with daily O₃ data, so that modeling of O₃ levels can be improved under influences of daily burn activities. Less frequency of high O₃ days was observed in April since 2011, which may be partly due to implementation of the Flint Hills Smoke Management Plan which promoted better timing of burns.