Environmental sampling of volatile organic compounds during the 2018 Camp Fire in Northern California

Trace analysis of volatile organic compounds (VOCs) during wildfires is imperative for environmental and health risk assessment. The use of gas sampling devices mounted on unmanned aerial vehicles (UAVs) to chemically sample air during wildfires is of great interest because these devices move freely about their environment, allowing for more representative air samples and the ability to sample areas dangerous or unreachable by humans. This work presents chemical data from air samples obtained in Davis, CA during the most destructive wildfire in California's history - the 2018 Camp Fire – as well as the deployment of our sampling device during a controlled experimental fire while fixed to a UAV. The sampling mechanism was an in-house manufactured micro-gas preconcentrator (µPC) embedded onto a compact battery-operated sampler that was returned to the laboratory for chemical analysis. Compounds commonly observed in wildfires were detected during the Camp Fire using gas chromatography mass spectrometry (GC–MS), including BTEX (benzene, toluene, ethylbenzene, m+p-xylene, and o-xylene), benzaldehyde, 1,4-dichlorobenzene, naphthalene, 1,2,3-trimethylbenzene and 1-ethyl-3-methylbenzene. Concentrations of BTEX were calculated and we observed that benzene and toluene were highest with average concentrations of 4.7 and 15.1 µg/m³, respectively. Numerous fire-related compounds including BTEX and aldehydes such as octanal and nonanal were detected upon experimental fire ignition, even at a much smaller sampling time compared to samples taken during the Camp Fire. Analysis of the air samples taken both stationary during the Camp Fire and mobile during an experimental fire show the successful operation of our sampler in a fire environment.     

PM2.5 exposure as a risk factor for multiple sclerosis. An ecological study with a Bayesian mapping approach

Environmental Science and Pollution Research - Some environmental factors are associated with an increased risk of multiple sclerosis (MS). Air pollution could be a main one. This study was...     

Toxicity evaluation of vinasse and biosolid samples in diplopod midgut: heat shock protein in situ localization

Environmental Science and Pollution Research - Large amounts of residues generated by agricultural, urban and industrial activities are dumped daily on the soil. This practice deserves special...     

Bioassays for the evaluation of reclaimed opencast coal mining areas

Environmental Science and Pollution Research - This study aimed to use bioassays (single and multispecies) with organisms from different trophic levels to assess soil quality in reclaimed coal...     

Mercury distribution in medium-size rivers and reservoirs of the Sao Paulo state (southeast Brazil)

The aim of this work was to investigate mercury (Hg) levels in six meso-scale watersheds (Upper Paranapanema, Aguapeí, Peixe, S?o José dos Dourados, Mogi-Gua?u, and Piracicaba) of the S?o Paulo state to contribute to a more comprehensive understanding of Hg contamination in Brazil. Water, sediment, bivalves, and fish samples were collected during 2001 at 11 sites. Fish were also collected in the Jurumirim and Salto Grande Reservoirs which are 39 and 52 yr old since impoundment, respectively. Results showed that Hg concentrations were low in almost all samples, except fish from Jurumirim Reservoir (total mercury [T-Hg] = 1.14 +/- 0.55 mg kg(-1) wet wt.). In spite of industrialization and high population, the results showed that there was no important source of Hg contamination in the investigated areas. The higher concentrations found in fish from Jurumirim seem to be the result of processes that favor Hg mobilization and methylation as a consequence of the impoundment of the reservoir area. The same levels were not observed in the Salto Grande Reservoir, probably because these are no longer significant due to the long time since the impoundment. To understand the dynamics of methylmercury (MeHg) production and its accumulation in fish, further studies are needed in the Jurumirim Reservoir. The results show that even at low T-Hg concentrations in sediment and water, concentrations in fish can reach values that pose concerns for consumption. This emphasizes the importance of designing an optimized biomonitoring program that can provide warning of biogeochemical conditions that promote formation of MeHg.     

Gene expression changes in blood RNA after swimming in a chlorinated pool

Exposure to disinfection by-products(DBP) such as trihalomethanes(THM) in swimming pools has been linked to adverse health effects in humans, but their biological mechanisms are unclear. We evaluated short-term changes in blood gene expression of adult recreational swimmers after swimming in a chlorinated pool. Volunteers swam 40 min in an indoor chlorinated pool. Blood samples were drawn and four THM(chloroform,bromodichloromethane, dibromochloromethane and bromoform) were measured in exhaled breath before and after swimming. Intensity of physical activity was measured as metabolic equivalents(METs). Gene expression in whole blood m RNA was evaluated using Illumina Human HT-12v3 Expression-Bead Chip. Linear mixed models were used to evaluate the relationship between gene expression changes and THM exposure. Thirty-seven before-after pairs were analyzed. The median increase from baseline to after swimming were: 0.7 to 2.3 for MET, and 1.4 to 7.1 μg/m~3 for exhaled total THM(sum of the four THM).Exhaled THM increased on average 0.94 μg/m~3 per 1 MET. While 1643 probes were differentially expressed post-exposure. Of them, 189 were also associated with exhaled levels of individual/total THM or MET after False Discovery Rate. The observed associations with the exhaled THM were low to moderate(Log-fold change range:-0.17 to 0.15). In conclusion, we identified short-term gene expression changes associated with swimming in a pool that were minor in magnitude and their biological meaning was unspecific. The high collinearity between exhaled THM levels and intensity of physical activity precluded mutually adjusted models with both covariates. These exploratory results should be validated in future studies.     

The Influence of Model Structure on Conclusions about the Viability and Harvesting of Serengeti Wildebeest

We investigate how the viability and harvestability predicted by population models are affected by details of model construction. Based on this analysis we discuss some of the pitfalls associated with the use of classical statistical techniques for resolving the uncertainties associated with modeling population dynamics. The management of the Serengeti wildebeest (Connochaetes taurinus) is used as a case study. We fitted a collection of age-structured and unstructured models to a common set of available data and compared model predictions in terms of wildebeest viability and harvest. Models that depicted demographic processes in strikingly different ways fitted the data equally well. However, upon further analysis it became clear that models that fit the data equally well could nonetheless have very different management implications. In general, model structure had a much larger effect on viability analysis (e.g., time to collapse) than on optimal harvest analysis (e.g., harvest rate that maximizes harvest). Some modeling decisions, such as including age-dependent fertility rates, did not affect management predictions, but others had a strong effect (e.g., choice of model structure). Because several suitable models of comparable complexity fitted the data equally well, traditional model selection methods based on the parsimony principle were not practical for judging the value of alternative models. Our results stress the need to implement analytical frameworks for population management that explicitly consider the uncertainty about the behavior of natural systems.