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Rodrigues E.R.,National Autonomous University of Mexico | Gamerman D.,Federal University of Rio de Janeiro | Tarumoto M.H.,Sao Paulo State University | Tzintzun G.,Instituto Nacional Of Ecologia Y Cambio Climatico
Environmental and Ecological Statistics | Year: 2015

In this work we consider a non-homogenous Poisson model to study the behaviour of the number of times that a pollutant’s concentration surpasses a given threshold of interest. Spatial dependence is imposed on the parameters of the Poisson intensity function in order to account for the possible correlation between measurements in different sites. An anisotropic model is used due to the nature of the region of interest. Estimation of the parameters of the model is performed using the Bayesian point of view via Markov chain Monte Carlo (MCMC) algorithms. We also consider prediction of the days in which exceedances of the threshold might occur at sites where measurements cannot be taken. This is obtained by spatial interpolation using the information provided by the sites where measurements are available. The prediction procedure allows for estimation of the behaviour of the mean function of the non-homogeneous Poisson process associated with those sites. The models considered here are applied to ozone data obtained from the monitoring network of Mexico City. © 2014, Springer Science+Business Media New York. Source

Lopez-Granados E.,Universidad Michoacana de San Nicolas de Hidalgo | Mendoza M.E.,National Autonomous University of Mexico | Gonzalez D.I.,National Autonomous University of Mexico | Gonzalez D.I.,Instituto Nacional Of Ecologia Y Cambio Climatico
Revista Ambiente e Agua | Year: 2013

It is well-established that changes in land cover and land use (LCLU) are relevant to current local and global changes that are directly linked with food security, human health, urbanization, biodiversity, trans-border migration, environmental refuges, water and soil quality, runoff and sedimentation rates, and other processes. This paper examines LCLU change processes within the Cointzio watershed (Central Mexico). The analysis covers a 28-year time period from 1975 to 2003. LCLU changes were deduced from multi-temporal remote sensing analyses (1975, 1986, 1996, 2000 and 2003). Nearly all of the LCLU changes experienced in the Cointzio watershed occurred during the 1986-1996 period. Half of the 665 km2 of the watershed have changed during this period, in what corresponds to a ten-fold increase in the rate of change as compared to the 1975-1986 and 1996-2003 periods. These massive changes are probably related to the Immigration Reform and Control Act (IRCA) of 1986, which limited the transit of undocumented Mexican workers to the United States of America. The methodology applied in this research constitutes a low-cost alternative for evaluating the impact of LCLU change in watersheds. The magnitude of land use change differed during the periods of analyses in the watershed, functional zones and geoforms. The methodological approach applied in this analysis integrates standard procedures to evaluate land cover and land use change in watersheds. Due to the practical value of the results, the data and information generated during the analysis have been made available to local authorities. Source

Espinosa M.D.L.L.,National Autonomous University of Mexico | Martinez A.,National Autonomous University of Mexico | Martinez A.,Instituto Nacional Of Ecologia Y Cambio Climatico | Peralta O.,National Autonomous University of Mexico | Castro T.,National Autonomous University of Mexico
Environmental Chemistry | Year: 2016

Environmental context Dimethylsulfide (DMS), the main biogenic sulfur compound in the atmosphere, is produced by the marine biosphere and plays an important role in the atmospheric sulfur cycle. This study recorded the spatial variability of DMS and dissolved and particulate dimethylsulfoniopropionate (DMSP) in the water column of the southern Gulf of Mexico. The results suggest that the spatial variability of DMS and DMSP is directly related to the hydrodynamics of the study area. Abstract The spatial variability of dimethylsulfide (DMS) and dissolved and particulate dimethylsulfoniopropionate (DMSPd and DMSPp) was recorded in the southern Gulf of Mexico at three different depths (10, 30 and 60m) in January 2013. DMS and DMSP values were recorded through solid-phase microextraction coupled to gas chromatography. Average concentrations of DMS (2.8±1.5nM), DMSPd (1.7±0.9nM) and DMSPp (352±157nM) were significantly correlated with chlorophyll-a concentrations and the depth of the mixed layer. Vertical concentration profiles were similar, indicating a well-mixed water column with a thermocline at a depth of 50-100m. Average DMS sea-to-air flux was 5.0±1.7μmolm-2day-1. The greatest fluxes were recorded at the stations in the western region of the study area, owing to the combined effect of high DMS concentrations (3.7-7.21nM) and a high wind speed (4.4-6.8ms-1). The greatest concentrations were recorded at the stations nearest the coast. The distribution of DMS and DMSP was apparently related to the oceanic hydrodynamics. © CSIRO 2016. Source

Baker C.S.,Oregon State University | Steel D.,Oregon State University | Calambokidis J.,Cascadia Research Collective | Falcone E.,Cascadia Research Collective | And 15 more authors.
Marine Ecology Progress Series | Year: 2013

ABSTRACT: We quantified the relative influence of maternal fidelity to feeding grounds and natal fidelity to breeding grounds on the population structure of humpback whales Megaptera novae - angliae based on an ocean-wide survey of mitochondrial (mt) DNA diversity in the North Pacific. For 2193 biopsy samples collected from whales in 10 feeding regions and 8 breeding regions during the winter and summer of 2004 to 2006, we first used microsatellite genotyping (average, 9.5 loci) to identify replicate samples. From sequences of the mtDNA control region (500 bp) we identified 28 unique haplotypes from 30 variable sites. Haplotype frequencies differed markedly among feeding regions (overall FST = 0.121, FST = 0.178, p > 0.0001), supporting previous evidence of strong maternal fidelity. Haplotype frequencies also differed markedly among breeding regions (overall FST = 0.093, FST = 0.106, p > 0.0001), providing evidence of strong natal fidelity. Although sex-biased dispersal was not evident, differentiation of microsatellite allele frequencies was weak compared to differentiation of mtDNA haplotypes, suggesting male-biased gene flow. Feeding and breeding regions showed significant differences in haplotype frequencies, even for regions known to be strongly connected by patterns of individual migration. Thus, the influence of migratory fidelity seems to operate somewhat independently on feeding and breeding grounds over an evolutionary time scale. This results in a complex population structure and the potential to define multiple units to conserve in either seasonal habitat.© Inter-Research 2013. www.int-res.com. Source

Mugica-Alvarez V.,Metropolitan Autonomous University | Santiago-de la Rosa N.,Metropolitan Autonomous University | Figueroa-Lara J.,Metropolitan Autonomous University | Flores-Rodriguez J.,Metropolitan Autonomous University | And 2 more authors.
Science of the Total Environment | Year: 2015

Sugarcane burning is an agricultural practice implemented to ease farm worker duties; nevertheless, as a consequence, tons of particles are emitted to the atmosphere. Additionally, during harvesting the sugar-mills operate the whole day emitting hundreds of tons of pollutants. Therefore, health risks to neighboring population should be a major governmental concern, leading first to identification and quantification of toxic compounds, such as polycyclic aromatic hydrocarbons (PAHs). In order to establish the magnitude of the problem, four sampling campaigns of PM10 and PM2.5 were carried out in this study, during harvesting and no-harvesting seasons in two municipalities of México, with different climatic and social conditions. Concentrations of PM10, PM2.5, and organic compounds were determined daily, followed by extraction, identification and quantification of the 17 EPA-established PAHs from all samples. The results showed that during harvest, the PM10 mass increased lightly in Chiapas, but approximately twice in Morelos, whereas total PAH concentrations increased twice and six times, respectively. The most abundant PAHs, namely: indene [1,2,3cd] pyrene, benzo[b]fluoranthene, benzo[a]pyrene and dibenzo [a,h] anthracene are composed of 5 or more aromatic rings. Of the total PAHs quantified, 44% to 52% corresponded to carcinogenic compounds, consequently, the overall carcinogenic potential increased twice or three times. Principal component analysis with varimax rotation was applied to source apportionment at each site, suggesting three different sources during harvesting: the combustion process in the sugar mill, sugarcane burning and vehicular emissions. The combustion markers for sugar mill are, BAA, BBF, BKF, BAP, IND and BGP, whereas for sugarcane burning were ANT, PHE, FLT and PYR. The results obtained indicate that processing and burning sugarcane are the main sources of the PAH levels measured, proving that the health risks are boosted during harvesting due to increases of PM and PAHs. © 2015 Elsevier B.V. Source

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