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De La Torre B.H.,Instituto Nacional Of Ecologia Y Cambio Climatico Inecc | Castro G.G.,CICESE | Borrego S.A.,CICESE | Garcia A.G.,National Autonomous University of Mexico | Gomez R.A.,National Autonomous University of Mexico
Hidrobiologica | Year: 2015

Time series of new phytoplankton production (Pnew) off Baja California from 1970 to 2008 computed using statistical models of temperature-nitrate relationship in ten groups of coastal and oceanic stations (Lines 90, 107, 120, 137 and 157) of the CalCOFI-IMECOCAL network, are presented. Pnew was calculated from the ∫-ratio and total primary production (Ptotal). Spatially, the most productive areas of the region were Lines 90, 120 and 157. Pnew of lines 107 and 137 had relatively low values. These two lines marked the border between the Northern and Southern areas of the studied region. Seasonally, Pnew was high in the spring-summer transition, decreased in summer and autumn, and increased in winter. Pnew was related to coastal upwelling index, and we conclude that for an index of less than 200 m3/s/100 m, Pnew increases and its maximum occurs in phase with the coastal upwelling index. For an upwelling index greater than 200 m3/s/100 m Pnew decreases and both series are out of phase. Source

Carabali G.,National Autonomous University of Mexico | Torres-Jardon R.,National Autonomous University of Mexico | Castro T.,National Autonomous University of Mexico | Salcedo D.,National Autonomous University of Mexico | And 11 more authors.
Urban Climate | Year: 2014

Results of atmospheric measurements during Cal-Mex field campaign are presented in this work. Cal-Mex was designed to provide insight into trans-border pollution transport in the Tijuana-San Diego area overlapping the last stage of project Cal-Nex. PM2.5, size distribution, optical properties, ozone and reactive nitrogen species among others, were continuously measured at Parque Morelos (PQM), the supersite for Cal-Mex, located inside the metropolitan area of Tijuana. Although PM and ozone levels at PQM were low during the campaign, we show that besides Tijuana sharing the same air basin with San Diego, it also shares the same synoptic conditions that leads to the occurrence of ozone events in the metropolitan area of Los Angeles. Furthermore, comparisons of ozone, NOy, HNO3, mass absorption efficiency (MAE), aerosol absorption (σabs) and scattering (σsct) coefficients show common features between Cal-Mex PQM and Pasadena at Cal-Tech, one of the Cal-Nex project supersites. Air parcels arriving to PQM from NW (San Diego) exhibit MAE characteristics of aged aerosol. In addition, NOx/NOy ratios are in the transition stage between photochemically young and aged parcels, indicating that, maybe, aged parcels were enriched with more locally recent emissions. © 2014 Elsevier B.V. Source

Martinez-Balleste A.,Instituto Nacional Of Ecologia Y Cambio Climatico Inecc | Mandujano M.C.,National Autonomous University of Mexico
Economic Botany | Year: 2013

The Consequences of Harvesting on Regeneration of a Non-timber Wax Producing Species (Euphorbia antisyphilitica Zucc.) of the Chihuahuan Desert. For two centuries large quantities of non-timber candelilla (Euphorbia antisyphilitica Zucc., Euphorbiaceae) have been harvested from wild populations in northern Mexico. The wax that candelilla produces is used for various purposes by many different types of industries. Although extraction is regulated by the government, lack of ecological information has led to concern for overexploitation and population decreases. In the arid region of Cuatrocienegas, Coahuila, Mexico, we measured growth and reproduction in candelilla populations with variable harvest rates. Interviews were used to determine how harvest criteria and volume relate to plant performance and to learn about current extraction policies. We found the average annual harvest to be high (8,273.02 ± 2,076.09 kg/per person/per year) but the population size to be consistent (9,278 to 73,250 individuals/ha). Initial number of stems and height per plant at first census, time elapsed since last harvest, as well as seasonal changes affected individual plant performance. Relative growth rate (TR) was higher but also more variable among small plants relative to larger plants, making them more vulnerable to harvest effects. TR and fecundity rates are negatively affected when less than two years elapsed between harvests. Nowadays, although fewer local people work in candelilla extraction, those from the lowest socioeconomic brackets depend on it most. The incorporation of the ecological information obtained here into Mexican law will ensure better management of this NTFP resource. Also, improving the techniques of wax extraction and promoting fair trade to increase the price paid to producers could reduce the negative impacts on plant performance and ensure sustainable use of natural populations. © 2013 The New York Botanical Garden. Source

Velasco A.,Instituto Nacional Of Ecologia Y Cambio Climatico Inecc | Arcega-Cabrera F.,National Autonomous University of Mexico | Oceguera-Vargas I.,National Autonomous University of Mexico | Ramirez M.,Instituto Nacional Of Ecologia Y Cambio Climatico Inecc | And 3 more authors.
Environmental Science and Pollution Research | Year: 2016

Within the Global Mercury Observation System (GMOS) project, long-term continuous measurements of total gaseous mercury (TGM) were carried out by a monitoring station located at Celestun, Yucatan, Mexico, a coastal site along the Gulf of Mexico. The measurements covered the period from January 28th to October 17th, 2012. TGM data, at the Celestun site, were obtained using a high-resolution mercury vapor analyzer. TGM data show values from 0.50 to 2.82 ng/m3 with an annual average concentration of 1.047 ± 0.271 ng/m3. Multivariate analyses of TGM and meteorological variables suggest that TGM is correlated with the vertical air mass distribution in the atmosphere, which is influenced by diurnal variations in temperature and relative humidity. Diurnal variation is characterized by higher nighttime mercury concentrations, which might be influenced by convection currents between sea and land. The back trajectory analysis confirmed that local sources do not significantly influence TGM variations. This study shows that TGM monitoring at the Celestun site fulfills GMOS goals for a background site. © 2016 Springer-Verlag Berlin Heidelberg Source

Minguillon M.C.,CSIC - Institute of Environmental Assessment And Water Research | Campos A.A.,Instituto Nacional Of Ecologia Y Cambio Climatico Inecc | Cardenas B.,Instituto Nacional Of Ecologia Y Cambio Climatico Inecc | Blanco S.,Instituto Nacional Of Ecologia Y Cambio Climatico Inecc | And 2 more authors.
Atmospheric Environment | Year: 2014

This work was carried out in the framework of the Cal-Mex project, which focuses on investigating the atmosphere along Mexico-California border region. Sampling was carried out at two sites located in Tijuana urban area: Parque Morelos and Metales y Derivados. PM2.5 and PM10 24h samples were collected every three days from 17th May 2010 to 27th June 2010, and were used for gravimetric and chemical analyses (major and minor elements, inorganic ions, organic and elemental carbon) of PM. A subsequent Positive Matrix Factorization (PMF) analysis was performed.PM2.5 and PM10 average concentrations during Cal-Mex were relatively lower compared to usual annual averages. Trace elements concentrations recorded in the present study were lower than those recorded in Mexico City in 2006, with the exception of Pb at Metales y Derivados, attributed to the influence of a specific industrial source, which also includes As, Cd and Tl. Apart from this industrial source, both urban sites were found to be affected by similar sources with respect to bulk PM. Fine PM (PM2.5) was mainly apportioned by fueloil and biomass combustion and secondary aerosols, and road traffic. Coarse PM (PM2.5-10) was mainly apportioned by a mineral source (sum of road dust resuspension, construction emissions and natural soil) and fresh and aged sea salt. The road traffic was responsible for more than 60% of the fine elemental carbon and almost 40% of the fine organic matter. © 2013 Elsevier Ltd. Source

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