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The Holocene calcareous tufa deposits are located in the north-central sector of the state of Hidalgo, Mexico. These deposits outcrop on the Upper Jurassic Chipoco Formation in the Molango Manganese District. Calcareous tufa deposits correspond to carbonate formations of inactive tufas disconnected from the current hydrological network. To better understand the textural, geochemical, and biological characteristics and environmental conditions during their formation, a detailed study involving field analysis, X-ray diffraction analysis, X-ray fluorescence analysis, and morphometric analysis with light microscopy, and scanning electron microscopy was carried out. Similarly, 14C analysis was undertaken to determine the age of the deposit. On this basis, two biofacies were defined, one with stem structures and the other with Phyto clasts, bryophytes (Plagiomnium cuspidatum), and copepods, limited both at the base and the top by lenticular-shaped erosive surfaces and sigmoidal clinoforms. These bio facies formed in lacustrine and paludal environments, and barrier waterfalls. From a geomorphological point of view, the accumulations of these calcareous tufas originated on slopes and/or at the foot of karstic springs, where the accumulation of material originated from the height of the spring with respect to the bottom of the valley, giving rise to a set of stepped tuffaceous plains with a wedge-shaped profile, colonized by important masses of bryophyte mounds, copepods, and vascular plants. This suggests a swampy environment where sedimentation took place in shallow water accumulations, where there is clear evidence of exposure and pedogenetic modification, indicating wet and dry episodes that translate into seasonal fluctuations in the water table. Six mineral phases were observed including silicates, carbonates and arsenates. The 14C analysis indicates that the plant found in the charcoal sample within the calcareous tufa deposit is of Holocene age. [ABSTRACT FROM AUTHOR]

Charcoal production is an activity that dates back over the years. The objective of the study was to determine the temperature and heating ramp in industrial carbonization processes using different kiln types and to quantify its impact on yield and quality of charcoal from different firewood species. The selection of sites, kiln types, and species investigated was based on those with highest production in Mexico. Brazilian beehive kilns using Arbutus xalapensis, Quercus durifolia, and Quercus sideroxyla species were analyzed; modified Brazilian beehive kilns with Pithecellobium dulce and Tamarindus indica; Argentine half-orange kilns with Quercus magnoliifolia and Q. sideroxyla, industrial metal kilns with Brosimum alicastrum, Vitex gaumeri, Manilkara zapota, and Pouteria unilocularis. The process time, temperature, heating ramp, production yield, and quality of charcoal produced were determined. Data were analyzed in a completely random statistical design. The industrial type kilns showed the highest production yield (>35%), and the Brazilian beehive kilns obtained the longest carbonization time (>240 h). On the other hand, the modified Brazilian beehive kilns obtained the best energetic characteristics (>75% fixed carbon and <16% volatile material). A carbonization process with a slow heating ramp (<1 °C min−1) and temperatures of 500–600 °C can generate a charcoal with export quality. [ABSTRACT FROM AUTHOR]

This paper introduces a methodological framework for assessing the sustainability of solid biofuels in Mexico. The designed framework comprises 13 normalized indicators and two diagnostic studies, covering the economic, social, environmental, and institutional sustainability dimensions, and their intersections. Indicators are normalized using the concept of load capacity of a system, similarly to the planetary boundaries. Thus, the graphical representation of results facilitates their multidimensional analysis. The framework was applied to three case studies: traditional fuelwood in rural households, charcoal for restaurant grilling, and electricity cogeneration from sugarcane bagasse. This was part of an iterative process of testing and refining the framework and simultaneously demonstrating its application in the Mexican bioenergy context. This led to the conclusion that the resulting framework (a) provides a useful, quantitative, and comprehensive overview of both broad and specific sustainability aspects of the assessed system; (b) requires a balance of accessible but also scattered or sensitive data, similarly to most existing frameworks; (c) is highly flexible and applicable to both modern and traditional solid biofuels; and (d) is simple to communicate and interpret for a wide audience. Key directions for improvement of the framework are also discussed. [ABSTRACT FROM AUTHOR]

Firewood and charcoal are used on a daily basis both in rural areas and in cities. This type of energy is produced by one of the most ancient traditional methods, known as coppice, which harvest tree sprouts. There is controversy about its effects on forests: it preserves populations and tree cover of species used, but reduces density, inhibits sexual reproduction and generates genetic erosion. We inquired if it was possible to identify a loss of genetic diversity in oak populations traditionally used for charcoal by the Zongolica Nahuas in Veracruz state, Mexico. We studied populations of Quercus laurina, Quercus calophylla and Quercus rugosa in three different altitudes. Molecular analysis with eight nuclear codominant microsatellites was performed to determine the diversity, structure and gene flow of these species. Results for Q. laurina were Na = 8.458, I = 1.766, Ho = 0.679, polymorphism = 100%, Fis = 0.079, with intraindividual variation of 81.55%. For Q. calophylla: Na = 7.250, I = 1.563, Ho = 0.646, polymorphism = 91.67%, Fis = 0.083, with intraindividual variation of 83.80%. For Q. rugosa: Na = 6.958, I = 1.510, Ho = 0.574, polymorphism = 91.67%, Fis = 0.204, with intraindividual variation of 81.99%; this species shows signals of an early genetic isolation process. Our findings indicate that Quercus genetic diversity for the three species is high and comparable with oak species in Mexico and worldwide. We conclude that at the present, coppice is preserving a historical diversity in adult trees kept alive through sprouting. Nonetheless, problems with coppice systems elsewhere, unregulated harvesting and expansion of pine plantation in the region suggest that further studies, hand in hand with a landscape management approach that improve charcoal and firewood production, may be valuable for Sierra de Zongolica genetic biodiversity conservation. [ABSTRACT FROM AUTHOR]

An integrative methodology, including controlled heating experiments, petrography, taphonomy, systematics of charcoal fragments, solid‐state 13C nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry (DSC), and 14C dating, are used to discriminate in situ (anthropogenic) versus transported charcoal accumulations in the Ancestors Chamber at the Aktun Ha cenote and its potential relationship with the initial settlement of the Yucatán Peninsula in Mexico. Rock heating experiments demonstrated changes in color, weight loss, and recrystallization fabrics under temperatures from 200°C to 900°C. At temperatures of up to 600°C, calcite changed to portlandite. Taphonomic examination of the charcoal revealed that the fragments were not transported by water. Anatomical studies of the charcoal revealed the presence of species similar to modern examples used as fuel. The solid‐state 13C nuclear magnetic resonance (NMR) spectroscopy confirmed different aromatization degrees, and DSC provided information related to the hearth shape and combustion conditions throughout the thermal event. The 14C ages determined on charcoal, 9,200 ± 30 yr. BP (10,490–10,460 and 10,435–10,250 cal BP) and 9,440 ± 30 yr. BP (10,740–10,585 cal BP), are similar to ages previously reported from Aktun Ha and are the oldest determined on charcoal that may have an association with human activity on the Yucatán Peninsula. [ABSTRACT FROM AUTHOR]

Introduction: Knowledge about palynology in the Heliconia genus basically concerns species from Central and South America, while studies of species in the Mexican Neotropic are limited. Objective: To contribute to the palynological knowledge and understand the morphological interrelation of pollen from the Heliconia genus of the Mexican Neotropic, as part of reproductive biology studies that may contribute in future works of genetic improvement. Methods: The study was conducted in nine species (12 accessions) of Heliconia native to Mexico which are found in the Germplasm Bank of the National Institute of Agricultural and Livestock Forestry Research (INIFAP). Floral pollen was collected in anthesis and stored for 24 h in 2 % glutaraldehyde and 50 % ethanol, then washed in 50 % ethanol and dehydrated in 70, 90 and 100 % alcohol for 30 min. The samples were left to dry at the critical point of the CO2, mounted in aluminum cylinders covered with double conductive adhesive carbon tape and analyzed with a layer of approximately 20 nm gold-palladium. Samples were observed in MEB model TOPCON, SM-510. Results: Pollen measures, 50.22 µm to 70.56 µm, is heteropolar and has an euoblate, suboblate or oblate-spheroidal shape. Distal and proximal faces presented different degrees of convexity; both with micro-echinate or micro-verrucate ornamentation. Morphological characteristics, pollen shape, shape of the proximal and distal faces, as well as ornamentation, showed some homogeneity. However, five groups were formed through the analysis of hierarchical grouping (R² = 0.05). Group I present some micro-perforations in the tectum, high density of micro-echinates and high convexity of the proximal face. In contrast to Group I, Group II has their distal face convex with half density of micro-echinates and a plane-subconvex proximal face. Group III is represented by H. latispatha and group IV is represented by H. librata, both groups have small pollen (for the present study). Although, H. latispatha has a verrucae distal face and a plane proximal face, germinating pore that is distinctively protruding, and H. librata has verrucae in both faces. In group V, H. collinsiana has a distinctively protruding germinating pore and a "corrugated circle-shaped" in the proximal face. Among varieties, H. collinsiana is 10 µm higher than H. collinsiana var. velutina in its equatorial plane. Conclusions: Heterogeneity of characteristics allowed pollen groups to be generated; whilst relatively homogeneous characteristics allowed for recognition of species and varieties within the groups. The morphology of the Heliconia species in Mexico confirms the previously described characteristics; however, additional features such as the presence of micropores and the corrugated circle-shaped in the proximal face stand out. [ABSTRACT FROM AUTHOR]

Copyright of Agro Productividad is the property of Colegio de Postgraduados and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work, the content of polycyclic aromatic hydrocarbons (PAHs) in total suspended particles and particulate matter with an aerodynamic diameter ≤ 2.5 µm (PM2.5) was analyzed using gas chromatography–mass spectrometry. In addition, a sequential chemical analysis of C-rich particles was performed through the parallel coupling of micro-Raman spectroscopy and scanning electron microscopy with X-ray scattering detection. Samples were collected at four sites in the Monterrey metropolitan area, Mexico. A total of 13 PAHs were quantified; indeno(1,2,3-cd)pyrene, chrysene, and benzo(a)anthracene were the most abundant. The total PAH concentrations at the four sampling sites ranged from 1.34 to 8.76 μg/m3. The diagnostic relation of the PAHs indicates that these compounds were emitted by the burning of gasoline and diesel and by the burning of charcoal and biomass. The sequential analysis correlated the morphology and the elemental/molecular composition of the C-rich particles, associated with the PAHs, with their possible emission sources. The estimated lifetime excess cancer risk for inhalation was higher than that established by the World Health Organization, which clearly makes this a potential health risk for the population. [ABSTRACT FROM AUTHOR]

Management of conservation conflicts is a challenge of growing relevance for the effectiveness of protected areas worldwide, particularly in the case of socially inclusive areas such as biosphere reserves. For a successful management of the protected area, is critical to consider the social use of natural resources carried out by local populations linked to reserves, especially in socio-ecological contexts facing potential conservation conflicts (i.e., conflicts that have not yet arisen). We addressed the importance of an early detection of potential conflicts through the study of artisanal charcoal production by Yucatec Mayan communities located in the zone of influence of a biosphere reserve in Northwest Yucatan Peninsula, Mexico. Through semi-structured interviews with charcoal producers and in-depth interviews with environmental authorities linked to the reserve, we discuss the advantages associated to early detection of potential conservation conflicts for biosphere reserves' management. [ABSTRACT FROM AUTHOR]

El Chichón volcano in southeastern Mexico (Chiapas) has produced compositionally homogeneous trachyandesite throughout its ca. 372 kyr eruptive history, but crystal-scale heterogeneity reveals a complex interplay between magmas generated and stored at different crustal levels. High-sensitivity ion microprobe 238U-230Th zircon dating from the last two eruptions of El Chichón (1982 and 550 BP) demonstrates that most zircon crystallized between 0 and ca. 40 ka. Few zircon crystals date back to ca. 130 kyr, and none to the Middle Pleistocene phase of eruptions. Trace elements and oxygen isotope variations in zircon indicate fairly stable conditions in the magma chamber between ca. 20 and 130 ka, with average Ti-in-zircon temperatures estimated at 712 °C and δ18O values of +6.6‰. However, excursions to high Ti-in-zircon temperatures and high δ18O values in zircon occurred at ca. 24 ka. These excursions also mark the onset of subsequent progressive changes to occasionally higher Ti-in-zircon temperatures, lower δ18O values, and more primitive magma compositions (e.g., high Eu/Eu*, Zr/Hf and Th/U). Systematic rim-ward decrease in δ18O is recorded by juvenile zircon domains which quasi-continuously crystallized for up to 30 kyr prior to eruption. Textural relationships and O-isotopic variations within single zircon crystals are thus evidence for magma recharge causing initial resorption of xenocrystic zircon, rapid zircon re-saturation driven by local supersaturation, and effective magma mixing with sediment-contaminated high-δ18O melts from a boundary layer at the contact of the magma reservoir to country rock. Initial thermal and compositional defrosting of an intermediate boundary layer and its crystal cargo may have been rapid due to the brief duration of high-temperature recharge events, as evidenced by the preservation of zircon xenocrysts. The delay of at least 12 kyr between major recharge episodes recorded by zircon and the onset of Holocene eruptions at brief recurrence intervals suggests that frequent eruptions only started when trachybasaltic magma recharge continued or intensified during the Holocene. • Correlative high-resolution 230Th-238U, δ18O, and trace element data for zircon from El Chichón 1982 and 550 BP eruptions. • Most zircon crystallized since ca. 40 kyr on average with δ18O of ~6.6‰ and at ~712 °C. • Rimward δ18O decreases consistent with assimilation following magma recharge and mixing. • Higher zircon temperatures and δ18O at 24 ka mark reservoir heating which may have led to frequent Holocene eruptions. • Since ca. 24 ka zircon records more primitive and hotter magma conditions consistent with heating and rejuvenation. [ABSTRACT FROM AUTHOR]

Here, we report on an incomplete human skeleton, soot patches related to anthropogenic fireplaces, and cut marks on the mandible of an extinct peccary, from the submerged Muknal cave southwest of Tulum on the Mexican Yucatán peninsula. The human individual, here named ‘Muknal Grandfather’, was identified as a male based on cranial parameters. The age at the time of death was estimated to be between 40 and 45 years. We propose that the human bones have been brought to the cave during the latest Pleistocene or early Holocene, but not later than 8600 14C yr BP (ca. 9600 cal BP), as a secondary burial of a partial skeleton. The peccary mandible was placed close to the burial site, possibly as part of the same ritual. The Muknal cave therefore served as a place for funeral rituals. [ABSTRACT FROM AUTHOR]

ABSTRACT: Numerous charcoal accumulations discovered in the submerged Chan Hol cave near Tulum, Quintana Roo, Mexico, have been 14C‐dated revealing ages between 8110 ± 28 14C a BP (9122–8999 cal a BP) and 7177 ± 27 14C a BP (8027–7951 cal a BP). These charcoal concentrations, interpreted here as ancient illumination sites, provide strong evidence that the Chan Hol cave was dry and accessible during that time interval. Humans used the cave for at least 1200 years during the early and middle Holocene, before access was successively interrupted by global sea level rise and flooding of the cave system. Our data thus narrow the gap between an early settlement in the Tulum area reaching from the late Pleistocene (∼13 000 a) to middle Holocene (e.g. 7177 14C a BP), and the Maya Formative period at approximately 3000 a bp. Yet, no evidence has been presented to date for human settlement during the ∼4000‐year interval between 7000 and 3000 a. This is remarkable as settlement in other areas of south‐eastern Mexico (e.g. Chiapas, Tabasco) and in Guatemala was apparently continuous. [ABSTRACT FROM AUTHOR]

Energy production is one the most important topics worldwide. Native forests are good contributors for the production of bioenergy. However, in environmentally difficult conditions, such as arid and semi-arid lands, native trees species produce low woody volume. Alternatives of raw sources from forest plantations of fast growing species, such as eucalyptus, should be analyzed. Firewood production and physical properties ofEucalyptus camaldulensisandE. microthecaon semi-arid land were determined. Yield and quality of charcoal produced at 450, 650, 850, and 1050°C from sapwood and hardwood under laboratory conditions were analyzed. Data were analyzed as random blokes, and ANOVA tests were developed to determine differences in charcoal yield and quality between temperatures and anatomical sections on both species.Eucalyptus microthecaproduced higher firewood volume (71.10 m3ha−1) thanE. camaldulensis(19.78 m3ha−1). Green (1.0 to 1.3 g cm−3), oven-dry (0.8 to 1.1 g cm−3), and basic densities (0.6 to 0.9 g cm−3) showed statistical differences between species and wood type. Statistical differences (p< 0.0001) in the charcoal yield of both species were found;E. microthecaheartwood produced the highest charcoal yield (44%) at a temperature of 450°C. Correlation coefficient between basic density and charcoal yield at all temperatures was high (r= 0.36 to 0.72). Values of moisture content, ash, volatile materials, fixed carbon, and calorific value meet the international standard requirements. [ABSTRACT FROM AUTHOR]

During the 1940s, urban Mexico began to shift from fuelwood to petroleum for its household energy needs. I trace this energy transition in Mexico City, interweaving histories of production and consumption, city and hinterland. The household energy transition highlights a series of overlapping policy shifts in 1940s Mexico: a retreat from rural social justice and the support of urban industrialization that pivoted on the redistribution of national oil wealth. By underscoring the role of political power in energy transitions, I also contribute to the larger field of energy history, which has prioritized energy regimes in the North Atlantic. [ABSTRACT FROM AUTHOR]

Abstract: Fuelwood and charcoal are fundamental fuel sources for the residential sector in Mexico. A Business-As-Usual (BAU) projection by means of a spatially-explicit approach was developed to assess national fuelwood and charcoal consumption for the period 2010 to 2030. The model was calibrated for 1990–2000 and 2010 projections were validated against official census data for the same year. For 2010, we estimated that fuelwood and charcoal accounted for 48% of total residential energy demand. The projection of fuelwood consumption declined slightly from 19.4 Mt (dry matter) or 310 PJ in 2010 to 18.4 Mt or 294 PJ by 2030. An important future growth of mixed fuelwood–LPG users is expected pointing out that fuel stacking rather than fuel switching out of fuelwood would prevail. Charcoal consumption increased from 3.8 Mt (dried wood equivalent) or 61 PJ to 4.7 Mt or 75 PJ during the same period. A relevant outcome of the spatial assessment was the uncovering of large variations in fuelwood and charcoal use trends among spatial units (municipalities), hidden by the national aggregated trends. This opens up the opportunity to analyze regional variability to identify priority areas regarding fuelwood and charcoal use. [Copyright &y& Elsevier]

Charcoal particles vary in size and form, but they can preserve morphological characteristics used to infer the type of vegetation being burnt. To deduce potential fuel and fire type, we reconstructed local fire activity analyzing macrocharcoal morphologies and pollen data of the sediment core CHA08-V from Lake Chalco from the sub-stage MIS 5a to MIS 3, with CHAR data and Z-Score analysis. We identified the following fuel types: i) wood , characterized by blocky and quadrilateral morphologies with solid, foliated or striated surface textures; ii) grass , represented by rectangular-porous and rectangular-latticed morphologies; and iii) herbs , characterized by long-thin filaments and polygonal porous particles. Arboreal pollen components were associated to wood morphotypes whereas non-arboreal pollen related to herbs and grass morphotypes, indicating that variation in vegetation composition was important regulating factor determining fire types in the Basin of Mexico. This study provides the first long-term record of charcoal morphotypes for Mexico region to emphasize the importance of charcoal morphotypes analyses to complement paleoenvironmental interpretation of past fire regimes. • The first long-term record of charcoal morphotypes in Mexico to determine the fuel combusted. • Identification of twelve charcoal morphotypes associated with the burning of wood, leaves, grasses and herbaceous material. • Mixed morphotypes associated with surface fires occasionally transitioning to crown fires in the Basin of Mexico. [ABSTRACT FROM AUTHOR]

Abstract: We present a cost-effective statistical approach that integrates satellite imagery, environmental variables and ground inventory data to map the spatial distribution of aboveground woody biomass suitable for charcoal making. The study was conducted in the Cuitzeo basin located in central Mexico, where charcoal is produced from oak forests covering approximately 10% of the total area (4033km2). Diameters of trees and sprouts in 78 plots of 0.2ha each was measured. Allometric equations previously developed locally that only require tree diameters were employed to estimate the amount of woody biomass suitable for charcoal making i.e. the amount of wood that is loaded into the kilns. The performance of two statistical techniques for the interpolation of field data was assessed by cross-validation; these techniques were linear regression and regression-kriging, the second taking into account the spatial autocorrelation of data. Spectral bands, vegetation indices, texture measurements and variables derived from a Digital Elevation Model were examined as explanatory variables. Accounting for spatial autocorrelation (regression-kriging) improved the model''s R 2 from 0.61 to 0.69, representing a relative error reduction of 11.3% (from 11.01 to 9.77t ha−1 of wood suitable for charcoal). The available stock was compared to current estimates of charcoal demand in the Cuitzeo basin and insights were given on how this information can be used to estimate the annual sustainable production potential of oak in order to account for supply–demand balances. [Copyright &y& Elsevier]

A two-year project of survey, surface collection, and excavation on the hill of Cerro Danush within the site of Dainzxi-Macuilxóchitl in Oaxaca, Mexico, was focused on identifying and characterizing the Late Classic (A.D. 600-850/900) and Early Postclassic (AX). 850/900-1300) components of the site, which coincide with the political fragmentation and reorganization of complex society within the Valley of Oaxaca. The transition in sociopolitical organization from the Classic to Postclassic has been the subject of several research projects, but few, if any, have clearly identified an Early Postclassic settlement. A radiocarbon analysis of charcoal samples collected during the excavation of a residential complex on Cerro Danush reveals its most recent period of occupation to be between A.D. WOO and 1300, placing it firmly within the Early Postclassic. The excavation data are contextualized with data from the surface collection, illuminating patterns of Late Classic political fragmentation and Early Postclassic household resilience. Since Dainzú-Macuilxóchitl emerged in the Late Postclassic (A.D. 1300-1521) as a powerful city-state, exploring its Early Postclassic component contributes to the study of how societies reorganize on a local level after the collapse of centralized authority, such as the Classic period Monte Albán state. [ABSTRACT FROM AUTHOR]

Abstract: Sustainable production systems for woodfuels in developing countries require basic information on tree productivity, and particularly on their coppicing productivity under current forms of management. We report biomass equations and sprouting productivity of two oak species (Quercus castanea and Quercus laeta) subject to traditional forms of woodfuel harvesting at Cuitzeo basin in central Mexico. Biomass components analyzed were total aboveground biomass (AGB), woody biomass suitable for charcoal making (WSC) and residues (foliage and small branches). The estimation of total aboveground biomass (AGB) and woody biomass suitable for charcoal making (WSC) of individual trees, when expressed as a function of DBH in the form y = a(DBH) b , resulted in values of pseudo-R2 higher than 92%. The Mean Annual Increment (MAI) of both species increased with site age. Significant differences were found in regrowth rates of these species. Maximum charcoal potential productivity in kg ha−1 year−1 is achieved between 30 and 50 years depending on the decay rate of coppicing-shoot density over time. This roughly doubles current harvest cycles of 10–15 years followed by charcoalers. Oaks in developing countries have the potential to be used as a mid-term rotation coppice species for energy purposes. We argue that the results shown in this study are an important input for designing appropriate management strategies for traditional oak charcoal production in developing countries. [Copyright &y& Elsevier]

Abstract: Temperate forest dominated by Quercus L. spp. cover large parts of central Mexico and rural communities depend on these forests for wood and charcoal. The impact of charcoal production on enzymatic and metabolic profiles of soil microorganisms in the 0–15cm layer were investigated during the dry and rainy season. A KILN site, used for charcoal production, is prepared by clearing all vegetation, removing litter and soil from the surrounding area. The wood is piled up in the centre of the KILN site and covered with litter and soil. Incomplete combustion with a minimum of flame production is maintained for 12 days. The charcoal production had a negative effect on the functional diversity and enzymatic microbial activity in soil. Community level physiological profiles (CLPP) analyses showed a lower average well color development, substrate richness, and functional diversity in soil at the KILN sites compared to the undisturbed soil. Cluster analysis dendrograms and canonical discriminant analysis of CLPP indicated that substrate utilization at the KILN sites was different from undisturbed forest soil. The activity of six enzymes, i.e. CM-cellulase, β-glucosidase, N-acetyl-β-d-glucosaminidase, nitrate reductase, urease and proteinase, decreased from 44% to 90% at the KILN sites compared to the undisturbed forest soil. It was found that charcoal production at a KILN site showed lower functional diversity and enzymatic microbial activity than in the surrounding forest soil as a result of loss of litter and organic matter and changes in microclimatic conditions. [Copyright &y& Elsevier]

Swidden agriculture in Mesoamerica is commonly associated with the hot and humid lowlands and with small isolated communities. Charcoal-rich sediments discovered in Tlaxcala, however, suggest that it was practiced in the cold highlands in the Formative and Classic periods. The headwaters of the Xilomantla drainage incised a nine-meter deep channel shortly before 200 b.c., in response to increased runoff from slopes degraded by agriculture. It was filled back within a few hundred years with sands and muds containing recurrent laminae of charred plant matter that reflect the annual burning of secondary scrub in fallowed fields. A gully in the La Ladera drainage received high inputs of charcoal from the surroundings of a nearby settlement between ca. a.d. 400 and 900. The farming practices inferred from these deposits have no exact ethnographic analog. They inflicted lasting environmental damage, but were upheld for several centuries despite changes in settlement patterns. [ABSTRACT FROM PUBLISHER]

Paleoecological archives from three paleomeander sites and one archeological feature located in the lower Río Verde Valley, Oaxaca, Mexico, are used to develop a spatial understanding of the patterns of prehistoric agricultural land use over the last ~3000 years. Multiproxy paleoecological data at each site (i.e. magnetic susceptibility, micro- and macroscopic charcoal, pollen and stable carbon isotopes) provide a history of land use. By examining the spatial differences in agricultural indicators at all the sites through time, augmented with our understanding of changes in demography and settlement patterns determined through the archeological record, we are able to reconstruct the complex human/land interactions in the western portion of the valley. [ABSTRACT FROM AUTHOR]

Sediment cores from the San Bernardino Ciénega near Douglas, Arizona and Agua Prieta, Sonora, Mexico were examined to reconstruct the fire history of this region and inform restoration efforts. A ∼8000 year vegetation and fire history record was reconstructed from these sediments using fossil pollen and charcoal. Results from the fire reconstruction show an increase in fire activity coincident with the onset of ENSO, and an increase in fire frequency during the Medieval Climate Anomaly. Preliminary pollen data show taxa that reflect winter-dominated precipitation (Ephedra and Artemisia) correspond to times of greater fire activity. These fire data shed light on the long-term history of fire in desert environments that may be helpful in understanding what fire regimes may be expected with global warming and also how to best incorporate fire into management plans. [Copyright &y& Elsevier]

Abstract: Temperate forests dominated by Quercus spp. cover large parts of Central Mexico and rural communities depend on these forests for wood and charcoal. The impacts of charcoal production on selected chemical properties including C and N dynamics, and populations of ammonifiers, nitrifiers and denitrifiers were investigated on surface soils (0–15cm) collected during the dry and rainy season of these forests. Organic C was halved in soil at the kiln sites compared to undisturbed forest soil. Concentrations of exchangeable Ca2+, K+ and Mg2+ increased >1.6 times at kiln sites and pH increased from 4.5 in undisturbed soil to 7.0 at kiln sites. The kiln sites had 1.3 times and 2.4 times lower microbial biomass C and N, respectively, than undisturbed forest sites during the rainy season. Although the effect of charcoal production on NH4 +, NO2 − and NO3 − concentrations was small, the ammonifying, nitrifying and denitrifiers were 16 times lower at the kiln sites than in the undisturbed forest soil. This research found that the charcoal production had a negative effect on the cultivable microorganisms involved in N cycling and the soil microbial biomass C and N compared to undisturbed forest soil. Differences in inorganic N dynamics were more affected by seasonality, i.e. precipitation, than by charcoal production. [Copyright &y& Elsevier]

Abstract  A 3.4 m core was obtained for paleoecological analysis from Naja Lake in the Lacandon region of southeastern Mexico. This is the first study of the Lacandon area aimed at reconstructing late Holocene environmental history. The basal section of the core yielded an AMS date of 2020 14C years b.p. The Naja pollen record shows that the lower montane rain forest characterized by Moraceae, Mimosoideae, Leguminosae and Combretaceae/Melastomataceae, coexisted with a pine-oak forest throughout the late Holocene. No Zea mays pollen was found during routine pollen counts, but the presence of both secondary pollen taxa and abundant charcoal particles suggest some degree of regional human impact. A marked increase in Pinus pollen, together with a reduction in lower montane rain forest taxa, is interpreted as evidence for a strong, protracted drought from 1260 to 730 14C years b.p. [ABSTRACT FROM AUTHOR]

Scrubby mesquite trees infest large regions of the Mexican-American borderland. In this same area, demand for mesquite wood and charcoal places pressure on mature trees. This paper examines consumption of this biomass fuel on both sides of the Sonora-Arizona border and the demands that consumption places on the environment in Northern Sonora. In Sonora multi-stemmed trees provide wood for heating homes and cooking stoves upon which coffee pots bubble and large, flat tortillas cook to perfection. At the opposite extreme, large, mature trees fall to the chainsaw and charcoal pits to provide North American restaurants and backyard cooks with a chic and flavorful grilling fuel. This research in northern Sonora reveals details of this hidden industry. This study provides important information and discussion about biomass use in a dry region. Studies like this, which consider direct use of biomass resources, are important, especially in fight of present and future industrial, population, and urban growth along the border, which all place additional pressure on natural resources. [ABSTRACT FROM AUTHOR]

Copyright of Historia Mexicana is the property of El Colegio de Mexico AC and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article documents the impact of a multi-million-dollar trade of wood and charcoal on the dry borderland region of northern Sonora, Mexico. It discusses the history of the use of mesquite in the borderlands which served as a primary source for food, fuel, shelter, medicine and weapons. It details how borderland residents used biomass for various purposes including firewood for survival. Demand for mesquite charcoal in the U.S. leads to an elaborate system of manufacture and marketing.

Abstract: Using charcoal detectors and electrets, radon concentrations were measured at 12 different locations in Mexico, homes in particular, throughout Chihuahua State. While these measurements were short-term, long-term measurements were also conducted around Chihuahua and Aldama cities using LR-115 II type detectors. In addition, LR-115 II type detectors were deployed for comparative purposes between Ciudad Juarez (Mexico) and El Paso (Texas). Significant average radon values were obtained in Aldama and Parral at 225 and 173 Becquerel per cubic meter (Bq m−3), respectively. Over 30% of the homes sampled in Aldama, Cuauhtemoc, Parral and Chihuahua had radon concentrations greater than 148 Bq m−3. [Copyright &y& Elsevier]

The use of radiocarbon dating to analyze mortar and charcoal inclusions within mortar or plaster is a useful way to date the construction of architecture, particularly when options for other chronometric methods are limited. In the Yalahau region of northern Quintana Roo, Mexico, members of the Yalahau Regional Human Ecology Project have faced challenges in dating buildings made of large blocks of stone in the Megalithic architectural style. The Megalithic style poses serious problems for any analysis, as excavating into structures with stones weighing several tons can be dangerous, expensive, and time consuming. Additionally, there are no associated sculptures, texts with dates, or other traditionally accessible chronological markers. These factors have resulted in a reliance on a ceramic chronology despite the uncertainty of the dating of many ceramic types in this region, as well as the questionable contextual associations between recovered ceramics and architectural construction phases. Megalithic-style structures at the ancient Maya site of El Naranjal have residual mortar with charcoal inclusions left behind during the mortar-making processes that can be extracted and dated with AMS 14C methods. Several samples of mortar and charcoal were obtained from structures 1 and 10 from exposed exterior walls and an interior vault. The resulting dates confirm the date for the construction based on ceramics excavated from the same site. [ABSTRACT FROM AUTHOR]

The present research work shows the effect on the carbonation of Portland cement-based mortars (PC) with the addition of green materials, specifically residues from two groups: agricultural and industrial wastes, and minerals and fibres. These materials have the purpose of helping with the waste disposal, recycling, and improving the durability of concrete structures. The specimens used for the research were elaborated with CPC 30R RS, according to the Mexican standard NMX-C-414, which is equivalent to the international ASTM C150. The aggregates were taken from the rivers Lerma and Huajumbaro, in the State of Michoacan, Mexico, and the water/cement relation was 1:1 in weight. The carbonation analyses were performed with cylinder specimens in an accelerated carbonation test chamber with conditions of 65 +/− 5% of humidity and 25 +/− 2 °C temperature. The results showed that depending on the PC substitutions, the carbonation front advance of the specimens can increase or decrease. It is highlighted that the charcoal ashes, blast-furnace slags, and natural perlite helped to reduce the carbonation advance compared to the control samples, consequently, they contributed to the durability of concrete structures. Conversely, the sugarcane bagasse ash, brick manufacturing ash, bottom ash, coal, expanded perlite, metakaolin, and opuntia ficus-indica dehydrated fibres additions increased the velocity of carbonation front, helping with the sequestration of greenhouse gases, such as CO2, and reducing environmental pollution. [ABSTRACT FROM AUTHOR]

Charcoal rot is an emerging disease for peanut crops caused by the fungus Macrophomina phaseolina. In Mexico, peanut crop represents an important productive activity for various rural areas; however, charcoal rot affects producers economically. The objectives of this research were: (a) to identify and morphologically characterize the strain "PUE 4.0" associated with charcoal rot of peanut crops from Buenavista de Benito Juárez, belonging to the municipality of Chietla in Puebla, Mexico; (b) determine the in vitro and in vivo antagonist activity of five Trichoderma species on M. phaseolina, and (c) determine the effect of the incidence of the disease on peanut production in the field. Vegetable tissue samples were collected from peanut crops in Puebla, Mexico with the presence of symptoms of charcoal rot at the stem and root level. The "PUE 4.0" strain presented 100% identity with M. phaseolina, the cause of charcoal rot in peanut crops from Buenavista de Benito Juárez. T. koningiopsis (T-K11) showed the highest development rate, the best growth speed, and the highest percentage of radial growth inhibition (PIRG) over M. phaseolina (71.11%) under in vitro conditions, in addition, T. koningiopsis (T-K11) showed higher production (1.60 ± 0.01 t/ha−1) and lower incidence of charcoal rot under field conditions. The lowest production with the highest incidence of the disease occurred in plants inoculated only with M. phaseolina (0.67 ± 0.01 t/ha−1) where elongated reddish-brown lesions were observed that covered 40% of the total surface of the main root. [ABSTRACT FROM AUTHOR]

We present pollen and microscopic charcoal evidence from securely dated lake sediments, located in the Tuxtlas region of Veracruz, Mexico. Two periods of agricultural activity are recognized. The earliest phase reflects a low level of forest clearance and agriculture. The data provides a minimum date of 4830 cal. BP for the introduction of maize agriculture to the region. The second phase indicates intensive and prolonged human activity within the tropical forest. Commencing approximately 2600 years ago and ending a thousand years later, this episode reflects Pre-Classic to Middle Classic agricultural intensification. Coincident with this phase, we find evidence for drier climatic conditions. Subsequent to each episode of disturbance the forest regenerated within approximately 300 years. [ABSTRACT FROM AUTHOR]

In this work, the particulate matter (PM) from three different monitoring stations in the Monterrey Metropolitan Area in Mexico were investigated for their compositional, morphological, and optical properties. The main aim of the research was to decipher the different sources of the particles. The methodology involved the ex situ sequential analysis of individual particles by three analytical techniques: scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), polarized light microscopy (PLM), and micro-Raman spectroscopy (MRS). The microanalysis was performed on samples of total suspended particles. Different morphologies were observed for particles rich in the same element, including prismatic, spherical, spheroidal, and irregular morphologies. The sequential microanalysis by SEM-EDS/PLM/MRS revealed that Fe-rich particles with spherical and irregular morphologies were derived from anthopogenic sources, such as emissions from the metallurgical industry and the wear of automobile parts, respectively. In contrast, Fe-rich particles with prismatic morphologies were associated with natural sources. In relation to carbon (C), the methodology was able to distinguish between the C-rich particles that came from different anthopogenic sources—such as the burning of fossil fuels, biomass, or charcoal—and the metallurgical industry. The optical properties of the Si-rich particles depended, to a greater extent, on their chemical composition than on their morphology, which made it possible to quickly and accurately differentiate aluminosilicates from quartz. The methodology demonstrated in this study was useful for performing the speciation of the particles rich in different elements. This differentiation helped to assign their possible emission sources. [ABSTRACT FROM AUTHOR]

In the present study, the characteristics of leachate generated from dumpsite called 'Zapote' located in southern region of Tamaulipas, Mexico were evaluated. The adsorption of non-biodegradable organic matter measured as chemical oxygen demand (COD), color and heavy metals from leachate on activated carbon (AC) prepared in acid media from Guadua amplexifolia bamboo has been studied. In addition, the computation of kinetic parameters during the adsorption process as well as the most probable mechanisms was determined. The ACs were analyzed by using scanning electron microscopy and Fourier transform infrared spectroscopy. The experimental data showed that the ACs removed up to 81.4% of color and reduced COD up to 91.6% after 9 h of reaction at 60°C. For heavy metals, the maximum adsorption uptake was achieved at pH = 8.0 within 20 min with removal percentages of 87.0% (Pb(II)), 43.0% (Cu(II)) and 30.5% (Ni(II)). A pseudo-second-order model explained the adsorption kinetics most effectively for Pb, Ni and Cu, while a pseudo-first order was found for Zn. The AC synthesized from the G. amplexifolia species could be potentially used as an effective adsorbent in the reduction of COD, and removal of color and heavy metals.

Archaeological research in the Gulf Coast of Tabasco reveals the earliest record of maize cultivation in Mexico. The first farmers settled along beach ridges and lagoons of the Grijalva River delta. Pollen from cultivated Zea appears with evidence of forest clearing about 5100 calendar years B.C. (yr B.C.) [6200 (14)C years before the present (yr B.P.)]. Large Zea sp. pollen, typical of domesticated maize (Zea mays), appears about 5000 calendar yr B.C. (6000 yr B.P.). A Manihot sp. pollen grain dated to 4600 calendar yr B.C. (5800 yr B.P.) may be from domesticated manioc. About 2500 calendar yr B.C. (4000 yr B.P.), domesticated sunflower seeds and cotton pollen appear as farming expanded.