Urban parks in the cities play a crucial role in promoting sustainability and enhancing the quali... more Urban parks in the cities play a crucial role in promoting sustainability and enhancing the quality of life for their residents. In an urban ecosystem, we have to make some trade-offs between the cultural and ecological ecosystem services. The soil ecosystem services depend on specific ecological conditions, therefore information on their potential to provide fundamental services is a basic requirement when constructions are planned in green areas. Mexico City, like other cities in Latin America, has very few green areas that are constantly threatened by sealing. Based on morpho-pedological landscapes (MpL) we quantify the soil carbon sequestration (SOC) and infiltration capacity in Chapultepec park. Among the 12 MpL we found the highest content of SOC in hillslopes with mixed tree vegetation and Phaeozem and the lowest in grass-dominant plain with Technosols and Leptosols. However, the SOC retention decreased by 40-50% because of sealing surfaces. For each MpL, the value of the soil saturated hydraulic conductivity calculated from pedotransfer functions (Ksc) was markedly lower than the Ksm measured with the double ring infiltrometer. In all MpL, both Ksc and Ksm were always higher than the reported maximum rainfall intensity. In the MpLs with more sealing, the runoff reaches more than 40% of the precipitated water. Based on these results, it is recommended to implement different actions such as allowing the leaves on the soils, the de-sealing of obsolete infrastructure, as well as locating the new constructions on Technosols and Leptosols to maintain Chapultepec park as a SOC sink with infiltration potential.
... through the incineration of plant residues after agricultural burning are poorly studied, but... more ... through the incineration of plant residues after agricultural burning are poorly studied, but their contribution to the overall balance of HCs in the atmosphere is suspected to be significant (Fernandez et al., 20035. Fernandez, MB and ... Ortiz, PMA, Siebe, C. and Cram, S. 2005. ...
Trace metal species in the water column of a canal system forming a wetland filled with wastewate... more Trace metal species in the water column of a canal system forming a wetland filled with wastewater were analyzed to determine their correlation with metal accumulation in the gills of locally fished Oreochromis niloticus. The metal concentrations in the suspended particles and water dissolved were analyzed. The metal species were calculated using Windermere Humic Aqueous Model version VII showing that the high organic matter and major cation contents were important parameters. Also, the free ion metal concentration was expected to correlate with the organic matter aromaticity; however, organic compounds other than humic susbtances seem to be complexing the metals in the system. Additionally, no clear correlation could be found between metal accumulation in gills and any of the dissolved metal species. Nonetheless, certain trends could be seen between the calculated metal species and metal accumulation in the tilapia from the suspended particles.
Urban agriculture plays an important role in supplying produces to big cities; however, the quali... more Urban agriculture plays an important role in supplying produces to big cities; however, the quality of water used for irrigation can hinder this activity. Hence, the purpose of this study was to evaluate metal inputs, as well as their transfer and translocation factors, in lettuce (Lactuca sativa L.) crops cultivated in an urban plot. The research was conducted during the dry and rainy seasons. In the former, crops were irrigated with treated wastewater, whereas during the latter, crops were maintained just with rainwater. Composite samples for soils and plants were collected from the same plot during two crop cycles in 2013. Some edaphic variables were measured. Total metal concentration was determined, for both, soils and lettuce plants (leaves and roots). Water soluble and exchangeable soil metal fractions were also analyzed. A multivariate analysis of variance was performed to test for differences between seasons, among the variables analyzed. There were significant differences in edaphic characteristics between seasons. However, there was no difference in total metal content, except for Mn. Concentration of soluble metals was lower than exchangeable metal concentration, for both seasons. There was no correlation in total metal concentration between soils and plants. Transfer factor values were higher for Cd, Mn and Zn for the dry season, while for Cu, Fe and Pb were higher during the rainy season, as well as the translocation factors for all metals. Soil characteristics, together with transfer and translocation factors, showed temporal variations, leading to different metal concentrations in the edible lettuce tissues between the two analyzed crop cycles. The incorporation of metals is particular for each site, season and crop management type. Our results indicate that the metal concentration in lettuce tissues places no harm to human health. However, management strategies for urban agriculture must consider specific studies for each site.
Dehydrogenase activity (DHA) in soils contaminated by arsenic-bearing tailings was correlated wit... more Dehydrogenase activity (DHA) in soils contaminated by arsenic-bearing tailings was correlated with total arsenic and total water-soluble arsenic (As(III)+As(V)) to evaluate the impact of tailings dispersion on the oxidative capacity of soil microorganisms. Georeferenced surface soil samples (0-10 cm depth) were collected at different distances from a tailings dam. In the samples farthest from the dam, all water-soluble arsenic (avg. 0.6+/-0.1 mg kg(-1)) was As(V). The highest concentration of water-soluble As(III)+As(V) (>1.9 mg kg(-1)) was found where As(III) was present. DHA averaged 438.9+/-79.3 microg INTF g(-1) h(-1) at the greatest distance from the dam and decreased to 92.3+/-27.1 microg INTF g(-1) h(-1) with decreasing distance from the dam. Pearson correlation coefficient between DHA and samples containing water-soluble As(V) (r=-0.87) was greater than that between DHA and total water-soluble arsenic (r=-0.57). The correlation between DHA and soluble arsenic containing both As(V) and As(III) was not significant (r=0.24). In soils with detectable As(III) concentrations where wet conditions prevail (i.e., reducing conditions), there is an abiotic response in addition to a biotic one. The correlation between DHA and total water-soluble As(III)+ As(V) was higher (r=-0.79) when the abiotic response was excluded. Our study demonstrated the importance of distinguishing between total and available fraction and its species and the need to evaluate biological functions in addition to purely geochemical analyses. DHA bioassay combined with other microbial properties offers a good tool for evaluating soil microbial activity and status and is a suitable indicator of the oxidative capacity of soil microorganisms affected by tailings in an oxidizing environment; however, under reducing conditions, abiotic responses must also be studied.
The conservation of geosites in a region can foster its sustainability and develop geotourism. Th... more The conservation of geosites in a region can foster its sustainability and develop geotourism. These geosites provide geoeducation, raise people's awareness on natural hazards and increase their resilience. Low-income cities located in tectonically active areas combine high geohazards with high vulnerability and low sustainability. Geosites in these cities should be a tool to decrease people's vulnerability and foster sustainable development. Mexico City is an ideal case study for its environmental and social issues and its setting in an active 2 continental volcanic arc. The 1,700 yrs-old Xitle volcano, located in the city's SW corner, is a small scoria cone that erupted once, feeding an extensive lava field on which >600,000 people now live. The lavas are very well exposed due to thin soils and extensive quarrying. The Xitle lavas covered the first urban center in the Mexico basin, except for the main pyramid that has become a major archeological site. The cone and lavas have significant geodiversity, sustaining a unique and biodiverse ecosystem. The country's largest university preserves the lavas in an ecological reserve. We describe four exceptional geosites, assess their values, and discuss their relevance for addressing issues such as nature preservation, environmental sustainability, social inequalities, and natural hazards. The Xitle volcano provides a wide range of benefits for the city that are nonetheless unknown to its inhabitants. We describe ongoing initiatives to disseminate such information, such as the Geopedregal site, and propose ways that this heritage could be further protected and used by the city in a sustainable way.
Environmental Monitoring and Assessment, Jun 18, 2008
This study evaluated the spatial and temporal distribution of metals in the coral reef system Cay... more This study evaluated the spatial and temporal distribution of metals in the coral reef system Cayos Arcas and Triangulos in the Campeche Bank region, off the Yucatan peninsula in Mexico. No information has been generated before for the incorporation of natural and non-natural occurring metals, some of which are possibly endowed by the oil marine station Cayo Arcas. The multivariate exploratory study of the metals on the coral skeletons, showed the formation of two distinct groups. The metals that have the highest influence on the differentiation of the groups are the metals that are natural constituents of the coral skeletons, in particular Sr can explain much of the differences between the groups, and to a much lesser extent are the metals that could be indicators of pollution. This differentiation suggests that, in our case, the environment around the corals has a higher impact than the non-naturally occurring metals (and possible indicators of pollution). The two groups formed corresponded to: the coral cores influenced by open sea variables and the coral cores in the inner part of the keys which is less exposed to open sea variables. A chronological study was made to two samples that had the longest coral section and were situated in two clearly distinctive zones: an exposed surface subjected to high wave forces and another that was less exposed. Ni and Zn show an accumulation trend in both coral samples, while Ba showed an increase in incorporation around 1980 when the Cayo Arcas oil marine station was constructed.
<p>Geological elements in cities are usually damaged and invisible to their inhabitants, de... more <p>Geological elements in cities are usually damaged and invisible to their inhabitants, despite the wide range of benefits they provide to them. In particular, they offer them an opportunity to learn about their geological setting (= sense of place) and be aware of associated risks (= sense of risk). Such geoheritage comes in different forms that ought to be identified and described precisely in order to be preserved and used. The gigantic capital city of Mexico is settled in a paleolake basin embedded in&#160;a diverse volcanic landscape. City inhabitants face numerous hazards (floods, landslides, debris flows, subsidence, earthquakes, drought, fires) that create high risks with combined natural&#160;and&#160;anthropogenic&#160;causes due to uncontrolled city growth. The&#160;geoheritage of the city is mostly formed by monogenetic (one-event) volcanoes&#160;that are an important&#160;resource for geoconservation and geoeducation. We present two case studies that were investigated by students near their homes, which was a strategy employed during the COVID-19 pandemic to allow them to undertake field work. The first study area is a popular neighborhood (Lomas de Padierna) that was rooted in the&#160;1970s on basaltic lavas from the ca. AD200 Xitle cone. In this highly urbanized area, the geological nature is only visible as&#160;sparse&#160;vertical outcrops along streets and&#160;small&#160;surface exposures in private gardens and road central reservations. Such sites are seldom maintained by the locals who rarely recognize their value. Debris flows during rain storms cause a chronic hazard. The second area consists of a chain of several cones, a dome and a tuff ring (Sierra Santa Catarina) located in the southeastern part of the basin, that conserves elements of the native fauna and flora. Depicted in the great landscape paintings of the Mexico basin made in the 19<sup>th</sup> century, mining activities and illegal settlements have severely degraded this site since the 1970s, even after the creation of a protected area in 1994 and a conservation area in 2003. Enhanced cone erosion causes frequent landslides affecting settlements. Data on the age and eruptive style of these volcanoes is surprisingly limited, given their importance for hazard assessment.</p><p>This work reveals the diverse visages of geoheritage in a large city, showing their low level of scientific knowledge and public appreciation, which account for their pronounced degree of degradation. Hence, the memory of past geological events, awareness of impending hazards, and vital mineral and organic resources are disappearing quickly, further increasing the risks faced by the city.&#160; The vulnerability of people to hazards can be linked to their poor knowledge of their environment. The dissemination of information on local geosites may be highly valuable to raise environmental awareness and reduce risks. In this respect, we plan to make and distribute leaflets to local schools and community centers.</p>
The objective of this paper is to offer an approach to assess the risk associated with Municipal ... more The objective of this paper is to offer an approach to assess the risk associated with Municipal Solid Wastes, in a geospatial context. Initially, a risk index including hazard, vulnerability and other important variables was built. The built model is based on multi-criteria evaluation techniques and geographic information systems. Subsequently, the constructed index was used to model possible damage in various municipalities of the state of Chiapas, Mexico. The results indicate that the highest levels of risk are found in places with unfavorable conditions, such as high rates of waste generation, low waste collection coverage, steep slopes, etc. that cover 6.22% of the study area. The areas with high risk level are mainly found in the southeast of the municipalities of Villa Corzo and Villaflores, and cover 27.06% of the study area. The places of low and very low risk levels are concentrated in the center and northeast of the study area, in the municipalities of Suchiapa, Chiapa de Corzo and Acala, and cover 38.6% of the area. At the municipal level, Berriozábal, Villaflores and Villa Corzo have the highest levels of risk in most of their territory; the high levels of risk presented in Berriozábal are due to the limited territorial area that it occupies in the study area. In Villaflores and Villa Corzo, the high levels of risk are due to the high population dispersion. A large part of Tuxtla Gutiérrez territory presents low and medium risk levels, especially within the population settlement. The peripheral areas show the highest levels of risk, because the waste collection service is not provided very often. Finally, the Cohen’s kappa statistic used to validate the precision of the model gave a value of 0.34, which means that the spatial model can be considered acceptable despite its low value. Although this work is only a general approach to spatial risk modeling at a regional scale, it provides interesting information. Moreover, it adds to the few efforts that exist in the literature to model the risk associated with wastes.
El presente trabajo de investigacion se realizo en la zona de la planicie aluvial baja del estado... more El presente trabajo de investigacion se realizo en la zona de la planicie aluvial baja del estado de Tabasco, especificamente en el distrito petrolero de Cinco Presidentes. El objetivo fue conocer el intervalo de concentraciones de hidrocarburos aromaticos policiclicos (HAPs) presentes en suelos con diferentes usos, bajo la influencia de una zona petrolera, con el fin de tipificar el origen de dichos compuestos organicos. En las muestras de suelos se identificaron 30 compuestos aromaticos por cromatografia de gases acoplada a un espectrofotometro de masas (CG-MS) en el modo de monitoreo de ion selectivo (SIM). Las concentraciones de HAPs varian en funcion al uso de suelo. El de uso ganadero presento aproximadamente 70 ng g -1 , mientras en los suelos con vegetacion natural, el que presento la mas alta concentracion fue el popal-apompal (45 ng g -1 ). En tanto que en los cocoteros se detecto una concentracion de 10 ng g -1 . Estos resultados coinciden con las concentraciones reportad...
The conservation of geosites in a region can foster its sustainability and develop geotourism. Th... more The conservation of geosites in a region can foster its sustainability and develop geotourism. These geosites provide geoeducation, raise people's awareness on natural hazards and increase their resilience. Low-income cities located in tectonically active areas combine high geohazards with high vulnerability and low sustainability. Geosites in these cities should be a tool to decrease people's vulnerability and foster sustainable development. Mexico City is an ideal case study for its environmental and social issues and its setting in an active 2 continental volcanic arc. The 1,700 yrs-old Xitle volcano, located in the city's SW corner, is a small scoria cone that erupted once, feeding an extensive lava field on which >600,000 people now live. The lavas are very well exposed due to thin soils and extensive quarrying. The Xitle lavas covered the first urban center in the Mexico basin, except for the main pyramid that has become a major archeological site. The cone and lavas have significant geodiversity, sustaining a unique and biodiverse ecosystem. The country's largest university preserves the lavas in an ecological reserve. We describe four exceptional geosites, assess their values, and discuss their relevance for addressing issues such as nature preservation, environmental sustainability, social inequalities, and natural hazards. The Xitle volcano provides a wide range of benefits for the city that are nonetheless unknown to its inhabitants. We describe ongoing initiatives to disseminate such information, such as the Geopedregal site, and propose ways that this heritage could be further protected and used by the city in a sustainable way.
Resources Environment and Information Engineering, 2021
In the field of solid waste management, key concepts such as risk, impact and hazards have been u... more In the field of solid waste management, key concepts such as risk, impact and hazards have been used interchangeably and have had imprecise meanings and scopes; this can lead to a partial or biased vision, for example in relation to municipal solid waste management policies. This paper presents a review of the literature on the theme of municipal solid waste and risk. Analysis of scientific publications from the years 1970 to 2020 shows that the concept of risk in the field of solid waste has been approached from various perspectives and different interpretations. Of all risk components, vulnerability has been the least addressed in the literature, because technical aspects such as hazard modeling predominate in this field. Most of the publications have studied the final disposal stage, since open dumpsites and landfills are still the most common methods for disposing of solid waste. Finally, a reference framework is proposed.
The Mixteca Alta has some of the most important traces of Mesoamerican culture and is characteriz... more The Mixteca Alta has some of the most important traces of Mesoamerican culture and is characterized by a variety of conspicuous erosional features strongly related to traditional farming practices carried out for more than 3500 years. These features represent a valuable geoheritage that can show the relationship between geology and society and promote the knowledge of Earth sciences among members of the general and specialized public. These erosional features include gullies, badlands, erosive amphitheatres derived from fluvial and mass-wasting processes, alluvial deposits, palaeosols and water and sediment traps used for farming purposes (locally known as lamabordos). Other sites of interest include examples of intrusive magmatic dikes, spheroidal weathering and sites of palaeontological interest. The identification of these sites leads to the proposal of three geotrails; these represent the basis for geotourism in the study area, as an alternative for local economic development.
In Tabasco the petroleum industry pollutes soil recurrently by oil spills. We analysed Pb, V, Ni ... more In Tabasco the petroleum industry pollutes soil recurrently by oil spills. We analysed Pb, V, Ni and Cr concentrations in water samples, and total metal contents and metal fractions in soil samples of contaminated and non-contaminated soils and in sediments. Besides, we determined Eh, pH, DOC and major ions in water and Eh, pH, C org in soils and sediments. Sediments contained considerably larger heavy metal (HM) concentrations than soils. Local background concentrations of V, Ni and Cr in soils are larger than global means and oil spillages have not added these metals in quantities that exceed the natural variation. Spillage of formation water increases Pb concentrations in soils, particularly in mobile fractions. The contribution of the oil industry to HM loads is diluted by large fluvial water and sediment discharges and difficult to assess by comparison of total metal contents. Therefore, easily mobile metal fractions are much better indicators.
El aluminio (Al) es el tercer elemento más abundante en la corteza terrestre. Su forma química de... more El aluminio (Al) es el tercer elemento más abundante en la corteza terrestre. Su forma química depende de los valores de pH del suelo. En suelos ácidos el Al se libera y solubiliza principalmente en la forma iónica de Al3+, la cual es tóxica para la mayoría de las plantas. Los principales efectos tóxicos del Al se observan en el ápice de la raíz, inhibiendo la división y elongación celular, lo que origina una raíz def iciente en la absorción de agua y nutrientes, dando como resultado la inhibición del crecimiento, y, por lo tanto, una disminución en la productividad de las plantas. Actualmente, el Al se encuentra disponible en suelos que no son naturalmente ácidos y se utilizan como tierras de cultivo. Esto ha generado una línea de investigación en relación con el efecto del Al en diferentes especies de plantas, por ejemplo, los sitios de acumulación y concentración en los diferentes órganos vegetales. En este contexto, el objetivo de la presente revisión es proporcionar una guía pa...
The Xochimilco area in the southeastern part of Mexico City has a variety of socioeconomic activi... more The Xochimilco area in the southeastern part of Mexico City has a variety of socioeconomic activities, such as periurban agriculture, which is of great importance in the Mexico City metropolitan area. Pesticides are used extensively, some being legal, mostly chlorpyrifos and malathion, and some illegal, mostly DDT. Sediments are a common sink for pesticides in aquatic systems near agricultural areas, and Xochimilco sediments have a complex composition with high contents of organic matter and clay that are ideal adsorption sites for organochlorine (OC) and organophosphorus (OP) pesticides. Therefore, it is important to have a quick, affordable, and reliable method to determine these pesticides. Conventional methods for the determination of OC and OP pesticides are long, laborious, and costly owing to the high volume of solvents and adsorbents. The present study developed and validated a method for determining 18 OC and five OP pesticides in sediments with high organic and clay contents. In contrast with other methods described in the literature, this method allows isolation of the 23 pesticides with a 12 min microwave-assisted extraction (MAE) and one-step cleanup of pesticides. The method developed is a simpler, time-saving procedure that uses only 3.5 g of dry sediment. The use of MAE eliminates excessive handling and the possible loss of analytes. It was shown that the use of LC-Si cartridges with hexane-ethyl acetate (75 + 25, v/v) in the cleanup procedure recovered all pesticides with rates between 70 and 120%. The validation parameters demonstrated good performance of the method, with intermediate precision ranging from 7.3 to 17.0%, HorRat indexes all below 0.5, and tests of accuracy with the 23 pesticides at three concentration levels demonstrating recoveries ranging from 74 to 114% and RSDs from 3.3 to 12.7%. M odern agricultural techniques have increased food production but have also generated inorganic and organic toxic residues from the conditioning, fertilization, and pest control of crops. These substances have affected surrounding fields and water bodies through runoff, infiltration, wash down, deposition, tile drain flow, leaching, or surface water overspray (1-3). Important components of these residues are the organochlorine (OC) and organophosphorus (OP) pesticides; they have been detected in soil and aquatic systems (4-7) and are partly responsible for biodiversity loss and deterioration of habitats in aquatic systems (8-10). An important study case is Xochimilco in the southeastern part of Mexico City. The Xochimilco wetland, consisting of a canal network and the surrounding ex-lacustrine area, supports a variety of socioeconomic activities, such as periurban agriculture that includes the traditional "chinampas" and greenhouses as well as tourism and urban activities. All of these have a direct impact on the canals. In particular, periurban agriculture in Xochimilco is of great importance to the Mexico City metropolitan area, where extensive pest control is carried out with legal pesticides, mainly chlorpyrifos and malathion (10), or with illegal pesticides, mainly DDT [1,1′-(2,2,2-trichlor-1,1ethandiyl)bis(4-chlorbenzol)]. The presence of OC pesticides is also attributable to their extensive use in earlier years before they were banned. Sediments are a common sink for pesticides in aquatic systems near agricultural plots. Xochimilco sediments have a complex composition with fine-grained sands, about 50% volcanic ash, textures ranging from silty clay to silty clay loam that retain a high amount of moisture, and high organic matter content (around 30%). With clay values near to 40% and loam values above 40% (11), these are ideal adsorption sites for OC and OP pesticides (12, 13). The canals are host to several endemic and endangered species, and more than 120 bird species have been recorded. Nowadays, modern methods for the determination of contaminants have been proposed to solve time and solvent consumption problems as an alternative to traditional methods; they must be able to produce analytically accurate results and be economically efficient for routine analysis (14). The isolation of pesticides from environmental samples is often difficult and time-consuming. It has been estimated that the sample preparation step in most determinations consumes
Urban parks in the cities play a crucial role in promoting sustainability and enhancing the quali... more Urban parks in the cities play a crucial role in promoting sustainability and enhancing the quality of life for their residents. In an urban ecosystem, we have to make some trade-offs between the cultural and ecological ecosystem services. The soil ecosystem services depend on specific ecological conditions, therefore information on their potential to provide fundamental services is a basic requirement when constructions are planned in green areas. Mexico City, like other cities in Latin America, has very few green areas that are constantly threatened by sealing. Based on morpho-pedological landscapes (MpL) we quantify the soil carbon sequestration (SOC) and infiltration capacity in Chapultepec park. Among the 12 MpL we found the highest content of SOC in hillslopes with mixed tree vegetation and Phaeozem and the lowest in grass-dominant plain with Technosols and Leptosols. However, the SOC retention decreased by 40-50% because of sealing surfaces. For each MpL, the value of the soil saturated hydraulic conductivity calculated from pedotransfer functions (Ksc) was markedly lower than the Ksm measured with the double ring infiltrometer. In all MpL, both Ksc and Ksm were always higher than the reported maximum rainfall intensity. In the MpLs with more sealing, the runoff reaches more than 40% of the precipitated water. Based on these results, it is recommended to implement different actions such as allowing the leaves on the soils, the de-sealing of obsolete infrastructure, as well as locating the new constructions on Technosols and Leptosols to maintain Chapultepec park as a SOC sink with infiltration potential.
... through the incineration of plant residues after agricultural burning are poorly studied, but... more ... through the incineration of plant residues after agricultural burning are poorly studied, but their contribution to the overall balance of HCs in the atmosphere is suspected to be significant (Fernandez et al., 20035. Fernandez, MB and ... Ortiz, PMA, Siebe, C. and Cram, S. 2005. ...
Trace metal species in the water column of a canal system forming a wetland filled with wastewate... more Trace metal species in the water column of a canal system forming a wetland filled with wastewater were analyzed to determine their correlation with metal accumulation in the gills of locally fished Oreochromis niloticus. The metal concentrations in the suspended particles and water dissolved were analyzed. The metal species were calculated using Windermere Humic Aqueous Model version VII showing that the high organic matter and major cation contents were important parameters. Also, the free ion metal concentration was expected to correlate with the organic matter aromaticity; however, organic compounds other than humic susbtances seem to be complexing the metals in the system. Additionally, no clear correlation could be found between metal accumulation in gills and any of the dissolved metal species. Nonetheless, certain trends could be seen between the calculated metal species and metal accumulation in the tilapia from the suspended particles.
Urban agriculture plays an important role in supplying produces to big cities; however, the quali... more Urban agriculture plays an important role in supplying produces to big cities; however, the quality of water used for irrigation can hinder this activity. Hence, the purpose of this study was to evaluate metal inputs, as well as their transfer and translocation factors, in lettuce (Lactuca sativa L.) crops cultivated in an urban plot. The research was conducted during the dry and rainy seasons. In the former, crops were irrigated with treated wastewater, whereas during the latter, crops were maintained just with rainwater. Composite samples for soils and plants were collected from the same plot during two crop cycles in 2013. Some edaphic variables were measured. Total metal concentration was determined, for both, soils and lettuce plants (leaves and roots). Water soluble and exchangeable soil metal fractions were also analyzed. A multivariate analysis of variance was performed to test for differences between seasons, among the variables analyzed. There were significant differences in edaphic characteristics between seasons. However, there was no difference in total metal content, except for Mn. Concentration of soluble metals was lower than exchangeable metal concentration, for both seasons. There was no correlation in total metal concentration between soils and plants. Transfer factor values were higher for Cd, Mn and Zn for the dry season, while for Cu, Fe and Pb were higher during the rainy season, as well as the translocation factors for all metals. Soil characteristics, together with transfer and translocation factors, showed temporal variations, leading to different metal concentrations in the edible lettuce tissues between the two analyzed crop cycles. The incorporation of metals is particular for each site, season and crop management type. Our results indicate that the metal concentration in lettuce tissues places no harm to human health. However, management strategies for urban agriculture must consider specific studies for each site.
Dehydrogenase activity (DHA) in soils contaminated by arsenic-bearing tailings was correlated wit... more Dehydrogenase activity (DHA) in soils contaminated by arsenic-bearing tailings was correlated with total arsenic and total water-soluble arsenic (As(III)+As(V)) to evaluate the impact of tailings dispersion on the oxidative capacity of soil microorganisms. Georeferenced surface soil samples (0-10 cm depth) were collected at different distances from a tailings dam. In the samples farthest from the dam, all water-soluble arsenic (avg. 0.6+/-0.1 mg kg(-1)) was As(V). The highest concentration of water-soluble As(III)+As(V) (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;1.9 mg kg(-1)) was found where As(III) was present. DHA averaged 438.9+/-79.3 microg INTF g(-1) h(-1) at the greatest distance from the dam and decreased to 92.3+/-27.1 microg INTF g(-1) h(-1) with decreasing distance from the dam. Pearson correlation coefficient between DHA and samples containing water-soluble As(V) (r=-0.87) was greater than that between DHA and total water-soluble arsenic (r=-0.57). The correlation between DHA and soluble arsenic containing both As(V) and As(III) was not significant (r=0.24). In soils with detectable As(III) concentrations where wet conditions prevail (i.e., reducing conditions), there is an abiotic response in addition to a biotic one. The correlation between DHA and total water-soluble As(III)+ As(V) was higher (r=-0.79) when the abiotic response was excluded. Our study demonstrated the importance of distinguishing between total and available fraction and its species and the need to evaluate biological functions in addition to purely geochemical analyses. DHA bioassay combined with other microbial properties offers a good tool for evaluating soil microbial activity and status and is a suitable indicator of the oxidative capacity of soil microorganisms affected by tailings in an oxidizing environment; however, under reducing conditions, abiotic responses must also be studied.
The conservation of geosites in a region can foster its sustainability and develop geotourism. Th... more The conservation of geosites in a region can foster its sustainability and develop geotourism. These geosites provide geoeducation, raise people's awareness on natural hazards and increase their resilience. Low-income cities located in tectonically active areas combine high geohazards with high vulnerability and low sustainability. Geosites in these cities should be a tool to decrease people's vulnerability and foster sustainable development. Mexico City is an ideal case study for its environmental and social issues and its setting in an active 2 continental volcanic arc. The 1,700 yrs-old Xitle volcano, located in the city's SW corner, is a small scoria cone that erupted once, feeding an extensive lava field on which >600,000 people now live. The lavas are very well exposed due to thin soils and extensive quarrying. The Xitle lavas covered the first urban center in the Mexico basin, except for the main pyramid that has become a major archeological site. The cone and lavas have significant geodiversity, sustaining a unique and biodiverse ecosystem. The country's largest university preserves the lavas in an ecological reserve. We describe four exceptional geosites, assess their values, and discuss their relevance for addressing issues such as nature preservation, environmental sustainability, social inequalities, and natural hazards. The Xitle volcano provides a wide range of benefits for the city that are nonetheless unknown to its inhabitants. We describe ongoing initiatives to disseminate such information, such as the Geopedregal site, and propose ways that this heritage could be further protected and used by the city in a sustainable way.
Environmental Monitoring and Assessment, Jun 18, 2008
This study evaluated the spatial and temporal distribution of metals in the coral reef system Cay... more This study evaluated the spatial and temporal distribution of metals in the coral reef system Cayos Arcas and Triangulos in the Campeche Bank region, off the Yucatan peninsula in Mexico. No information has been generated before for the incorporation of natural and non-natural occurring metals, some of which are possibly endowed by the oil marine station Cayo Arcas. The multivariate exploratory study of the metals on the coral skeletons, showed the formation of two distinct groups. The metals that have the highest influence on the differentiation of the groups are the metals that are natural constituents of the coral skeletons, in particular Sr can explain much of the differences between the groups, and to a much lesser extent are the metals that could be indicators of pollution. This differentiation suggests that, in our case, the environment around the corals has a higher impact than the non-naturally occurring metals (and possible indicators of pollution). The two groups formed corresponded to: the coral cores influenced by open sea variables and the coral cores in the inner part of the keys which is less exposed to open sea variables. A chronological study was made to two samples that had the longest coral section and were situated in two clearly distinctive zones: an exposed surface subjected to high wave forces and another that was less exposed. Ni and Zn show an accumulation trend in both coral samples, while Ba showed an increase in incorporation around 1980 when the Cayo Arcas oil marine station was constructed.
<p>Geological elements in cities are usually damaged and invisible to their inhabitants, de... more <p>Geological elements in cities are usually damaged and invisible to their inhabitants, despite the wide range of benefits they provide to them. In particular, they offer them an opportunity to learn about their geological setting (= sense of place) and be aware of associated risks (= sense of risk). Such geoheritage comes in different forms that ought to be identified and described precisely in order to be preserved and used. The gigantic capital city of Mexico is settled in a paleolake basin embedded in&#160;a diverse volcanic landscape. City inhabitants face numerous hazards (floods, landslides, debris flows, subsidence, earthquakes, drought, fires) that create high risks with combined natural&#160;and&#160;anthropogenic&#160;causes due to uncontrolled city growth. The&#160;geoheritage of the city is mostly formed by monogenetic (one-event) volcanoes&#160;that are an important&#160;resource for geoconservation and geoeducation. We present two case studies that were investigated by students near their homes, which was a strategy employed during the COVID-19 pandemic to allow them to undertake field work. The first study area is a popular neighborhood (Lomas de Padierna) that was rooted in the&#160;1970s on basaltic lavas from the ca. AD200 Xitle cone. In this highly urbanized area, the geological nature is only visible as&#160;sparse&#160;vertical outcrops along streets and&#160;small&#160;surface exposures in private gardens and road central reservations. Such sites are seldom maintained by the locals who rarely recognize their value. Debris flows during rain storms cause a chronic hazard. The second area consists of a chain of several cones, a dome and a tuff ring (Sierra Santa Catarina) located in the southeastern part of the basin, that conserves elements of the native fauna and flora. Depicted in the great landscape paintings of the Mexico basin made in the 19<sup>th</sup> century, mining activities and illegal settlements have severely degraded this site since the 1970s, even after the creation of a protected area in 1994 and a conservation area in 2003. Enhanced cone erosion causes frequent landslides affecting settlements. Data on the age and eruptive style of these volcanoes is surprisingly limited, given their importance for hazard assessment.</p><p>This work reveals the diverse visages of geoheritage in a large city, showing their low level of scientific knowledge and public appreciation, which account for their pronounced degree of degradation. Hence, the memory of past geological events, awareness of impending hazards, and vital mineral and organic resources are disappearing quickly, further increasing the risks faced by the city.&#160; The vulnerability of people to hazards can be linked to their poor knowledge of their environment. The dissemination of information on local geosites may be highly valuable to raise environmental awareness and reduce risks. In this respect, we plan to make and distribute leaflets to local schools and community centers.</p>
The objective of this paper is to offer an approach to assess the risk associated with Municipal ... more The objective of this paper is to offer an approach to assess the risk associated with Municipal Solid Wastes, in a geospatial context. Initially, a risk index including hazard, vulnerability and other important variables was built. The built model is based on multi-criteria evaluation techniques and geographic information systems. Subsequently, the constructed index was used to model possible damage in various municipalities of the state of Chiapas, Mexico. The results indicate that the highest levels of risk are found in places with unfavorable conditions, such as high rates of waste generation, low waste collection coverage, steep slopes, etc. that cover 6.22% of the study area. The areas with high risk level are mainly found in the southeast of the municipalities of Villa Corzo and Villaflores, and cover 27.06% of the study area. The places of low and very low risk levels are concentrated in the center and northeast of the study area, in the municipalities of Suchiapa, Chiapa de Corzo and Acala, and cover 38.6% of the area. At the municipal level, Berriozábal, Villaflores and Villa Corzo have the highest levels of risk in most of their territory; the high levels of risk presented in Berriozábal are due to the limited territorial area that it occupies in the study area. In Villaflores and Villa Corzo, the high levels of risk are due to the high population dispersion. A large part of Tuxtla Gutiérrez territory presents low and medium risk levels, especially within the population settlement. The peripheral areas show the highest levels of risk, because the waste collection service is not provided very often. Finally, the Cohen’s kappa statistic used to validate the precision of the model gave a value of 0.34, which means that the spatial model can be considered acceptable despite its low value. Although this work is only a general approach to spatial risk modeling at a regional scale, it provides interesting information. Moreover, it adds to the few efforts that exist in the literature to model the risk associated with wastes.
El presente trabajo de investigacion se realizo en la zona de la planicie aluvial baja del estado... more El presente trabajo de investigacion se realizo en la zona de la planicie aluvial baja del estado de Tabasco, especificamente en el distrito petrolero de Cinco Presidentes. El objetivo fue conocer el intervalo de concentraciones de hidrocarburos aromaticos policiclicos (HAPs) presentes en suelos con diferentes usos, bajo la influencia de una zona petrolera, con el fin de tipificar el origen de dichos compuestos organicos. En las muestras de suelos se identificaron 30 compuestos aromaticos por cromatografia de gases acoplada a un espectrofotometro de masas (CG-MS) en el modo de monitoreo de ion selectivo (SIM). Las concentraciones de HAPs varian en funcion al uso de suelo. El de uso ganadero presento aproximadamente 70 ng g -1 , mientras en los suelos con vegetacion natural, el que presento la mas alta concentracion fue el popal-apompal (45 ng g -1 ). En tanto que en los cocoteros se detecto una concentracion de 10 ng g -1 . Estos resultados coinciden con las concentraciones reportad...
The conservation of geosites in a region can foster its sustainability and develop geotourism. Th... more The conservation of geosites in a region can foster its sustainability and develop geotourism. These geosites provide geoeducation, raise people's awareness on natural hazards and increase their resilience. Low-income cities located in tectonically active areas combine high geohazards with high vulnerability and low sustainability. Geosites in these cities should be a tool to decrease people's vulnerability and foster sustainable development. Mexico City is an ideal case study for its environmental and social issues and its setting in an active 2 continental volcanic arc. The 1,700 yrs-old Xitle volcano, located in the city's SW corner, is a small scoria cone that erupted once, feeding an extensive lava field on which >600,000 people now live. The lavas are very well exposed due to thin soils and extensive quarrying. The Xitle lavas covered the first urban center in the Mexico basin, except for the main pyramid that has become a major archeological site. The cone and lavas have significant geodiversity, sustaining a unique and biodiverse ecosystem. The country's largest university preserves the lavas in an ecological reserve. We describe four exceptional geosites, assess their values, and discuss their relevance for addressing issues such as nature preservation, environmental sustainability, social inequalities, and natural hazards. The Xitle volcano provides a wide range of benefits for the city that are nonetheless unknown to its inhabitants. We describe ongoing initiatives to disseminate such information, such as the Geopedregal site, and propose ways that this heritage could be further protected and used by the city in a sustainable way.
Resources Environment and Information Engineering, 2021
In the field of solid waste management, key concepts such as risk, impact and hazards have been u... more In the field of solid waste management, key concepts such as risk, impact and hazards have been used interchangeably and have had imprecise meanings and scopes; this can lead to a partial or biased vision, for example in relation to municipal solid waste management policies. This paper presents a review of the literature on the theme of municipal solid waste and risk. Analysis of scientific publications from the years 1970 to 2020 shows that the concept of risk in the field of solid waste has been approached from various perspectives and different interpretations. Of all risk components, vulnerability has been the least addressed in the literature, because technical aspects such as hazard modeling predominate in this field. Most of the publications have studied the final disposal stage, since open dumpsites and landfills are still the most common methods for disposing of solid waste. Finally, a reference framework is proposed.
The Mixteca Alta has some of the most important traces of Mesoamerican culture and is characteriz... more The Mixteca Alta has some of the most important traces of Mesoamerican culture and is characterized by a variety of conspicuous erosional features strongly related to traditional farming practices carried out for more than 3500 years. These features represent a valuable geoheritage that can show the relationship between geology and society and promote the knowledge of Earth sciences among members of the general and specialized public. These erosional features include gullies, badlands, erosive amphitheatres derived from fluvial and mass-wasting processes, alluvial deposits, palaeosols and water and sediment traps used for farming purposes (locally known as lamabordos). Other sites of interest include examples of intrusive magmatic dikes, spheroidal weathering and sites of palaeontological interest. The identification of these sites leads to the proposal of three geotrails; these represent the basis for geotourism in the study area, as an alternative for local economic development.
In Tabasco the petroleum industry pollutes soil recurrently by oil spills. We analysed Pb, V, Ni ... more In Tabasco the petroleum industry pollutes soil recurrently by oil spills. We analysed Pb, V, Ni and Cr concentrations in water samples, and total metal contents and metal fractions in soil samples of contaminated and non-contaminated soils and in sediments. Besides, we determined Eh, pH, DOC and major ions in water and Eh, pH, C org in soils and sediments. Sediments contained considerably larger heavy metal (HM) concentrations than soils. Local background concentrations of V, Ni and Cr in soils are larger than global means and oil spillages have not added these metals in quantities that exceed the natural variation. Spillage of formation water increases Pb concentrations in soils, particularly in mobile fractions. The contribution of the oil industry to HM loads is diluted by large fluvial water and sediment discharges and difficult to assess by comparison of total metal contents. Therefore, easily mobile metal fractions are much better indicators.
El aluminio (Al) es el tercer elemento más abundante en la corteza terrestre. Su forma química de... more El aluminio (Al) es el tercer elemento más abundante en la corteza terrestre. Su forma química depende de los valores de pH del suelo. En suelos ácidos el Al se libera y solubiliza principalmente en la forma iónica de Al3+, la cual es tóxica para la mayoría de las plantas. Los principales efectos tóxicos del Al se observan en el ápice de la raíz, inhibiendo la división y elongación celular, lo que origina una raíz def iciente en la absorción de agua y nutrientes, dando como resultado la inhibición del crecimiento, y, por lo tanto, una disminución en la productividad de las plantas. Actualmente, el Al se encuentra disponible en suelos que no son naturalmente ácidos y se utilizan como tierras de cultivo. Esto ha generado una línea de investigación en relación con el efecto del Al en diferentes especies de plantas, por ejemplo, los sitios de acumulación y concentración en los diferentes órganos vegetales. En este contexto, el objetivo de la presente revisión es proporcionar una guía pa...
The Xochimilco area in the southeastern part of Mexico City has a variety of socioeconomic activi... more The Xochimilco area in the southeastern part of Mexico City has a variety of socioeconomic activities, such as periurban agriculture, which is of great importance in the Mexico City metropolitan area. Pesticides are used extensively, some being legal, mostly chlorpyrifos and malathion, and some illegal, mostly DDT. Sediments are a common sink for pesticides in aquatic systems near agricultural areas, and Xochimilco sediments have a complex composition with high contents of organic matter and clay that are ideal adsorption sites for organochlorine (OC) and organophosphorus (OP) pesticides. Therefore, it is important to have a quick, affordable, and reliable method to determine these pesticides. Conventional methods for the determination of OC and OP pesticides are long, laborious, and costly owing to the high volume of solvents and adsorbents. The present study developed and validated a method for determining 18 OC and five OP pesticides in sediments with high organic and clay contents. In contrast with other methods described in the literature, this method allows isolation of the 23 pesticides with a 12 min microwave-assisted extraction (MAE) and one-step cleanup of pesticides. The method developed is a simpler, time-saving procedure that uses only 3.5 g of dry sediment. The use of MAE eliminates excessive handling and the possible loss of analytes. It was shown that the use of LC-Si cartridges with hexane-ethyl acetate (75 + 25, v/v) in the cleanup procedure recovered all pesticides with rates between 70 and 120%. The validation parameters demonstrated good performance of the method, with intermediate precision ranging from 7.3 to 17.0%, HorRat indexes all below 0.5, and tests of accuracy with the 23 pesticides at three concentration levels demonstrating recoveries ranging from 74 to 114% and RSDs from 3.3 to 12.7%. M odern agricultural techniques have increased food production but have also generated inorganic and organic toxic residues from the conditioning, fertilization, and pest control of crops. These substances have affected surrounding fields and water bodies through runoff, infiltration, wash down, deposition, tile drain flow, leaching, or surface water overspray (1-3). Important components of these residues are the organochlorine (OC) and organophosphorus (OP) pesticides; they have been detected in soil and aquatic systems (4-7) and are partly responsible for biodiversity loss and deterioration of habitats in aquatic systems (8-10). An important study case is Xochimilco in the southeastern part of Mexico City. The Xochimilco wetland, consisting of a canal network and the surrounding ex-lacustrine area, supports a variety of socioeconomic activities, such as periurban agriculture that includes the traditional "chinampas" and greenhouses as well as tourism and urban activities. All of these have a direct impact on the canals. In particular, periurban agriculture in Xochimilco is of great importance to the Mexico City metropolitan area, where extensive pest control is carried out with legal pesticides, mainly chlorpyrifos and malathion (10), or with illegal pesticides, mainly DDT [1,1′-(2,2,2-trichlor-1,1ethandiyl)bis(4-chlorbenzol)]. The presence of OC pesticides is also attributable to their extensive use in earlier years before they were banned. Sediments are a common sink for pesticides in aquatic systems near agricultural plots. Xochimilco sediments have a complex composition with fine-grained sands, about 50% volcanic ash, textures ranging from silty clay to silty clay loam that retain a high amount of moisture, and high organic matter content (around 30%). With clay values near to 40% and loam values above 40% (11), these are ideal adsorption sites for OC and OP pesticides (12, 13). The canals are host to several endemic and endangered species, and more than 120 bird species have been recorded. Nowadays, modern methods for the determination of contaminants have been proposed to solve time and solvent consumption problems as an alternative to traditional methods; they must be able to produce analytically accurate results and be economically efficient for routine analysis (14). The isolation of pesticides from environmental samples is often difficult and time-consuming. It has been estimated that the sample preparation step in most determinations consumes
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