Understanding the oral bioaccessibility of lead (Pb) present in soils in urbanized areas is important for the human exposure risk assessment. In particular, the role of the soil-mineralogy in the ...oral bioaccessibility has not been extensively studied. To investigate bioaccessibility, five types of periurban soils were collected, samples were spiked with the same amount of lead-chromates from traffic paint, and subjected to the in vitro Physiological Based Extraction Test (PBET). Ten samples of urban topsoils were collected at elementary schools playgrounds, Pb-bioaccessibility was measured, and a prediction equation for bioaccessibility was constructed. Mineralogy, and metal content were identified with a combination of X-ray powder diffraction, scanning electron microscopy, and portable X-ray fluorescence techniques. Traffic paint sample is made of 15% quartz (SiO2), 13% crocoite (PbCrO4), 55% calcite (CaCO3), and 17% kaolinite (Al2Si2O5(OH)4) and it contains high metal content (Pb, Cr, Zn, and Ca). Studied soils are characterized by variable amounts of acid-neutralizing minerals (carbonates) and low metal content. Spiked soils contained almost equal concentration of Pb, Cr, and Zn, because the contribution of these metals is from the added paint. However, obtained Pb-bioaccessibility at gastric and intestinal conditions are variable (40 to 51% gastric, 24 to 70.5% intestinal). Carbonate content shows significant correlation (p < 0.05) with Cr, Ca, calcite, crocoite, and Pb-bioaccessible at gastric conditions. Correlation of Pb-bioaccessible at intestinal conditions is significant (p < 0.05) with kaolinite.
Variability of Pb-bioaccesibility in urban environments is commonly associated to differences in Pb-sources, however, our results show that the bioaccessibility of the same pollutant behaves different for each soil type. This suggests that soil mineralogy may play a role in Pb-releasing at gastrointestinal conditions. Soil information about mineralogical characteristics from this study may help to reduce exposure to lead from urban sources if data are incorporated into urban planning.
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•Bioaccessibility of lead was analyzed using PBET.•Natural soils were spiked with lead-based paint.•Soils mineralogy affect lead bioaccessibility.•Soil type influences health-risk assessment.
Mexico ranks second in shrimp (Litopenaeus vannamei) production of in Latin America with significant annual growth, however, during 2011 shrimp production fell by almost 50 % due to the presence of ...the white spot syndrome virus (WSSV). In this context, a life cycle analysis (LCA) and data envelopment analysis (DEA) were performed on 76 commercial farms severely affected by the presence of WSSV in northwestern Mexico. The application of this combined methodology allowed a detailed quantification of different environmental impact categories. During the presence of WSSV, there was a negative effect on the feed conversion ratio (FCR) (>40 %), higher consumption of seawater (38 %), and energy (38 %). Consequently, operational outputs related to the discharge of nitrogen and phosphorus increased by 60 and 57 %, respectively. Similarly, CO2 emissions, increased by 38 % relative to a typical year of production. Overall, the main critical points in the impact categories analyzed are related to food (98 %), use of diesel (23 %), and rearing (24 %), dominating pollutants emissions in all categories. Consequently, an improvement scenario was evaluated related to innovation in the formulation of foods supplied with immunostimulants, which confer protection against pathogenic microorganisms. This scenario lead to a reduction environmental impact of about 82 %. The results of this analysis will be a useful resource in the design of mitigation strategies with innovation processes that allow maintaining yields for shrimp producers in this region and at the same time reduce the environmental impacts generated.
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•LCA and DEA are useful to quantify environmental impact•Environmental impacts of a viral disease affecting shrimp farming were studied•Alternative feed and renewable energies are mitigation alternatives for shrimp crop•Results help designing environmental mitigation strategies with innovation processes
Extreme climatic events are changing the structure and functioning of forests worldwide, and often reducing abruptly their capacity to provide ecosystem services, especially to rural communities ...intimately connected to their environment. In this paper, we analyze climate-induced changes to provisioning ecosystem services, including forest resources available and used by rural communities, and local perceptions about how these services changed after recent extreme climatic events inside and outside a Biosphere Reserve in northwestern Mexico. Our approach integrates quantitative and qualitative techniques from traditional (50 local interviews) and scientific (forest surveys in 24 1-ha plots) ecological knowledge. Our integrated analysis suggests widespread tree mortality was the main ecological effect of recent extreme climatic events, especially in forests regrowing in the reserve former agricultural land, overturning decades of forest natural regeneration. Reserve inhabitants, strongly relying on their surrounding forests for self-consumption, identified climatic events as the main driver of forest change. In addition to climatic events, people outside the reserve recognized selective logging for charcoal production and in general forest exploitation as key drivers of forest change, consistent with the decline of hardwood species revealed by our field surveys. The persistence of an eroding environmental dimension (e.g., unsustainable use of forest resources) outside reserves could increase the long-term vulnerability of rural socioecosystems to extreme climatic events. The protecting role of biosphere reserves will be essential to preserve old-growth forests more resistant to temperature extremes and aid the process of forest natural regeneration after climate-induced disturbance. In order to protect native biodiversity and reduce climate vulnerability, coupled human-environment systems such as Biosphere Reserves should genuinely and rightfully engage local people in management decisions, prioritizing policies that build more sustainable livelihoods and enhance the adaptive capacity of socioecosystems to cope with climate variability.
Using catalytic converters is one of the most effective methods to control vehicle emissions. A washcoat of cerium oxide-zirconia (CeO2–ZrO2) has been used to enhance the performance of the catalytic ...converter device. To date, the prevalence of this material in the environment has not been assessed. In this study, we present evidence of the existence of inhalable zirconia in urban dust. Samples of the washcoat, exhaust pipe, topsoil, and road dust were analyzed by X-ray fluorescence, X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, photoluminescence (PL) spectroscopy, and thermally stimulated luminescence (TSL). The results showed a CeO2–ZrO2 phase separation after sintering. This causes the emission of ZrO2, CeO2, and CeZrOx particles smaller than 1 μm, which can likely reach the alveolar macrophages in the lungs. The Ce-Zr content in road dust exceeds geogenic levels, and a significant correlation of 0.87 (p < 0.05) reflects a common anthropic source. Chronic exposure to such refractory particles may result in the development of non-occupational respiratory diseases. The inhalable crystalline compounds emitted by vehicles are a significant environmental health hazard, revealing the need for further investigation and assessment of zirconia levels generated by automobiles in urban areas worldwide.
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•Inhalable zirconia crystals are emitted by aged catalytic converters.•CeO2-ZrO2 phase separation occurs after sintering.•Raman, PL, and TSL allowed the identification of minute zirconia in dust.•Inhalable refractory zirconia is identified as micro to nanocrystals.
A reduction in greenhouse gas (GHG) emissions from productive activities can contribute to climate change mitigation by diminishing the future impacts on natural and socioeconomic systems. Nitrous ...oxide is one of the most important GHGs and agriculture represents its main anthropogenic source. Using a standardized life cycle assessment (LCA) methodology, this study aims to identify and quantify the GHG emissions associated with the different stages of wheat production using local information to develop localized climate change mitigation strategies in one of the most intensive agricultural areas in the world. A set of mitigation scenarios created based on inputs and information obtained directly from producer's associations and farmers were evaluated. These scenarios range from the traditional approaches to the more innovative strategies currently being applied. They are considered to maintain the same yields considering changes mainly in fertilization, tillage and machinery efficiency. We found that the main source of GHGs in wheat production in the Yaqui Valley is fertilizing, with an average of 83% of the life cycle emissions in all the production scenarios proposed. The second contributing activity is tillage, accounting for 13% of Global Warming Potential (GWP) in conventional systems and 1% with ‘no tillage’ strategies. Results show that the manufacture of fertilizers accounted for 42% of the fertilizing emissions and 35% of the total life cycle emissions of wheat. In addition, by using more efficient tractors that decreased diesel inputs, emissions from conventional tillage can be reduced by 33% and emissions from no tillage can be reduced by 24%. The application of the LCA methodology allowed providing a more detailed quantification of the GHG and environmental impacts of different wheat production processes. Compared to other studies, the mitigation strategies developed from this work have a better chance of being adopted by producers because there were developed based on the actual practices proposed by the farmers and consider existing approaches currently being promoted by producer's associations for cost reduction purposes. In this sense, the results of this LCA suggest that implementation of innovation strategies in fertilizing, tillage, and machinery efficiency can both reduce costs and mitigate GHG emissions in intensive wheat production systems all over the world.
Despite the documented effects on human and animal health, particles smaller than 0.1 µm in diameter found in soils, sediments, and the atmosphere remain unregulated. Yet, cerium and titanium oxide ...nanoparticles associated with traffic increase mortality, cause behavioral changes, and inhibit the growth in amphibians. Mites of the genus
Hannemania
spend their early stages in the soil before becoming exclusive parasites of amphibians. Unlike other mites,
Hannemania
is found inside the epidermis of amphibians, thus facilitating the intake of particles, and leading to direct and chronic exposure. To better understand this exposure path, we sampled amphibians hosting mites in a river potentially polluted by traffic sources. Particles collected from mites were studied by scanning electron microscopy and Raman spectroscopy while sediment samples were analyzed for total metal content by portable X-ray fluorescence. Our results indicate that sediment samples showed significant correlations between elements (Zr, Mn, Ti, Nb, Fe) often associated with components in catalytic converters and a level of Zr that exceeded the local geochemical background, thus suggesting an anthropic origin. Furthermore, particles adhered to mites exhibited the characteristic Raman vibrational modes of ceria (CeO
2
, 465 cm
−1
), ceria-zirconia (CeO
2
-ZrO
2
, 149, 251, and 314 cm
−1
), and rutile (TiO
2
, 602 cm
−1
), pointing out to the deterioration of catalytic converters as the most likely source. This research highlights both the importance of unregulated catalytic converters as a source of ultrafine Ce-Ti particle pollution and the role of sub-cutaneous mites as a vector of these particles for amphibian exposure.
According to the Intergovernmental Panel on Climate Change (IPCC), global temperatures have risen at an alarming pace since the early 20th century and this warming has been more pronounced since the ...1970s. Temperature variations are significant because of their relation with thermal comfort and public health. In this study, we characterize the impacts of increasing maximum air temperatures in Sonora, Mexico. Heat days (HDs) and heat waves (HWs) were used as indicators to investigate historical trends in extreme heat. Furthermore, HDs were represented using a generalized linear regression model during the observed period (1966–2015) to generate future scenarios related to extreme heat and subsequently compared with six downscaled general circulation models (CNRM‐CM5, CSIRO Mk3.6.0, HadGEM2‐CC, HadGEM2‐ES, IPSL‐CM5A‐LR and IPSL‐CM5A‐MR) under low and high radiative scenarios (RCP4.5 and RCP8.5). Results of this work indicate that climate stations in Sonora have exhibited increases in the number of HDs and HWs in the historical record that can be associated to physical factors such as elevation, urban land cover and the percent of annual rainfall during the summer. Statistical and model‐based projections indicate that these trends will continue in the future up to 2060, with less moderate increases and high uncertainty noted for the difference scenarios of the downscaled models. These observed and projected trends in extreme heat are important for identifying adaptation strategies in the public and environmental health sectors in Sonora.
Observed trends in summer maximum temperatures and future projections of heat days were found to be increasing in the state of Sonora, Mexico. Warming trends and projections are higher in cities as compared to rural areas and in regions of more pronounced influence of the North American monsoon. Our results suggest that a faster warming could occur in the future compared to the historical period with a high degree of uncertainty, having potential consequences on human health, biodiversity and economy activities.
The rapid transformation and pollution of ecosystems have severely impacted biodiversity. Specifically, anthropogenic activities have imposed adverse effects on amphibians, with evidence suggesting ...that these activities alter parasite and pathogen interactions within their hosts. To investigate these interactions in areas affected by different anthropogenic activities, our study focused on analyzing a pathogen and a parasite known to interact within the amphibian skin (spongy epidermis layer) and both compromising amphibian health:
Batrachochytrium dendrobatidis
(
Bd
), a fungus responsible for chytridiomycosis, a disease associated with massive population declines in amphibians and the
Hannemania
sp. mite in Mexico. Four sampling areas along the Sonora River were selected, representing different human activities: mining, livestock, wastewater discharge, agriculture, and one in an urban zone. We analyzed 135 amphibians across 10 anuran species. Among these, the most abundant species (
Lithobates yavapaiensis
) exhibited the highest prevalence of both pathogen and parasite (90.1% and 27.3%, respectively) and was significantly associated with the intensity of
Bd-
infection. The prevalence of
Hannemania
mites varied significantly across sampling sites as did
Bd
prevalence and infection load, with the highest
Bd
load found at the wastewater discharge site. A significant association between the intensity of
Bd
-infection and both mite abundance and amphibian species was observed when the sampling site was considered. Additionally, sites with
Bd
-positive individuals and
Hannemania
parasitism coincide with refractory elements characterized by mechanical or corrosion resistance. The persistence of these elements in the environment, along with the small particle size (<850 nm) found in sediments, poses a potential risk of internalization, bioaccumulation (e.g., Fe, Co, and Ti), and their transfer through the food chain. It is thus essential to consider monitoring environmental and biotic factors that modulate the relationships between parasites, pathogens, and amphibians if we are to propose conservation strategies adapted to disturbed environments.
Hydrologic connectivity refers to the processes and thresholds leading to water transport across a landscape. In dryland ecosystems, runoff production is mediated by the arrangement of vegetation and ...bare soil patches on hillslopes and the properties of ephemeral channels. In this study, we used runoff measurements at multiple scales in a small (4.67 ha) mixed shrubland catchment of the Chihuahuan Desert to identify controls on and thresholds of hillslope‐channel connectivity. By relating short‐ and long‐term hydrologic records, we also addressed whether observed changes in outlet discharge since 1977 were linked to modifications in hydrologic connectivity. Hillslope runoff production was controlled by the maximum rainfall intensity occurring in a 30‐min interval (I30), with small‐to‐negligible effects of antecedent surface soil moisture, vegetation cover, or slope aspect. An I30 threshold of nearly 10 mm/h activated runoff propagation from the shrubland hillslopes and through the main ephemeral channel, whereas an I30 threshold of about 16 mm/h was required for discharge from the catchment outlet. Since storms rarely exceed I30, full hillslope‐channel connectivity occurs infrequently in the mixed shrubland, leading to <2% of the annual precipitation being converted into outlet discharge. Progressive decreases in outlet discharge since 1977 could not be explained by variations in precipitation metrics, including I30, or the process of woody plant encroachment. Instead, channel modifications from the buildup of sediment behind measurement flumes may have increased transmission losses and reduced outlet discharge. Thus, alterations in channel properties can play an important role in the long‐term (45‐year) variations of rainfall–runoff dynamics of small desert catchments.
The dependence of arid and semiarid ecosystems on seasonal rainfall is not well understood when sites have access to groundwater. Gradients in terrain conditions in northwest México can help explore ...this dependence as different ecosystems experience rainfall during the North American monsoon (NAM), but can have variations in groundwater access as well as in soil and microclimatic conditions that depend on elevation. In this study, we analyze water‐energy‐carbon fluxes from eddy covariance (EC) systems deployed at three sites: a subtropical scrubland, a riparian mesquite woodland, and a mountain oak savanna to identify the relative roles of soil and microclimatic conditions and groundwater access. We place datasets during the NAM season of 2017 into a wider context using previous EC measurements, nearby rainfall data, and remotely‐sensed products. We then characterize differences in soil, vegetation, and meteorological variables; latent and sensible heat fluxes; and carbon budget components. We find that lower elevation ecosystems exhibited an intense and short greening period leading to a net carbon release, while the high elevation ecosystem showed an extensive water use strategy with delayed greening of longer duration leading to net carbon uptake during the NAM. Access to groundwater appears to reduce the dependence of deep‐rooted riparian trees at low elevation and mountain trees on seasonal rainfall, allowing for a lower water use efficiency as compared to subtropical scrublands sustained by water in shallow soils. Thus, a transition from intensive to extensive water use strategies can be expected where there is reliable access to groundwater.
Plain Language Summary
How arid and semiarid ecosystems depend on seasonal rainfall is not well understood, especially when sites have access to groundwater. We explored this topic by studying three ecosystems in northwest México which all experience summer rainfall, but have variations in groundwater access and elevation‐related properties. Using the eddy covariance method, we quantified water, energy and carbon dioxide exchanges in a subtropical scrubland, a riparian mesquite woodland, and a mountain oak savanna over one summer season. We placed datasets during the summer season of 2017 into a wider context using previous measurements, nearby rainfall data, and remotely‐sensed vegetation products. We found that lower elevation ecosystems had an intense and short greening period, while a high elevation ecosystem showed delayed greening of a longer duration. Those ecosystems with more abundant groundwater also had more carbon dioxide uptake during the summer. Access to groundwater appeared to reduce the dependence of ecosystems with trees on the summer season rainfall, thus allowing for longer greening periods and more carbon uptake.
Key Points
Departures from average rainfall modulated ecosystem responses in 2017 leading to intense early greening with shorter than average duration
Access to groundwater leads to higher ET and lower water use efficiency at sites with deep‐rooted riparian and mountain trees
Low elevation sites were a seasonal carbon source, whereas a high elevation site with a lower dependance to rainfall was a carbon sink
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