North-central Mexico Research Articles

Mining struggles in north-central Mexico: Between mining tradition, poverty, and environmentalism

The present study is centered on characterizing the conflicts associated with mining in Sonora and Zacatecas, two states in north-central Mexico. We consider the municipal surroundings where they emerge, via cartographical analysis of some variables including mining frontiers and poverty. The predominant conflict types show that communities are not inclined to accept mining as presented in government or corporate discourses; rather, communities struggle to improve their living conditions and preserve their natural surroundings. We can observe that in long-time mining locations, there is greater acceptance of the mining industry, so that the conflicts which arise tend to be concerned with labor or with eco-territorial matters of coexistence and pecuniary assets, although there are also alternatives; meanwhile, in places with recent mining penetration and deep-rooted agro-fisheries activities, conflicts tend to be eco-territorial regarding alternatives and territorial defense. However, the advance of the mining frontier configures the coexistence of different temporal regimes, based on complex spatio-temporal patterns where different types of environmentalism overlap with demands for opposition, negotiation, or collaboration in the same place.

Auto-Machine-Learning Models for Standardized Precipitation Index Prediction in North–Central Mexico

Certain impacts of climate change could potentially be linked to alterations in rainfall patterns, including shifts in rainfall intensity or drought occurrences. Hence, predicting droughts can provide valuable assistance in mitigating the detrimental consequences associated with water scarcity, particularly in agricultural areas or densely populated urban regions. Employing predictive models to calculate drought indices can be a useful method for the effective characterization of drought conditions. This study applied an Auto-Machine-Learning approach to deploy Artificial Neural Network models, aiming to predict the Standardized Precipitation Index in four regions of Zacatecas, Mexico. Climatological time-series data spanning from 1979 to 2020 were utilized as predictive variables. The best models were found using performance metrics that yielded a Mean Squared Error, Mean Absolute Error, and Coefficient of Determination ranging from 0.0296 to 0.0388, 0.1214 to 0.1355, and 0.9342 to 0.9584, respectively, for the regions under study. As a result, the Auto-Machine-Learning approach successfully developed and tested Artificial Neural Network models that exhibited notable predictive capabilities when estimating the monthly Standardized Precipitation Index within the study region.

Structural architecture of the Mapimí Biosphere Reserve and its surroundings, north-central Mexico: New insights from U–Pb geochronology and interpreted structural data

The Mapimí Biosphere Reserve is in northeastern México, near the boundary between the Mesozoic Coahuila platform and the Mexican central basin. A large portion of the Reserve is a broad bolson where isolated mountains are surrounded by flat terrain. Two slightly elevated areas (benches) are subtle topographic features in the Reserve. There, in rolling hills occur folded, Upper Cretaceous – Paleogene, poorly-lithified and -exposed transitional and continental sediments and tilted Paleogene volcanic and subvolcanic rocks. Each bench occupies a band that is ∼75 × 20 km. A land strip where playa lakes and salt-flats occur separates the benches. Deformation style within the benches differ from those in regions where platform carbonates or Mexican central basin rocks dominate. Structures within the benches are gentle, open folds and medium sized (15 - 3 km in diameter) structural domes and basins. Furthermore, orientation of the fold axes shows a wide scatter. There is at least one folded structure in the Reserve that displays an interference pattern that indicates refolding. Post-Oligocene normal faults bound the benches and overprinted on the folded structures. However, the most important normal fault, which cuts in half two domes and one structural basin, lacks a clear topographic scarp. The occurrence of broad exposures of the Upper Cretaceous Indidura Formation in flat areas, interpreted as the footwall block of a major normal fault, is consistent with the interpretation that the benches are rocky pediments partially covered by alluvium and/or eolian sediments. Thus, it appears that Cenozoic extension has been inactive for a long period of time in this portion of the Mexican Basin and Range province. The best evidence of NNW, down to the SW normal faults within the Reserve is in the Sierra de Mohóvano. There, an array of domino-style normal faults cut Oligocene volcanic rocks and gravel deposits. The master fault of the domino array is adjacent and parallel to a fold in Mesozoic marine rocks.We attribute the unusual characteristic of the folds in the Reserve to 1) the region is near the boundary among the large calcareous platform and the basin, and the boundary had a significant curvature, concave toward the W. This geometry caused complex deformation during crustal shortening, as tectonic transport associated with the Mexican orogen is toward the NE, 2) a significant difference in competence between the poorly consolidated transitional and continental deposits and the more competent rocks in the carbonate platform also played a role in the formation of the structures, as folds in the benches formed during the waning stage of the Mexican orogen, as suggested by the detrital zircon U–Pb ages, which are as young as ∼30 Ma, 3) Oligocene magmatic activity caused the emplacement of laccoliths, which locally modified older folds forming domes, 4) finally, Basin and Range extension (<27 Ma) cut across the folded sediments and overlying volcanic rocks. Evidence of extension in the Reserve is subtle as normal faults have remained inactive for a long time, while isostatic uplift and erosion developed the pediment, effectively masked most fault scarps.

Calibration and Evaluation of the SIMPLE Crop Growth Model Applied to the Common Bean under Irrigation

Bean production is at risk due to climate change, declining water resources, and inadequate crop management. To address these challenges, dynamic models that predict crop growth and development can be used as fundamental tools to generate basic and applied knowledge such as production management and decision support. This study aimed to calibrate and evaluate the SIMPLE model under irrigation conditions for a semi-arid region in north-central Mexico and to simulate thermal time, biomass (Bio), and grain yield (GY) of common beans cv. ‘Pinto Saltillo’ using experimental data from four crop evapotranspiration treatments (ETct) (I50, I75, I100, and I125) applied during the 2020 and 2021 growing seasons. Both experiments were conducted in a randomized complete block design with three replicates. Model calibration was carried out by posing and solving an optimization problem with the differential-evolution algorithm with 2020 experimental data, while the evaluation was performed with 2021 experimental data. For Bio, calibration values had a root-mean-square error and Nash and Sutcliffe’s efficiency of &lt;0.58 t ha−1 and &gt;0.93, respectively, while the corresponding evaluation values were &lt;1.80 t ha−1 and &gt;0.89, respectively. The I50 and I100 ETct had better fit for calibration, while I50 and I75 had better fit in the evaluation. On average, the model fitted for the predicted GY values had estimation errors of 37% and 22% for the calibration and evaluation procedures, respectively. Therefore, an empirical model was proposed to estimate the harvest index (HI), which produced, on average, a relative error of 6.9% for the bean-GY estimation. The SIMPLE model was able to predict bean biomass under irrigated conditions for these semi-arid regions of Mexico. Also, the use of both crop Bio and transpiration simulated by the SIMPLE model to calculate the HI significantly improved GY prediction under ETct. However, the harvest index needs to be validated under other irrigation levels and field experiments in different locations to strengthen the proposed model and design different GY scenarios under water restrictions for irrigation due to climate change.

An evolutionary parsimonious approach to estimate daily reference evapotranspiration

The reference evapotranspiration (ETo) is an essential component in hydrological and ecological processes. The objective of this research is to develop an explicit model to estimate ETo only using commonly measurable meteorological parameters such as relative humidity, air temperature, and wind speed, where the measurements corresponding to solar radiation are omitted. The model was generated using Genetic Programming (GP), evaluated, and validated with reference data ETo using FAO56-PM. This reference data was obtained from different climates (warm-temperate and arid-warm) and latitudes, acquired from CIMIS stations in the state of California, United States, and the El Porvenir station in the state of Coahuila, located in north-central Mexico. After applying the proposed methodology, a total of 3754 results were generated, demonstrating a significant improvement in the estimation of ETo compared to the Hargreaves–Samani model. A particularly noteworthy result revealed that our approach outperformed the Hargreaves–Samani model in the training phase by 27%, and in the testing phase by 16%, on average. In order to achieve a generalized model, a dataset encompassing meteorological stations in two different climates (warm-temperate and arid-warm) and various latitudes was utilized. The obtained outcome unveiled a highly effective model for estimating ETo in diverse climatic contexts, eliminating the need for local adjustments. This model significantly surpassed the Hargreaves–Samani model, exhibiting superior performance by 17% during the training phase and 18% during the testing phase. These results conclusively underscore the capability of our approach to provide more accurate and reliable ETo estimates. These results conclusively underscore the capability of our approach to provide more accurate and reliable ETo estimates. Finally, to validate the model, four different datasets with climates similar to those used for model creation (warm-temperate, warm-arid) and different latitudes were employed. The validation stage results clearly indicate the superiority of our reference evapotranspiration ETo11 model over the Hargreaves–Samani model by 51% in warm-temperate climates. For the dataset with arid-warm climate, our model continued to show satisfactory results, surpassing the Hargreaves–Samani model by 8%. GP emerges as an innovative and effective alternative for simplified model development. This approach introduces a novel paradigm that facilitates the efficient development of models, standing out for its simplicity and effectiveness in generating solutions.

MINERAL STATUS OF LACTATING EWES IN THE ARID AND SEMI-ARID ZONES OF NORTH-CENTRAL MEXICO

Profitable sheep production depends greatly on the mineral content of range forages, as adequate nutrition is a prerequisite for reaching the animal’s optimum performance. The objective was to determine the contents of calcium (Ca), phosphorus (P), copper (Cu), zinc (Zn), and manganese (Mn) in range forages and blood serum of grazing, lactating ewes in the arid and semi-arid zones of North-Central Mexico. Samples of forages and blood of lactating ewes were collected in two seasons (spring and winter) from four randomly selected sheep farms located in the state of Aguascalientes. The P content was analyzed using the colorimetrical method, while levels of Ca, Cu, Zn, and Mn were determined by spectrophotometry. Forage mineral content averaged 0.20% P, 0.34% Ca, 8 ppm Cu, 483 ppm Mn, and 29 ppm Zn. In blood serum, mineral content reached 20 ppm P, 147 ppm Ca, 0.52 ppm Cu, 2.9 ppm Mn, and 0.80 ppm Zn in winter, and values of 20.5 ppm P, 177 ppm Ca, 0.57 ppm Cu, 3.13 ppm Mn, and 0.89 ppm Zn in spring. Overall, in both spring and winter seasons, 58-100% of sampled forages showed Ca, P, Cu, and Zn deficiencies, but all of them fitted the optimal content of Mn. Blood samples showed similar patterns in winter and spring seasons, Ca was not deficient (145-180 ppm vs. optimal range: 90-120 ppm), but P, Cu, and Zn were deficient (P: 9-21 ppm vs. optimal range: 50-65 ppm; Cu: 0.51-0.58 vs. optimal range: 0.60-1.5 ppm; and Zn: 0.71-0.92 ppm vs. optimal range: 0.50-1.2 ppm); Mn was slightly over the optimal range (2.89-3.2 μg/L vs. optimal range: 2 to 40 μg/L). In some cases, forage mineral content might not be related to blood serum contents. However, it should be desirable to understand all the uncontrolled factors in addition to the mineral interactions that could interfere with further studies.

Taxonomic review of Berriasian and Valanginian ammonites from Zacatecas State (north-central Mexico) studied by Burckhardt in 1906

A review of sixteen ammonoid specimens of the Berriasian and Valanginian age from Zacatecas, as recorded by Burckhardt in 1906, is presented as part of a larger-scale study of Valanginian ammonoid faunas from Mexico. The present update includes also museographic information and new images of Burckhardt's ammonites, as well as nine 3D models for better display of specimens. Six taxa have been identified to the species and two to generic level. In comparison to the original identifications of Burckhardt, four taxa have been transferred at the generic and four at the specific levels. Using stratigraphic range data from the literature, we assign the present ammonoid specimens to the uppermost upper Berriasian to lower Valanginian interval. The following biozones have been recognized: Tirnovella alpillensis, ‘Thurmanniceras’ pertransiens and Neocomites neocomiensiformis; with two subzones: ‘Thurmanniceras’ otopeta and Neocomites premolicus. Furthermore, a paleobiogeographic analysis of the taxa revised here indicates a clear affinity with contemporaneous ammonoid assemblages from the Mediterranean region.

Association of obesity, diabetes, and hypertension with arsenic in drinking water in the Comarca Lagunera province (north-central Mexico)

Chronic endemic regional hydroarsenicism (CERHA) is a global issue that affects over 200 million people exposed to arsenic (As) in drinking water. This includes 1.75 million individuals residing in La Comarca Lagunera, a region in north-central Mexico. Arsenic levels in this region typically exceeds the WHO guideline of 10 µg L−1. Biochemical alterations related to the human As metabolism may increase the risk of overweight and obesity (O&O), type 2 diabetes (T2D), and hypertension (AHT). In our study, we investigated the role of As in drinking water as a risk factor for these metabolic diseases. We focused on populations with historically moderate (San Pedro) and low (Lerdo) drinking water As levels and people with no historical evidence of As water contamination. The exposure assessment to As was based on measurements of the drinking water (medians 67.2, 21.0, 4.3 µg L−1) and urinary As concentrations in women (9.4, 5.3, 0.8 µg L−1) and men (18.1, 4.8, 1.0 µg L−1). A significant correlation between As in drinking water and urine evidenced the As exposure in the population (R2 = 0.72). Adjusted odds ratios with 95% confidence intervals evidenced higher chances of being diagnosed with T2D (1.7, 1.2–2.0) and AHT (1.8, 1.7–1.9) in individuals living in San Pedro than those in Lerdo. Still, there was no significant association with obesity. Individuals living in CERHA towns were found to have a higher risk of obesity (1.3–1.9), T2D (1.5 to 3.3), and AHT (1.4 to 2.4) compared to those residing in non-CERHA towns. Finally, obesity is more probable in women [inverse of OR and 95%CI 0.4 (0.2–0.7)] compared to men, while men is more likely to be diagnosed with T2D [OR = 2.0 (1.4–2.3)] and AHT [OR = 2.0 (1.5–2.3)] than women, independently of the municipality.

Effect of storage and pre-germination treatments on seeds of Arbutus xalapensis from north-central Mexico

Effect of storage and pre-germination treatments on seeds of Arbutus xalapensis from north-central Mexico

Arsenic and fluorine in groundwater in northern Mexico: spatial distribution and enrichment factors.

North-central Mexico has groundwater contaminated with arsenic (As) and fluoride (F). Based on the dispersion patterns of these solutes, their sources are linked to felsic volcanic rock fragments and secondary minerals (clays, iron oxyhydroxides) within the alluvium fill of the aquifers. However, little is known about the effect of the enrichment factors for F and As in this area. Natural enrichment factors include evaporation, Ca/Na, and competitive adsorption and desorption from solid phases. This study used 1237 groundwater quality data measurements from 305 sampling sites collected between 2012 and 2019 in the state of Durango in north-central Mexico. To determine the contribution of enrichment factors to As and F content, the study area was divided into four sections, two being in the mountainous part of the state and two in the high plateaus. The data were compared among sections and analyzed using Spearman correlation and Piper and Block diagrams. The results indicate that the main solute enrichment mechanisms are evaporation and weathering of silicates and evaporites. Among the four sections, As, pH, and HCO3 seemed not to vary, F varied slightly, and nitrate and total dissolved solids varied the most. The lack of variation in As among sections is associated to its strong adsorption to clay minerals and iron oxyhydroxides, whereas the diminished F content in the eastern sections is likely linked to the adsorption of F to precipitating calcite (since groundwater is saturated with respect to calcite (SIcalcite = 0.43) and undersaturated for fluorite (SIfluorite = - 1.16). These processes shed light on the distribution of F and As in this area, and are likely operating in other states in northern Mexico and in semi-arid areas elsewhere.

Temporal trends of daily extreme temperature indices in North-Central Mexico

Temporal trends of daily extreme temperature indices in North-Central Mexico

Towards Automated/Semiautomated Extraction of Faults from Lidar Data

The Pajarito fault system is a complex zone of deformation and a seismically active region nestled within the Rio Grande rift in north-central New Mexico. Numerous laterally discontinuous faults and associated folds and fractures interact in a manner that has important implications for seismic hazards and risk mitigation. Previous efforts have established a foundation for the location of lineaments and structures in the Pajarito fault system; however, ensuring the completeness of the current lineament mapping is required for identifying areas for field validation, evaluating the potential for future seismic activity, and better understanding fault interaction. Assistance with this fault-mapping task via automated or semiautomated techniques as applied to lidar data over a large area of interest is highly desirable. A proof-of-concept processing flow which transforms lidar point-cloud data into a raster of surficial fault candidates is described and illustrated herein. These initial results hold great promise toward achieving our ultimate goal.

Modeling the adoption of a garlic variety (Allium sativum L.) in Mexico through survival analysis

The objective of this research was to analyze the adoption behavior over time for the improved variety of garlic CEZAC 06, and the factors associated with the adoption process through survival analysis (SA), in North-Central Mexico. The data comes at farm level and was collected in 2019 through a questionnaire given to 40 garlic farmers in Zacatecas, Mexico. The results show that 62.5 % of the farmers who adopted CEZAC 06 carried out this process in the first two years after they were first introduced to it. The factors that played a role in the adoption process were: farmer age, how long the farmer had been in business for, number of hectares availables for garlic production, yield, number of college-educated family members, income from crop farming, income from garlic farming, agriculture-related courses taken, financial aid from the federal government, and being part of any type of organization. Improving yield and the quality of the garlic bulb requires an adequate extension system that allows farmers to receive updated and reliable information on the importance of technological innovation. Highlights The analysis also suggested that new technologies should be transmitted at higher rates to increase adoption. This can be done by implementing courses aimed at farmers with low educational backgrounds, small plots of land and low productivity levels. The factors affecting the adoption process were: farmer age, how long the farmer had been in business, yield, etc. CEZAC 06 will increase yield and rural farmers could improve the quality of the bulb as a marketable surplus. This work contributes to the scarce literature on the application of survival analysis to agricultural technologies.

Geology and geochemistry of jasperoids from the ‘Montaña de Manganeso’ district, San Luis Potosí, north-central Mexico

Large outcrops of jasperoids occur in the ‘Montaña de Manganeso’ mining district in north-central Mexico. They range from massive manganiferous jasperoids to highly brecciated, hematitic jasperoid. The jasperoids of ‘Montaña de Manganeso’ occur mainly as replacements of limestone, sandstone and shale, commonly nearby high-angle fault systems. The mineralogy of the jasperoids consist of quartz and its polymorphs (chalcedony, tridymite and cristobalite), Fe-Mn oxyhydroxides, calcite and minor barite. Many outcrops show evidence of several periods of brecciation and silicification. The geochemical signature of the jasperoids suggests that silicification was product of hydrothermal activity. The jasperoids display enrichment in elements of hydrothermal provenance such as Ba, Sr, As, Cr, Mo, Sb, Ni, Zn and Cu, whereas are strongly depleted in the elements indicative of clastic sources such as Ti, K, Th and Zr. Element ratios such as (Fe+Mn)/Ti, Al/(Al+Fe+Mn), Fe/Mn and U /Th, along with the Al-Fe-Mn and Fe-Mn-(Ni+Co+Cu)×10 ternary diagrams confirm a hydrothermal origin. Low ∑REE, an enrichment of LREE over HREE, negative Ce anomalies and positive Y anomalies (YPASS/HoPAAS) also support the hydrothermal processes. The geological evidence, in the form of a feeder zone and extensive hydrothermal alteration, show that the silica forming the rocks originated from ascending hot fluids.

PRODUCTIVE BEHAVIOR OF Dactylopius coccus Costa ON TWO CONFINED Opuntia ficus-indica (L.) Mill CULTIVARS

Recently, the commercial breeding of Dactylopius coccus in confined environments has been developed not to depend on seasonal production and ensure the supply chain. Previous studies have shown the technical viability of their breeding of i Opuntia in a repository also called "Nopaloteca". However, considering the genetic diversity of Opuntia in each region, it is necessary to evaluate alternative cultivars to maximize the efficiency of that production system. The evaluated cultivars were Esmeralda and Villanueva (Opuntia ficus-indica (L.) Mill.). Four height levels (m) within the “Nopaloteca” (N1: 0.5; N2: 1.0; N3: 1.5 and N4: 2.0) and two harvest indices (pre and post oviposition) were evaluated regarding their effects on the carminic acid concentration (CAC, %) and fresh weight (FW, g) of D. Coccus. The results showed no significant difference in the CAC of the D. coccus colonies in both cultivars (18 %); however, the highest FW was reached in the cv. Esmeralda with 6.3 g per cladode (p ≤ 0.05). The highest CAC was found in the N4 treatment (2.0 m) with 18.6 % (p ≤ 0.05); while the highest average FW values (p ≤ 0.05) were in the intermediate levels of the N2 (1.0 m) and N3 (1.5 m) treatments, with 6.4 and 6.1 g per cladode, each. The post oviposition phase harvest of D. coccus resulted in a higher CAC concentration (20.4 %); meanwhile, in the pre-oviposition phase, 15.6 % was harvested (p ≤ 0.05). Due to the productivity and quality obtained, the Esmeralda cultivar could be used as an alternative host for the intensive breeding of D. coccus in confinement, in north-central Mexico.

Chromosome Numbers in Verbesina (Asteraceae, Heliantheae, Verbesininae)

We report chromosome counts for 107 samples of Verbesina collected in Ecuador, Mexico, and Venezuela. These counts represent 77 species with 47 of these belonging to species never counted before. Most samples have the hypothesized diploid number for the genus of 2n = 34; a few taxa have 2n = 36; 19 collections are polyploid. Polyploidy was found in a majority of the South American samples counted (13/23); polyploidy was not broadly distributed in samples counted for Mexican species (6/84). We report the first octoploid for a collection of Verbesina, V. pedunculosa from northcentral Mexico at n (4x) = 68. Previously published counts for Verbesina amount to 175 records representing 90 species. Together with the counts we report here, chromosome numbers are now known for 137 species of Verbesina.

PSXIII-22 Heat stress in north central Mexico and time of exposure to it, measured by the Environmental Temperature Index

Abstract The Temperature Humidity Index (THI) is the most used to identify the risk of heat stress for dairy cattle, which is based on the environmental temperature (ºC) and humidity (%), and of which they are currently considered 68 points as the threshold for high producing dairy cows. In the Comarca Lagunera, located in north central Mexico, 21% of the Mexican dairy production is generated annually, despite its environmental conditions characterized by temperatures up to 41.5 ° C in the summer, low relative humidity and high solar radiation. The objective was to identify the average number of days in which a THI ≥68 is reached per month in each season of the year with 1, 8 and 16 h of exposure in dairy farms of the region, for which, the information recorded every 10 min was analyzed daily in five farms for 6 years (2015–2020), using the DiGiTH ™ application (DiGiTH Technologies, Mexico) and through ANOVA (proc GLM; SAS Inst. Inc., Cary, NC, USA), to identify differences seasonal for this variable. The attached table shows that spring and summer were the seasons in which the highest number of average days per month were recorded, and winter in which the fewest days were recorded. Regarding the hours of exposure, it is observed that spring and summer are very similar in 1 and 8 hours of exposure, while for autumn and winter a clearer decrease is observed according to the hours of exposure for these seasons. These results indicate a very marked seasonal variability and in terms of the hours of exposure, which should be considered in order to adopt the measures to reduce the negative effects for the dairy cattle of the region.

PSVIII-13 Are the heat stress days increasing in central northern Mexico?

Abstract The Lagunera region, located in north central Mexico (24° 01′-26° 48 ‘LN and 101° 52′-101° 52′ 104° 40′ LO), produce the 21% of the national Mexican cow’s milk despite its climatic conditions (temperatures that fluctuate between 12.7 °C in January and 28.5 °C in June, with extremes of -5 °C and 41.5 °C, in addition to high solar radiation). The Temperature Humidity Index (THI) is the most useful indicator to define if there are heat stress conditions. To identify whether the days in which THI ≥68 (considering the threshold for signs of heat stress to appear in high-producing lactating cows) are increasingly reached at least one hour a day, the information of this indicator was recorded every 10 min daily, from 5 cow farms for 6 years (2015–2020), using the DiGiTH™ application (DiGiTH Technologies, Mexico), and regressions were run to identify if there is a relationship between the years of study and the THI levels. At any level of THI (≥68), there is a tendency to increase the number of days (10.05 d per year; R2 0.37); Disaggregating the data by THI level, this trend is also observed for levels 68 to 71 and 72 to 76 THI, registering an increase of 11.33 d (R2 0.45) and 9.03 d per year (R2 0.45) respectively. At the 77 - 79 THI level there is no trend, while at the ≥80 THI level, a decrease of 5.66 d per year was registered (R2 0.79). The results suggest that in this region, the days of heat stress are increasing, except for the level ≥80 THI, which indicates that palliative measures for heat stress should be intensified, and it is necessary to identify the reason for the decrease in heat stress days at the most dangerous level for livestock.

Mapping salinization and trace element abundance (including As and other metalloids) in the groundwater of north-central Mexico using a double-clustering approach

This study aimed to determine the reliability of the double-clustering method to understand the spatial association and distribution of major and minor constituents in the groundwater of an arid endorheic basin in central Mexico (Comarca Lagunera Region). The results of the double-clustering approach were compared with well-known spatial statistics such as spatial autocorrelations (Moran index) and the local indicator of spatial association (LISA). Fifty-five groundwater samples were collected from diverse wells within the basin, and the major ions, metalloids, and trace elements were determined. Overall, the double-clustering analysis was an effective tool for identifying lithogenic/anthropogenic processes occurring in the basin and for establishing zones with high or low abundance of major ions and trace elements, even where processes affecting the groundwater quality were spatially dispersed. Although 89% of the samples showed As higher than the threshold value of 10 μg/L proposed by the World Health Organization for drinking water, both the double-clustering and LISA analyses identified As hotspots in the alluvial aquifer, where the extraction of deeper and warmer groundwater might promote the concomitant release of the metalloids As, Sb, and Ge and the trace elements V and W. Similarly, both statistical analyses identified mountainous sectors where the weathering of silicates and carbonates plays a key role in the abundance of HCO3−, Ga, and Ba. However, the LISA analysis failed to identify hotspots of carbonate-derived elements such as Ca, Mg, Sr, and U and silicate-derived elements such as Ca, Mg, K, Sr, Rb, Cs, Pb, Ni, and Y. Otherwise, the double-clustering analysis clearly defined high- and low-concentration zones for all these elements in the study region. Unlike the LISA analysis, the double-clustering approach was also successful in determining alluvial areas with high concentrations of Si and Ti and areas where the concentrations of Na, Cl−, SO42−, NO3−, B, Li, Cu, Re, and Se in groundwater were elevated, increasing the groundwater salinity. Overall, this study demonstrated that the double-clustering is an easy-to-apply approach, capable of visualizing disperse zones where specific anthropogenic processes may threaten the groundwater quality.

Epidemiology of Neospora caninum infection in free-range chickens (Gallus gallus domesticus) in north central Mexico.

The objective of the present study was to investigate the epidemiology of natural infection by N. caninum in free-range chickens from Aguascalientes, Mexico, through identifying the presence of antibodies, its association with certain risk factors, and estimate the frequency of parasite DNA detection in the brain. The study included 150 clinically healthy chickens from 81 small family farms distributed throughout the state, from which blood and brain samples were taken. Serum samples were processed by indirect immunofluorescence considering a dilution of 1:50 as a positive reaction, while the DNA detection was done by PCR; the association between the presence of antibodies and the potential risk factors was estimated through logistic regression. The general anti-N. caninum presence of antibodies in the studied population was 46% (69/150, CI 95% 38-54), with titers of 1:50 in 38, 1:100 in 24, and 1:200 in 7, finding positive cases in 49% of the farms and in 91% of the municipalities that integrate the state. The presence of antibodies found in the municipalities was estimated in a range of 20 to 75%. The frequency of DNA detection was 6% (9/150, CI 95% 2-11). The grain supplementation was identified as the unique risk factor for infection (OR = 2.82; 95% CI, 1.18-6.73, p < 0.019).