Presence of DDT and Lindane in a Karstic Groundwater Aquifer in Yucatan,Mexico

Pollution caused by pesticides is becoming relevant because of their harmful environmental effects. The persistence, bioaccumulation and toxicity of some organochloride pesticides have resulted in their restricted use since 1970 and a requirement to monitor them in many countries. Pesticides have endocrine, immunological, reproductive and carcinogenic effects in both humans and animals. The facilitated infiltration of substances results in the pollution of hydric underground resources in karstic limestone such as that found in the state of Yucatan. Observing the north occidental region of the state of Yucatan is particularly important as it is characterized by agricultural activities (wide use of pesticides), significant human settlements and underground water flows oriented towards the north coast. In this study, the underground water quality of a karstic aquifer was evaluated by quantifying the presence of organochlorine pesticides in 29 wells located throughout the Mérida‐Progreso transect, Yucatan, Mexico. The presence of DDT, lindane and their metabolites was detected at concentrations above the permissible limits stated by Mexican regulatory standards (NOM‐127‐SSA1‐1994 2010) in the majority of wells studied. Continuous monitoring of the underground hydric resources in this region is therefore essential to raising awareness of pollution risks and the vulnerability of the coastal north to the contamination of the underground water flows.     

A detailed paleomagnetic and rock-magnetic investigation around Cretaceous-Paleogene boundary: the Autlan (Western Mexico) volcanic sequence revisited

We present a detailed rock-magnetic and paleomagnetic survey from Autlan volcanic succession in western Mexico. The principal aim of this study is to extend paleomagnetic data from Autlan lavas in order to confirm vertical-axis rotation observed in reconnaissance study and to evaluate long-term variation of the geomagnetic field strength based on existing and global data. The mean inclination (44.7°) is in agreement with the expected inclination for 60 and 70 Ma, as derived from available reference poles for the North American craton. The declination (333.6°), however, is significantly different from those expected, which suggests a statistically significant counterclockwise tectonic rotation ranging between 10° ± 6° and 14° ± 7°. As a measure of paleosecular variation (PSV), we obtained a geomagnetic field dispersion of 9.6° (upper and lower limits: 7.2°–11.9°) in perfect agreement with the previously published PSV compilation of selected Cretaceous data from lavas. The mean virtual dipole moments available for Autlan lavas are about 65% of the present geomagnetic axial dipole but are in reasonably good agreement with other comparable quality determinations between 5 and 90 Ma. This reinforces the hypothesis that low geomagnetic field strengths persisted for the entire Jurassic extending into the Upper Cretaceous.     

Rock-magnetic and paleomagnetic survey on dated lava flows erupted during the Bruhnes and Matuyama chrons: the Mascota Volcanic Field revisited (Western Mexico)

A rock magnetic and paleomagnetic investigation was performed on some selected, radiometrically dated lava flows from the Mascota Volcanic Field (MVF), western Trans- Mexican Volcanic Belt. A set of rock-magnetic experiments and standard paleomagnetic analysis were carried out on 19 sites spanning the time interval from 2268 to 72 kyr. The paleomagnetic directions are anchored to absolute radiometric ages while no such information was available in previous studies. This makes possible to correctly evaluate the fluctuation of Earth’s magnetic field from Pliocene to Pleistocene and reveal the firm evidence of possible Levantine excursion. Both Ti-poor and Ti-rich titanomagnetites seem to carry the remanent magnetization with Curie temperatures ranging from 350°C to 537°C. Thirteen flows correspond to the Brunhes chron, one of them exhibits transitional directions, while the remaining six sites belong to the Matuyama chron. New and existing dataset for MVF were used to estimate the paleosecular variation parameters. The selected data include 35 Plio-Quaternary lava flows. After excluding the poor quality data, as well as the transitional directions, the mean paleodeclination is 356.1° and oaleoinclination 39.9°, which agree well with the geocentric axial dipole (GAD) and the expected paleodirections for the Plio-Pleistocene, as derived from the reference poles for the stable North America. The corresponding mean paleomagnetic poles are paleolongitude 226.7° and paleolatitude 86.0°. The virtual geomagnetic pole scatter for the MVF is 15.2°, which is consistent with the value expected from model G at latitude of 20° (this model provides an interpretation of the paleosecular variation at different latitudes for the time of interest). The combined paleomagnetic data, supported by positive reversal test, indicate no paleomagnetically detectable vertical-axis rotations in the study area. The evidence of one transitional directions was detected, which may correspond to the Levantine excursion (360-370 kyr) or unnamed event between 400-420 kyr.     

Influence of volcanic activity on spring water chemistry at Popocatepetl Volcano, Mexico

The results of the 7 years (1994–2000) of monthly monitoring of spring water before and during eruptions show response to volcanic activity. Low salinity and temperature characterize most of the springs, which are located on the flanks of Popocatepetl Volcano. The pH ranges from 5.8 to 7.8 and temperature from 3 to 36 °C. Oxygen and hydrogen isotopic data show that the water is of meteoric origin, but SO₄²⁻, Cl⁻, F⁻, HCO₃⁻, B, and SO₄²⁻/Cl⁻ variations precede main eruptive activity, which is considered linked to influx of magmatic gases and acid fluids that react with sublimates and host rock and mix with the large water system. Na⁺, Ca²⁺, SiO₂ and Mg²⁺ concentrations in the water also increased before eruptive activity. The computed partial pressure of CO₂ in equilibrium with spring waters shows values higher than air-saturated water (ASW), with the highest values up to 0.73 bar of pCO₂. Boron is detected in the water only preceding the larger eruptions. When present, boron concentration is normally under health standard limits, but in two cases the concentration was slightly above. Other components are within health standard limits, except for F⁻ in one spring.     

Modelling the influence of snow accumulation and snow-ice formation on the seasonal cycle of the Antarctic sea-ice cover

 Recent observational and numerical studies of the maritime snow cover in the Antarctic suggest that snow on top of sea ice plays a major role in shaping the seasonal growth and decay of the ice pack in the Southern Ocean. Here, we make a quantitative assessment of the importance of snow accumulation in controlling the seasonal cycle of the ice cover with a coupled snow–sea-ice–upper-ocean model. The model takes into account snow and ice sublimation and snow deposition by condensation. A parametrisation of the formation of snow ice (ice resulting from the freezing of a mixture of snow and seawater produced by flooding of the ice floes) is also included. Experiments on the sensitivity of the snow–sea-ice system to variations in the sublimation/condensation rate, the precipitation rate, and the amount of snowfall transported by the wind into leads are discussed. Although we focus on the model response in the Southern Hemisphere, results for the Arctic are also discussed in some cases to highlight the relative importance of the processes under study in both hemispheres. It is found that the snow loss by sublimation can account for the removal of 0.45 m of snow per year in the Antarctic and that this loss significantly affects the total volume of snow ice. A precipitation decrease of 50% is conducive to large reductions in the Antarctic snow and snow-ice volumes, but it leads only to an 8% decrease in the annual mean ice volume. The Southern Ocean ice pack is more sensitive to increases in precipitation. For precipitation rates 1.5 times larger than the control ones, the annual mean snow, ice, and snow-ice volumes augment by 30, 20, and 180%, respectively. It is also found that the transfer to the ocean of as much as 50% of the precipitating snow as a result of wind transport has almost negligible effects on the total ice volume. All the experiments exhibit a marked geographical contrast in the ice-cover response, with a much larger sensitivity in the western sector of the Southern Ocean than in the eastern sector. Our results suggest that snow-related processes are of secondary importance for determining the sensitivity of the Arctic sea ice to environmental changes but that these processes could have an important part to play in the response of the Antarctic sea-ice cover to future, or current, climatic changes. Received: 30 June 1997/Accepted: 2 October 1998     

Wavelet methods: application to the study of the stable atmospheric boundary layer under non-stationary conditions

In this work, some wavelet methods are introduced to study the atmospheric boundary layer under stable conditions, where intermittent events and non-stationary turbulence take place. Such behavior makes classical methods, based on Fourier transform, difficult to use or even of no application.The wavelet transform is used to detect and characterize some structures in the stable atmospheric boundary layer. First, a wave-like event with a 16 min period is detected and analyzed in a wind record. The sum of some Morlet wavelets is proposed as a model for the oscillations. Afterwards, the wavelet transform is introduced to the study of non-stationary small scale turbulence. It provides the time evolution of the energy and a good location in time of the spots of turbulence. Finally, some wavelet tools are used to characterize a traveling structure, provided that it is simultaneously detected at different locations. The phase differences in the wavelet transform give the wavelength and the phase speed of the oscillations, whereas a double transform method is introduced to estimate the group velocity of the structure.     

Performances and prospects of the “ROSEBUD” dark matter search experiment

A cryogenic search for WIMP Dark Matter with small sapphire bolometers through the WIMP scattering off Al₂O₃ nuclei, the ROSEBUD (Rare Objects SEarch with Bolometers UndergrounD) experiment, is being installed in the Canfranc Underground Laboratory (Spain) at 2450 m water equivalent. The performances of the bolometers, the radioactive background expected from the measurement of the radiopurity of the ROSEBUD components and the estimated sensitivity of the experiment for low mass WIMP detection are presented.     

First evidence of complex dental practice about 1300 BP in Mesoamerica revealed by absolute geomagnetic intensity

Deliberated dental modifications and mutilations are known since prehistoric times. The Mayas and other ancient cultures in Mesoamerica were considered pioneers of such practice. The evidences of therapeutic intervention, however, are still poorly documented and credible examples are extremely scarce. One of the burials excavated at the locality of La Mina (Michoacan, Mexico) corresponds to a 30-35 year old male individual named Alvaro, who presented a well-marked dental deformation. Moreover, Alvaro had a quite deep and symmetrical perforation in the upper right canine–a treatment similar to the procedure of endodontics or root canal. The archaeological context of Alvaro’s habitat was dated using the archaeomagnetic method applied to pottery samples unambiguously correlated to the burial. The analysis supplied a time interval between 647 and 825 AD suggesting the first evidence of complex dental practice in the Americas.     

An integrated magnetic,geochemical and archeointensity investigation of casting debris from ancient metallurgical sites of Michoacán,Western Mesoamerica

The ability of baked clay-elaborated objects to record the temporal variations of both direction and intensity of the geomagnetic field at the time of their elaboration or last use has been widely used during the last decades to fill the gaps left by available time-discrete volcanic-rock logs for a better knowledge of the evolution of the geomagnetic field. Further refinement of the secular variation curves has motivated the search for alternative non-conventional materials as attractive targets for archeomagnetic studies. Both clay and copper have been used since pre-Hispanic times for the elaboration of a wide variety of ornamental and utilitarian objects in Mesoamerica. Previous studies carried out in Europe and Israel have shown the usefulness of copper slags as one of these non-conventional materials. We present the results of an integrated study carried out on ten copper slags from seven ancient metallurgical sites of Michoacán. The analysis included a series of rock magnetism experiments, scanning electron microscope analysis, archeointensity determinations following the Thellier-Coe method and their corresponding dating. Based on the results obtained the slag-set analyzed can be divided in two main groups: low Fe concentrations (associated with high Cu concentrations) for slags comprising the first group, and high Fe concentrations (associated with low Cu concentrations) for slags from second group. Slags from the first group are characterized by almost reversible thermomagnetic curves, while those corresponding to the second group show a quite irreversible behavior. A crystalline (vitreous) structure within the massive surface of the slags is observed for those coming from the second (first) group. These striking features could reflect significant differences in the metallurgical process followed at these sites, which according to archeological and historical evidences correspond to Colonial and pre-Hispanic usage metallurgical sites; first and second group, respectively. The good experimental behavior exhibited by these materials demonstrates the suitability of copper slag to obtaining absolute archeointensity data which can be used to improve the existing Mesoamerican archeomagnetic record. This in turn, can be used both for geomagnetic field modelling purposes and archeomagnetic dating.     

Using Audience Physiology to Assess Engaging Conservation Messages and Animal Taxa

Abstract

We used heart rate change as a tool to study how positive and negative wildlife conservation messaging impacts a viewer, and which types of animal images stimulate greatest reaction. We used scenes from five wildlife conservation videos available from environmental organization websites and YouTube, with positive and negative messaging. We found both very positive and very negative messaging in videos may be similarly effective in engaging viewers. A trend in greater changes in heart rate when insects, mammals, and birds appear on the screen suggests generally high human interest in these taxa, potentially due to avoidance and attraction responses. The number of scenes (N?=?54) in which various taxa appear reflects bias toward mammals (65%) and birds (17%) to capture viewers’ attention. Arousal is a primary step in engaging an audience to attend to a message. Physiological research offers innovative new techniques to evaluate public responses to communications about biodiversity conservation.