RESUMO
Silver (Ag) production in Hispanic America between the 16th and 19th centuries is thought to be one of the largest sources of anthropogenic mercury (Hg) emissions in history. Recent reviews of the chemistry behind the patio process, which used Hg amalgamation to extract Ag from ore, reveal that a large amount of the Hg may not have been immediately released to the atmosphere; instead, it may have been captured in the form of calomel (Hg2Cl2, in which Hg exists as monovalent HgI) and remained in the local environment. Here we show that Hg used in the patio process centuries ago in the Guanajuato Mining District of Mexico continues to elevate present-day concentrations of gaseous elemental mercury (GEM) throughout the region. In the ground-level air, GEM ranged from 8 to 454 ng m-3, exceeding the Northern Hemispheric average (~1.4 ng m-3) by up to two orders of magnitude. Much higher concentrations, up to 44,700 ng m-3, were found in the interstitial air of reprocessed mineral wastes, sediment, and soil. These highly elevated present-day GEM values are due, at least in part, to the disproportionation of legacy calomel, as supported by the presence of HgI in the reprocessed wastes and by the GEM release pattern from calomel disproportionation. Our results imply that the contribution of historical Ag refining to atmospheric Hg emissions must be re-evaluated to account for calomel and its subsequent disproportionation and releases of GEM to the present-day.
Assuntos
Poluentes Atmosféricos , Mercúrio , Poluentes Atmosféricos/análise , Monitoramento Ambiental/métodos , Mercúrio/análise , México , PrataRESUMO
The thermal quality of the habitat is key for the regulation of body temperature in terrestrial ectotherms and, therefore, permits them to carry out their fundamental biological activities. In thermally heterogeneous environments, ectotherms might follow different behavioral or physiological strategies to maintain their body temperature within biologically adequate boundaries, for which they depend on microhabitat selection. These aspects are, thus, relevant in the context of habitat degradation and land-use change. In this study, we characterized the thermal ecology of three lizard species (genus Xantusia) that differ in microhabitat use along the Baja California peninsula, Mexico. We made three predictions: (1) the three species will follow different thermoregulatory strategies according to habitat thermal quality; (2) the thermal requirements and tolerances of these species will match the environmental or microenvironmental thermal conditions; and (3) due to their habitat and range restriction, the species studied will be highly vulnerable to climate change. Our results indicate the existence of thermoregulatory mechanisms in Xantusia to face thermal heterogeneity, including behavioral thermoregulation by choosing different microhabitats, shifts in activity periods, and adaptation to particular high thermal quality microhabitats. Furthermore, despite their association to specific microhabitats and specialized physiology, the studied species will not be adversely affected by climate change, as the increased microenvironmental temperatures will lead to a higher habitat thermal quality and lower costs of thermoregulation. However, we do not discard other indirect adverse effects of climate change not considered in this study.
Assuntos
Regulação da Temperatura Corporal/fisiologia , Lagartos/fisiologia , Distribuição Animal , Animais , Comportamento Animal , Meio Ambiente , México , Especificidade da Espécie , TemperaturaRESUMO
In recent years, there has been an increase in the descriptions of members of the lizard genus Lepidophyma. Herein, we describe a new species of Lepidophyma from the Huasteca Potosina region of Mexico, previously confused with L. gaigeae, from which it differs in lacking parietal spot, among other characteristics. We inferred its phylogenetic position and provide information on its thermal and hydric physiology, as well as on some other aspects of natural history. Molecular and morphological data supported the independent taxonomic status of the new species, indicating its placement as the sister taxon of L. gaigeae and a wide morphological separation between these species. Lepidophyma lusca sp. nov. has a diurnal-crepuscular activity period and occurs at lower elevations than L. gaigeae. Also, the new species differ from its sister taxon in its physiology, as reflected by its tendency toward higher thermal parameters and water loss rates. With the description of L. lusca sp. nov., the number of species in the genus Lepidophyma rises to 21.