Natural factors and mining activity bearings on the water quality of the Choapa basin, North Central Chile: insights on the role of mafic volcanic rocks in the buffering of the acid drainage process

This contribution analyzes water chemical data for the Choapa basin, North Central Chile, for the period 1980-2004. The parameters considered are As, Cu Fe, pH, EC, SO??2, Cl?1, and HCO[Formula: see text], from samples taken in nine monitoring stations throughout the basin. Results show rather moderate contents of As, Cu, and Fe, with the exception of the Cuncumén River and the Aucó creek, explained by the influence of the huge porphyry copper deposit of Los Pelambres and by the presence of mining operations, respectively. When compared against results obtained in previous researches at the neighboring Elqui river basin, which host the El Indio Au-Cu-As district, a much reduced grade of pollution is recognized for the Choapa basin. Considering the effect of acid rock drainage (ARD)-related Cu contents on the fine fraction of the sediments of both river basins, the differences recorded are even more striking. Although the Los Pelambres porphyry copper deposit, on the headwaters of the Choapa river basin, is between one and two orders of magnitude bigger than El Indio, stream water and sediments of the former exhibit significantly lower copper contents than those of the latter. A main factor which may explain these results is the smaller degree of H(?+?)-metasomatism on the host rocks of the Los Pelambres deposit, where mafic andesitic volcanic rocks presenting propylitic hydrothermal alteration are dominant. This fact contrast with the highly altered host rocks of El Indio district, where most of them have lost their potential to neutralize ARD.     

Multi-year monitoring of estuarine sediments as ultimate sink for DDT, HCH, and other organochlorinated pesticides in Argentina

Forty-nine superficial sediment samples used in this study were collected from eight sites in the Bahia Blanca Estuary, located in the Buenos Aires Province southwest, Argentina, in a period between April 2005 and March 2009, to assess the concentration levels, spatial and seasonal distribution, and putative input sources of 18 selected organochlorine pesticides (OCs), following UNEP-IAEA procedures. Average concentration levels in sediments ranged between 3.54 and 63.79 ng g^???1, d.w. (mean = 15.99 ng g^???1, d.w.), for ??OCs, and from nondetectable to 8.03 ng g^???1, d.w. (mean = 2.16 ng g^???1, d.w.), and from nondetectable to 3.20 ng g^???1 (mean = 0.97 ng g^???1, d.w.) for hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs), respectively. Principal component analysis allowed the classification of sampling sites according to the main OCs inputs over the estuary. In comparison to other worldwide locations and to the world coastal sediment concentrations range, sediment DDTs and HCHs levels were in the low range; on the opposite, ??OCs average was in the medium range. OCs seasonal distribution was found to be highly correlated with the precipitations seasonality and sowing seasons in the adjacent agriculture fields. In addition, an ecotoxicological risk assessment pointed industrial and agriculture catchment zones with intermediate probability of adverse effects to biota, while the city sewage outfall was classified with none indication of an immediate threat. Data indicated that the estuary sediments were functioning as a sink for persistent OC pesticides (either in use or banned), however, it was found a declining trend on their environmental burden.     

Nitrogen and phosphorus budgets for the Yucat��n littoral: An approach for groundwater management

Human activities have altered the balance of ecosystems to the detriment of natural environments. Eutrophication is a serious risk in Yucatán, a state in the eastern peninsula of México where groundwater supplies the only freshwater to a karst shelf environment. While economic development in Yucatán is increasing, environmental awareness is lagging, and efficient waste treatment systems are lacking. To assess potential nitrogen and phosphorus inputs into the coastal zone of Yucatán, we analyzed government reports and the chemical composition of groundwater and aquaculture wastewater. Swine, poultry, and tourism are revealed as the main continental nutrient sources, while groundwater with high nitrate concentrations is the principal coastal nutrient source, a pattern similar to other river discharges around the world. This study demonstrates that environmental risk management practices must be implemented in the Yucatán region to protect groundwater quality.     

Comparing the Number of Ozone Exceedances in Different Seasons of the Year in Mexico City

Ozone air pollution is a serious problem in several cities of the world. Hence, to analyse the behaviour of this pollutant is a very important issue. One problem of interest is to study the behaviour of the inter-occurrences times between two ozone exceedances, i.e. between two days in which the pollutant’s measurement surpasses a given threshold. Another interest resides in comparing the behaviour of ozone measurements in different seasons of the year. In this paper we use some Poisson models to analyse this problem. The time interval at which the ozone measurements were taken is split into subintervals corresponding roughly to the seasons of the year. We consider three parametric forms for the mean of the Poisson model, and consequently for the mean of the inter-occurrences times. In each model, the parameters describing its mean are estimated using Bayesian inference via Markov chain Monte Carlo methods. The models are applied to the ozone measurements provided by the Mexico City monitoring network. Theoretical results suggest that an increase has occurred in the mean inter-exceedances times and this is corroborated by the observed data. Differences between the behaviour of the pollutant during different seasons of the year are also detected as well as similarities in the same season in different years. Besides estimating the mean of the Poisson models, inference for the possible presence and location of change-points indicating change of parameters of the model is also performed.     

Adsorptive and photocatalytic activity of Fe3O4-functionalized multilayer graphene oxide in the treatment of industrial textile wastewater

Environmental Science and Pollution Research - Multilayer graphene oxide (mGO) was synthesized and functionalized via co-precipitation method to produce magnetic Fe3O4-functionalized multilayer...     

Mercury and selenium concentrations in the crab Callinectes arcuatus from three coastal lagoons of NW Mexico

Environmental Science and Pollution Research - Mercury and selenium concentrations and Se:Hg molar ratio in edible muscle and hepatopancreas of the crab Callinectes arcuatus from coastal lagoons of...     

Participation in the convention on migratory species: A biogeographic assessment

The Convention on the Conservation of Migratory Species of Wild Animals (CMS) is a Multilateral Environmental Agreement (MEA) focused on species that regularly travel across international borders. Despite covering an important group of species, CMS is under-utilized compared to other conservation-focused MEAs. CMS suffers from a lack of participation across North America and most of Asia. Our goal is to illustrate differences in species richness and average range-size across signatory and nonsignatory nation-states using range–diversity plots. We also show differences in the cost of CMS membership relative to species patterns to highlight which countries may be discouraged from becoming CMS signatories. Despite containing many CMS species, large economies such as the United States, Russia, and China are not members of the convention. To facilitate migratory species conservation into the future, CMS should seek to fill gaps in participation, potentially directing recruitment efforts toward nonsignatory states that would receive the largest benefit at the lowest relative cost.     

Management of domoic acid monitoring in shellfish from the Catalan coast

Monitoring of amnesic shellfish poisoning (ASP) toxins in shellfish from the Catalan coast started in 2001. No ASP toxins were detected in any of the analyses performed before 2008. On 22 January 2008, domoic acid (DA) was detected in Donax trunculus (0.5 mg?kg^?1) and confirmed by rapid resolution liquid chromatography–tandem mass spectrometry (0.6 mg?kg^?1). A total of 974 shellfish samples were analyzed from January 2008 to December 2011, covering all the Catalan production areas and the most important marketed species. DA was detected in 23.8 % of the samples and was recorded every month in all areas and all species, except Ostrea edulis, although the percentage of samples with DA and DA content varied widely among samples. DA exceeded the regulatory level of 20 mg?kg^?1 twice: in Callista chione sampled on February 2008 and in D. trunculus sampled on April 2010. DA content in Bolinus brandaris appeared constant and close to 4.5 mg?kg^?1 for months in 2009. Mytilus galloprovincialis, Crassostrea gigas, and Ruditapes sp. presented very low concentrations of DA in the Ebro Delta bays, despite 113 alert situations according to Pseudo-nitzschia spp. abundances and the high number of shellfish samples analyzed. The origin of DA in Catalan shellfish remains unknown.     

Protective action of zinc against lead poisoning in tilapia Oreochromis niloticus

The accumulation of lead (Pb) in tilapias Oreochromis niloticus, acclimatized in cement tanks, and fed once a day with pellets of commercial food with lead nitrate, was investigated by square wave anodic stripping voltammetry (SWV). The head (including head bones, proteins, and brain) was the main target of lead uptake by tilapias, with a small amount in muscle tissue. A high concentration of Pb was found in feces which indicated low absorption by the organism when fed with high Pb concentration. The protective effects of zinc (Zn) against the Pb poisoning, the accumulation of Pb in the heads of the fishes of 107.8?±?3.1?mg?kg^?1 and in the viscera of 57.1?±?2.9?mg?kg^?1 with consequent decrease of calcium (Ca) concentration, were observed. In spite of the experimental time of 16 months and higher Pb concentration in the dietary food of 320?mg?kg^?1, no death of tilapias was observed due to the protective action of Zn.