Agave salmiana Plant Communities in Central Mexico as Affected by Commercial Use

Agave salmiana is a native plant species harvested for the commercial production of mezcal (Agave spirits) in the highlands of central Mexico. The objective of this study was to identify vegetation changes in natural communities where A. salmiana has been differentially harvested for commercial purposes. Three plant community categories were identified in the state of Zacatecas based on their history of A. salmiana utilization: short (less than 10 years of use), moderate (about 25 years), and long (60 or more years). Species cover, composition, and density were evaluated in field surveys by use category. A gradient of vegetation structure of the communities parallels the duration of A. salmiana use. A. salmiana density was greatest (3,125 plants ha⁻¹) in the short-use areas and less (892 plants ha⁻¹) in the moderate-use areas, associated with markedly greater density of shrubs (200%) and Opuntia spp. (50%) in moderate-use areas. The main shrubs were Larrea tridentata, Mimosa biuncifera, Jatropha dioica and Buddleia scordioides while the main Opuntia species were Opuntia leucotricha and Opuntia robusta. A. salmiana density was least (652 plants ha⁻¹) in the long-use areas where shrubs were less abundant but Opuntia spp. density was 25% higher than in moderate-use areas. We suggest that shrubs may increase with moderate use creating an intermediate successional stage that facilitates the establishment of Opuntia spp. Long-term Agave use is generating new plant communities dominated by Opuntia spp. (nopaleras) as a replacement of the original communities dominated by A. salmiana (magueyeras).     

Social participation and climate change

Social participation has been broadly analysed by comparing case studies of different types of socio-economic developments in Brazil and the United Kingdom (UK). A key objective has been to consider how effective social participation has been in incorporating society’s points of view in the decision making process. In most cases, it would appear that very little can be done by stakeholders to change big decisions on development policies that support public and private development because in reality social participation often only provides an opportunity for discussion and agreement on specific issues regarding how development will be undertaken and how stakeholders will be affected. Although Brazil and the United Kingdom have socio-economic and cultural differences, it is necessary to emphasize that education, self-organization and knowledge of civil rights are crucial for an effective social participation process. As climate change is an important topic for present and future generations and that some of the development activities analysed in this study will emit greenhouse gases, this study also attempts to investigate if climate change mitigation strategies have been integrated into the social participation process. Investigation shows that there is little evidence that climate change mitigation actions involving stakeholders have been integrated into development strategies or have been part of social participation schemes in the case studies analysed. Having said that, the study also describes positive examples of climate change mitigation actions in different parts of the world that involve local people in ‘carbon-neutral’ or ‘social-carbon’ projects and proposes the creation of a carbon-neutral committee that would be responsible for coordinating climate change mitigation measures within development proposals such as the ones analysed in this study.     

Atmospheric nitrogen fluxes at the Belgian coast: 2004–2006

Daily and seasonal variations in dry and wet atmospheric nitrogen fluxes have been studied during four campaigns between 2004 and 2006 at a coastal site of the Southern North Sea at De Haan (Belgium) located at coordinates of 51.1723° N and 3.0369° E. Concentrations of inorganic N-compounds were determined in the gaseous phase, size-segregated aerosol (coarse, medium, and fine), and rainwater samples. Dissolved organic nitrogen (DON) was quantified in rainwater. The daily variations in N-fluxes of compounds were evaluated with air-mass backward trajectories, classified into the main air-masses arriving at the sampling site (i.e., continental, North Sea, and Atlantic/UK/Channel).The three, non-episodic campaigns showed broadly consistent fluxes, but during the late summer campaign exceptionally high episodic N-deposition was observed. The average dry and wet fluxes for non-episodic campaigns amounted to 2.6 and 4.0 mg N m^?2 d^?1, respectively, whereas during the episodic late summer period these fluxes were as high as 5.2 and 6.2 mg N m^?2 d^?1, respectively.Non-episodic seasons/campaigns experienced average aerosol fluxes of 0.9–1.4 mg N m^?2 d^?1. Generally, the contribution of aerosol NH₄⁺ was more significant in the medium and fine particulate fractions than that of aerosol NO₃^?, whereas the latter contributed more in the coarse fraction, especially in continental air-masses. During the dry mid-summer campaign, the DON contributed considerably (～15%) to the total N-budget.Exceptionally high episodic aerosol-N inputs have been observed for the late summer campaign, with especially high deposition rates of 3.6 and 2.9 mg N m^?2 d^?1 for Atlantic/UK/Channel and North Sea-continental (mixed) air-masses, respectively. During this pollution episode, the flux of NH₄⁺ was dominating in each aerosol fraction/air-mass, except for coarse continental aerosols. High deposition of gaseous-N was also observed in this campaign with an average total N-flux of 2–2.5-times higher than in other campaigns.     

Integrative assessment of coastal pollution in a Ría coastal system (Galicia, NW Spain): correspondence between sediment chemistry and toxicity

Elutriate embryo-larval bioassays with sea-urchins (Paracentrotus lividus) and ascidians (Ciona intestinalis) were conducted concurrently with trace metal analyses as part of an integrative assessment of sediment pollution at Ría de Pontevedra (Galicia, NW Spain). High metal contents in sediments were found in localised areas from the inner part of the estuary indicating a clear anthropogenic influence. In particular, very high Cu, Zn and Pb levels were found at sites P2 and P3, which were also the most toxic to the embryo-larval bioassays. Sediment quality guidelines were used to help in the ecological interpretation of sediment chemistry data and to identify pollutants of concern. Cu and Zn in P3 were consistently above the effects range median (ERM) values, which seem to be good predictors of toxicity to sea-urchin and ascidian embryos. A toxic unit approach, based on published EC(50) values and metal levels in elutriates, was used to assess the harmful ecological effects associated to sediment chemistry. Toxicity detected in P3 may be explained on the basis of the toxic unit model; however, the high toxicity detected at P2 may be attributable not only to the metals quantified in the analyses but also to unmeasured organic pollutants. Multidimensional scaling applied independently to the toxicology and chemistry data resulted in a good agreement between both types of configurations. Moreover, the Mantel test revealed a significant correlation (r(M)=0.481; p=0.019) between metal concentrations and toxicity data profiles, supporting the correspondence between configurations.     

Evaluation of genotoxic effects of benzene and its derivatives in workers of gas stations

The search for reliable biomarkers of human exposure to benzene and its derivatives is still subject of research. Many of the proposed biomarkers have limitations ranging from the low sensitivity to the wide variability of results. Thus, the aim of our study was to assess the frequencies of chromosomal abnormalities (CA) and sister chromatid exchanges (SCE) in workers of gas stations, with (cases, n?=?19) and without (local controls, n?=?6) risk of exposure to benzene and its derivatives, comparing them with the results from the general population (external controls, n?=?38). The blood dosages of benzene, toluene, and xylenes were measured in all participants. Blood solvent levels were compared with the findings obtained in cytogenetic evaluation and a research protocol which included data of the workplace, lifestyle, and health of the individuals. We did not detect the presence of benzene and its derivatives and did not find chromosomal damage that may be associated with the gas station activity in cases. Moreover, although we found an association of increased SCE and the working time in the local controls, the values found for SCE are within normal limits. Thus, our evaluation of SCE and CA reflected the levels of benzene and its derivatives observed in the blood. We believe, therefore, that SCE and CA may actually constitute possible tests for the evaluation of these exposures. However, we believe that further studies, including individuals at risk, are important to confirm this assertion.     

Assessment of the trophic status of four coastal lagoons and one estuarine delta, eastern Brazil

Anthropogenic eutrophication of aquatic ecosystems continues to be one of the major environmental issues worldwide and also of Brazil. Over the last five decades, several approaches have been proposed to discern the trophic state and the natural and cultural processes involved in eutrophication, including the multi-parameter Assessment of Estuarine Trophic Status (ASSETS) index model. This study applies ASSETS to four Brazilian lagoons (Mundaú, Manguaba, Guarapina, and Piratininga) and one estuarine delta (Paraíba do Sul River), set along the eastern Brazilian coast. The model combines three indices based on the pressure–state–response (PSR) approach to rank the trophic status and forecast the potential eutrophication of a system, to which a final ASSETS grade is established. The lagoons were classified as being eutrophic and highly susceptible to eutrophication, due primarily to their longer residence times but also their high nutrient input index. ASSETS classified the estuary of the Paraíba do Sul river with a low to moderate trophic state (e.g., largely mesotrophic) and low susceptibility to eutrophication. Its nutrient input index was high, but the natural high dilution and flushing potential driven by river flow mitigated the susceptibility to eutrophication. Eutrophication forecasting provided more favorable trends for the Mundaú and Manguaba lagoons and the Paraíba do Sul estuary, in view of the larger investments in wastewater treatment and remediation plans. The final ASSETS ranking system established the lagoons of Mundaú as “moderate,” Manguaba as “bad,” Guarapina as “poor,” and Piratininga as “bad,” whereas the Paraíba do Sul River Estuary was “good.”     

Seasonal trends of atmospheric nitrogen dioxide and sulfur dioxide over North Santa Clara, Cuba

Atmospheric nitrogen dioxide (NO₂) and sulfur dioxide (SO₂) levels were monitored simultaneously by means of Radiello passive samplers at six sites of Santa Clara city, Cuba, in the cold and the warm seasons in 2010. The dissolved ionic forms of NO₂ and SO₂ as nitrate and sulfite plus sulfate, respectively, were determined by means of ion chromatography. Analysis of NO₂ as nitrite was also performed by UV–Vis spectrophotometry. For NO₂, significant t tests show good agreement between the results of IC and UV–Vis methods. The NO₂ and SO₂ concentrations peaked in the cold season, while their minimum levels were experienced in the warm season. The pollutant levels do not exceed the maximum allowable limit of the Cuban Standard 39:1999, i.e., 40 μg/m³ and 50 μg/m³ for NO₂ and SO₂, respectively. The lowest pollutant concentrations obtained in the warm season can be attributed to an increase in their removal via precipitation (scavenging) while to the decreased traffic density and industrial emission during the summer holidays (e.g., July and August).     

Cost–benefit analysis of waste reduction in developing countries: a simulation

Waste reduction activities such as recycling, composting, and pig feeding in Peru and other developing countries are mainly informal but already reduce about 15 % of waste generation. Although much research on informal recycling in Latin America recommends partnership with current waste pickers, there is a lack of methodologies on how to systematize these activities. This paper proposes a mathematical model that calculates yields and costs of separate waste collection, and analyzes and measures the effect of improvements such as source separation by residents and location of recycling and composting centers. The analysis finds that the largest effect comes from source separation. In this case, separate collection yield can be increased from the current 30 kg/waste picker/day to about 200 kg/waste picker/day, and the cost can be reduced from 110 US$/t to 20 US$/t. These changes affect the profitability of the recycling and composting business. The environmental and social effects of these improvements are also discussed.     

Objective classification of ecological status in marine water bodies using ecotoxicological information and multivariate analysis

Some relevant shortcomings have been identified in the current approach for the classification of ecological status in marine water bodies, leading to delays in the fulfillment of the Water Framework Directive objectives. Natural variability makes difficult to settle fixed reference values and boundary values for the Ecological Quality Ratios (EQR) for the biological quality elements. Biological responses to environmental degradation are frequently of nonmonotonic nature, hampering the EQR approach. Community structure traits respond only once ecological damage has already been done and do not provide early warning signals. An alternative methodology for the classification of ecological status integrating chemical measurements, ecotoxicological bioassays and community structure traits (species richness and diversity), and using multivariate analyses (multidimensional scaling and cluster analysis), is proposed. This approach does not depend on the arbitrary definition of fixed reference values and EQR boundary values, and it is suitable to integrate nonlinear, sensitive signals of ecological degradation. As a disadvantage, this approach demands the inclusion of sampling sites representing the full range of ecological status in each monitoring campaign. National or international agencies in charge of coastal pollution monitoring have comprehensive data sets available to overcome this limitation.     

Residual and cumulative effects of soil application of sewage sludge on corn productivity

The objective of this study was to evaluate the effect of frequent and periodic applications of sewage sludge to the soil, on corn productivity. The experiment was carried out as part of an experiment that has been underway since 1999, using two types of sludge. One came from the Barueri Sewage Treatment Station (BS, which receives both household and industrial sludge) and the other came from the Franca Sewage Treatment Station (FS, which receives only household sludge). The Barueri sludge was applied from 1999 up to the agricultural year of 2003/2004. With the exception of the agricultural years of 2004/2005 and 2005/2006, the Franca sludge was applied up to 2008/2009. All the applications were made in November, with the exception of the first one which was made in April 1999. After harvesting the corn, the soil remained fallow until the next cultivation. The experiment was set up as a completely randomized block design with three replications and the following treatments: control without chemical fertilization or sludge application, mineral fertilization, and dose 1 and dose 2 of sludge (Franca and Barueri). The sludges were applied individually. Dose 1 was calculated by considering the recommended N application for corn. Dose 2 was twice dose 1. It was evident from this work that the successive application of sludge to the soil in doses sufficient to reach the productivity desired with the use of nitrogen fertilizers could cause environmental problems due to N losses to the environment and that the residual and cumulative effects should be considered when calculating the application of sludge to soil.