What is left behind when the lights go off? Comparing the abundance and composition of litter in urban areas with different intensity of nightlife use in Mar del Plata,Argentina

Nightlife activities represents an important source of urban litter; the latter often being left behind or abandoned in public places and streets. Mar del Plata is a very important city on the Atlantic coast of Argentina and is the main tourism destination in the South Atlantic region of South America. However, few studies on urban litter related to nightlife activities have been conducted in the area. Here we assessed (i) the abundance and composition of litter, and (ii) the spatial and temporal variations of its abundance, diversity, richness and evenness in urbanized areas with different intensity of nightlife activities from April 2008 to March 2009. An overall of 13,503 items were counted. Around 92% of the total litter was comprised by cigarette butts, papers and plastics. We found significant spatial differences in the abundance of litter between sampling sites, with the greatest amounts of litter at the Alem site followed by the Hipólito site (both with an intensive nightlife activity) compared with the Chauvin site (a quiet high-income neighborhood). The composition of litter of the Alem and the Hipólito sites was relatively similar and both sites differ with respect to the Chauvin site. Cigarette butts, papers, and plastics were the items that contributed most to the dissimilarity between sampling sites. The diversity of litter was the single community parameter that significantly differed from the other seasons. We discussed the potential effect of nightlife activities on the amounts and quality of urban litter in the city of Mar del Plata.     

Large-scale shrimp farming in coastal wetlands of Venezuela,South America: Causes and consequences of land-use conflicts

In Venezuela, large-scale shrimp farming began in the 1980s. By 1987, the Ministry of Environment and Natural Resources (MARNR) had received 14 proposals for approval. A developer illegally started the construction of ponds at the Píritu Lagoon in the State of Anzoátegui before the authorization process was completed. This action triggered a land-use conflict. This study identifies the causes for public protest and determines the consequences of this conflict for land-use management. The results show that public protest was based on the impacts of the partial construction of ponds. These impacts were related to direct removal of wetlands, interruption of natural patterns of surface flows, and alteration of feeding grounds of some bird species with migratory status. Consequences were identified in relation to the role that nongovernmental organizations (NGOs) play in land-use conflicts and the actions that MARNR could take in the future to prevent and solve similar situations.     

Assessing the influence of urban geometry on noise propagation by using the sky view factor

The impact of traffic noise can be prevented by suitable planning measures. This study analyses the relationship between urban geometry and traffic noise, recognizing that the arrangement of buildings and streets greatly influences urban noise. The study was carried out in Braga, a medium-sized Portuguese city, by selecting locations with different urban geometries. At each site, the equivalent continuous sound level was measured. Furthermore, the urban geometry was evaluated by using the sky view factor, a parameter which shows the degree of sky obstructed by buildings. Results show an inverse proportionality between noise and the sky view factor. The highest noise levels were found in areas with a low sky view factor. The results also indicate that the sky view factor is a parameter which can potentially be used in research on urban noise.     

Development and non-indigenous species at the global scale

This paper investigates the explanatory power of development, prosperity and regulatory capability as proximate causes of non-indigenous species (NIS) occurrence in different countries, doing this by statistically analysing a global cross-sectional data set. Since the quantification of development is subject to much discussion, two different indicators are tested: gross domestic product (GDP) per capita and the United Nations human development index (HDI). A corruption index is used as an indicator of regulatory capacity. In addition, variables capturing country openness, which facilitates NIS introduction, and habitat conditions, which determine NIS establishment, are included as explanatory variables. The GDP indicator together with the corruption index fits the NIS data best, where the number of NIS is higher in countries with larger incomes. However, countries with relatively high income but low institutional capacity show a larger number of NIS than countries with a similar level of income but with higher institutional capacity. The results also point to the significant contributions of openness and habitat fragmentation to NIS occurrences in the countries.     

In situ experiments for element species-specific environmental reactivity of tin and mercury compounds using isotopic tracers and multiple linear regression

The fate of mercury (Hg) and tin (Sn) compounds in ecosystems is strongly determined by their alkylation/dealkylation pathways. However, the experimental determination of those transformations is still not straightforward and methodologies need to be refined. The purpose of this work is the development of a comprehensive and adaptable tool for an accurate experimental assessment of specific formation/degradation yields and half-lives of elemental species in different aquatic environments. The methodology combines field incubations of coastal waters and surface sediments with the addition of species-specific isotopically enriched tracers and a mathematical approach based on the deconvolution of isotopic patterns. The method has been applied to the study of the environmental reactivity of Hg and Sn compounds in coastal water and surface sediment samples collected in two different coastal ecosystems of the South French Atlantic Coast (Arcachon Bay and Adour Estuary). Both the level of isotopically enriched species and the spiking solution composition were found to alter dibutyltin and monomethylmercury degradation yields, while no significant changes were measurable for tributyltin and Hg(II). For butyltin species, the presence of light was found to be the main source of degradation and removal of these contaminants from surface coastal environments. In contrast, photomediated processes do not significantly influence either the methylation of mercury or the demethylation of methylmercury. The proposed method constitutes an advancement from the previous element-specific isotopic tracers’ approaches, which allows for instance to discriminate the extent of net and oxidative Hg demethylation and to identify which debutylation step is controlling the environmental persistence of butyltin compounds.     

Farming dynamics and social capital: A case study in the urban fringe of Mexico City

Urban development has important implications for farmland preservation and natural resource management in local peri-urban communities. Social science research on recent changes in rural landscape of mega-cities tends to be limited to case studies in Latin-American nations. This study analyses the socioecomic dynamics of farming land use and the interactions between multiple cultural variables and the environment. Fieldwork was carried out during the 2002–2003 period in rural livelihoods of the five high mountain towns of south Mexico City. Data obtained from participatory survey and ethnographic techniques were integrated to assess changes in rural landscape and resource management and how urbanization, deforestation and market oriented agricultural production result in different livelihoods within a similar urban fringe context. The dynamic of mixture of urban and rural landscapes is based on farm productivity and social capital factors. The study concludes that policy support for regional agricultural production systems through enhancing ecosystems services, environmental protection and economic development is needed for sustainable development of local communities. Readers should send their comments on this paper to BhaskarNath@aol.com within 3 months of publication of this issue     

Uranium speciation in river sediments contaminated by phosphate ores

Large amounts of phosphate ores with high concentrations of uranium were dumped by a phosphate plant into the Flix water reservoir in the Ebre River, Catalonia, NE Spain. These phosphate wastes have been mixed over the years with effluents from other industries as well as with the sediments of the river, resulting in a complex mixture of solid wastes and sediments. No investigations on uranium speciation in such sediments were made because of the complexity of the sediments composition as well as the relatively low uranium content. However, these studies are necessary in order to predict the release of the uranium to the river waters. Here, we studied uranium speciation in sediments from two sampling points of the Flix water reservoir and at depths from 5 to 113 cm. We used room temperature time-resolved laser fluorescence spectroscopy and a three-step sequential extraction procedure described by the Standards, Measurements, and Testing Programme of the European Union. We found that uranium was mainly present in the sediment samples as meta-autunite [Ca(UO₂)₂(PO₄)₂·10–12H₂O], whose low solubility will result in a low release of uranium to the river waters. In addition, we found that some uranium was linked to sediments by forming surface complexes. We therefore made the first study of uranium speciation in the sediments of the Flix water reservoir.