Antimicrobial activity of thin metallic silver flakes, waste products of a manufacturing process

The aim of the research was to develop new products and processes from a manufacturing waste from an Italian metallurgic company. The company produced thin silver metallic films and the production scraps were silver flakes. The possibility to use the silver flakes in water disinfection processes was studied. The antimicrobial activity of the flakes was investigated in batch using Escherichia coli as Gram-negative microorganism model. The flakes did not show any antimicrobial activity, so they were activated with two different processes: thermal activation in reducing atmosphere and chemical activation, obtaining, respectively, reduced flakes (RF) and chemical flakes (CF). The flakes, activated with either treatment, showed antimicrobial activity against E. coli. The kill rate was dependent on the type of activated flakes. The chemical flakes were more efficient than reduced flakes. The kill rate determined for 1 g of CF, 1.0 ± 0.2 min⁻¹, was greater than the kill rate determined for 1 g of RF, 0.069 ± 0.004 min⁻¹. This was confirmed also by the minimum inhibitory concentration values. It was demonstrated that the antimicrobial capability was dependent on flakes amount and on the type of aqueous medium. Furthermore, the flakes maintained their properties also when used a second time. Finally, the antimicrobial activities of flakes were tested in an effluent of a wastewater treatment plant where a variety of heterotrophic bacteria were present.     

Phytoextraction of Pb,Cr, Ni,and Zn using the aquatic plant Limnobium laevigatum and its potential use in the treatment of wastewater

In order to study the bioaccumulation of Pb, Cr, Ni, and Zn and the stress response, the floating aquatic plant Limnobium laevigatum was exposed to increasing concentrations of a mixture of these metals for 28 days, and its potential use in the treatment of wastewater was evaluated. The metal concentrations of the treatment 1 (T1) were Pb 1 μg L⁻¹, Cr 4 μg L⁻¹, Ni 25 μg L⁻¹, and Zn 30 μg L⁻¹; of treatment 2 (T2) were Pb 70 μg L⁻¹, Cr 70 μg L⁻¹, Ni 70 μg L⁻¹, and Zn 70 μg L⁻¹; and of treatment 3 (T3) were Pb 1000 μg L⁻¹, Cr 1000 μg L⁻¹, Ni 500 μg L⁻¹, and Zn 100 μg L⁻¹, and there was also a control group (without added metal). The accumulation of Pb, Cr, Ni, and Zn in roots was higher than in leaves of L. laevigatum, and the bioconcentration factor revealed that the concentrations of Ni and Zn in the leaf and root exceeded by over a thousand times the concentrations of those in the culture medium (2000 in leaf and 6800 in root for Ni; 3300 in leaf and 11,500 in root for Zn). Thus, this species can be considered as a hyperaccumulator of these metals. In general, the changes observed in the morphological and physiological parameters and the formation of products of lipid peroxidation of membranes during the exposure to moderate concentrations (T2) of the mixture of metals did not cause harmful effects to the survival of the species within the first 14 days of exposure. Taking into account the accumulation capacity and tolerance to heavy metals, L. laevigatum is suitable for phytoremediation in aquatic environments contaminated with moderated concentrations of Cr, Ni, Pb, and Zn in the early stages of exposure.

     

Biomarkers of a native fish species (Cnesterodon decemmaculatus) application to the water toxicity assessment of a peri-urban polluted river of Argentina

Environmental monitoring by means of biomarker parameters assessed in different species is a useful tool. It has the advantage of providing a quantitative response as well as valuable information of ecological relevance on the chronic adverse effects caused by water pollution. The aim of this study was to assess the response of biochemical and physiological parameters of Cnesterodon decemmaculatus, a native teleost, simultaneously caught in two sites of Reconquista river, a highly polluted peri-urban river. This study compared the measured parameters with that of specimens of the same species captured in an unpolluted body water, and correlated the detected changes with the physicochemical profile of the water at each site. A comparison was made of selected parameters of gill, brain and liver and of somatic indices of fish collected from polluted and reference sites. The main parameters whose changes allowed to discriminate between sampling sites were gill (Na(+),K(+))-ATPase, brain acetylcholinesterase (AChE) and liver aminotransaminases activities; tissues' protein content and liver somatic index (LSI) were also sensitive biomarkers in brain and liver, respectively. The results showed that the response of the measured biomarkers allowed for the differentiation of sampling sites according to their water quality and confirmed that Cnesterodon decemmaculatus may be a useful test organism for the biomonitoring of freshwater environments. In addition, the simultaneous measurement of the physicochemical parameters of the water samples showed a good correspondence between the biomarkers responses and the environmental chemical stress conditions.     

A Numerical Model for the Transport of Chromium and Fine Sediments

A mathematical model which represents the transport processes of heavy metals and fine sediments in a fluvial stream was developed. The model consists of a three-equation system: the first one for total chromium concentration in the water column, C _Tw, the second one for total suspended sediment concentration, S _w, and the third one for chromium concentration in bed sediments, r. The third equation represents the chromium exchange between the water column and bed sediments by two processes: diffusion of soluble chromium and erosion/deposition of chromium sorbed to sediments. The basic assumption of the model is the instantaneous equilibrium. The main parameters are the partition coefficients in the water column and bed sediments, the depth of the active bed sediment layer, and the mass transfer coefficient between the water column and sediment pore water. The numerical model approximates the equations of advection–dispersion for chromium in water and suspended sediments by using a Eulerian third-order scheme. Numerical vs. analytical solutions were considered satisfactory for different initial, boundary, and sedimentological conditions. In order to estimate the impact of a chromium side discharge, the model was implemented for the Salado River in a reach of 65.6-km long (Santa Fe, Argentina). The results showed the effect of chromium discharge on almost the whole reach, then the vulnerability of the water quality in the Salado River when the flow was low was evidenced. When comparing the computed and measured results, the former showed a reasonable representation of the presence of chromium in water and bed sediments.     

Assessment of community-based initiatives in sustainable management of Indian dry deciduous forests

SUMMARY

This work is devoted to analyzing the pros and cons of the proposed San Ignacio Lagoon (SIL) salt production project in Baja California Sur, México. The analysis of the project was done taking into account the technical data of the main potential effects of the SIL project, and by comparing the SIL proposed actions with the data of Ojo de Liebre Lagoon, where an almost identical salt production project has been operating for more than 44 years. The analysis was done from the following perspectives: biodiversity, biosphere reserve management, and socioeconomic development. The resulting analysis of the pros and cons of the SIL salt production project addresses key aspects of sustainable development in Third World nations. The resulting analysis indicates that the SIL salt production project is compatible with the biodiversity conservation of the zone. The SIL salt production project seems to be one of the best options to attain the sustainable use of natural resources of the most arid and isolated zone of all México.     

Sustainable shrimp fishery management recommendations for a coastal lagoon in Baja California Sur,Mexico

The Baja California Peninsula is considered México's most productive in terms of commercial fisheries. Very few quantitative assessments of the economic importance of this region exist, especially considering artisanal fisheries and their relationships with ecological data. Datasets from government records on shrimp capture in Magdalena Bay, an arid coastal lagoon of Baja California Sur were collected, analysed and correlated with ecological data. Over the 10-year period analysed, fisheries from Magdalena Bay made up 27.5% of the shrimp capture of the state, contributing over US$15.5 million to the economy of the country. The impressive value of this resource warrants considerable attention in the design of land-use plans for the future of the region. Analysis of ecological and economical data on shrimp fishery activities in the Magdalena Bay region enables us to propose recommendations to enhance the sustainable development of the local inhabitants. A thorough assessment of the potential value of alternative economic activities should be conducted to determine their potential to provide similar productive use of the natural resources of the region as the shrimp fishery. Also, from a more specific management viewpoint, harvest rates of small shrimp in the channels should be reduced.     

Contributions of sustainability science to the study of environmental health problems

From the ontological point of view, environmental health problems do not differ from problems of unsustainability. This leads us to think that sustainability science could contribute to resolve important questions that studies on environmental health are not resolving. A literature review was made in order to analyse the scope and limitations of studies on environmental health problems. Based on the characteristics of environmental health studies, we highlighted some examples of questions that are being ignored and analysed four contributions that sustainability science could make to solve them. These contributions come from three key components of sustainability science: (1) the unit of analysis—social–ecological systems, (2) a theory—resilience theory and, specifically, social–ecological resilience, (3) and the approaches of complex systems and transdisciplinarity. From a sustainability science perspective, four contributions could be made: environmental health problems are redefined as social–ecological systems; environmental health is assumed to be the result of adaptation processes; the environment and society are recognized as systems, not as matrices of factors; and human action acquires content and structure and, in turn, explains the behaviour of environmental health problems.     

Phytoavailability and fractions of iron and manganese in calcareous soil amended with composted urban wastes

Little is known about the effects of applying composted urban wastes on the phytoavailability and distribution of iron (Fe) and manganese (Mn) among chemical fractions in soil. In order to study this concern several experiments in pots containing calcareous soil were carried out. The received treatments by adding separately two rates (20 and 80 Mg ha-1) of municipal solid waste (MSW) compost and/or municipal solid waste and sewage sludge (MSW-SS) co-compost. The cropping sequence was a lettuce crop followed by a barley crop. It was observed that treatments amended with composted urban wastes tended to promote slight increases in lettuce yield compared to the control. The highest Fe levels in lettuce were found when higher rates of MSW-SS co-compost were applied; these values were significant compared to those obtained in the other treatments. In all cases, the application of organic materials increased the concentration and uptake of Mn in lettuce compared to the control; however, these increases were significant only when higher rates of MSW compost were applied. The organic amendments had beneficial delayed effects on barley yields, showing, in most cases, significant increases compared to the control. In this context, treatments with MSW compost were found to be more effective than the equivalent treatments amended with MSW-SS co-compost. Compared to the control, composted urban wastes increased Fe concentration in straw and rachis, and decreased Fe concentration in barley grain. Similarly, a decreased concentration of Mn in the dry matter of barley crop grown in soils treated with composted urban wastes was observed.     

Lead isotope ratios in lichen samples evaluated by ICP-ToF-MS to assess possible atmospheric pollution sources in Havana,Cuba

Epiphytic lichens, collected from 119 sampling sites grown over “Roistonea Royal Palm” trees, were used to assess the spatial distribution pattern of lead (Pb) and identify possible pollution sources in Havana (Cuba). Lead concentrations in lichens and topsoils were determined by flame atomic absorption spectrophotometry and inductively coupled plasma (ICP) atomic emission spectrometry, respectively, while Pb in crude oils and gasoline samples were measured by ICP-time of flight mass spectrometry (ICP-ToF-MS). Lead isotopic ratios measurements for lichens, soils, and crude oils were obtained by ICP-ToF-MS. We found that enrichment factors (EF) reflected a moderate contamination for 71% of the samples (EF > 10). The ²⁰⁶Pb/²⁰⁷Pb ratio values for lichens ranged from 1.17 to 1.20 and were a mixture of natural radiogenic and industrial activities (e.g., crude oils and fire plants). The low concentration of Pb found in gasoline (<7.0 μg L^?1) confirms the official statement that leaded gasoline is no longer used in Cuba.