Soil heavy metal content on the hillslope region of Rio de Janeiro,Brazil: reference values

The increasing concern regarding the preservation of soil quality suggests the adoption of quality reference values as a first step in environmental monitoring actions. In this context, the objective of this study was to establish soil quality reference values for Al, Zn, Mn, Cd, Fe, Pb, Ni, Cr, and Cu and to correlate several soil properties with the occurrence of these elements in the hillslope region of Rio de Janeiro State. Sixty-two samples were collected at depths of 0–20 and 20–40 cm and analyzed using the USEPA method 3051A. After clustering analysis, the samples were separated into three groups. Classification functions were obtained based on the variables pH - Mg - Fe - Mn, i.e., the variables that were best related to heavy metal content. We determined to establish the quality reference values for the 75th percentile of the three groups. The relief forms of the area, which facilitate the transport of soil fine-particle fractions and accumulation in lowlands, were revealed to be one of most important factors in understanding the distribution of soil heavy metals.     

Modeling road building,deforestation and carbon emissions due deforestation in the Ecuadorian Amazon: the potential impact of oil frontier growth

In the Ecuadorian Amazon roads play the major role in transforming land cover. Since the beginning of the oil development in this region, oil exploration and road building have been linked. The objectives of this paper are twofold: First, to present a scenario of future deforestation as result of expanding the oil frontier in the Ecuadorian Amazon until the year 2030. Second, to produce an analysis of possible carbon emission scenarios as results of the deforestation produced. This paper tries to shed light into how the development of new oil concessions impact land associated environmental services. The paper uses spatial explicit simulations, that are based on parameters built using past land transitions from areas that experimented oil development, and that explain possible outcomes in the year 2030 using current and predicted road network. Simulations indicate that under current transition probabilities and a conservative scenario road construction, more than 2 million hectares will be affected, which is 35% of the area covered by concessions, which would release 51 to 148 MT of carbon to the atmosphere. This paper illustrates the strong links between road building and deforestation, where even small amount of road construction can have large effects on land cover.     

Prediction of radionuclide aging in soils from the Chernobyl and Mediterranean areas

The aging of soil-pollutant interaction, which may lead to an increase in pollutant fixation, is the main driving force in the natural attenuation of contaminated soils. Here a test was evaluated to predict the aging of radiostrontium and radiocesium in soils from the Chernobyl and Mediterranean areas. After contamination, soils were maintained at various temperatures for up to 12 mo, with or without drying-wetting (DW) cycles. Changes in the quantity of radionuclide reversibly sorbed over time were monitored using an extraction test (1 mol L(-1) NH(4)Cl; 10 mL g(-1); 16 h). The fixed fraction could not be predicted from soil properties controlling the sorption step. Aging was not as relevant for Sr as for Cs. The time elapsed since contamination was the main factor responsible for the slight (up to 1.3-fold) decreases in Sr extraction yields. The additional effect of DW cycles was negligible. Instead, all factors accelerated Cs aging due to the enhancement of Cs trapping by clay interlayer collapse, with up to 20-fold increases in Cs fixation. The DW cycles also caused secondary effects on the Cs-specific sorption pool, which were beneficial or detrimental depending on the soil type. Extraction yields from laboratory aged samples agreed with those from field samples taken a few years after the Chernobyl accident. These results confirm the prediction capacity of the laboratory test and its usefulness in risk assessment exercises and in the design of intervention actions, particularly because neither fixation nor aging were related to the soil properties, such as clay content.     

Lead, cadmium and arsenic bioavailability in the abandoned mine site of Cabezo Rajao (Murcia, SE Spain)

An in vitro method that simulated the physiological conditions of the digestive process was applied to samples taken from an old mining site, providing information on the levels of metals (Cd, Pb and As) that can be ingested and assimilated by humans. Samples were first characterized by determining pH, texture, mineralogical composition and total metal contents. The mean pH value was 5.4, ranging from 3.1 to 8.4. The mean total metal content for Pb was 2,632+/-59 mg kg(-1), 65+/-1.5 mg kg(-1) for Cd and 279.9+/-9.9 mg kg(-1) for As. Cadmium was the most bioavailable metal both in the stomach and intestinal phases (mean value of 47% and 27.8%, respectively), followed by lead (25.3% and 11.5%) and arsenic (4.9% and 0.5%). A Pearson correlation matrix suggested that pH and mineralogical composition were important factors controlling metal bioavailability from materials in abandoned mining sites.     

Planktonic ciliates in a hypertrophic pond: functional role and importance

Taxonomical composition and abundance of the planktonic ciliate assemblage in a Lake Tezozomoc, a hypertrophic pond located into an urban park in Mexico City, was investigated along the rainy season (May to October). The aims of the study were to know the main trophic roles and ecological significance of ciliates in a highly productive environment. A low number of taxa (27) and a wide abundance fluctuation (104-387 cil ml(-1)) were found. The most abundant species (up to 162 cil ml(-1)) was Halteria grandinella, an oligotrich ciliate that graze on bacteria and picoplankton, but also several big body sized species that feed on pico and nanoplankton were abundant. Sudden temporal changes in species dominance occurred. Ciliate biomass was very high and fluctuated widely (1.6-88 10(6) microm(3) ml(-1)) being dominated by the >50 microm size fraction that mainly included the pico and nanoplankton feeders. Ciliates are a very important component in the plankton of hypertrophic lakes and their main control factor seems to be the grazing by big-body size Daphnia species.     

Optimizing rearing conditions of hatchling loliginid squid

Eggs laid by the California market squid (Loligo opalescens) were collected from spawning grounds and reared in the laboratory. The eggs were maintained in a rearing tank that was part of a closed, recirculating system. The system included seven 220-l circular tanks with attached filtration. Five experiments were conducted to test hatchling survival. One of them evaluated survival on three different food types: (a) enriched Artemia sp. nauplii, (b) wild zooplankton and (c) a mixture of a and b plus mysid shrimp. This mixture of food types (c) was offered to the hatchlings in the other four experiments. High mortality occurred in all experiments between days 1 and 15 post-hatching. However, survival over the entire time span of the experiments (45-60 days) was between 36% and 60%. These survival rates are well above previously reported survival rates for the same time period, and overall are up to 35% better than any survival results ever attained for the routine culture of Loligo spp. squid. Results suggest that high survival can be achieved by: (1) rearing hatchlings in a recirculating system consisting of small round tanks designed to maintain water quality and pH within narrow limits (8.1-8.4), (2) maintaining low current speed (1.0-1.4 cm s^-1) to reduce skin damage and to enhance hatchling-prey interactions, (3) increasing feeding rate by feeding small amounts of food at regular intervals (every 2-3 h) during day time hours and keeping prey densities above 50 prey l^-1, (4) feeding hatchlings with enriched Artemia nauplii during days 1-30 post-hatching and (5) feeding a variety of prey types and sizes to match the different sizes and hunting abilities of same-aged but heterogeneously developing hatchlings. The results from this study will enhance future culturing efforts for the commercially important loliginid squid.     

Sorption-desorption tests to assess the risk derived from metal contamination in mineral and organic soils

We obtained the sorption isotherms of Cd, Cu, Pb and Zn from seven soils with contrasting properties, including mineral and organic soils. The distribution coefficients (Kd) were determined from batch tests in a solution that simulated the soil solution cationic composition. The Kd values of the target metals varied greatly depending on soil type and initial metal concentration. Sorption isotherms were fitted to Freundlich and Langmuir models, and derived parameters were correlated to soil properties through the construction of a correlation matrix and application of Principal Component Analysis. The batch Kd showed a satisfactory agreement with the Kd obtained from field-contaminated soils. The sorption tests were complemented with the estimation of the reversibility of metal sorption by the application of an extraction test. The extraction yields, which did not relate to the initial metal concentration, depended on the metal-soil combination, and showed no correlation to batch Kd values. The risk derived from a contamination event was estimated through the quantification of a Retention Factor, defined as the ratio of the Kd versus the extraction yield. Results showed that this was an excellent index to highlight which metal and soil represent the most vulnerable scenarios after a contamination event.     

Guatemala strives for environmental and economic sustainability in the Rio Dulce region

Conditions in Guatemala's Rio Dulce National Park (RDNP) present an immediate decision-making challenge concerning the reversal of current destructive environmental trends, and in establishing policies for restoration, protection, and sustainable use. This article summarises results of environmental assessment activities undertaken at three levels: an environmental impact assessment (EIA) of a proposed industrial forestry activity, an environmental assessment of management options for the Rio Dulce National Park, and water management planning for the Rio Dulce/Lago Izabal watershed. A key result of the EIA was to prohibit construction of a barge terminal within the boundaries of the park because it could set a precedent for future development. Management options for the park focused on establishing land-use controls, dealing with river transport more effectively, and identifying funding mechanisms to implement solutions. At the watershed scale, a strategic approach was recommended to identify priority issues for initiating change toward sustainability in the region.