Soil quality alteration by mouldboard ploughing in a commercial farm devoted to no-tillage under Mediterranean conditions

In semi-arid Mediterranean areas, studies about conservation tillage (CT) systems have demonstrated advantages in crop yield, soil water storage and soil protection. However, the benefits observed with CT in trials with experimental plots (normally of small dimensions) might not be so clear in large commercial farms. In many areas of SW Spain, farmers often do an occasional tillage with mouldboard ploughing (MP) to avoid potential compaction problems and to encourage the emergence of seedlings. The present study deals with the effect of the application of MP on soil quality: total organic carbon, water soluble carbon, active carbon, microbial biomass carbon, dehydrogenase, β-glucosidase and o-diphenol oxidase activities and crop development (wheat) in a commercial farm devoted to no-tillage (NT) since 1995. In 2006, MP was applied on a band of the soil, while the rest was left under the strict conservation system. The direct and residual effects of MP in the two subsequent years were evaluated. In the first year MP caused a decrease in soil quality that persisted in the following two years. Emergence, nutrient accumulation, nutrient efficiency ratios and yield of wheat were slightly enhanced by MP in the first year. However, this trend was the opposite in the two subsequent years. Although in other scenarios traditional tillage has been applied to avoid soil compaction and to increase crop yield, under our experimental conditions the occasional mouldboard ploughing application was not justified.     

Maternal energy expenditure does not change with flight costs or food availability in the pied flycatcher (Ficedula hypoleuca): costs and benefits for nestlings

We manipulated parental work load without changing brood size in a population of pied flycatchers Ficedula hypoleuca by removing two primaries (7 and 9) from each wing of females, thus reducing wing area and increasing flight costs. At other nests, we offered supplementary food in the form of live mealworms (10–20 g daily from hatching) to reduce brood demand and thus parental foraging costs. Other nests were left as controls. The daily energy expenditure of females feeding 12-day-old nestlings was measured with doubly labelled water D₂ ¹⁸O. Females in both treatments expended the same amount of energy, fed at the same rate and had similar body masses to birds in the control group. No effect of treatment on male mass and feeding effort was detected. More nestlings, however, died in nests of handicapped females. Nestlings of handicapped females had significantly lower body mass and haematocrit values than nestlings in food-supplemented nests, with nestlings in control nests occupying an intermediate position. The effects of both treatments on nestling mass, haematocrit values and mortality rates were only noticeable in nests infested with mites. Maternal energy expenditure is apparently constrained and offspring pay the costs imposed by reduced provisioning rate or increased demand caused by ectoparasites, while receiving benefits when food supply improves. The presumption that avian reproductive costs derive from changes in a flexible energy output may not be met in many cases. Received: 24 October 1998 / Received in revised form: 15 March 1999 / Accepted: 26 April 1999     

Zooplankton community resilience after press-type anthropogenic stress in temporary ponds.

Temporary ponds are physically disturbed environments that fluctuate on seasonal and interannual scales. These ecosystems are also susceptible to anthropogenic perturbation such as contamination inputs. However, the interactive effects of natural disturbance and anthropogenic stress on ecosystem processes and community dynamics have hardly been assessed in these ecosystem types. We used a multiple before-after control-impact (MBACI) design to study zooplankton community recovery from low and high inputs of a fire retardant in artificially constructed ponds over three hydroperiods. The retardant caused a decline in species richness and an increase in rotifers during summer and winter months relative to controls and pretreatment dates, and the duration of these changes varied among retardant treatments. In nonmetric, multidimensional scaling analyses the increased rotifer densities were reflected in loops that showed recurring deviations from and (upon collapse) approaches to reference conditions, while the effects of the anthropogenic stressor persisted in the ponds. The amplitudes of fluctuation followed no regular patterns; it varied with retardant treatment level and was higher in the third hydroperiod compared to the second in one of the treatments. From a temporal perspective, this non-dampened pattern suggests a new cause-effect mechanism for disturbance ecology, which we refer to as a "protracted press disturbance, roller coaster response" relationship. This model emphasizes stochastic oscillations in community composition, punctuated by periods in which the community approaches reference conditions. From the applied viewpoint, this model suggests that the accurate detection of perturbation and the implementation of sound management and restoration strategies will require intensive sampling designs that span multiple hydroperiods in persistently degraded ponds.     

Toxicity of new pyrethroid in pest insects Asciamonuste and Diaphania hyalinata,predator Solenopsis saevissima and stingless bee Tetragonisca angustula

There is increasing demand for new products for vegetable pest management. Thus, the aim of this study was to assess the toxicity of pyrethroids with acid moiety modifications to measure the insecticidal activity of these compounds on the lepidopteran vegetable pests Diaphania hyalinata (L.) (Lepidoptera: Pyralidae) and Asciamonuste (Latreille) (Lepidoptera: Pieridae) and evaluate their selectivity for the predatory ant Solenopsis saevissima (F. Smith) (Hymenoptera: Formicidae) and pollinator Tetragonisca angustula (Latreille) (Hymenoptera: Apidae: Meliponinae). Racemic mixtures of five new pyrethroids (30 µg molecule mg^?1 insect body weight) resulted in high (100%) and rapid (stable LD₅₀ after 12 h) mortality in D. hyalinata and A. monuste. In A. monuste, the trans-pyrethroid [12] isomer showed similar toxicity to permethrin. For D. hyalinata, the trans-pyrethroid [9] isomer and cis-pyrethroid [10] isomer were as toxic as permethrin. Due to their low selectivity, these new pyrethroids should be applied on the basis of ecological selectivity principles to minimize impacts on nontarget organisms S. saevissima and T. angustula.     

Lichen microalgae are sensitive to environmental concentrations of atrazine

The identification of new organisms for environmental toxicology bioassays is currently a priority, since these tools are strongly limited by the ecological relevance of taxa used to study global change. Lichens are sensitive bioindicators of air quality and their microalgae are an untapped source for new low-cost miniaturized bioassays with ecological importance. In order to increase the availability of a wider range of taxa for bioassays, the sensitivity of two symbiotic lichen microalgae, Asterochloris erici and Trebouxia sp. TR9, to atrazine was evaluated. To achieve this goal, axenic cultures of these phycobionts in suspension were exposed to a range of environmental concentrations of the herbicide atrazine, a common water pollutant. Optical density and chlorophyll autofluorescence were used as endpoints of ecotoxicity and ecophysiology on cell suspensions. Results show that lichen microalgae show high sensitivity to very low doses of atrazine, being higher in Asterochloris erici than in Trebouxia sp. TR9. We conclude that environmental concentrations of atrazine could modify population dynamics probably through a shift in reproduction strategies of these organisms. This seminal work is a breakthrough in the use of lichen microalgae in the assessment of micropollution effects on biodiversity.     

Portlandite wet-synthesis process from phosphogypsum waste using hydroxide medium: application in both CO2 capture and brine water salinity reduction

Journal of Material Cycles and Waste Management - Portlandite (Ca(OH)2) preparation from phosphogypsum waste (PGW) was evaluated in numerous works; however, the use of this compound is not applied...     

Changes in organic matter composition during composting of two digested sewage sludges

Changes in the chemical and chemical-structural composition of the organic matter of two different sewage sludges (aerobic and anaerobic) mixed with sawdust (1:1 and 1:3, v/v) during composting were determined by monitoring chemical and microbiological parameters as well as by pyrolysis-gas chromatography. Composting was carried out in periodically turned outdoor piles, which were sampled for analysis 1, 30, 60 and 90 days after the beginning of the composting process. Both volatile organic matter and the water soluble C fraction decreased during composting, indicating that the more labile C fractions are mineralized during the process. Microbial activity as measured by microbial respiration (CO(2) evolved from compost samples during incubation) also decreased with composting, reflecting the more stable character of the resulting compost. No major differences were observed between the four composts studied as regards their chemical-structural characteristics. The acetonitrile, acetic acid and phenol pyrolytic fragment tended to increase with composting. Although the final composts were more aromatic in nature than the starting materials, a low degree of humification was observed in all four composts studied, as determined by their high proportion of polysaccharides and alkyl compounds. For this reason, the relationship between pyrolytic fragments, such as benzene/toluene or benzene+toluene/pyrrol+phenols, which are used as indices of humification for soil organic matter, are not of use for such poorly evolved sludge composts; instead, ratios that involve carbohydrate derivatives and aromatic compounds, such as furfural+acetic/benzene+toluene or acetic/toluene, are more sensitive indices for reflecting the transformations of these materials during composting. Both the chemical and microbiological parameters and pyrolytic analysis provided valuable information concerning the nature of the compost's organic matter and its changes during the composting process.     

PM source apportionment and trace metallic aerosol affinities during atmospheric pollution episodes: a case study from Puertollano, Spain

Source apportionment study was performed, applying principal component analysis to the results of 221 chemical analyses of PM10 and PM2.5 samples collected daily from the industrial (but low traffic) Spanish town of Puertollano over a 14-month period during 2004-2005. Results reveal compositional variations attributable to different mixtures of natural and anthropogenic materials, mainly soil and rock dust (crustal), marine salt (only in PM10), petrochemical refinery emissions, and particles attributed to the combustion of local coal, which is unusually rich in Pb and Sb. During the study period there were 34 pollution episodes when PM10 exceeded 50 tg m(-3), mostly due to winter air temperature inversions, regional atmospheric stagnation, or African dust incursions (North African, NAF days: usually in summer). Whereas the crustal component during NAF episodes averaged 52% with a PM2.5/PM10 ratio of 0.54, this dropped to 29% and a PM2.5/PM10 of 0.67 during non-NAF days when anthropogenic materials predominated. Abnormally enhanced concentrations of pathfinder metallic trace elements provide additional evidence for source apportionment: thus aerosols with raised levels of Pb and Sb are associated with local coal combustion, Ni and V can be linked to petrochemical PM emissions, and Ti, Mn, Rb, and Ce are particularly characteristic of crustal dust incursions.     

Evaluating urban PM10 pollution benefit induced by street cleaning activities

Despite their burden in urban particulate air pollution, road traffic non-exhaust emissions are often uncontrolled and information about the effectiveness of mitigation measures on paved roads is still scarce. The present study is aimed to evaluate the effectiveness of mechanical sweeping/water flushing treatments in mitigating urban road dust resuspension and to quantify the real benefit in terms of ambient PM₁₀ concentrations. To this aim a specific campaign was carried out in a heavily trafficked central road of Barcelona (Spain), a Mediterranean city suffering from a traffic-related pollution, both for a high car density and a frequent lack of precipitation. Several street washings were performed by means of mechanical sweepers and pressure water during night in all traffic lanes and sidewalks. PM₁₀ levels were simultaneously compared with four reference urban background air quality stations to interpret any meteorological variability. At the downwind measurement site, PM₁₀ concentrations registered a mean daily decrease of 8.8 μg m^?3 during the 24 h after street washing treatments. However 3.7–4.9 μg m^?3 of such decrease were due to the meteorological variability detected at the upwind site, as well as at two of the reference sites. This reveals that an effective decrease of 4–5 μg m^?3 (7–10%) can be related to street washing efficiency. Mitigation of road dust resuspension was confirmed by investigating the chemical composition of airborne-PM₁₀ filters. Concentrations of Cu, Sb, Fe and mineral matter decrease significantly with respect to concentrations of elemental carbon, used as tracer for exhaust diesel emissions. High efficiency of street washing in reducing road dust loads was found by performing periodic samplings both on the treated and the untreated areas.