Study on PCDDs/PCDFs and co-PCBs content in food samples from Catalonia (Spain)

The results of a surveillance programme on polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and co-planar polychlorinated biphenyls (co-PCBs) determination in 70 foodstuffs samples produced all over the four provinces of Catalonia is presented. The study included the analyses of raw milk, pure virgin olive oil, butter, chicken, pork and mussel samples collected between November 1999 and January 2000. Milk, virgin oil, pork or butter presented a variable dioxin and co-PCBs content, even though the limits proposed in the draft of the EC Regulation for its commercialization in the European countries were not reached. The levels of PCDDs/PCDFs and co-PCBs determined in chicken samples varied between 0.36–3.59 pg I-TEQ/g fat chicken (0.4–3.8 WHO-TEQ/g fat). Just one case presented remarkable content of dioxins (about 30 pg I-TEQ/g fat) with a complex congener-specific profile which indicates the presence of an external contamination. On the other hand, a congener-specific profile dominated by 2,3,7,8-TCDF and OCDD was observed in mussel samples from Catalonia. This fact was also observed in mussel samples from other sites in Spain.     

A review of postfeeding larval dispersal in blowflies: implications for forensic entomology

Immature and adult stages of blowflies are one of the primary invertebrate consumers of decomposing animal organic matter. When the food supply is consumed or when the larvae complete their development and migrate prior to the total removal of the larval substrate, they disperse to find adequate places for pupation, a process known as postfeeding larval dispersal. Several important ecological and physiological aspects of this process were studied since the work by Green (Ann Appl Biol 38:475, 1951) 50 years ago. An understanding of postfeeding larval dispersal can be useful for determining the postmortem interval (PMI) of human cadavers in legal medicine, particularly because this interval may be underestimated if older dispersing larvae or those that disperse longer, faster, and deeper are not taken into account. In this article, we review the process of postfeeding larval dispersal and its implications for legal medicine, in particular showing that aspects such as burial behavior and competition among species of blowflies can influence this process and consequently, the estimation of PMI.     

Age-size plasticity for reproduction in monocarpic plants

Empirical and theoretical investigations of monocarpy have usually addressed the question of minimum or threshold sizes for reproduction. However, the range of flowering sizes observed in many monocarpic species is extraordinarily large (well beyond what can be called a "threshold"), and the sizes of flowering and nonflowering plants may overlap greatly. We attempt to explain these reproductive patterns in terms of optimal reaction norms predicted by simple deterministic life history models. We assume that individuals differ in their growth trajectories due to the heterogeneous quality of microsites and ask how the optimal age and size at flowering varies with environmental variation in growth and for different assumptions about fecundity and mortality. Under two very different growth functions (one with no age- or size-related decline in growth rate and another with such a decline as size approaches an asymptote), the optimal reaction norms imply considerable plasticity for size at reproduction, particularly when poor growth is associated with higher mortality or lower asymptotic size. Deterministic models such as these may be more applicable to long-lived than to short-lived monocarps, because fitness potential should be less affected by stochastic variability in yearly growing condition in the former than in the latter. We consider the case of a tropical monocarpic and masting tree species, Cerberiopsis candelabra (Apocynaceae), and show that our model results can account for wide ranges of reproductive size and overlap in size of flowering and nonflowering plants, in accord with observation. We suggest that empirical attention to norms of reaction across growth environments will be a more profitable approach than investigation of size thresholds per se.     

The distribution of lianas and their change in abundance in temperate forests over the past 45 years

Lianas (woody vines) are an important and dynamic component of many forests throughout the world, and increases in CO2, mean winter temperature, and forest fragmentation may promote their growth and proliferation in temperate forests. In this study, we used a 45-year data set to test the hypothesis that lianas have increased in abundance and basal area in the interiors of 14 deciduous temperate forests in Wisconsin (USA) since 1959. We also censused woody plants along a gradient from the forest edge to the interior in seven of these forests to test the hypothesis that the abundance of lianas declines significantly with increasing distance from the forest edge. We found that lianas did not increase in abundance within the interiors of temperate forests in Wisconsin over the last 45 years. However, relative and absolute liana abundance decreased sharply with increasing distance from forest edges. Our findings suggest that forest fragmentation, not climate change, may be increasing the abundance of lianas in northern deciduous temperate forests, and that lianas may further increase in abundance if the severity of forest fragmentation intensifies.     

The effects of plant distribution and frugivore density on the scale and shape of dispersal kernels

For many plant species, seed dispersal is one of the most important spatial demographic processes. We used a diffusion approximation and a spatially explicit simulation model to explore the mechanisms generating seed dispersal kernels for plants dispersed by frugivores. The simulation model combined simple movement and foraging rules with seed gut passage time, plant distribution, and fruit production. A simulation experiment using plant spatial aggregation and frugivore density as factors showed that seed dispersal scale was largely determined by the degree of plant aggregation, whereas kernel shape was mostly dominated by frugivore density. Kernel shapes ranged from fat tailed to thin tailed, but most shapes were between an exponential and that of the solution of a diffusion equation. The proportion of dispersal kernels with fat tails was highest for landscapes with clumped plant distributions and increased with increasing number of dispersers. The diffusion model provides a basis for models including more behavioral details but can also be used to approximate dispersal kernels once a diffusion rate is estimated from animal movement data. Our results suggest that important characteristics of dispersal kernels will depend on the spatial pattern of plant distribution and on disperser density when frugivores mediate seed dispersal.     

Exposure of caged mussels to metals in a primary-treated municipal wastewater plume

The biological availability of metals in municipal wastewater effluents is strongly influenced by the physical and chemical conditions of both the effluent and the receiving water. Aquatic organisms are exposed to both dissolved and particulate (food ingestion) forms of these metals. In the present study, the distribution of metals in specific tissues was used to distinguish between exposure routes (i.e. dissolved vs. particulate phase) and to examine metal bioavailability in mussels exposed to municipal effluents. Caged Elliptio complanata mussels were deployed at sites located between 1.5 km upstream and 12 km downstream of a major effluent outfall in the St. Lawrence River. Metals in surface water samples were fractionated by filtration techniques to determine their dissolved, truly-dissolved (<10 kDa), total-particulate and acid-reactive-particulate forms. At the end of the exposure period (90 days), pooled mussel soft tissues (digestive gland, gills, gonad, foot and mantle) were analyzed for several metals. The results showed that gills and digestive gland were generally the most important target tissues for metal bioaccumulation, while gill/digestive gland metal ratios suggest that both exposure routes should be considered for mussels exposed to municipal effluents. We also found that Ag and Cd in the dispersion plume nearest the outfall, in contrast to other metals such as Cu and Zn, are more closely associated with colloids and were generally less bioavailable than at the reference site in the St. Lawrence River.     

Measuring detoxification and maturity in compost made from "alperujo", the solid by-product of extracting olive oil by the two-phase centrifugation system

Olive-mill wastes and by-products from the edible olive oil industry contain a high non-stabilised organic load, including organic acids, phenolic compounds and fats with antimicrobial and phytotoxic properties, which make them unsuitable for direct agricultural application. The most abundant olive-mill by-product in Spain is "alperujo" (AL), a solid material with a lack of consistency and low porosity due to its high water content and small particle size, which can be suitably composted by adding bulking agents. Six piles were prepared by mixing AL with cotton waste, grape stalk, olive leaf and fresh cow bedding, then successively composted, five of them managed by forced ventilation assisted by mechanical turning and the sixth only turned. After monitoring the process, the relationship between the germination index (GI) and the presence of some potentially phytotoxic compounds, as well as several maturity and stability indices, was assessed. As composting advanced, the GI increased and both the fat and water-soluble phenol contents decreased, indicating a gradual detoxification as the composts matured. The values of the maturity and stability indices were frequently different from the values reported for other composts.     

Detection of advected, reacting redox fronts from self-potential measurements

We report on an experiment aimed at testing the use of self-potential measurements to monitor the motion and mixing of redox reactants advected through a well-controlled, laboratory-scale, artificial aquifer system. A rectangular, plastic tank was filled up with water-saturated sand and an array of unpolarizable electrodes was installed in the sand body. A nearly uniform, steady-state flow was established by tilting the tank and controlling the water level in reservoirs at both ends. Then, we simultaneously injected a known quantity of KMnO(4) and FeCl(2), respectively, into two separate compartments forming the upstream reservoir. We thus generated two abrupt fronts, one oxidizing and the other reducing, which subsequently travelled in parallel by advection through the sand body. The KMnO(4) and FeCl(2) solutions were in contact and reacted with each other in a region located along the median vertical plane parallel to the flow direction. During flow, the electrical potential differences between each electrode and a reference located in the downstream reservoir were recorded. In the unreacted FeCl(2) region the electric potential showed sudden variations successively occurring at increasing distances in the flow direction, associated with the passage of the FeCl(2) front. These signals essentially corresponded to the junction potential produced by the difference in ionic mobility of Fe(2+) and Cl(-). In the unreacted KMnO(4) region sharp signals, but with much smaller amplitudes, were also observed. Near the vertical median plane on the FeCl(2) side, we observed a second front associated with the spreading of the reaction zone. The shape and evolution of the reaction zone was largely controlled by the precipitation of Fe(OH)(3).     

Assessment of natural attenuation of volatile aromatic hydrocarbons in agricultural soil contaminated with diesel fuel

A diesel fuel spill was simulated on a 12-m(2) plot of agricultural land, at a concentration of 1 Lm(-2) of soil. The natural attenuation of Volatile Aromatic Hydrocarbons (VAHs) was monitored at different soil depths over a period of 50 days. The natural attenuation of VAHs in the surface layer would be attributed to two processes, namely: volatilisation (mainly linked to the boiling point of each VAH, with t(1/2) from 2 to 71 min for benzene and p-isopropyltoluene, respectively); and dissipation (related to the boiling point as well as the analyte-soil matrix interaction, with t(1/2) from 2 to 169 h for benzene and p-isopropyltoluene, respectively). As expected, in the deeper layers, dissipation prevails over volatilisation. 50 days after the spill, only two VAHs were detected in the surface layer, at concentrations of 5-20 ngg(-1), which had disappeared after 80 days of the spill.     

Heavy metals contents in agricultural topsoils in the Ebro basin (Spain). Application of the multivariate geoestatistical methods to study spatial variations

In this work the content of seven heavy metals (Cd, Cr, Cu, Hg, Ni, Pb and Zn) and other parameters (the pH, organic matter, carbonates and granulometric fraction) in agricultural topsoil in the Ebro basin are quantified, based on 624 samples collected according to an 8 by 8 km square mesh. The average concentrations (mg/kg) obtained were: Cd 0.415+/-0.163, Cr 20.27+/-13.21, Cu 17.33+/-14.97, Ni 20.50+/-22.71, Pb 17.54+/-10.41, Zn 17.53+/-24.19 and Hg 35.6+/-42.05 microg/kg. The concentration levels are relatively low in areas of high pH and low organic matter content concentration. The results of factor analysis group Cd, Cu, Hg, Pb and Zn in F1 and Cr y Ni in F2. The spatial heavy metals component maps based on geostatistical analysis, show definite association of these factors with the soil parent material. The local anomalies (found in Cu, Zn and Pb) are attributed to anthropogenic influence.