Application of activated sludge model no. 3 for the modeling of organic matter biodegradation at thermophilic temperatures.

The primary aim of our research was to investigate the applicability of activated sludge models (ASM) for aerobic thermophilic processes, especially autothermal thermophilic aerobic digestion (ATAD). The ASM3 model (Gujer et al., 1999) theoretically seems to be the most suitable, because storage plays an important role in a batch-feed cycle system like ATAD. The ASM3 model was extended with an activation step of the thermophilic organisms. This model was calibrated and verified by independent test results, demonstrating its ability to describe the process. The growth (microH = 26.04 day(-1)), storage (k(STO) = 20.39 day(-1)), hydrolysis (kH = 11.15 day(-1)) and decay rates (b 9H,O2) = 1.28 day(-1), b(STO,O2 = 1.10 day-1)) obtained from calibration are significantly higher at 55 degrees C than at mesophilic temperatures, justifying the faster metabolism at higher temperatures. An inert fraction of the biomass (characterized by the model parameter f(i) = 0.4) was found to be significantly greater than in the mesophilic case. This can be attributed to the lower diversity of the thermophilic species and thus to their narrower substrate spectra.     

Factors influencing cannibalism in the wolf spider Pardosa agrestis (Araneae, Lycosidae)

Cannibalistic tendencies are well known in spiders and may be a significant factor influencing population size. The wolf spider, Pardosa agrestis, is the dominant non-web-building spider in a wide range of central European agricultural habitats. Preliminary field observations indicated an extended reproductive period, which results in a very wide size distribution of juvenile instars. We hypothesised that if cannibalism is enhanced by differences in size, especially during periods when prey is scarce, these populations might be susceptible to cannibalism in an ecologically significant way. Laboratory studies were conducted on juvenile P. agrestis in arenas. We analysed the following specific aspects of cannibalism: (1) the effect of the weight ratio between the opponents; (2) the effect of weight per se, and (3) the role of hunger level in determining cannibalistic tendencies of spiders. The role of weight and hunger were analysed in separate experiments, in both cases by controlling for the other variable. The results showed that cannibalism was strongly positively correlated with both weight ratio and hunger, but absolute size/age of an individual could not predict the occurrence of a cannibalistic event. These experiments generated the plausible hypothesis that cannibalism might be an important phenomenon in the regulation of real populations, which should be tested specifically in future field experiments. Received: 15 December 1997 / Accepted after revision: 10 October 1998     

A spatial clustering perspective on autocorrelation and regionalization

We revisit one of the classical problems in geography and cartography where multiple observations on a lattice (N) need to be grouped into many fewer regions (G), especially when this number of desired regions is unknown a priori. Since an optimization through all possible aggregations is not feasible, a hierarchical classification scheme is proposed with an objective function sensitive to spatial pattern. The objective function to be minimized during the assignment of observations to regions (classification) consists of two terms: the first characterizes accuracy and the second, model complexity. For the latter, we introduce a spatial measure that characterizes the number of homogeneous patches rather than the usual number of classes. A simulation study shows that such a classification procedure is less sensitive to random and spatially correlated error (noise) than non-spatial classification. We also show that for conditional autoregressive error (noise) fields the optimal partitioning is the one that has the highest within-units generalized Moran coefficient. The classifier is implemented in ArcView to demonstrate both a socio-economic and an environmental application to illustrate some potential applications.

Dissolved organic matter fractions formed during composting of winery and distillery residues: evaluation of the process by fluorescence excitation-emission matrix

The aim of the present paper is to assess the maturity degree reached by different samples of several mixtures from winery and distillery residues composted using the Rutgers composting system, by means of excitation-emission matrix (EEM) fluorescence spectroscopy. The composts were sampled once a week for about 200d. EEM spectra indicate the presence of different fluorophores. The fluorescence intensities of these peaks show trends related to the maturity of the composting samples selected. The "contour density" of EEM maps is strongly modified through time. We have used the quantitative method of fluorescence regional integration (FRI). The EEMs were delineated into five excitation-emission regions. The degree of compost maturity could be correlated with the percentage of the volumetric integration under the EEM within each region. Further refinement of these techniques should provide a relatively rapid method for assessing the suitability of the compost to soil application.     

Determination of selected neonicotinoid insecticides by liquid chromatography with thermal lens spectrometric detection

We studied the analysis of trace amounts of neonicotinoid insecticides by liquid chromatography coupled with a thermal lens spectrometric detector (TLS). This multi-residue analysis method is based on the reversed phase separation on C₁₈ column, isocratic elution and collinear dual beam TLS detection. The insecticides thiamethoxam, imidacloprid, acetamiprid and thiacloprid were detected with retention times of 4.4, 5.7, 6.5 and 8.5 min and limits of quantifications of 50, 89, 10, and 25 μg/L, respectively. The retention times agreed well with those obtained by the same chromatographic method but using a diode-array detector (DAD). The limits of quantifications for imidacloprid were identical in both techniques. However, the limits of quantifications for thiamethoxam, acetamiprid and thiacloprid were up to 8.5 times lower using the TLS detector compared to the diode-array detector. The applicability of the developed procedure was tested on spiked river water and potato samples.     

Safening activity of natural hydroxamic acids and analogous compounds against herbicide injury to maize

Abstract

Safening activities of natural compounds DIMBOA, DIBOA, and MBOA, as well as synthetic 1,4‐benzoxazin‐3‐ones were tested against acetochlor and EPTC injuries to maize. No safening activities of natural products and from low to moderate activity of synthetic benzoxazinones were observed. In order to explain inefficacy of natural compounds we studied the influence of these molecules on enzymes participating in metabolic detoxication of acetochlor and EPTC. Pretreatment with DIMBOA elevated maize cytochrome P450 levels. Pretreatments with chemicals containing 1,4‐benzoxazin‐3‐one backbone did not alter glutathione S‐transferase enzyme activities. However, all natural products inhibited glutathione S‐transferase activity of roots and shoots in vitro after addition to the enzyme. Safening ineffectiveness of natural hydroxamic acids may be explained by their inhibitory effects on GST enzymes due to their reaction with sulfhydryl groups on the enzyme.     

Environmental assessment of water-courses of the Turvo Limpo River basin at the Minas Gerais State, Brazil

A study was performed to evaluate the environmental contamination in the Turvo Limpo River basin which receives effluent discharges from domestic (residential and commercial) activities. The watercourses examined were the São Bartolomeu Stream, Turvo Sujo River, and Turvo Limpo River, located in the Minas Gerais State, Brazil. Water samples were collected at the river-side and analyzed for evaluation of pollutant inputs. The pH, temperature, electrical conductivity, redox potential (Eh), dissolved oxygen (DO), total and settleable solids, visual color, hardness, chemical oxygen demand (COD), biochemical oxygen demand (BOD), chloride, total phosphate, total nitrogen, ammonia nitrogen, nitrate, total coliforms and E. coli, as well as the Cd, Pb, Cu, and Zn speciation were determined in the watercourses. The data obtained were compared with those of the Brazilian Environmental Standards and with data from non-contaminated areas. River water characteristics in some sites were far from the limit values established for superficial waters with satisfactory quality. For instance, the BOD values reached 411 mg L^?1 for a maximum limit of 10.0 mg L^?1, while the ammonia nitrogen concentration reached 28 mg L^?1 for a maximum limit of 13.3 mg L^?1. Some sites showed E. coli values above those of non-contaminated regions. Besides the effects of sewage discharges into the water-courses, agriculture activities and the use of the area for cattle husbandry influenced the quality of the river waters, for instance, the pH of a spring-water sample reached the value of 4.3. The São Bartolomeu Stream has been contributing to the deterioration of the water quality of the Turvo Sujo River, while the Turvo Limpo River has also been affected by anthropogenic discharges in the Turvo Sujo River. The speciation of Cd, Cu and Pb showed that these metals were mainly found in the particulate fraction (i. e., associated with the suspended material). Fifty five percent of the water samples showed labile Zn concentrations greater than that of the nonlabile Zn.     

Trophic field overlap: A new approach to quantify keystone species

It is a current challenge to better understand the relative importance of species in ecosystems, and the network perspective is able to offer quantitative tools for this. It is plausible to assume, in general, that well-linked species, being key interactors, are also more important for the community. Recently a number of methods have been suggested for quantifying the network position of species in ecological networks (like the topological importance metric, TI). Most of them are based on node centrality indices and it may happen that the two most important species in a food web have very similar interaction structure and they can essentially replace each other if one becomes extinct. For conservation considerations it is a challenge to identify species that are richly connected and, at the same time, have a relatively unique and irreplaceable interaction pattern. We present a new method and illustrate our approach by using the Kuosheng Bay trophic network in Taiwan. The new method is based on the interaction matrix, where the strength of the interaction between nodes i and j depends only on topology. By defining a threshold separating weak and strong interactors, we define the effective range of interactions for each graph node. If the overlaps between pairs of these ranges are quantified, we gain a metric expressing how unique is the interaction pattern of a focal node (TO). The combination of centrality (TI) and uniqueness (TO) is called topological functionality (TF). We compare the nodal importance rank provided by this metric to others based on a variety of centrality measures. The main conclusion is that shrimps seem to have the most unique interaction pattern despite that their structural importance has been underestimated by all conventional centrality indices. Also, our network analysis suggests that fisheries disturb the ecosystem in a more critical network position than the impingement by the local power plant.