Identification of surfactant degradation products as toxic organic compounds present in sewage sludge

A cost-effective strategy combining chemical analysis and bioassays for the identification of polar toxic compounds in sewage sludge is reported. ToxAlert 100 bioluminescence inhibition assay was used in combination with chemical analysis involving extraction, clean-up, chromatographic separation and mass spectrometry detection. This methodology was applied to real samples of sludge from three wastewater treatment plants (WWTP) located in Catalonia (Spain) during a 3 month period. In the first step, sewage sludge was lyophilized, treated by sonication with a mixture of methanol and chloroform and finally cleaned up using a sequential solid phase extraction (SSPE) with an octadecylsilica cartridge (C18) in series with a polymeric Lichrolut EN cartridge (Lic EN). In the second step, the toxicity of each fraction of the sludge sample was investigated using the ToxAlert 100. The unequivocal identification and quantification of polar organic cytotoxic substances present in the fractionated extracts were determined by liquid chromatography-mass spectrometry (LC-MS). Major toxic compounds identified were: non-ionic polyethoxylated surfactants (nonylphenol polyethoxylates, alcohol polyethoxylates), their intermediates (polyethylene glycol polyethoxylated, nonylphenol carboxylates and polyethoxylated alcohol carboxylates), linear alkylbenzenesulfonates and heavy metals. The toxic response (in terms of bioluminescence inhibition using ToxAlert 100), defined by the 50% effective concentration (EC50), and the toxicity units (TU) for every standard non-ionic surfactant were calculated. The results provided the identification of polar cytotoxic compounds as well as the evaluation of their contribution to the total toxicity observed in sewage sludge.     

Forest health conditions in North America

Some of the greatest forest health impacts in North America are caused by invasive forest insects and pathogens (e.g., emerald ash borer and sudden oak death in the US), by severe outbreaks of native pests (e.g., mountain pine beetle in Canada), and fires exacerbated by changing climate. Ozone and N and S pollutants continue to impact the health of forests in several regions of North America. Long-term monitoring of forest health indicators has facilitated the assessment of forest health and sustainability in North America. By linking a nationwide network of forest health plots with the more extensive forest inventory, forest health experts in the US have evaluated current trends for major forest health indicators and developed assessments of future risks. Canada and Mexico currently lack nationwide networks of forest health plots. Development and expansion of these networks is critical to effective assessment of future forest health impacts.     

Behavior of bensulfuron-methyl in an agricultural alkaline soil

A field experiment to determine the available bensulfuron-methyl (BSM) in the upper soil layer was conducted in an agricultural area in the South of Spain. To facilitate herbicide analysis, two application rates were employed, 200 g ha(-1) and 5 kg ha(-1). Samples of upper soil and soil solution were collected. Soil solution was sampled by means of metallic samplers, placed at a depth of 35 cm. In the plots receiving the lower dose ceramic suction, porous cups were also installed. Results from soil solution samples showed that the maximum BSM concentration was found after 8-10 days for the high irrigation supply (945 mm) and after 18-25 days for the lower irrigation regime (405 mm). The mathematical model FOCUSPELMO 1.1.1 was applied to interpret the data obtained in the field experiments. In general, there was a reasonable agreement between experimental and simulated data for soil samples, although the model did not acceptably predict herbicide concentrations in water soil samples. Ceramic cups sampled a higher soil water volume and more frequently than did the metallic samplers. However some variable results were attributed to preferential flow.     

Microbiological characterization and specific methanogenic activity of anaerobe sludges used in urban solid waste treatment

This study presents the microbiological characterization of the anaerobic sludge used in a two-stage anaerobic reactor for the treatment of organic fraction of urban solid waste (OFUSW). This treatment is one alternative for reducing solid waste in landfills at the same time producing a biogas (CH(4) and CO(2)) and an effluent that can be used as biofertilizer. The system was inoculated with sludge from a wastewater treatment plant (WWTP) (Río Frío Plant in Bucaramanga-Colombia) and a methanogenic anaerobic digester for the treatment of pig manure (Mesa de los Santos in Santander). Bacterial populations were evaluated by counting groups related to oxygen sensitivity, while metabolic groups were determined by most probable number (MPN) technique. Specific methanogenic activity (SMA) for acetate, formate, methanol and ethanol substrates was also determined. In the acidogenic reactor (R1), volatile fatty acids (VFA) reached values of 25,000 mg L(-1) and a concentration of CO(2) of 90%. In this reactor, the fermentative population was predominant (10(5)-10(6)MPN mL(-1)). The acetogenic population was (10(5)MPN mL(-1)) and the sulphate-reducing population was (10(4)-10(5)MPN mL(-1)). In the methanogenic reactor (R2), levels of CH(4) (70%) were higher than CO(2) (25%), whereas the VFA values were lower than 4000 mg L(-1). Substrate competition between sulphate-reducing (10(4)-10(5)MPN mL(-1)) and methanogenic bacteria (10(5)MPN mL(-1)) was not detected. From the SMA results obtained, acetoclastic (2.39 g COD-CH(4)g(-1)VSS(-1)day(-1)) and hydrogenophilic (0.94 g COD-CH(4)g(-1)VSS(-1)day(-1)) transformations as possible metabolic pathways used by methanogenic bacteria is suggested from the SMA results obtained. Methanotrix sp., Methanosarcina sp., Methanoccocus sp. and Methanobacterium sp. were identified.     

Evaluation of the critical factors controlling stability of chromium, copper, arsenic and zinc in iron-treated soil

Various environmental factors are expected to affect the mobility of elements in chemically stabilized soils. The aim of this study was to evaluate the effects of pH, oxidizing-reducing potential (Eh), liquid-to-solid ratio (L/S), presence of organic matter (OM) and microbial activity (MA) on the mobility of chromium, copper, arsenic and zinc in zerovalent iron (Fe(0))-stabilized soil. A 2(5) full factorial design was applied to assess the leaching of the elements from the treated soil. The factor having the most impact on the mobility of Cr, Cu and Zn was pH; low pH (3) led to the release of these elements. Arsenic remobilization was controlled by L/S and MA, whilst Eh, though also significant, had less influence. In the identified worst-case scenarios, more than half of the total Zn and Cu and 14% of As can be expected to remobilize from the treated soil. The leaching procedure concerning sample agitation and type of filtration showed to substantially affect the results of As leaching, especially in OM rich soil.     

Neighborhood phylodiversity affects plant performance

Facilitation and competition are ecological interactions that are crucial for the organization of plant communities. Facilitative interactions tend to occur among distantly related species, while the strength of competition tends to decrease with phylogenetic distance. The balance between both types of interactions will ultimately determine the specific composition of multispecies associations. Although multispecies patches are the arena in which coexistence develops among different phylogenetic groups within communities, the specific processes that occur across life stages have not been explored. Here we study how different species, in composing discrete patches in central Mexico, exert competitive or facilitative effects on seeds and seedlings. We relate these interactions to phylogenetic relationships among nurse species and beneficiary species, and among members of the patches. Survivorship and growth rates of the columnar cactus Neobuxbaumia mezcalaensis were highly positively related to increasing phylogenetic distance to different nurse species, to the presence of related species in patches, and to mean phylogenetic distances to the rest of the species in the patch. Each of these three elements influenced N. mezcalaensis differently, with different nurse species varying substantially in their early effects on emergence, and the nearest relatives and species composition of patches varying in their late effects on survival and growth. Our results emphasize that evolutionary relationships among co-occurring species in vegetation clumps exert direct and indirect effects on plants, affecting individual performance and species coexistence.     

A research model--forecasting incident rates from optimized safety program intervention strategies

INTRODUCTION/PROBLEM: Property damage incidents, workplace injuries, and safety programs designed to prevent them, are expensive aspects of doing business in contemporary industry. The National Safety Council (2002) estimated that workplace injuries cost $146.6 billion per year. Because companies are resource limited, optimizing intervention strategies to decrease incidents with less costly programs can contribute to improved productivity. METHOD: Systematic data collection methods were employed and the forecasting ability of a time-lag relationship between interventions and incident rates was studied using various statistical methods (an intervention is not expected to have an immediate nor infinitely lasting effect on the incident rate). RESULTS/SUMMARY: As a follow up to the initial work, researchers developed two models designed to forecast incident rates. One is based on past incident rate performance and the other on the configuration and level of effort applied to the safety and health program. Researchers compared actual incident performance to the prediction capability of each model over 18 months in the forestry operations at an electricity distribution company and found the models to allow accurate prediction of incident rates. IMPACT ON INDUSTRY: These models potentially have powerful implications as a business-planning tool for human resource allocation and for designing an optimized safety and health intervention program to minimize incidents. Depending on the mathematical relationship, one can determine what interventions, where and how much to apply them, and when to increase or reduce human resource input as determined by the forecasted performance.     

Ecological Information System: Analyzing the Communication and Utilization of Scientific Information in Mexico

/ This study is concerned with the role that communication can play in facilitating the utilization of ecological information by different sectors of society involved in environmental decision-making. The ecological information system is used as a conceptual framework. This system is a model for the analysis of interactions between three sectors involved in the management of natural resources: researchers in ecology, change agents, and rural producers. Two case studies of organizations carrying out scientific research aimed at finding and implementing sustainable strategies of resource management were carried out. The purpose was to examine how real situations function in terms of communication strategies and to analyze such situations in relation to the model proposed. The analysis revealed the importance of promoting the feedback of information from change agents and rural producers to the research sector and the incorporation of this information into the research process. It also emphasized the relevance of having "active utilizer constituencies" within the rural producers who make demands upon the entire system in order to satisfy information needs. The creation of linkage systems facilitating the connection between the generation and utilization of information was supported. In particular, the establishment of special teams within research institutions is proposed, which could promote the links between the sectors through the use of communication as an instrument of work.     

Sediment grain size estimation using airborne remote sensing, field sampling, and robust statistic

Remote sensing has been used since the 1980s to study parameters in relation with coastal zones. It was not until the beginning of the twenty-first century that it started to acquire imagery with good temporal and spectral resolution. This has encouraged the development of reliable imagery acquisition systems that consider remote sensing as a water management tool. Nevertheless, the spatial resolution that it provides is not adapted to carry out coastal studies. This article introduces a new methodology for estimating the most fundamental physical property of intertidal sediment, the grain size, in coastal zones. The study combines hyperspectral information (CASI-2 flight), robust statistic, and simultaneous field work (chemical and radiometric sampling), performed over Santander Bay, Spain. Field data acquisition was used to build a spectral library in order to study different atmospheric correction algorithms for CASI-2 data and to develop algorithms to estimate grain size in an estuary. Two robust estimation techniques (MVE and MCD multivariate M-estimators of location and scale) were applied to CASI-2 imagery, and the results showed that robust adjustments give acceptable and meaningful algorithms. These adjustments have given the following R(2) estimated results: 0.93 in the case of sandy loam contribution, 0.94 for the silty loam, and 0.67 for clay loam. The robust statistic is a powerful tool for large dataset.     

Collective Action in the Management of a Tropical Dry Forest Ecosystem: Effects of Mexico’s Property Rights Regime

Dilemmas of natural resources governance have been a central concern for scholars, policy makers, and users. Major debates occur over the implications of property rights for common resources management. After the Mexican Revolution (1910–1917), land was distributed mainly as ejidos conceived as a hereditary but unalienable collective form of property. In 1992, a new Agrarian Law was decreed that allows individual ownership by removing various restrictions over the transfer of land. Scholars have examined the reform mainly focusing on land-tenure changes and environmental fragmentation. This study examines how the new ownership regime is affecting collective decision-making in ejidos located in a tropical dry forest (TDF) ecosystem. Information on decision-making processes before and after the 1992 reform was gathered through 52 interviews conducted in four ejidos selected along a gradient including agricultural, cattle-raising, and TDF use. The new individualized land property system reduced collective action in ejidos but did not trigger it. Collective action responses to the 1992 reform were buffered by self-organization each ejido already had. Heterogeneous users who shared a short history and showed little understanding of TDF and low dependence on its resources seemed to explain why ejidos have not been able to share a sense of community that would shape the construction of institutions for the collective management of forest resources. However, when a resource is scarce and highly valuable such as water the same users showed capacities for undertaking costly co-operative activities.