Electrodisinfection of real swine wastewater for water reuse

Environmental Chemistry Letters - Swine production generates large volumes of wastewater, rich in organic matter, nutrients and pathogens. Electrodisinfection is used to remove organic matter and...     

SELECTING TREND TESTS FOR WATER QUALITY SERIES WITH SERIAL CORRELATION AND MISSING VALUES1

ABSTRACT: The use of nonparametric tests for monotonic trend has flourished in recent years to support routine water quality data analyses. The validity of an assumption of independent, identically distributed error terms is an important concern in selecting the appropriate nonparametric test, as is the presence of missing values. Decision rules are needed for choosing between alternative tests and for deciding whether and how to pre-process data before trend testing. Several data pre-processing procedures in conjunction with the Mann-Kendall tau and the Seasonal Kendall test (with and without serial correlation correction) are evaluated using synthetic time series with generated serial correlation and missing data. A composite test (pre-testing for serial correlation followed by one of two trend tests) is evaluated and was found to perform satisfactorily.     

Lateral migration and offsite surface emission of landfill gas at City of Montreal Landfill Site

An evaluation of lateral landfill gas migration was carried out at the Saint-Michel Environmental Complex in Montreal, City of Montreal Landfill Site, Canada, between 2003 and 2005. Biogas concentration measurements and gas-pumping tests were conducted in multilevel wells installed in the backfilled overburden beside the landfill site. A migration event recorded in autumn 2004 during the maintenance shutdown of the extraction system was simulated using TOUGH-LGM software. Eleven high-density instantaneous surface monitoring (ISM) surveys of methane were conducted on the test site. Gas fluxes were calculated by geostatistical analyses of ISM data correlated to dynamic flux chamber measurements. Variograms using normal transformed data showed good structure, and kriged estimates were much better than inverse distance weighting, due to highly skewed data. Measurement-based estimates of yearly off-site surface emissions were two orders of magnitude higher than modelled advective lateral methane flux. Nucleodensimeter measurements of the porosity were abnormally high, indicating that the backfill was poorly compacted. Kriged porosity maps correlated well with emission maps and areas with vegetation damage. Pumping tests analysis revealed that vertical permeability was higher than radial permeability. All results suggest that most of the lateral migration and consequent emissions to the atmosphere were due to the existence of preferential flow paths through macropores. In December 2006, two passively vented trenches were constructed on the test site. They were successful in countering lateral migration.     

RESEARCH: Shrub Propagation Techniques for Biological Control of Invading Tree Species

Cornus stolonifera, Salix petiolaris, and Spiraea alba clones already located within the corridor of an electrical power line. To establish the efficiency of treatments, we examined the statistical differences of growth traits between species and treatments. An analysis of the effects of layering shows, after the first growth season, differences for all growth traits in only one species, Spiraea alba. After the second growth season, we observed the development of new aerial stems. Layering favors horizontal expansion of shrubs over height development. The third year after treatment, the effect of layering is reduced except for Cornus stolonifera, which continuously increases, as shown by the significant progression of the clone issued from the layer even five years after treatments. With the cutting back technique, we expected a distinct vertical growth of the shrubs at the expense of increasing the crown diameter. This technique would be best associated with the rejuvenation of clones, followed by a layering of new shoots to allow a horizontal expansion of the shrubs. Therefore, the formation of a dense shrub community by layering should be considered a valuable approach for the biological control of undesirable trees in powerline rights-of-way.     

Is sex-biased maternal care limited by total maternal expenditure in polygynous ungulates?

We examined data on sex-specific differences in neonatal weight, litter size and adult female body weight in 32 populations of polygynous ungulates of 18 different species to test for the existence of a trade-off between sex-biased maternal care and the total amount of maternal expenditure. This corresponds to an extension of the hypothesis of Byers and Moodie (1990) that sex-biased maternal care is limited by a high level of maternal expenditure. We did not find any relationship between sex-biased care and two measures of total maternal expenditure. We highlighted high intraspecific variability in sex-biased care and very low intraspecific variability in total maternal expenditure. Even when this between-population variability in sex-biased care was accounted for, no relationship between sex-biased maternal care and maternal expenditure was detected. Apart from difficulties in finding suitable measures for both variables, two other reasons may account for the lack of a relationship between sex-biased maternal care and total maternal expenditure. Firstly, male offspring seem to be more affected than female offspring by harsh environmental conditions. This may lead to the variation observed in the extent of sex-specific differences in birth weight within a single species. If we assume that for a given maternal expenditure reproductive costs incurred by mothers are highest during harsh conditions, this could indicate the existence of a trade-off between sex-biased maternal care and maternal expenditure at the intra-specific level, thereby supporting the Byers and Moodie hypothesis. Secondly, polygyny is only a poor predictor of sex-biased care and factors such as compensatory growth or extended periods of growth may be expected to modify predictions for different species. Thus, environmental conditions and relative effects of maternal care on male and female lifetime reproductive success are better predictors of sex-biased care than total maternal expenditure.Communicated by P.M. Kappeler     

Small queens in the ant Ectatomma tuberculatum: a new case of social parasitism

Social parasites exploit the worker force of colonies of other social insects to rear their own young. Social parasitism occurs in several Hymenoptera and is particularly common in several tribes of the ant subfamilies Myrmicinae and Formicinae. Here, we document the occurrence of miniaturized queens (microgynes) in colonies of Ectatomma tuberculatum, an ant belonging to the subfamily Ectatomminae. Behavioral observations and genetic analyses show that microgynes concentrate their reproductive efforts almost exclusively on the production of sexual offspring (microgynes and males), whereas the regular, large queens (macrogynes) produce workers in addition to sexuals. According to mitochondrial and nuclear markers, gene flow between microgynes and macrogynes is extremely limited. Whereas the co-occurrence of microgynes and macrogynes in the related species Ectatomma ruidum constitutes an intraspecific polymorphism associated with alternative dispersal tactics, microgynes found in colonies of E. tuberculatum appear to be a distinct species and to represent the first case of social parasitism in the poneromorph subfamilies of ants.     

Assessment of environmental changes in the Orinoco River delta

Major anthropogenic driven changes in the hydrologic and sedimentation patterns of the Orinoco River have had an impact on environmental conditions in the delta. The abrupt water flow reduction from 3,600 to 200 m³ s^–1 in one of its major distributaries resulting from dam construction forced its transformation from a fresh-water body into a tidal channel with an increase in salinity level (as far as 100 km upstream) and with well-mixed water at the mouth and estuarine connection to the Paria Gulf. Three different sectors along this distributary can be identified (indicated by the Na/Cl ratio in the water). As a result, noticeable changes have occurred in the mangrove community which moved about 60 km further upstream. The changes have also promoted the formation of new islands of sediment progradation at the mouth of this distributary, where successional colonization and species replacement by different species of grasses and mangroves take place. Electronic Publication     

Active capping demonstration in the Anacostia river,Washington, D.C.

An active capping demonstration project in Washington, D.C., is testing the ability to place sequestering agents on contaminated sediments using conventional equipment and evaluating their subsequent effectiveness relative to conventional passive sand sediment caps. Selected active capping materials include: (1) AquaBlokTM, a clay material for permeability control; (2) apatite, a phosphate mineral for metals control; (3) coke, an organic sequestration agent; and (4) sand material for a control cap. All of the materials, except coke, were placed in 8,000‐ft test plots by a conventional clamshell method during March and April 2004. Coke was placed as a 1.25‐cm layer in a laminated mat due to concerns related to settling of the material. Postcap sampling and analysis were conducted during the first, sixth, and eighteenth months after placement. Although postcap sampling is expected to continue for at least an additional 24 months, this article summarizes the results of the demonstration project and postcap sampling efforts up to 18 months. Conventional clamshell placement was found to be effective for placing relatively thin (six‐inch) layers of active material. The viability of placing high‐value or difficult‐to‐place material in a controlled manner was successfully demonstrated with the laminated mat. Postcap monitoring indicates that all cap materials effectively isolated contaminants, but it is not yet possible to differentiate between conventional sand and active cap layer performance. Monitoring of the permeability control layer indicated effective reductions in groundwater seepage rates through the cap, but also showed the potential for gas accumulation and irregular release. All of the cap materials show deposition of new contaminated sediment onto the surface of the caps, illustrating the importance of source control in maintaining sediment quality. © 2006 Wiley Periodicals, Inc.