Dissipation of 2,4-D in soils of the Humid Pampa region, Argentina: a microcosm study

Phenoxy herbicides like 2,4-dichlorophenoxyacetic acid (2,4-D) are widely used in agricultural practices. Although its half life in soil is 7-14d, the herbicide itself and its first metabolite 2,4-dichlorophenol (2,4-DCP) could remain in the soil for longer periods, as a consequence of its intensive use. Microcosms assays were conducted to study the influence of indigenous microflora and plants (alfalfa) on the dissipation of 2,4-D from soils of the Humid Pampa region, Argentina, with previous history of phenoxy herbicides application. Results showed that 2,4-D was rapidly degraded, and the permanence of 2,4-DCP in soil depended on the presence of plants and soil microorganisms. Regarding soil microbial community, the presence of 2,4-D degrading bacteria was detected even in basal conditions in this soil, possibly due to the adaptation of the microflora to the herbicide. There was an increment of two orders of magnitude in herbicide degraders after 15d from 2,4-D addition, both in planted and unplanted microcosms. Total heterotrophic bacteria numbers were about 1x10(8) CFUg(-1) dry soil and no significant differences were found between different treatments. Overall, the information provided by this work indicates that the soil under study has an important intrinsic degradation capacity, given by a microbial community adapted to the presence of phenoxy herbicides.     

Influence of thermally activated paper sludge on the behaviour of blended cements subjected to saline and non-saline environments

Background, aim and scope  One of the problems to affect Portland cement matrices is low resistance to aggressive agents, due principally to the presence of a high content of portlandite in the hydrated cements. Pozzolanic materials have played an important role in the improving the durability of cement-based materials for decades. This work studies the behaviour of cement mortar matrices blended with 10% calcined paper sludge (source for metakaolinite) and exposed to different environmental conditions (saline and non-saline environments) after 6 and 12 months of exposure. Materials and methods  Two cements were studied: an ordinary Portland cement (CEM 1, 42.5R), acting as reference cement, and a blended cement formulated by mixing 90% (by mass) of CEM 1, 42.5R with 10% (by mass) of paper sludge calcined at 700°C for 2 h. The specimens were exposed 1 year to saline and non-saline environments. All the mineralogy samples were studied through X-ray diffraction and scanning electron microscopy (SEM) equipped with an energy dispersive X-ray analyser. The in-depth study on ionic mobility was performed on samples subjected to natural exposure (coast and tableland) for 6 and 12 months. Results  Portland cement was composed of quartz, calcite, calcium hydroxide and tobermorite gels. The pozzolanic cement (10% calcined paper sludge) is of the same composition but a high calcite concentration and barium carbonate. SEM analysis from coastline show deposits of variable composition. The deposits are identified on the surface of different mineral components. The minerals from tableland are much fractured, i.e. calcite and feldspars. Inside the fractures, the deposits and the ions are located and trapped superficially. Discussion  SEM analysis of control cement Portland and 10% calcined paper sludge shows deposits on quartz and calcite with a very high concentration of Pb, Zn, Cl and barium sulphate. A very porous aspect is due to the presence of the different aggregate types. This porous configuration permits retention of the ion environment. The pozzolanic cement in environments subject to the saline mist favours the retention and transport of ions observed. Something similar also happens with the increase in exposure to outdoor weather. Non-saline samples show temperature changes (ice or thaw cycles). Barium retention is kept on the surface in fracture lines by the gelification processes. In general, it may be inferred that an increase in exposure time increases the diffusion of ions towards test piece interiors. The chemical composition profiles show that the ions present different penetration speeds. Conclusions  The results indicate the better vulnerability of pozzolanic cements from calcined paper sludge in saline and non-saline environments. The cements with a 10% addition of calcined paper sludge favour retention and transport of ion has been observed. Recommendations and perspectives  Today, projects are centred on a new recycling line for industrial waste of this kind, with special attention on its incorporation in cement manufacture as a pozzolanic material, setting the most appropriate activation conditions of the mineralogical compound in this waste (kaolinite and metakaolinite) and taking them as a starting point for this project. The use of pozzolanic cement with 10% addition of calcined paper sludge is a system which favours ionic retention.     

Understanding the impact of democratic logics on participatory resource decision-making in New Zealand

This paper claims that participatory approaches to water resource management in New Zealand are highly influenced by how institutional and community actors understand and practise democracy, including indigenous Māori rights under the Treaty of Waitangi. Drawing on case study analysis from a six-year research programme in which the aim was to evaluate existing and new methods for participatory decision-making, we highlight how different but co-existing democratic beliefs and practices, referred to as democratic logics can shape relationships between governance/decision-making bodies and affected communities. One particular case is examined in detail to illustrate how the various “logics” were strengthened, extended and challenged through participatory research methodologies. Our key message is that revealing and articulating existing democratic logics for participation can help promote and facilitate new participatory approaches, as well as increase robustness and community buy-in to local government decision-making.     

Assessing performance and closure for soil vapor extraction: integrating vapor discharge and impact to groundwater quality

Soil vapor extraction (SVE) is typically effective for removal of volatile contaminants from higher-permeability portions of the vadose zone. However, contamination in lower-permeability zones can persist due to mass transfer processes that limit the removal effectiveness. After SVE has been operated for a period of time and the remaining contamination is primarily located in lower-permeability zones, the remedy performance needs to be evaluated to determine whether the SVE system should be optimized, terminated, or transitioned to another technology to replace or augment SVE. Numerical modeling of vapor-phase contaminant transport was used to investigate the correlation between measured vapor-phase mass discharge, MF(r), from a persistent, vadose-zone contaminant source and the resulting groundwater contaminant concentrations. This relationship was shown to be linear, and was used to directly assess SVE remediation progress over time and to determine the level of remediation in the vadose zone necessary to protect groundwater. Although site properties and source characteristics must be specified to establish a unique relation between MF(r) and the groundwater contaminant concentration, this correlation provides insight into SVE performance and support for decisions to optimize or terminate the SVE operation or to transition to another type of treatment.     

A proposed methodology to determine accuracy of location and extent of geographically isolated wetlands

The disposal of industrial and sewage water is a problem of increasing importance throughout the world. In India, and most of the developing countries untreated sewage and industrial wastes are discharged on land or into the running water streams which is used for irrigating crops. These wastes often contain high amount of trace elements which may accumulate in soils in excessive quantities on long term use and enter the food chain through absorption by the plants. Among the trace metals, Cd has received the greater attention because of its easy absorption and accumulation in plants and animals to levels toxic for their health. The objective of this study conducted in three industrially different cities viz., Ludhiana, Jalandhar and Malerkotla was to monitor the extent of Cd accumulation in soils and plants receiving untreated sewage water. Plant and soil samples were collected from sewage and tubewell irrigated areas. Soil samples were analysed for texture, pH, EC, organic carbon (OC), CaCO(3), bioavailable DTPA-Cd and plant samples were analysed for total Cd. In sewage irrigated soils, the mean values of pH were lower but organic carbon and electrical conductivity were generally higher both in surface and sub-surface layers of all the three cities as compared to tubewell irrigated soils. The mean DTPA- extractable Cd in sewage irrigated soil was 6.3- and 4.36-fold in Ludhiana, 3.38- and 1.71-fold in Jalandhar and 3.35- and 6.67-fold in Malerkotla in 0-15 and 15-30 cm soil depth, respectively, compared with the values in tubewell irrigated soils. The accumulation of DTPA-Cd in sewage irrigated soils was restricted to 30 cm depth after which the values were generally close to values in tubewell irrigated soils. Soil pH, OC, CaCO(3), clay and silt collectively accounted for 37.1%, 65.1% and 53.9% DTPA-extractable bioavailable Cd in soils of Ludhiana, Jalandhar and Malerkotla, respectively. Lower R(2) values in Ludhiana suggest that factors other than the ones mentioned may be affecting Cd availability. At all sites plants receiving sewage irrigation had elevated levels of Cd as compared to the plants receiving tubewell irrigation. The mean Cd content of sewage irrigated plants irrespective of the city was 5.96 microg g(-1) dry matter as compared to 0.98 microg g(-1) dry matter in tubewell irrigated plants. The results suggest that the intake of Cd obtained from consumption of crops grown on sewage irrigated soils would be much higher than the tolerable limits set by WHO and may, therefore, prove potentially toxic leading to various health ailments to humans and animals.     

Effects of Hurricane Katrina on benthic macroinvertebrate communities along the northern Gulf of Mexico coast

The effects of Hurricane Katrina on benthic fauna and habitat quality in coastal waters of Louisiana, Mississippi, and Alabama, USA, were assessed in October, 2005, 2 months after the hurricane made landfall between New Orleans, LA and Biloxi, MS. Benthic macrofaunal samples, sediment chemical concentrations, and water quality measurements from 60 sites in Lake Pontchartrain and Mississippi Sound were compared with pre-hurricane conditions from 2000–2004. Post-hurricane benthic communities had significant reductions in numbers of taxa, H′ diversity, and abundance as well as shifts in composition and ranking of dominant taxa. These effects were not associated with changes in chemical contamination, organic enrichment of sediments, or hypoxia and were likely due to hurricane-related scouring and changes in salinity.     

Application of a three-tier framework to assess ecological condition of Gulf of Mexico coastal wetlands

A multi-level coastal wetland assessment strategy was applied to wetlands in the northern Gulf of Mexico (GOM) to evaluate the feasibility of this approach for a broad national scale wetland condition assessment (US Environmental Protection Agency’s National Wetlands Condition Assessment). Landscape-scale assessment indicators (tier 1) were developed and applied at the sub-watershed (12-digit hydrologic unit code (HUC)) level within the GOM coastal wetland sample frame with scores calculated using land-use maps and geographic information system. Rapid assessment protocols (tier 2), using a combination of data analysis and field work, evaluated metrics associated with landscape context, hydrology, physical structure, and biological structure. Intensive site monitoring (tier 3) included measures of soil chemistry and composition, water column and pore-water chemistry, and dominant macrophyte community composition and tissue chemistry. Relationships within and among assessment levels were evaluated using multivariate analyses with few significant correlations found. More detailed measures of hydrology, soils, and macrophyte species composition from sites across a known condition gradient, in conjunction with validation of standardized rapid assessment method, may be necessary to fully characterize coastal wetlands across the region.     

Inferring episodic atmospheric iron fluxes in the Western South Atlantic

Iron (Fe) and other trace elements such as Zn, Mn, Ni and Cu are known as key-factors in marine biogeochemical cycles. It is believed that ocean primary productivity blooms in iron deficient regions can be triggered by iron in aeolian dust. Up to now, scarce aerosol elemental composition, based on measurements over sea at the Western South Atlantic (WSA), exist. An association between the Patagonian semi-desert dust/Fe and chlorophyll-a variability at the Argentinean continental shelf is essentially inferred from models. We present here experimental data of Fe enriched aerosols over the WSA between latitudes 22°S–62°S, during 4 oceanographic campaigns between 2002 and 2005. These data allowed inferring the atmospheric Fe flux onto different latitudinal bands which varied from 30.4 to 1688 nmolFe m^?2 day^?1 (October 29th–November 15th, 2003); 5.83–1586 nmolFe m^?2 day^?1 (February 15th–March 6th, 2004) and 4.73–586 nmolFe m^?2 day^?1(October 21st–November 5th, 2005).     

Indoor- and outdoor-derived contaminants in urban and rural homes in Ottawa, Ontario, Canada

Indoor and outdoor air contaminants have largely been treated separately in studies of their respective effects on respiratory and nonrespiratory health. In this paper, we report the results of a comprehensive study of key contaminants in 10 urban and 10 rural homes in Ottawa, Ontario, Canada. The analyses included house dust mite and cat allergens along with the fungal inflammatory polysaccharide beta1,3-D-glucan in settled dust and fine particulate matter, coarse particulate matter, ergosterol, glucan, and endotoxin from air samples. In addition, black carbon was continuously measured for 7 days. A detailed physical assessment of the house and patterns of use were undertaken, including a careful inspection for mold and water damage, as well as measurements of air leakage. The performance of the houses and the range and distribution of the contaminants measured were largely similar to that of previous Canadian studies. For certain combinations, it is thought that the presence of both allergen and inflammatory materials increases asthma symptoms. House-by-house comparisons of airborne concentrations of inflammatory compounds measured (endotoxin, fine particulate matter, and fungal glucan) with dust mite allergens indicated that certain houses had relatively higher amounts of both kinds of materials.     

Understanding water quality trading: the basics

The United States has entered a new era in water quality protection: the era of market-based incentives. In January 2003, the United States Environmental Protection Agency (EPA) issued its National Water Quality Trading Policy (Trading Policy) (USEPA, 2003). This action has generated greater interest in water quality trading and has prompted EPA to develop tools and training to assist interested parties in understanding what water quality trading is and what constitutes a successful trading program.