Trace metals in sediments of Southeast Pacific Fjords, north region (42.5 degrees to 46.5 degrees S)

Analyses of trace metals in benthic sediments from selected fjords and channels between 41 degrees 30' and 46 degrees 50'S, 75 degrees -72.3 degrees W were made after the CIMAR 1 Fjords expedition co-ordinated by CONA-Chile in 1995; the metals analyzed include Ba, Cd, Co, Cr, Cu, Ni, Pb, Sr, V and Zn. The objective of this study was to establish baseline values for these metals and to compare them with similar studies made in comparable, but geographically distinct, environments. Box core samples were collected at 35 stations and metal analysis was by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) using the MESS-2 reference standard. The ranked abundance by metal was Ba > Sr > V > Zn > Cr > Cu approximately Ni approximately Pb > Co > Cd; these metals were not homogenous across the region and coefficients of variation were >10%. There were distinct groupings by metal and geographical area including the fjords, basins and channels. Depth profiles of the metal concentrations also varied spatially, e.g. Guafo, Laguna San Rafael, Moraleda, Corcovado, Quitralco, and Jacaf were predominantly homogeneous with depth profiles indicative of pristine systems experiencing few human impacts. In contrast, Aysen, Cupquelan and Puyuguapi Fjords had higher concentrations towards the surface, indicating elevated inputs in recent years. No major differences in metal content of the sediments were observed when compared with values from comparable natural systems in the northern hemisphere. Principal component analysis (PCA) grouped several seemingly isolated locations as having the same metal signature and indicated the pattern of dispersion across the region.     

Measuring the gypsum content of C&D debris fines

Construction and demolition (C&D) debris recycling facilities often produce a screened material intended for use as alternative daily cover (ADC) at active landfills or for shaping and grading at closed landfills. This product contains soil and small pieces of wood, concrete, gypsum drywall, shingles and other components of C&D debris. Concerns have been raised over the contribution of gypsum drywall in C&D debris fines to odor problems at landfills where the product is used. To address such concerns, limitations may be placed on the percentage of gypsum (or sulfate) that can occur, and standardized testing procedures are required to permit valid compliance testing. A test procedure was developed for measuring the gypsum content in C&D debris fines. The concentration of sulfate leached in an aqueous solution was used to estimate the initial gypsum content of the sample. The impact of sample size and leaching time were evaluated. Precision and accuracy increased with increasing gypsum content. Results from replicate samples had an average relative standard deviation of 9%. The gypsum content of fines obtained from different facilities in the US varied widely from 1% to over 25%. These variations not only occurred between differing facilities, but within batches produced within a single facility.     

Can urban tree roots improve infiltration through compacted subsoils for stormwater management?

Global land use patterns and increasing pressures on water resources demand creative urban stormwater management. Strategies encouraging infiltration can enhance groundwater recharge and water quality. Urban subsoils are often relatively impermeable, and the construction of many stormwater detention best management practices (D-BMPs) exacerbates this condition. Root paths can act as conduits for water, but this function has not been demonstrated for stormwater BMPs where standing water and dense subsoils create a unique environment. We examined whether tree roots can penetrate compacted subsoils and increase infiltration rates in the context of a novel infiltration BMP (I-BMP). Black oak (Quercus velutina Lam.) and red maple (Acer rubrum L.) trees, and an unplanted control, were installed in cylindrical planting sleeves surrounded by clay loam soil at two compaction levels (bulk density = 1.3 or 1.6 g cm(-3)) in irrigated containers. Roots of both species penetrated the more compacted soil, increasing infiltration rates by an average of 153%. Similarly, green ash (Fraxinus pennsylvanica Marsh.) trees were grown in CUSoil (Amereq Corp., New York) separated from compacted clay loam subsoil (1.6 g cm(-3)) by a geotextile. A drain hole at mid depth in the CUSoil layer mimicked the overflow drain in a stormwater I-BMP thus allowing water to pool above the subsoil. Roots penetrated the geotextile and subsoil and increased average infiltration rate 27-fold compared to unplanted controls. Although high water tables may limit tree rooting depth, some species may be effective tools for increasing water infiltration and enhancing groundwater recharge in this and other I-BMPs (e.g., raingardens and bioswales).     

Geologic vs. geographic constraints on cement resources

This study evaluates the importance of geologic and geographic factors in constraining the location of limestone mining operations for the production of cement in the Great Lakes region of the United States. Cities and their infrastructure require abundant cement, which is manufactured from limestone and other quarry products, but expansion of cities limits the locations of these operations. Possible locations of limestone and cement operations are controlled by geologic factors including distribution and mineralogy of geologic formations as well as depth of overburden, and geographic factors including location of wetlands, cities, and other surface features that preclude development of quarries and manufacturing operations. Overlay analysis was used to evaluate the importance of these factors. Results show that, although limestone underlies about a third of the region, almost 50 percent of this limestone is unavailable for quarrying due to coverage by the built environment, protected natural areas, or excessive overburden thickness. When characteristics such as limestone quality are also accounted for, accessible resources shrink to as little as 2 percent of the total land area. Although the remaining 2 percent of land area may supply local needs for some years, geologic factors clearly must be included in long-term regional land use planning.     

Can Pickering emulsion formation aid the removal of creosote DNAPL from porous media?

The purpose of this investigation was to examine the proposition that creosote, emplaced in an initially water saturated porous system, can be removed from the system through Pickering emulsion formation. Pickering emulsions are dispersions of two immiscible fluids in which coalescence of the dispersed phase droplets is hindered by the presence of colloidal particles adsorbed at the interface between the two immiscible fluid phases. Particle trapping is strongly favoured when the wetting properties of the particles are intermediate between strong water wetting and strong oil wetting. In this investigation the necessary chemical conditions for the formation of physically stable creosote-in-water emulsions protected against coalescence by bentonite particles were examined. It was established that physically stable emulsions could be formed through the judicious addition of small amounts of sodium chloride and the surfactant cetyl-trimethylammonium bromide. The stability of the emulsions was initially established by visual inspection. However, experimental determinations of emulsion stability were also undertaken by use of oscillatory rheology. Measurements of the elastic and viscous responses to shear indicated that physically stable emulsions were obtained when the viscoelastic systems showed a predominantly elastic response to shearing. Once the conditions were established for the formation of physically stable emulsions a "proof-of-concept" chromatographic experiment was carried out which showed that creosote could be successfully removed from a saturated model porous system.     

Characterizing the toxicity of pulsed selenium exposure to Daphnia magna

The acute toxicity of selenium (Se) to aquatic biota has been studied extensively for decades. However, most studies have used a constant concentration aqueous exposure of Se to an invertebrate species. Since constant concentration exposure of toxicants to invertebrates is unusual in the environment, episodic exposure or pulsed exposures may represent true risk to aquatic biota more accurately. This research was designed to characterize the toxicity effects of pulsed Se exposure to Daphnia magna. Selenium exposure was varied during a 21-d chronic toxicity test to examine the effects of exposure concentration, duration, and recovery on survival, growth, and reproduction of D. magna. While D. magna did not die during exposures, latent mortality was observed. Latent mortality increased with exposure concentration and duration. Hence, standard toxicity test using continuous exposures would underestimate Se toxicity. Risk assessment method using results of continuous exposure would underestimate risk of Se to biota. For double-pulse exposures, cumulative mortality on day 21 was higher when time interval between pulses was shorter. With the same total exposure time, continuous exposure caused higher toxicity than did pulsed exposures due to recovery and tolerance development in D. magna after earlier pulses. Growth and reproduction of surviving D. magna were not affected by pulsed Se exposure due to recovery of D. magna after removal of the pulses. Based on these results, risk assessment for Se should take latent effects and the effect of recovery in to account.     

Dietary exposure to DDT of secondary school students in Hong Kong

The aim of this study was to determine the dietary exposure of DDT in foodstuffs consumed in Hong Kong by secondary school students in Hong Kong in 2005. Food samples of domestic or imported food were collected randomly from local markets for the determination of DDT. The analytical method for this survey was based on isotope dilution technique. DDT isomers were determined at parts per billion (mugkg(-1)) levels in foods by pressured fluid extraction followed by gel permeation column cleanup and gas chromatography with mass spectrometry detection. Among the 98 composite samples, 25 were found positive with DDT levels greater than the limit of quantitation (LOQ) (1mugkg(-1) for each isomer of DDT). Only two of the meat products were found to contain low levels of the metabolites of DDT. A number of fish and shellfish were found to contain not just the metabolites of DDT, but also parent DDT. The main contribution to DDT was from seafood. The dietary intake of DDT for an average and high secondary school student consumers were estimated to be 0.145 and 0.291mugkg(-1)bwd(-1), respectively. Both levels fell well below the Provisional Tolerable Daily Intake (PTDI) of 10mugkg(-1)bwd(-1) established by the Joint Food Agriculture Organization/World Health Organization Meeting on Pesticide Residues (JMPR). It was concluded that both the average and high secondary school student consumers were unlikely to experience major toxicological effects of DDT.     

A review of municipal solid waste composition in the United Kingdom

The move from landfill-based to resource-based waste management systems requires a greater knowledge of the composition of municipal solid waste. This paper draws together the findings of municipal solid waste (MSW) compositional surveys undertaken in the United Kingdom. The results from recent surveys show a good agreement over the composition of household-collected waste, but less agreement over civic amenity site waste composition. There is insufficient data to allow comparisons of the commercial waste element of municipal waste or of the other components, and further work is necessary to produce more reliable estimates of the composition of these streams. The use of questionnaire surveys and analysis of the results suggests that the size and age profile of a household influence the generation of household-collected waste. Some research suggests that the waste container provided by the local authority and the socio-economic classification of a household also influence household-collected waste generation, but other studies failed to find this link. Further research is required to investigate this by surveying all of the waste disposal routes available to specific households.     

A Method for Setting the Size of Plant Conservation Target Areas

Abstract: Realistic time frames in which management decisions are made often preclude the completion of the detailed analyses necessary for conservation planning. Under these circumstances, efficient alternatives may assist in approximating the results of more thorough studies that require extensive resources and time. We outline a set of concepts and formulas that may be used in lieu of detailed population viability analyses and habitat modeling exercises to estimate the protected areas required to provide desirable conservation outcomes for a suite of threatened plant species. We used expert judgment of parameters and assessment of a population size that results in a specified quasiextinction risk based on simple dynamic models. The area required to support a population of this size is adjusted to take into account deterministic and stochastic human influences, including small-scale disturbance, deterministic trends such as habitat loss, and changes in population density through processes such as predation and competition. We set targets for different disturbance regimes and geographic regions. We applied our methods to Banksia cuneata, Boronia keysii, and Parsonsia dorrigoensis, resulting in target areas for conservation of 1102, 733, and 1084 ha, respectively. These results provide guidance on target areas and priorities for conservation strategies.