Analysis of the long-term behavior of solute transport with nonlinear equilibrium sorption using breakthrough curves and temporal moments

We analyzed the long-term behavior of breakthrough curves (BTCs) and temporal moments of a solute subjected to Freundlich equilibrium sorption (s = kc(n)). For one-dimensional transport in a homogeneous porous medium, we derived a power-law relation between travel time, tau, and solute displacement, chi, with the exponent being equal to the Freundlich n exponent. The mean solute velocity, derived from the first time moment, was found to change as tau(n-1). For n values larger than 0.66, the second time moment could be related to c chi(2/n), where c is a constant. An approach based on the use of a critical concentration was developed to estimate the presence of the asymptotic regime in the tail of the BTC. This approach was tested successfully using numerical case studies. One-dimensional numerical simulations with varying values of k, n and initial mass were run to verify the closed form analytical expressions for the large time behavior of temporal moments and the tailing part of breakthrough curves. Good agreement between the slope of the tailing part of log-log transformed BTCs and the predicted slope using asymptotic theory was found. Asymptotic theory in general underestimated the magnitude of the concentration in the tail. The quality of the estimated concentrations in the tail improved for small values of the dispersivity. Experimental BTCs of uranin and benazolin were analyzed in combination with sorption/desorption batch experiments using asymptotic theory. A good agreement between the value of n parameter derived from desorption experiment with benazolin and the value of the n parameter derived from the tail of the BTC was found.     

Population biology of the annual grassTriplasis purpurea in relation to distance from shore on Staten Island, New York

Four populations of the native annual grassTriplasis purpurea were surveyed on coastal beaches along the south shore of Staten Island, NY, to determine the potential of this species to colonize shoreline habitats mostly devoid of other vegetation. If the species can establish and maintain dense populations, it may have conservation value for urban beaches disturbed by human activities. For two populations, survivorship, growth, and reproduction were monitored at different distances from shore to determine the ability of this species to maintain viable populations. At three sites,T. purpurea occurred in >75% of all quadrats and the highest density was 1195 plants/m² at 74 m from shore in one recently disturbed site. Density generally increased with increasing distances from shore at low tide (from ca. 40 – 90 m). Plants showed the greatest growth and reproduction at close distances to shore (30 – 40 m); part of this effect was due to density in one population, but when density effects were removed statistically, there still remained a decline in growth and reproduction with increasing distance from shore. Improved vigor nearest to shore may be due to continual sand deposition. Survivorship showed a Type I pattern, with low mortality throughout the growing season. By colonizing newly-deposited and continually shifting sands,T. purpurea can contribute to the earliest stages of ecological succession along disturbed beaches in eastern North America and may be valuable to the development and management of urban coastal plant communities.     

Influence of diesel fuel on seed germination

The use of plant-based systems to remediate contaminated soils has become an area of intense scientific study in recent years and it is apparent that plants which grow well in contaminated soils need to be identified and screened for use in phytoremediation technologies. This study investigated the effect of diesel fuel on germination of selected plant species. Germination response varied greatly with plant species and was species specific, as members of the same plant family showed differential sensitivity to diesel fuel contamination. Differences were also seen within plant subspecies. At relatively low levels of diesel fuel contamination, delayed seed emergence and reduced percentage germination was observed for the majority of plant species investigated. Results suggest the volatile fraction of diesel fuel played an influential role in delaying seed emergence and reducing percentage germination. In addition, the remaining diesel fuel in the soil added to this inhibitory effect on germination by physically impeding water and oxygen transfer between the seed and the surrounding soil environment, thus hindering the germination response.     

Development and testing of a micro wind tunnel for on-site wind erosion simulations

Wind erosion processes affect soil surfaces across all land uses worldwide. Understanding the spatial and temporal scales of wind erosion is a challenging undertaking because these processes are diverse and highly variable. Wind tunnels provide a useful tool as they can be used to simulate erosion at small spatial scales. Portable wind tunnels are particularly valued because erosion can be simulated on undisturbed soil surfaces in the field. There has been a long history of use of large portable wind tunnels, with consensus that these wind erosion simulation tools can meet real world aerodynamic criteria. However, one consequence of striving to meet aerodynamic reality is that the size of the tunnels has increased, making them logistically difficult to work with in the field and resulting in a tendency to homogenise naturally complex soil surfaces. This homogenisation is at odds with an increasing awareness of the importance that small scale processes have in wind erosion. To address these logistical and surface homogenisation issues we present here the development and testing of a micro wind tunnel (MWT) designed to simulate wind erosion processes at high spatial resolution. The MWT is a duct-type design—0.05 m tall 0.1 m wide and with a 1.0 m working section. The tunnel uses a centrifugal motor to suck air through a flow‐conditioning section, over the working section and then through a sediment collection trap. Simulated wind velocities range from 5 to 18 m s^?1, with high reproducibility. Wind speeds are laterally uniform and values of u _* at the tunnel bed (calculated by measuring the pressure gradients within the MWT) are comparable with those of larger tunnels in which logarithmic profiles can be developed. Saltation sediment can be added. The tunnel can be deployed by a single person and operated on slopes ranging from 0 to 10°. Evidence is presented here that the MWT provides new and useful understanding of the erodibility of rangelands, claypans and ore stockpiles.     

Characterization of subsoil heterogeneity, estimation of grain size distribution and hydraulic conductivity at the Krauthausen test site using Cone Penetration Test

A Cone Penetration Test (CPT) survey with a high spatial resolution was performed in order to investigate the stratigraphy as well as the spatial variability of various soil properties of the Krauthausen test site. Analyses of the CPT measurements showed the subsurface to be dominated by a planar layered structure. Variogram analysis of the various CPT parameters disclosed that within each layer the soil properties have an anisotropic spatial correlation structure. A correlation analysis of the measured CPT data and co-located grain size distributions from soil samples was performed. Since the correlation coefficients were greater equal to 0.7, a reliable empirical relationship between the data sets could be developed. Based on this empirical relationship grain size distributions were estimated at CPT locations. The statistical processing of estimated and measured grain size distributions with respect to their spatial correlation structure disclosed good agreement between the data sets. The estimated grain size distributions from CPT data were used to estimate the hydraulic conductivity in the aquifer. The results provide detailed information of the spatial heterogeneity of the hydraulic conductivity at Krauthausen test site. The validation of these results, using a prior investigation of hydraulic conductivity statistics, suggests the CPT a fast and inexpensive tool for the estimation of three dimensional hydraulic conductivity fields with sufficient accuracy.     

Investigating habitat value to inform contaminant remediation options: case study

Habitat valuation methods were implemented to support remedial decisions for aquatic and terrestrial contaminated sites at the East Tennessee Technology Park (ETTP) on the US Department of Energy (DOE) Oak Ridge Reservation in Oak Ridge, TN, USA. The habitat valuation was undertaken for six contaminated sites: Contractor's Spoil Area, K-901-N Disposal Area, K-770 Scrapyard, K-1007-P1 pond, K-901 pond, and the Mitchell Branch stream. Four of these sites are within the industrial use area of ETTP and two are in the Black Oak Ridge Conservation Easement. These sites represent terrestrial and aquatic habitat for vertebrates, terrestrial habitat for plants, and aquatic habitat for benthic invertebrates. Current and potential future, no-action (no remediation) scenarios were evaluated primarily using existing information. Valuation metrics and scoring criteria were developed in a companion paper, this volume. The habitat valuation consists of extensive narratives, as well as scores for aspects of site use value, site rarity, and use value added from spatial context. Metrics for habitat value were expressed with respect to different spatial scales, depending on data availability. There was significant variation in habitat value among the six sites, among measures for different taxa at a single site, between measures of use and rarity at a single site, and among measures for particular taxa at a single site with respect to different spatial scales. Most sites had aspects of low, medium, and high habitat value. Few high scores for current use value were given. These include: wetland plant communities at all aquatic sites, Lepomid sunfish and waterbirds at 1007-P1 pond, and Lepomid sunfish and amphibians at K-901 pond. Aquatic sites create a high-value ecological corridor for waterbirds, and the Contractor's Spoil Area and possibly the K-901-N Disposal Site have areas that are part of a strong terrestrial ecological corridor. The only example of recent observations of rare species at these sites is the gray bat observed at the K-1007-P1 pond. Some aspects of habitat value are expected to improve under no-action scenarios at a few of the sites. Methods are applicable to other contaminated sites where sufficient ecological data are available for the site and region.     

Multi-elements atmospheric deposition study in Albania

For the first time, the moss biomonitoring technique and inductively coupled plasma–atomic emission spectrometric (ICP-AES) analytical technique were applied to study multi-element atmospheric deposition in Albania. Moss samples (Hypnum cupressiforme) were collected during the summer of 2011 and September–October 2010 from 62 sites, evenly distributed over the country. Sampling was performed in accordance with the LRTAP Convention–ICP Vegetation protocol and sampling strategy of the European Programme on Biomonitoring of Heavy Metal Atmospheric Deposition. ICP-AES analysis made it possible to determine concentrations of 19 elements including key toxic metals such as Pb, Cd, As, and Cu. Cluster and factor analysis with varimax rotation was applied to distinguish elements mainly of anthropogenic origin from those predominantly originating from natural sources. Geographical distribution maps of the elements over the sampled territory were constructed using GIS technology. The median values of the elements in moss samples of Albania were high for Al, Cr, Ni, Fe, and V and low for Cd, Cu, and Zn compared to other European countries, but generally were of a similar level as some of the neighboring countries such as Bulgaria, Croatia, Kosovo, Macedonia, and Romania. This study was conducted in the framework of ICP Vegetation in order to provide a reliable assessment of air quality throughout Albania and to produce information needed for better identification of contamination sources and improving the potential for assessing environmental and health risks in Albania, associated with toxic metals.     

Permutation/randomization-based inference for environmental data

Quantitative inference from environmental contaminant data is almost exclusively from within the classic Neyman/Pearson (N/P) hypothesis-testing model, by which the mean serves as the fundamental quantitative measure, but which is constrained by random sampling and the assumption of normality in the data. Permutation/randomization-based inference originally forwarded by R. A. Fisher derives probability directly from the proportion of the occurrences of interest and is not dependent upon the distribution of data or random sampling. Foundationally, the underlying logic and the interpretation of the significance of the two models vary, but inference using either model can often be successfully applied. However, data examples from airborne environmental fungi (mold), asbestos in settled dust, and 1,2,3,4-tetrachlorobenzene (TeCB) in soil demonstrate potentially misleading inference using traditional N/P hypothesis testing based upon means/variance compared to permutation/randomization inference using differences in frequency of detection (Δf _d). Bootstrapping and permutation testing, which are extensions of permutation/randomization, confirm calculated p values via Δf _d and should be utilized to verify the appropriateness of a given data analysis by either model.     

Case Studies of Minimizing Plating Bath Wastes in the Electronics Products Industry

In this paper the authors report on the results of case studies carried out under the sponsorship of the U.S. EPA to determine the effectiveness of four processes designed to reduce the amount of hazardous waste from plating operations. Data reported are based on the results of actual on-site sampling of the processes and encompass effectiveness, environmental, and economic considerations. Two of the case studies evaluating the use of sodium borohydride reduction as a substitute for lime/ferrous sulfate precipitation, found that the technology was a viable substitute in one case and was marginally acceptable in another. Another case study, involving carbon adsorption removal of organic contaminants from plating bath wastes, found that this technology significantly reduced both disposal costs and waste volume. A final case study of electrolytic recovery indicated that while acid copper electroplating rinses are amenable to electrolytic recovery, other metal-bearing rinses, such as those from solder (tin/lead) plating or etching are less appropriate.