http://netedu.xauat.edu.cn/jpkc/netedu/jpkc2009/szylyybh/content/wlzy/1/Review%20of%20Arsenic%20in%20natural%20water%20-%20Smedly.pdf

A review of the source, behaviour and distribution of arsenic in natural waters

Solid phase microextraction with thermal desorption using fused silica optical fibers

The science of the total environment

The use of equilibrium expressions for sorption to natural particles in fate and transport models is often invalid due to slow kinetics. This paper reviews recent research into the causes of slow sorption and desorption rates at the intraparticle level and how this phenomenon relates to contaminant transport, bioavailability, and remediation. Sorption kinetics are complex and poorly predictable at present. Diffusion limitations appear to play a major role. Contending mechanisms include diffusion through natural organic matter matrices and diffusion through intraparticle nanopores. These mechanisms probably operate simultaneously, but the relative importance of each in a given system is indeterminate. Sorption shows anomalous behaviors that are presently not well explained by the simple diffusion models, including concentration dependence of the slow fraction, distributed rate constants, and kinetic hysteresis. Research is needed to determine whether adsorption/desorption bond energies may play a role alon...

Mechanisms of Slow Sorption of Organic Chemicals to Natural Particles

found that field-scale dispersivities are several orders of.magnitude greater than lab-scale values for the same material; it is generally agreed that this difference is a reflection of the influence of natural heterogeneities which produce irregular flow patterns at the field scale. Consequently, laboratory measurements of dispersivity cannot be used to predict field values of dispersivity. Instead field-scale tracer tests are sometimes conducted to estimate dispersivity at a particular site. Early efforts to document the scale dependence of dispersivity [Lallemand-Barres and Peaudecerf, 1978; Anderson, 1979; Pickens and Grisak, 1981; Beims, 1983; Neretnieks, 1985] were based on field values of dispersivity reported in the literature and the test scales associated with those values. These studies were useful in that they indeed documented field evidence of the scale effect, but they were lacking in that they did not assess the reliability of the data presented. Because we felt that the data would be more

A Critical Review of Data on Field-Scale Dispersion in Aquifers

Using constant head step tests to determine hydraulic apertures in fractured rock.

Permanganate injection is increasingly applied for in situ destruction of chlorinated ethenes in groundwater. This laboratory and field study demonstrates the roles that carbon isotope analysis can play in the assessment of oxidation of trichloroethene (TCE) by permanganate. In laboratory experiments a strong carbon isotope fractionation was observed during oxidation of TCE with similar isotopic enrichment factors (−25.1 to −26.8 ‰) for initial KMnO4 concentrations between 67 and 1250 mg/L. At the field site, a single permanganate injection episode was conducted in a sandy aquifer contaminated with TCE as dense nonaqueous liquid (DNAPL). After injection, enriched δ13C values of up to +204% and elevated Cl- concentrations were observed at distances of up to 4 m from the injection point. Farther away, the Cl- increased without any change in δ13C of TCE suggesting that Cl- was not produced locally but migrated to the sampling point. Except for the closest sampling location to the injection point, the δ13C re...

/pdf/monitoring-oxidation-of-chlorinated-ethenes-by-permanganate-2mj0qh1f9q.pdf

Monitoring oxidation of chlorinated ethenes by permanganate in groundwater using stable isotopes: laboratory and field studies.

Detailed monitoring of groundwater in a shallow sand aquifer impacted by a large-flux septic system showed that water quality in the shallow water table zone below the tile bed was similar to that of smaller-flux septic systems in similar hydrologic settings where effluent residency in the unsaturated zone was of similar duration. During residency of about one week in the 4-m thick unsaturated zone, effluent NH+
4 was largely oxidized to NO−
3, about 75% of DOC was biodegraded, and acidity produced by the above reactions was neutralized by dissolution of calcite. Beneath the tile bed and extending laterally downgradient a distance of 80 m to the Lake Erie shoreline, a distinct plume of impacted groundwater was easily distinguished by elevated levels of electrical conductance, Cl−, NO−
3, HCO−
3, NA+, Ca2+, and K+ and by depressed levels of pH and dissolved oxygen. High NO−
3 levels that occur below the tile bed disappear, however, in the anaerobic plume core zone 10 to 70 m downgradient, apparently as a result of denitrification. The rich reserve of solid-phase organic carbon in the aquifer sediment (2.5%) probably provides much of the organic carbon for heterotrophic denitrification. This condition is in contrast to other septic system plumes in sand aquifers where high NO−
3 levels persist and where aquifer organic carbon values are much lower. Although NO−
3 is attenuated in the plume core, persistence of NO−
3 along the aerobic upper fringe of the plume demonstrates the ability of septic systems to cause significant water-quality degradation of sand aquifers when the conditions favorable for denitrification do not exist. The sharp boundary between the plume water and non-impacted water adjacent to and overlying the plume in the area 50 to 100 m downgradient from the tile bed, and the undiluted nature of non-reactive solutes such as Cl− throughout the core of the plume, demonstrates that dispersion has only a weak influence on the plume. This is consistent with dispersion studies in many other sand aquifers.

Hydrogeology Of An Unconfined Sand Aquifer And Its Effect On The Behavior Of Nitrogen From A Large-Flux Septic System

Contaminated groundwater is treated in-situ, by funnelling the water through a gate or gates (23) in a watertight in-ground wall (18). Treatment material in the gate (23) breaks down the contaminant, or otherwise removes the contaminant from the flowing water. A removable caisson is first driven into the ground, excavated, and then a receptacle, for the treatment material, is lowered into the hollow interior.

System for treating polluted groundwater

Use of direct-push sampling tools for rapid investigations of contaminated sits has proliferated in the past several years. A direct-push device, referred to as a ground water sampling profiler, was recently developed at the University of Waterloo. This tool differs from other direct-push tools in that point samples are collected at multiple depths in the same hole without retrieving, decontaminating, and re-driving the tool after each sampling event. The collection of point samples, rather than samples from a longer screened interval, allows an exceptional level of detail to be generated about the vertical distribution of contamination from each hole. The benefits of acquiring this level of detail are contingent on minimization of vertical cross contamination of samples caused by drag down from high concentration zones into underlying low concentration zones. In a detailed study of chlorinated solvent plumes in sand aquifers, the authors found that drag down using the profiler is minimal or non-detectable even when the tool is driven through high concentration zones of dissolved chlorinated solvent contamination. Chlorinated solvent concentrations, primarily PCE and TCE at or below a detection limit of 1 {micro}g/L, were obtained directly beneath plumes with maximum concentrations up to thousands of {micro}g/L. Minimal drag more » down, on the order of a few {micro}g/L to 20 {micro}g/L, may have been observed below chlorinated solvent concentrations of several tens of thousands to hundreds of thousands of {micro}g/L. Drag down through DNAPL zones was not evaluated. « less

John A. Cherry

Papers

Using constant head step tests to determine hydraulic apertures in fractured rock.

Monitoring oxidation of chlorinated ethenes by permanganate in groundwater using stable isotopes: laboratory and field studies.

Hydrogeology Of An Unconfined Sand Aquifer And Its Effect On The Behavior Of Nitrogen From A Large-Flux Septic System

System for treating polluted groundwater

Field Demonstrations Using the Waterloo Ground Water Profiler