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

Several kinds of uncertainty affect both the science of groundwater and, as a result, its management and governance. This work surveys groundwater contamination from the point of view of such uncertainties, focusing on aspects of ecosystem complexity, time, and space. We consider two cases of groundwater contamination: Per- and polyfluoroalkyl substances (PFAS) and hydraulic fracturing. We argue that to move towards sustainability of groundwater resources, there is urgent need for explicit inclusion of the precautionary principle (PP) at the level of both management and governance because the PP offers possibilities for dealing with various kinds of uncertainty more transparently. We conclude by noting that application of the PP is not just a matter of competent use of science for governance, but also a matter of central importance to the geoethical considerations advanced at this Porto conference on hydrogeoethics.

Groundwater Contamination Science and the Precautionary Principle

Are geology departments prepared for the 21st century

The relevance of key conclusions obtained from a tracer test performed at the Base Borden research site in Canada to solvent contamination in the UK is indicated. The tracer test represented a world unique opportunity to study groundwater contamination arising from a known DNAPL source zone in a natural aquifer environment. The test involved the controlled emplacement of a source zone of residual solvent DNAPL (dense non-aqueous phase liquid) below the water table from which a dissolved plume of chlorinated solvents developed. Significant data were collected on DNAPL dissolution, plume transport and remediation. Conclusions from the test are shown to be relevant to the development, investigation and remediation of solvent contamination in UK aquifers.

The relevance of a DNAPL-tracer test conducted at Base Borden, Canada, to solvent groundwater contamination in the UK

This research program addresses the nature and distribution of chlorinated solvent DNAPL sources in fractured clays and weathered shales, and the potential for natural attenuation of plumes derived from these sources Specific objectives include: (1) Investigate the factors controlling migration of chlorinated solvent DNAPLs in fine-grained, highly structured soils and weathered shale bedrock (2) Investigate the influence of ''matrix diffusion'' on the dissolution and apparent disappearance of residual DNAPL (3) Investigate potential for biodegradation of chlorinated solvents in fractured and weathered shales at an existing contaminated field site and through the use of laboratory studies in microcosms and undisturbed columns of fractured shale saprolite (4) Comparison of DNAPL behavior in different types of fractured clay-rich materials

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Behavior of Dense, Immiscible Solvents in Fractured Clay-rich Soils

The bomb tritium (3H) distribution patterns in the aquifer beneath an abandoned landfill at the Canadian Forces Base (CFB) Borden, Ontario, and in a sandy aquifer at Whiteshell Nuclear Research Establishments (WNRE) Pinawa, Manitoba, all in Canada, were delineated in great detail. A sampling and monitoring network of multilevel samplers and bundle piezometers were used. The directions of groundwater flow were established, and the boundary between the tritiated and non-tritiated zones of the two aquifers were closely demarcated. Using a cumulative mass balance method, the3H input mass into the aquifers was compared with the3H mass in groundwater storage to estimate the percentages of annual groundwater recharge from 1953 to 1978. Two recharge calculations for theeffective recharge zone and thetotal recharge area of the aquifers as established from the flownet analysis, and the distributions of dissolved geochemical constitutents showed that theeffective recharge zone calculations gave higher values of 30.6 cm/yr for CFB Borden and 20.1 cm/yr for WNRE while thetotal recharge areas gave lower values of 19.1 and 10.1 cm/yr for the Borden and WNRE aquifers respectively. The two recharge values provide possible minimum and maximum recharge estimates for the two study areas.

John A. Cherry

Papers

Groundwater Contamination Science and the Precautionary Principle

Are geology departments prepared for the 21st century

The relevance of a DNAPL-tracer test conducted at Base Borden, Canada, to solvent groundwater contamination in the UK

Behavior of Dense, Immiscible Solvents in Fractured Clay-rich Soils

Estimation of the percentage of annual groundwater recharge with bomb tritium using a cumulative mass balance method