Leach tests, field

Merritt, W. F., "High-Level Waste Glass Field Leach Test,"... 

Field leaching tests, where wastes are stored in big tanks, are also performed. Field leachates are collected on a regular basis, chemically monitored and tested with (at least) the same bioassays as those used in the simulation leaching tests, so as to compare the results with the upper procedure. 

Briefly recalled, the WASTOXHAS approach consists in characterizing the ecotoxicological hazard potential of contaminant fluxes from waste leachate obtained under defined conditions with two different dynamic leaching procedures laboratory simulated leaching tests and field leaching tests. The approach developed below considered a specific scenario that simulates a waste deposit receiving rain or run-off water (Perrodin et al., 2002). 

These waste simulation trials based on laboratory column experiments still needed to be validated using a field approach. Two field leaching tests were thus built on an experimental site (CERED, Vernon, France) to simulate real conditions of a waste deposit site receiving rain or run-off water (Perrodin et al., 2002). The first... 

Table 7. Characteristics of application of the field leaching tests for the municipal solid waste incinerator bottom ash (BA) and the slag from a second smelting of lead (2SL).

N-leaching tests on field scale with lysimeter or suction cups, as well as regular measurements of mineral N in the leaching horizon... 

Leaching of chemicals from complex materials or matrices is a complicated phenomenon in which many factors may influence the release of the specific organic compounds and inorganic ions. Important factors include major element chemistry, pH, redox, complexation, liquid to solid ratio, contact time, and biological activity. To describe fully the leaching of SWMs/COMs under field conditions, a battery of leaching tests was specifically designed to simulate various physical and chemical release mechanisms. 

In SNF corrosion tests, there has been a tendency to use the release of more soluble species Tc, Cs, and Mo as markers for fuel corrosion (Finn et al. 2002). As none of these elements are present in the U02 matrix, this approach may not reveal the actual fuel matrix corrosion rate. Furthermore, short-term leaching tests may not expose possible diffusion-limited (tl/2) release of gap and grain boundary species and assume excessive rates of reaction based on initial fast release rates. The microstructure, radiation field, and composition will change over time, so that tests carried out on fuel today may not be relevant to fuel behaviour 300 to 1000 years from now, once the high p-,y-field has decayed. 

WASTOXHAS was developed for assessing leaching hazardous impact of wastes in laboratory and field situations. It is a part of a tiered approach (Fig. 1). It assumes that classical batch leaching tests (see for example Sahuquillo et al., 2003), followed by application of relevant bioassays, have been initially undertaken for i) deciding to continue ecotoxic hazard assessment and ii) selecting adequate and sensitive bioassays. It can be eventually followed by a more complex and elaborate hazard assessment scheme based on microcosms or mesocosms. ... 

WASTOXHAS leaching tests must be carried out on columns (preferentially in polyethylene) with an internal diameter of at least 5 cm and a filling height of at least 4 times the internal diameter (NEN 7343, 1995). Filling test material into the columns must approximate field density, without altering either the waste physical or chemical properties or creating too much water preferential ways. 

The program involved leaching selected industrial chemical process residuals with leachate derived from municipal refuse in a pilot-scale field facility measuring the concentration of the compounds which leached from the wastes and comparing these field concentrations to those in the EP and other candidate leaching tests. The Toxicity Characteristic Leaching Procedure or TCLP, is the outgrowth of these studies. 

As with other fields of contaminated soil testing, the lack of standard reference materials results in the lack of ready means of having the performance of leaching tests accredited as part of a laboratory test accreditation procedure. This is potentially problematic as more and more legislation, including particularly European Directives such as the Landfill Directive, specify that testing must be carried out by competent and suitably accredited laboratories. 

Most leaching tests are performed in a laboratory. Whilst leaching tests are designed and intended to reflect reality, there is a limited amount of data available from field tests which can be used to correlate with those from laboratory tests hence validate their performance in relation to the situation in the field. One of the most common errors in the interpretation of results from leaching tests is to assume that, based on the commonly used shaking test at a liquid to solid ratio of 10 1, the resultant leachant is representative of the concentration of contaminants that will emerge from the base of a deposit of the material tested. Even if it is assumed that the factors such as leachant used, pH and redox are correctly applied in the test, the concentrations of contaminants in the leachate represent an average of the concentration which will be leached... 

Desai and Clarke (149) reported successful results using zinc-containing compounds. Sell et al. (ISO, 151) described surface treatment with chromium-copper-boron salts. Field weathering tests, leaching tests, and electron-probe microanalysis showed that this treatment was resistant to leaching and weathering. Water-soluble extractives in redwood and redcedar were fixed by treating the wood surface with dilute solutions of copper and chromium salts. This treatment permits direct application of latex paints to these woods (146). 

Van der Sloot HA (1996) Developments in evaluating environmental impact from utilization of bulk inert wastes using laboratory leaching tests and field verification. Waste... 

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