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Effect of Silica Polymerization on the Oxalate-Promoted Dissolution of Goethite
- Matthew J. Eick, Todd P. Luxton, Holly A. Welsh
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- Journal:
- Clays and Clay Minerals / Volume 57 / Issue 5 / October 2009
- Published online by Cambridge University Press:
- 01 January 2024, pp. 578-585
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- Article
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Numerous studies have investigated the ligand-promoted dissolution of Fe (oxyhydr)oxides. In natural environments, inorganic ligands can compete with organic ligands for surface sites on (oxyhydr)oxides which may influence dissolution rates. Published research of this interaction and its effect on the dissolution of (oxyhydr)oxides is rare. The objective of the present study was to examine the extent to which silica, as a naturally occurring competitive ligand added in the form of silicic acid, impacts the oxalate-promoted dissolution of the common soil Fe (oxyhydr)oxide goethite. Sorbed silica reduced the oxalate-promoted dissolution rate of goethite at all surface coverages investigated. As initial silica solution concentrations increased from 0.50 mM to 5.0 mM, relatively little change in the dissolution rate was observed. Fourier-transform infrared (FTIR) spectra indicated that, as silica-surface coverages increased, the silica underwent polymerization on the goethite surface. Initially, silicate was associated with surface functional groups, but as polymerization occurred some of the silica appeared to desorb from the goethite surface without being released into the bulk solution, suggesting that silica polymers formed discrete islands or surface clusters that grew away from the goethite surface rather than expanding epitaxially across the surface. Minimal changes were observed in the quantity of reactive goethite surface, which is responsible for the observed dissolution rates, as silica-surface coverages increased.
11 - Systematic Reviews and Cost–Benefit Analyses
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- By Brandon C. Welsh, Netherlands Institute for the Study of Crime and Law Enforcement, Peter H. van der Laan, VU University Amsterdam, Meghan E. Hollis, Northeastern University
- Edited by Brandon C. Welsh, Anthony A. Braga, Rutgers University, New Jersey, Gerben J. N. Bruinsma
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- Book:
- Experimental Criminology
- Published online:
- 05 June 2014
- Print publication:
- 09 September 2013, pp 253-276
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Summary
INTRODUCTION
Crime policy should be rational and based on the best possible research evidence. It is of course wholly naïve to think that the evidence base on the effectiveness of a particular program or strategy will be the sole influence on policy. There are many considerations involved in implementing new policies as well as in expanding effective ones or putting an end to ineffective or harmful ones. For example, there may be different government priorities, such as military defense spending, environmental protection, or medical care for seniors, that are competing for scarce public resources. National polls may show that the public is more concerned with issues other than crime and its control. Other factors include the worry by politicians that they may be perceived as soft on crime by supporting prevention instead of law and order measures (Gest 2001), as well as the short time horizons of politicians (Tonry and Farrington 1995), which makes programs that show results only in the longer term less appealing to those who come up for election every few years. Regrettably, evidence of what works best is rarely a factor in the development of crime policy. Political and other considerations seemingly drive much of the crime policy agenda.
An evidence-based approach attempts to avoid these mistakes by ensuring that the best available evidence is considered in any decision to implement a program or policy designed to reduce crime. Put another way, it is about making sure that this research is at center stage in political and policy decisions. As noted by Petrosino (2000: 636), “An evidence-based approach requires that the results of rigorous evaluation be rationally integrated into decisions about interventions by policymakers and practitioners alike.” An evidence-based approach is crucial to understanding where, when, and if different interventions reduce crime, as well as helping to establish why an intervention does or does not work.