Laboratory and Field Scale Evaluation of Geochemical Controls on Groundwater Transport of Nitroaromatic Ammunition Residues
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- 作者：Kenneth W. Weissmahr ; Markus Hildenbrand ; René ; P. Schwarzenbach ; and Stefan B. Haderlein
- 刊名：Environmental Science & Technology
- 出版年：1999
- 出版时间：August 1, 1999
- 年：1999
- 卷：33
- 期：15
- 页码：2593 - 2600
- 全文大小：107K
- 年卷期：v.33,no.15(August 1, 1999)
- ISSN：1520-5851
文摘
Sorption to soils and sediments of nitroaromatic explosivesmay be due to interactions with natural organic matter(NOM) or complex formation with clays, which stronglydepends on the type of exchangeable cations, i.e., the basesaturation of the clays. We examined the relativeimportance of these two processes for NAC sorption ataquifer material and evaluated the potential of decreasingor enhancing the mobility of NACs in contaminatedaquifers by stimulated cation exchange. Generally, sorptionon NOM of 2,4,6-trinitrotoluene (TNT) and relatednitroaromatic compounds (NACs) was low compared tosorption at clays, and no evidence for specific interactionswith NOM was found. Adsorbed NOM hardly affectedthe complex formation of NACs with clays. NAC sorptionat pure clays and at aquifer material depended on the K+-saturation of these materials. Typical aquifer materialcontaining 
1% NOM and 3-5% clays exhibited similarsorption features than pure clay minerals, suggesting thatNAC sorption to the bulk aquifer matrix was dominatedby complex formation at clays. We applied these laboratoryfindings to a two-step field test designed to control thegroundwater transport of NACs by the injection of electrolytes.4-Nitrotoluene (4-NT) and KCl were injected into a sandyaquifer, and their groundwater transport was monitored atan extraction well. Subsequent injection of CaCl2remobilized the previously adsorbed 4-NT due to ionexchange of Ca2+ for K+ at clays present in the aquifermatrix. The susceptibility of NAC sorption to the compositionof exchangeable cations at clays was confirmed for TNTand related NACs. Controlling the base saturation of the aquifermatrix by electrolyte injections thus opens new perspectivesfor gentle remediation of sites contaminated withnitroaromatic explosives.
1% NOM and 3-5% clays exhibited similarsorption features than pure clay minerals, suggesting thatNAC sorption to the bulk aquifer matrix was dominatedby complex formation at clays. We applied these laboratoryfindings to a two-step field test designed to control thegroundwater transport of NACs by the injection of electrolytes.4-Nitrotoluene (4-NT) and KCl were injected into a sandyaquifer, and their groundwater transport was monitored atan extraction well. Subsequent injection of CaCl2remobilized the previously adsorbed 4-NT due to ionexchange of Ca2+ for K+ at clays present in the aquifermatrix. The susceptibility of NAC sorption to the compositionof exchangeable cations at clays was confirmed for TNTand related NACs. Controlling the base saturation of the aquifermatrix by electrolyte injections thus opens new perspectivesfor gentle remediation of sites contaminated withnitroaromatic explosives.