Degradation of TNT contamination through self remediation
The project investigated the biodegradation and retention of contaminants in soil and surface waters caused by waste and wastewater generated during the manufacture of explosives during World War II. The focus of study was the transformation of trinitrotoluene (TNT), its metabolites and their transport in water, soil and sediments.
Summary
Former ordnance factories from World War II continue to be a huge source of environmental pollution even today. Wastewater from explosives manufacturing was discharged into surface waters untreated, while wastes, residues and failed batches were burnt or dumped in factory grounds. Moreover, due to their large requirement for water, explosives manufacturing plants were often sited in areas with plentiful ground water. These sites continue to be located close to drinking water protected areas (DWPA). The project partners examined natural transformation and retention processes in the former "Werk Tanne” ordnance factory in Clausthal-Zellerfeld. During the war, more than 100,000 tons of 2,4,6-trinitrotoluolene (2,4,6-TNT) were manufactured here. Column and batch tests were conducted with sediments and surface waters, and leachate was monitored to understand the reaction paths and metabolite formation of 2,4,6-TNT in water and in soil. In addition, the transport of polar metabolites of TNT and their interaction with the soil matrix was to be determined. The contaminant discharge from the soil was to be quantified using passive collectors.
Results:
- Contamination at the studied site was primarily caused by 2,4,6-TNT and its reduced nitrogen containing metabolites, i.e. 4-amino-2,6-dinitrotoluene and 2-amino-4,6-dinitrotoluene. Low concentrations of trinitrobenzene (TNB), trinitrobenzoic acid (TNBA) and amino-nitrobenzoic acid were also detected.
- Luminescent bacteria tests indicate a significant reduction in the toxicity of TNT, TNB and TNBA over the course of the transformation reactions.
- The top soil exhibits considerable retention capacity for TNT and 2-amino-4,6-dinitrotoluene (0.1 or 1% leaching).
- Degradation processes could be detected in the sediments of surface waters. These result in significantly reducing contaminant levels. TNBA, TNT, TNB as well as explosive compounds persistent in the top soil and surface waters (dinitrobenzoic acid, nitrobenzoic acid, amino-nitrobenzoic acid and dinitrotoluene sulphonic acid) were transformed in sediment batch tests.
- The pollutant spectrum in the examined ponds varied in summer and winter. The half-life (TH) for the microbiological transformation of TNT was found to be 26 days. The nutrient content in the water restricts degradation. TNB is degraded much faster (TH=5d). During this process dinitroaniline as well as a number of so far unknown azoxy compounds are formed.
- TNT is degraded fastest through photolysis (TH=4h). Degradation in ponds is more effective than in ultra-pure water. The reaction products are amino-nitrobenzoic acid (20%) and azoxy compounds (80%).
Promotion
Promoting Institutions
Federal Ministry of Education and Research (BMBF)
Promotional Program
Retention and Degradation Processes to Reduce Contaminations in Groundwater and Soil (KORA)
More Project Information
Project title: Verbundprojekt: Kontrollierter natürlicher Rückhalt und Abbau von Schadstoffen bei der Sanierung kontaminierter Böden und Grundwasser. Teilvorhaben 5.1: Nutzung von Selbstreinigungspotentialen in TNT-belasteten Oberböden am Standortbeispiel Clausthal-Zellerfeld
Project number: 0330526
Project period: 2003 - 2007
Project region: Germany (Hesse)
Project contact:
Herr Dr. Steinbach
Source: German National Library of Science and Technology Hannover (TIB)
