Development of an analytical framework to assess the risks posed to soil by emerging contaminants and chemicals of military concern.

Abstract

Soil provides multiple essential functions, such as provision of food and raw materials, a platform for urban development and human wellbeing and as a filtering and transforming medium. Many unregulated contaminants, often termed emerging contaminants, are globally released on soil creating potential risks, especially when undetected leading to significant impact on environmental receptors. The UK ministry of Defence plays an important role in soil protection as the biggest holder of Sites of Special Scientific Interest (SSSI) in the UK as well as being an active polluter in these protected areas through essential training activities. Therefore, there is a need to improve methods for early identification of emerging contamination to avoid long term environmental impacts and costly remediation. The research undertaken for this thesis has contributed to the development of a soil analytical framework to facilitate early identification of the deleterious effects of emerging contaminants and chemicals of military concern on soil. During this research two different scenarios were considered, firstly, when there is a significant body of ecotoxicological data available for a specific contaminant in the literature and secondly, when ecotoxicological data is not available. A scale based on potential hazards was created for the first scenario, which aims to classify chemicals into three categories - low, medium, and high environmental hazards. This scale serves as an inexpensive method to identify the risk of soil degradation. Results from this research showed that for the contaminants of interest (e.g. 1,3,5-trinitro-1,3,5-triazine - RDX, 2,4,6-Trinitrotoluene - TNT, Perfluorooctanoic Acid - PFOA, Perfluorooctane Sulfonate - PFOS and Cypermethrin) the low-level hazard values were lower than expected. These values were expected to correspond to existing Soil Screening Values (SSVs) and Ecological Soil Screening Levels (Eco-SSL), meaning that the contaminants are likely to have a negative impact on the soil at lower concentrations. For the second case, when data is not available experiments need to be undertaken to generate primary data. Insensitive High Explosives (IHE) compositions were identified as lacking data and explosive residues were collected and soil mesocosms were carried out to define the long-term consequences on soil. Field experiments were used to quantify IHE residue deposition concentrations from a standard 155 mm artillery shell, which was then used to estimate potential contamination after 100 detonations. These values were used to estimate low, medium and high contaminant concentration for soil mesocosm studies to quantify the impact on soil using indicators identified through literature review. A standardised procedure was developed based on this, which quantifies the consequences of explosives on soil. This procedure revealed that soils that are already degraded are more susceptible to the impact of explosives, which primarily affects the chemical and biological properties of the soil. . Specifically, this work has shown that the frequent use of IHE filled munitions on training ranges will have an effect on the quality of the soil even when low quantities of energetic residue are deposited. Results for this thesis represent a first step towards a more comprehensive soil analytical framework development providing early identification tools for soil protection.