The dumping of military munitions at sea, a common practice before the 1972 London Convention, has left millions of tons of unexploded ordnance (UXO) scattered across the seabed. With these metal casings corroding after 50-100 years, there is an increasing risk of toxic explosives leaking into the environment. Furthermore, the growing desire to use these seabed areas for offshore wind and solar farms means these munitions must be cleared, often through underwater detonation, which can itself deposit significant explosive residue. Addressing this serious environmental issue, a study by Joseph Sadler, Matar Movshovitz, and colleagues, published in Heliyon, investigated the behavior of the common high explosive TNT in seawater and tested sustainable methods for cleaning up the resulting contamination.

The experiments showed that TNT dissolves slower in seawater compared to distilled water. This difference is likely due to the high salt content and solids in seawater, which reduce the availability of water molecules needed to dissolve non-polar substances like TNT. Specifically, TNT concentrations in saline water were about 30% lower than in distilled water over the same time period. This observation suggests that the bulk explosive inside corroded ordnance may remain intact for longer periods of time than previously suggested, potentially taking decades for toxic levels of contamination to build up from slow leachingLeaching is the process where nutrients are dissolved and carried away from the soil by water. This can lead to nutrient depletion and environmental pollution. Biochar can help reduce leaching by improving nutrient retention in the soil.   More. However, the speed of dissolution was directly related to the water flow rate, with faster currents accelerating the process by maintaining a steep concentration gradient at the explosive’s surface.

Given the risk of contamination, especially during clearance operations, the researchers investigated effective and sustainable adsorption-based remediation methods using different carbons. They compared commercial activated carbon (AC) against a more sustainable option: biochar derived from waste rice husk and wheat straw. The materials were tested in both their original and ground forms, as increasing the surface area by grinding the material was expected to boost its cleaning ability. The results showed that both the commercial AC and the biochar were highly effective, reducing the TNT concentration in both distilled water and seawater by up to 90% after only 2 hours. Among the sustainable options, ground rice husk performed particularly well, adsorbing over 60% of the TNT in seawater within the first 15 minutes and showing a performance comparable to the best commercial activated carbons. This suggests that the ground rice husk is a promising, sustainable alternative for marine cleanup.

Further analysis showed that the way the material worked differed depending on the water type. For example, in seawater, TNT rapidly formed a monolayer on the ground rice husk, meaning the chemical structure of the biochar was very effective at grabbing the TNT over the competing salts. However, the physical environment of seawater caused visible surface damage to the biochar, potentially due to salt buildup, which could affect its long-term performance. The study also found that even when the ground rice husk and commercial carbon were confined in a small container, preventing them from mixing fully with the water, the commercial carbon still reduced the TNT concentration to below the detection limit in 135 minutes, while the ground rice husk achieved 95% adsorption after 24 hours. These findings contribute valuable practical knowledge toward developing effective, sustainable strategies for remediating TNT-contaminated water in marine environments.

Source: Sadler, J., Movshovitz, M., Persico, F., Mai, N., Lopez, C. F., Sen, N., Humphreys, L., Kadansky, E., Webb, S., Sharma, B., Wardrop, J., Coulond, F., Ladyman, M., & Temple, T. (2026). Controlled experiments on dissolution and remediation of 2,4,6-trinitrotoluene in distilled water and seawater. Heliyon, 12, e44241.