All over the world, aquatic sediments and soils are being contaminated by a vast array of agents: BTEX, petroleum, diesel, polycyclic aromatic hydrocarbons (PAHs) and other semi-volatile organic compounds. Sediment remediation is the technology used to neutralize contaminants and restore ecosystems to the state they were in before the contaminants were introduced. The choice of technology used in a particular instance is a factor of the amount of money that is available to the project and the timespan within which the decontamination needs to occur. The main factor driving the decision is the nature of the contaminant.
Sedimentary contamination refers specifically to underwater soils. When the sediment underlying rivers and harbors becomes compromised, their navigational and recreational use is impaired. As of 2004, the Environmental Protection Agency estimated there were roughly 144 sites that required cleaning up. Sixty of these were considered major enough to require tracking at the national level, while others could be tackled by state or local authorities, by voluntary action or by other federal agencies.
Soil remediation is tackled by three basic approaches: monitored natural recovery, dredging and in situ capping. The sources of the contamination include mining and industrial accidents like oil leaks, chemical spills, etc. As well as the contaminants mentioned earlier, things like pesticides, metals and organometals, cyanide, pthalate esters and hydrocarbons in the form of PCBs and mononuclear aromatic hydrocarbons enter the soil environment.
Some of these chemicals either do not dissolve or they only partially dissolve in water and end up sinking into the sediments of aquatic environments. This results in large amounts of contaminants that cannot be detected in the water column. The size and shape of particles, the ecology of benthic organisms and their organic content all contribute to the accumulation of contaminated sediments over time.
Once a government agency identifies a site to be remediated, prompt action is essential in order to protect human health as well as the environment. All remediation projects require regulatory oversight. In the USA, this is provided by the Region 9 of the EPA.
The remediation process is carried out at the nanotechnological level. This involves the use of nanoparticles. These are between one and 100 nanoparticles in size. A nanometer is the equivalent of 1 x 10 to the minus ninth meter. Nanoparticles have a high surface area:mass ratio, making them very reactive. Their minute size also allows them to infiltrate tiny nooks and crannies in sediments, bringing them into closer proximity to their target contaminants.
When a nanoparticle-sized decontaminant collides with a target contaminant, the result is a neutralizing chemical reaction. So far, the global NanoRem project has targeted as many as 70 sites all over the world that need to be treated. Most of these are groundwater projects, although wastewater treatment methods are being investigated.
Large-scale nanotechnology does not come cheap. The minute scale of these operations make them highly expensive. Filtering out visible particles is easy. As yet, there are no nanoparticle filters so the approach has to be chemical. Once we crack nanotechnology, the next step is maybe tackling contamination on the picometer scale, which are one thousand times smaller than nanometers.
Sedimentary contamination refers specifically to underwater soils. When the sediment underlying rivers and harbors becomes compromised, their navigational and recreational use is impaired. As of 2004, the Environmental Protection Agency estimated there were roughly 144 sites that required cleaning up. Sixty of these were considered major enough to require tracking at the national level, while others could be tackled by state or local authorities, by voluntary action or by other federal agencies.
Soil remediation is tackled by three basic approaches: monitored natural recovery, dredging and in situ capping. The sources of the contamination include mining and industrial accidents like oil leaks, chemical spills, etc. As well as the contaminants mentioned earlier, things like pesticides, metals and organometals, cyanide, pthalate esters and hydrocarbons in the form of PCBs and mononuclear aromatic hydrocarbons enter the soil environment.
Some of these chemicals either do not dissolve or they only partially dissolve in water and end up sinking into the sediments of aquatic environments. This results in large amounts of contaminants that cannot be detected in the water column. The size and shape of particles, the ecology of benthic organisms and their organic content all contribute to the accumulation of contaminated sediments over time.
Once a government agency identifies a site to be remediated, prompt action is essential in order to protect human health as well as the environment. All remediation projects require regulatory oversight. In the USA, this is provided by the Region 9 of the EPA.
The remediation process is carried out at the nanotechnological level. This involves the use of nanoparticles. These are between one and 100 nanoparticles in size. A nanometer is the equivalent of 1 x 10 to the minus ninth meter. Nanoparticles have a high surface area:mass ratio, making them very reactive. Their minute size also allows them to infiltrate tiny nooks and crannies in sediments, bringing them into closer proximity to their target contaminants.
When a nanoparticle-sized decontaminant collides with a target contaminant, the result is a neutralizing chemical reaction. So far, the global NanoRem project has targeted as many as 70 sites all over the world that need to be treated. Most of these are groundwater projects, although wastewater treatment methods are being investigated.
Large-scale nanotechnology does not come cheap. The minute scale of these operations make them highly expensive. Filtering out visible particles is easy. As yet, there are no nanoparticle filters so the approach has to be chemical. Once we crack nanotechnology, the next step is maybe tackling contamination on the picometer scale, which are one thousand times smaller than nanometers.