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.
Remediation of sediments is basically an aquatic problem. Once the soils and sediments underlying the nations harbors and inland waterways become compromised by contamination, their use for navigational or recreational purposes is seriously impaired. As at 2004, the Environmental Protection Agency (EPA) had identified approximately twelve dozen sites that needed to be remediated. Of these, 60 were thought to require attention at the national level, while others were deemed suitable for management by local or state authorities, by volunteers or by other federal authorities.
The three basic approaches to the control of contaminated sediments and soils are: in situ capping, dredging and monitored natural recovery. The main sources of sedimentary contamination are industrial accidents and mining incidents. Additional contaminants to those specified above include phthalate esters, metals and organometals (mercury, lead, etc.), cyanide, chlorinated hydrocarbons (PCBs) and mononuclear aromatic hydrocarbons (MAHs).
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 land remediation authority or other government authority requests that an area be remediated, immediate action is necessary for the protection of the environment as well as human health. Remediation is subject to regulatory oversight. In the United States, this oversight is provided by the Environmental Protection Agency (EPA), Region 9.
The process of remediation goes down right to the level of nanotechnology. Specifically, nanoremediation refers to the use of nanoparticles. These are defined as particles between one and one hundred nanometers in size. One nanometer is equal to one billionth of a meter. Nanoparticles have a high surface area per unit mass, which makes them highly reactive. Their small size also allows them to infiltrate tiny pores in sediments, making target contaminants more accessible.
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.
Remediation of sediments is basically an aquatic problem. Once the soils and sediments underlying the nations harbors and inland waterways become compromised by contamination, their use for navigational or recreational purposes is seriously impaired. As at 2004, the Environmental Protection Agency (EPA) had identified approximately twelve dozen sites that needed to be remediated. Of these, 60 were thought to require attention at the national level, while others were deemed suitable for management by local or state authorities, by volunteers or by other federal authorities.
The three basic approaches to the control of contaminated sediments and soils are: in situ capping, dredging and monitored natural recovery. The main sources of sedimentary contamination are industrial accidents and mining incidents. Additional contaminants to those specified above include phthalate esters, metals and organometals (mercury, lead, etc.), cyanide, chlorinated hydrocarbons (PCBs) and mononuclear aromatic hydrocarbons (MAHs).
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 land remediation authority or other government authority requests that an area be remediated, immediate action is necessary for the protection of the environment as well as human health. Remediation is subject to regulatory oversight. In the United States, this oversight is provided by the Environmental Protection Agency (EPA), Region 9.
The process of remediation goes down right to the level of nanotechnology. Specifically, nanoremediation refers to the use of nanoparticles. These are defined as particles between one and one hundred nanometers in size. One nanometer is equal to one billionth of a meter. Nanoparticles have a high surface area per unit mass, which makes them highly reactive. Their small size also allows them to infiltrate tiny pores in sediments, making target contaminants more accessible.
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.
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