The sediments and soils that underlie the nation's waterways are subjected to contamination by a range of chemicals - BTEX, diesel, petroleum, polycyclic aromatic hydrocarbons (PAHs) and other organic muddy junk. The process of neutralizing sediments and restoring them to the pristine condition is called sediment remediation. There are many technologies currently available for treating these sediments; the choice is a factor of the nature of the contaminant itself, factored in with the available budget and the urgency of the treatment.
When the sediments and soils beneath aquatic environments such as harbors and rivers becomes contaminated, their recreational and navigational use can be seriously compromised. By 2004, the Environmental Protection Agency (EPA) had identified approximately 12 dozen sites that needed attention. Of these, nearly half (60) were deemed sufficiently important to merit tracking at the national level; others were considered suitable for attention at the local level.
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 substances are either completely insoluble or only partially soluble in aqueous solvents and end up becoming embedded in aquatic sedimentation. This means these poisons are indetectable in the water column. The organic content of these particles, their size and shape, and the ecology of benthic oranisms (bottom feeders) all promote the steady accumulation of contaminated sediments.
When a government agency such as a land remediation agency identifies an area to be decontaminated, or remediated, imminent action is arequired to protect the environment, not to mention human health. This process is subject to regulatory oversight. In the USA, this is the purview of the EPA, Region Nine.
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.
The mechanism by which nanoparticles exert their effects is chemical in nature. A nanoparticle carrying decontaminant bumps into a target contaminant and the result is a detoxifyied product. So far, global NanoRem has cleaned up as many as 70 sites throughout the world. Although currently limited to groundwater projects, research is underway to extend the technology to wastewater treatment.
What makes nanoremediation fascinating is the scale of the contaminants being removed. It is easy to filter out particles on the micrometer level (one millionth of a meter); nanoparticles are more challenging. Onced the nanoremediation technology has been perfected, perhaps man can start developing technologies to tackle pico particles, which are one thousandth the size of a nanometer.
When the sediments and soils beneath aquatic environments such as harbors and rivers becomes contaminated, their recreational and navigational use can be seriously compromised. By 2004, the Environmental Protection Agency (EPA) had identified approximately 12 dozen sites that needed attention. Of these, nearly half (60) were deemed sufficiently important to merit tracking at the national level; others were considered suitable for attention at the local level.
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 substances are either completely insoluble or only partially soluble in aqueous solvents and end up becoming embedded in aquatic sedimentation. This means these poisons are indetectable in the water column. The organic content of these particles, their size and shape, and the ecology of benthic oranisms (bottom feeders) all promote the steady accumulation of contaminated sediments.
When a government agency such as a land remediation agency identifies an area to be decontaminated, or remediated, imminent action is arequired to protect the environment, not to mention human health. This process is subject to regulatory oversight. In the USA, this is the purview of the EPA, Region Nine.
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.
The mechanism by which nanoparticles exert their effects is chemical in nature. A nanoparticle carrying decontaminant bumps into a target contaminant and the result is a detoxifyied product. So far, global NanoRem has cleaned up as many as 70 sites throughout the world. Although currently limited to groundwater projects, research is underway to extend the technology to wastewater treatment.
What makes nanoremediation fascinating is the scale of the contaminants being removed. It is easy to filter out particles on the micrometer level (one millionth of a meter); nanoparticles are more challenging. Onced the nanoremediation technology has been perfected, perhaps man can start developing technologies to tackle pico particles, which are one thousandth the size of a nanometer.
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