Toxicity characteristic leaching procedure (TCLP) is a soil sample extraction method for chemical analysis employed as an analytical method to simulate
leaching
Leaching is the loss or extraction of certain materials from a carrier into a liquid (usually, but not always a solvent). and may refer to:
* Leaching (agriculture), the loss of water-soluble plant nutrients from the soil; or applying a small amou ...
through a
landfill
A landfill site, also known as a tip, dump, rubbish dump, garbage dump, or dumping ground, is a site for the disposal of waste materials. Landfill is the oldest and most common form of waste disposal, although the systematic burial of the waste ...
. The testing methodology is used to determine if a waste is characteristically hazardous, i.e., classified as one of the "D" listed wastes by the
U.S. Environmental Protection Agency
The Environmental Protection Agency (EPA) is an Independent agencies of the United States government, independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon pro ...
(EPA). The extract is analyzed for substances appropriate to the protocol.
Background
In the United States, the
Resource Conservation and Recovery Act
The Resource Conservation and Recovery Act (RCRA), enacted in 1976, is the principal federal law in the United States governing the disposal of solid waste and hazardous waste.United States. Resource Conservation and Recovery Act. , , ''et seq ...
(RCRA) of 1976 led to establishment of federal standards for the disposal of
solid waste
Municipal solid waste (MSW), commonly known as trash or garbage in the United States and rubbish in Britain, is a waste type consisting of everyday items that are discarded by the public. "Garbage" can also refer specifically to food waste, ...
and
hazardous waste
Hazardous waste is waste that has substantial or potential threats to public health or the environment. Hazardous waste is a type of dangerous goods. They usually have one or more of the following hazardous traits: ignitability, reactivity, co ...
. RCRA requires that
industrial waste
Industrial waste is the waste produced by industrial activity which includes any material that is rendered useless during a manufacturing process such as that of factories, mills, and mining operations. Types of industrial waste include dirt and ...
s and other wastes must be characterized following testing protocols published by EPA.
[ Part o]
"Test Methods for Evaluating Solid Waste, Physical/Chemical Methods."
Document no. SW-846. TCLP is one of these tests.
Application of test
The Environmental Compliance Supervisor at a typical municipal
landfill
A landfill site, also known as a tip, dump, rubbish dump, garbage dump, or dumping ground, is a site for the disposal of waste materials. Landfill is the oldest and most common form of waste disposal, although the systematic burial of the waste ...
(as defined by RCRA
Subtitle D) uses TCLP data to determine whether a waste may be accepted into the facility. If TCLP analytical results are below the TCLP D-list maximum contamination levels (MCLs) the waste can be accepted. If they are above these levels the waste must be taken to a
hazardous waste disposal facility and the cost of disposal may increase from about $50.00/ton to as much as $1200.00/ton.
As extremely contaminated material is expensive to dispose of, grading is necessary to ensure safe disposal and to avoid paying for disposal of "clean fill." The TCLP procedure is generally useful for classifying waste material for disposal options.
Spent abrasive or soil from a construction site usually needs to have a TCLP for lead done to determine where the waste goes next.
Procedure
TCLP comprises four fundamental procedures:
* Sample preparation for leaching
* Sample leaching
* Preparation of leachate for analysis
* Leachate analysis
In the TCLP procedure the pH of the sample material is first established, and then leached with an
acetic acid
Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main component ...
/
sodium hydroxide
Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations and hydroxide anions .
Sodium hydroxide is a highly caustic base and alkali ...
solution at a 1:20 mix of sample to solvent. For example, a TCLP jug may contain 100g of sample and 2000 mL of solution. The leachate mixture is sealed in extraction vessel for general analytes, or possibly pressure sealed as in zero-headspace extractions (ZHE) for
volatile organic compound
Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature. High vapor pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a ...
s and tumbled for 18 hours to simulate an extended leaching time in the ground. It is then filtered so that only the solution (not the sample) remains and this is then analyzed.
See also
*
Landfill gas monitoring
Landfill gas monitoring is the process by which gases that are collected or released from landfills are electronically monitored. Landfill gas may be measured as it escapes the landfill ("Surface Monitoring") or may be measured as it is collecte ...
References
* Davis, Sherry (2001)
"Regulated Metals: The Rule of 20."Pollution Prevention Institute, Kansas State University.
* Environment, Health and Safety Online
2008-03-07.
{{Refend
External links
- EPA
Environmental soil science
Hazardous waste
Landfill