The TCLP, or Toxicity Characteristic Leaching (not Leachate) Procedure is designed to determine the mobility of both organic and inorganic analytes present in liquid, solid, and multiphasic wastes. This is usually used to determine if a waste may meet the definition of EP Toxicity, that is, carrying a hazardous waste code under RCRA (40 CFR Part 261) of D004 through D052. As it is the generator's responsibility to make this determination, but generators often contract outside labs to perform the TCLP test, these questions and answers may be helpful to generators.
TCLP Requirements for the Method of Standard Addition
Total Constituent Analysis instead of TCLP Analysis
TCLP versus SPLP
TCLP Holding Times
Failing to Meet the Holding Times or Perform the Method as Written
TCLP Preservation Requirements
TCLP Duplicate Analysis
Changing the Acid Strength in the TCLP
Question: What are the requirements for performing the method of standard addition when analyzing TCLP extracts for lead by Method 6010B?
Answer: The criteria for the method of standard addition (MSA) are outlined in Sec. 8.4 of Method 1311. In general, when the recovery of the matrix spike is less than 50%, and the analyte of concern is within 20% of the regulatory concentration, the sample must be quantified by MSA. This requirement applies to all TCLP inorganic analytes and the methods used to determine those analytes, including ICP Method 6010B. Generally, most samples will not have to be analyzed by MSA, given the criteria listed in the method. However, the laboratory may choose to apply tighter criteria than those described in the method.
Question: Is it acceptable to perform a total constituent analysis instead of a TCLP analysis and then divide the total concentration by 20 to determine if a waste is non-hazardous, as is implied in Section 1.2 of Method 1311, TCLP?
Answer: Section 1.2 of the TCLP does allow for a total constituent analysis in lieu of the TCLP extraction. If a waste is 100% solid, as defined by the TCLP method, then the results of the total constituent analysis may be divided by twenty to convert the total results into the maximum leachable concentration. This factor is derived from the 20:1 liquid-to-solid ratio employed in the TCLP. If a waste has filterable liquid, then the concentration of the analyte in each phase (liquid and solid) must be determined. The following equation may be used to calculate this value:
[A x B] + [C x D]
___________________ = E
B + [20 (L/kg) x D]
A = Concentration of the analyte in liquid portion of the sample (mg/L)
B = Volume of the liquid portion of the sample (L).
C = Concentration of the analyte in solid portion of the sample (mg/kg)
D = Weight of the solid portion of the sample (kg)
E = Maximum theoretical concentration in leachate (mg/L)
The value obtained (E) can be used to show that the maximum theoretical concentration in a leachate from the waste could not exceed the concentration specified in the toxicity characteristic (TC) (40 CFR 261.24).
In addition, if the total constituent analysis results themselves are below the TC limits without dividing by 20, then the same argument holds true, i.e., the maximum theoretical concentration in the leachate could not exceed the TC limits.
Question: What is the appropriate leaching procedure to be used for determining the characteristic of toxicity per 40 CFR 261.24?
Answer: TCLP (Method 1311) only. Applications of other leaching procedures are regulatory decisions to be determined by the appropriate regulatory authority.
Question: What is the time limit for filtering the TCLP leachates after completing the tumbling?
Answer: There is no time limit specified in the method for the filtration of the leachate after tumbling. However, the lack of a specification should not be perceived as permission to delay filtration. The method assumes that the filtration will be conducted as soon as practical after the completion of the tumbling. If you are running a number of samples, it may take only a short while to filter all of the leachates, but you should not delay this filtration any longer than necessary (e.g., do not wait a day, but start the filtrations as soon as the tumbling is complete and proceed through all of the samples).
Question: What are the holding times for the samples before leaching, the leachates before extraction, and the extracts before analysis?
Answer: Three types of holding times are summarized in Sec. 8.5 of Method 1311. For the leachate that will be analyzed for organics (including volatiles, semivolatiles, and the herbicides), you have 14 days from the collection of the original sample until you have to start the leaching (extraction). For the metals, you have 180 days from collection until leaching, except for mercury, where leaching must start within 28 days.
The herbicides are grouped with the "semivolatiles" in Sec. 8.5 of the method, since both types of analytes are extracted with an organic solvent. The extractions of the semivolatiles and herbicides from the leachate must start within 7 days of the completion of the leaching procedure.
The instrumental (determinative) analyses for the semivolatiles and herbicides must be completed within 40 days of the completion of the solvent extractions. The determinative analyses for the volatiles must be completed within 14 days of the completion of the leaching procedure.
The determinative analyses for the metals must be completed within 180 days of the completion of the leaching procedure, except for mercury, where analyses must be completed within 28 days of the completion of the leaching procedure.
Question: What is the effect on the TCLP results if we miss any of the holding times specified in the method, or if we do not perform the procedure exactly as written?
Answer: The TCLP is a method-defined parameter and therefore, it must be performed as written, which includes meeting all specifications for holding and tumbling times. The effect of failing to perform the method as written is that the results are not valid for the purposes of determining whether the waste is hazardous based on the toxicity characteristic.
However, if the holding times are not met and the results for the analyses are over the numerical limits in the toxicity characteristic (40 CFR 261.24), then the data can be used by the generator to demonstrate that the waste failed the toxicity characteristic and therefore must be managed as a hazardous waste.
Question: What are the preservation requirements for the leachates in Method 1311?
Answer: As noted in Secs. 6.3 and 6.4 of the method, chemical preservatives must not be added to the original samples before leaching. However, the samples may be refrigerated, unless refrigeration will result in irreversible physical changes to the waste.
According to Sec. 6.6, once leached, the portion of the leachate for the metals analyses must be acidified with nitric acid to a pH < 2, unless precipitation occurs, in which case, consult Sec. 7.2.14 of the method for instructions.
The portions of the leachate to be analyzed for the organics must be preserved as described in the individual determinative methods. For volatiles, there is generally no need for further acidification, since the leachate is already at a pH below 7, which should retard any biological activity in the leachate. The portions of the leachate for volatiles, semivolatiles, and herbicides analyses must be stored with minimal headspace at 4 degrees C.
Question: Are we required to prepare a duplicate TCLP sample that is tumbled at the same time as the original sample?
Answer: Method 1311 does not address the need for a duplicate sample. The need for a duplicate sample could be specified in a quality assurance project plan (QAPP) or sampling and analysis plan (SAP) for any given project, but it is not a required part of the method per se.
Question: I work for the environmental regulatory agency in [insert the name of a foreign country] and we believe that the strength of the acid solution in Method 1311 should be increased in order to leach more of the contaminants from the sample. We also want to use it to test additional analytes. Are we allowed to do that?
Answer: First and foremost, since you represent an agency outside of the United States, you do not need EPA's permission or concurrence to develop or modify testing procedures for use in your country. Nevertheless, please understand that the TCLP is a method-defined parameter, which means that the results depend entirely on how the test is conducted.
The test was designed to model a theoretical scenario in which a waste is mismanaged by placing it in an unlined landfill containing municipal solid waste. The acetic acid solution in Method 1311 is designed to simulate the result of rainwater infiltrating the landfill, reacting with the municipal solid waste, and then leaching through the waste being tested. The numerical limits for the RCRA toxicity characteristic (40 CFR 261.24) were derived using the same scenario and were set at levels that would prevent the groundwater under the landfill from posing a threat to human health and the environment.
As a result, the specific details of Method 1311 and the numerical limits for the toxicity characteristic itself are linked together. Increasing the acid strength of the leaching fluid to leach a larger amount of any of the constituents changes the scenario that the test was designed to simulate. Therefore, one would have to consider changing the numerical limits for the constituents listed in the toxicity characteristic too. Similarly, if one adds constituents to the list of those to be tested, one would have to develop numerical limits for them using the same sort of model that EPA used for the toxicity characteristic.
If you are interested in recent developments in leaching science, you may wish to review the proceedings of EPA's July 1999 meeting on leaching at: http://www.epa.gov/sw-846/leaching.htm