Procedure for Requesting Archived Filters and Extracts
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Introduction
The Clean Air Status and Trends Network (CASTNET) receives requests for filters and filter extracts for special research projects. Samples include filters (Teflon, nylon, cellulose) or excess filter extracts that have been archived.
The CASTNET program managers will evaluate requests from external researchers that:
- Support the production of quality-assured data and information resources for CASTNET stakeholders through independent measurements of unique analytes and promotes the assessment of field and laboratory methods.
- Assures CASTNET remains responsive to stakeholder research needs by aiding scientists, policy makers, and educators to advance the understanding of deposition to aquatic or terrestrial ecosystems, emerging pollutants, climate effects, and human health impacts.
- Creates a mechanism to respond to emerging issues related, but not limited to, deposition, climate impacts, chemical transport, model development, PM formation, or enhanced measurement methods.
The CASTNET Program should be acknowledged in publications and presentations that utilize the sample results and copies of the publications should be submitted to the CASTNET Program Manager. Suggested acknowledgement for the archive samples is:
“Archived (or active) extracts were obtained from the Clean Air Status and Trends Network (CASTNET); WSP, Gainesville FL 32607”
Samples and Sample Availability Overview
For a detailed description of sample preparation, extraction and analysis please refer to the CASTNET QAPP and Laboratory SOPs.
The Teflon filter is a 47 mm Whatman membrane filter consisting of polytetrafluoroethelyne (PTFE) with polypropylene backing and 1.0 µm pore size. The nylon filter is a 47 mm diameter Measurement Technology Laboratories (MTL) nylon membrane filter with a 1.0 µm pore size. The cellulose filters are a Whatman 41 ashless circle filter with a 47 mm diameter. The cellulose filters are impregnated by the laboratory with a K2CO3 solution prior to deployment. The filter packs are assembled with 2-cellulose filters, a nylon filter and a Teflon filter. The filterpacks are coded with unique identifiers and the laboratory utilizes chain of custody forms throughout the process.
Once the filters are received in the laboratory they are disassembled, and each filter (Teflon, Nylon, and Cellulose) is placed in individual 30mL bottles (60 mL for the cellulose filters) and stored at 4° C until extraction.
The Teflon and Nylon filters are extracted with 25mL of extraction solution. The cellulose filters are extracted with 50 mL of extraction solution. All filters are extracted with a bromide stock solution diluted with DI water. The nylon filter extract also includes 30% H2O2 and NaOH solution. The cellulose filter extraction solution includes 30% H2O2 and HCl. Once the extract solution is added to the bottles with the filters, the bottles are added to a sonication bath.
Samples are made available on a quarterly basis, approximately 100 days after sample collection. The samples are stored for approximately 3-years after sample collection in a cooler (4° C). After 3-years the samples are disposed of. Table 1 shows the approximate amount of extract left which can be made available for special studies. Sufficient volume of sample will be retained for potential reanalysis until the data have been published on the CASTNET website.
Table 1 Approximate amount of sample volume available from each filter extraction after analysis. Columns show the amount of volume that remains from collection to 1-year and from 1-3 years after collection.
| Filter Type | Extract Volume < 1 year (mL) | Extract Volume > 1 year (mL) |
|---|---|---|
| Teflon | 10 | 15 |
| Nylon | 10 | 20 |
| Cellulose | 20 | 40 |
Evaluation Process
The evaluation process for sample requests is outlined below. The CASTNET federal partners and the contract laboratory will evaluate the requests based on the proposal supporting the CASTNET mission, technical feasibility and appropriateness, and an evaluation of the laboratory effort and cost to implement the request. The CASTNET program managers will evaluate requests for:
- Consistency with the CASTNET mission
- Application of samples to technically sound methods and scientific approaches
- Feasibility for the lab to accommodate the request
The review is not intended to assess the scientific merit of the project, but to assess the specific application of the CASTNET samples within the requestor’s project. The program managers will provide guidance to requestors on how the proposed approaches, applications, and methods could be strengthened to improve the justification for their proposal.
The following steps will be taken to evaluate the proposal:
- The Federal partners and the Laboratory Manager will determine if the request meets the evaluation criteria.
- If necessary, EPA’s CASTNET Program Manager will consult with EPA researchers on technical feasibility and methodology.
- If necessary, the CASTNET Program Manager will work with the requestor to address any concerns and guidance from the federal partners or EPA researchers.
- EPA will work with the WSP Laboratory to assess impact on staff time including sample receiving, shipping, storage, preservation, temperature control, material handling, and safety impacts.
- The CASTNET Program Manager will inform the requestor of the final decision and any further documentation needed to approve the study.
- The WSP Laboratory Manager will work with the requestor to set up payment and establish a timeline for shipping of samples.
- The requestor will acknowledge CASTNET in any publications or presentations that utilize the CASTNET archive samples as noted above in the Introduction.