New reporting conventions, described in the previous section, were applied to the four NWQL water matrix methods listed below, effective October 1, 1998. These methods were part of pilot studies testing the LT–MDL process. U.S. Geological Survey National Water Quality Laboratory Technical Memorandum 98.07 (1998) provides specific information regarding LT–MDL’s and reporting levels for the four methods.

  1. Low-level volatile organic compounds (VOC’s) by gas chromatography/mass spectrometry (schedules 2020 and 2021),
  2. Trace elements in filtered water by inductively coupled plasma–atomic emission spectrometry (ICP–AES),
  3. Ammonia plus organic nitrogen (micro-Kjeldahl digestion), and
  4. Phosphorus (micro-Kjeldahl digestion).

The NWQL has planned a phased implementation of the new reporting procedure for other methods. The first priority is to implement the procedure for high-demand water matrix methods, including all water matrix methods used by the National Water Quality Assessment (NAWQA) and National Stream Quality Accounting Network (NASQAN) programs. High-demand inorganic chemistry methods are those that have more than 750 samples submitted per year. High-demand organic chemistry methods are those with more than 250 samples submitted per year. There are some analytical methods that do not require assessment by the LT-MDL process; these include regulatory methods and some methods developed to assess high concentrations of constituents. No charge in the reporting levels of these analytical methods is planned.

In the next phase (fiscal year 1999) of implementation, LT–MDL’s are being determined for the following high-demand NWQL methods (Timme, 1995). Implementation of the new reporting conventions for these methods is planned for October 1, 1999.

Organic Chemistry Program:

  1. Total organic carbon, lab code 114.
  2. Dissolved organic carbon, lab code 113.
  3. Gross phenols, lab code 2322.
  4. Chlorophenoxyacid herbicides, schedules 79 and 1304.
  5. Organophosphorus pesticides, schedule 1319.
  6. Organochlorine pesticides, schedule 1324.
  7. Base/neutral and acid extractable (BNA) compounds, schedule 1383.
  8. Pesticides, solid-phase extraction, analysis by gas chromatography/mass spectrometry, schedules 2001 and 2010.
  9. Pesticides, solid-phase extraction, analysis by high performance liquid chromatography, schedules 2050 and 2051.

Inorganic Chemistry Program:

  1. Metals, inductively coupled plasma/atomic emission spectrometry, whole water recoverable.
  2. Metals, inductively coupled plasma/mass spectrometry methods, filtered- and whole-water recoverable.
  3. Metals, graphite furnace atomic absorption spectrometry, filtered- and whole-water recoverable.
  4. Ion-chromatography methods.
  5. All remaining NWQL water-matrix nutrient methods.
  6. Potassium, atomic absorption spectrometry.
  7. Mercury, cold vapor atomic absorption, filtered- and whole-water recoverable.
  8. Silica, colorimetry.

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