This test method may be used for the determination of calcium, magnesium, potassium, and sodium in atmospheric wet deposition samples.

Emphasis is placed on the easily contaminated quality of atmospheric wet deposition samples due to the low concentration levels of dissolved metals commonly present.

Annex A1 represents cumulative frequency percentile concentration plots of calcium, magnesium, potassium, and sodium obtained from analyses of over five thousand wet deposition samples. These data may be used as an aid in the selection of appropriate calibration standard concentrations. (3)

1.1 This test method is applicable to the determination of calcium, magnesium, potassium, and sodium in atmospheric wet deposition (rain, snow, sleet, and hail) by flame atomic absorption spectrophotometry (FAAS). (1)

1.2 The concentration ranges are listed below. The range tested was confirmed using the interlaboratory collaborative test (see Table 1 for a statistical summary of the collaborative test).

	MDL (mg/L) (2)	Range of Method (mg/L)	Range Tested (mg/L)
Calcium	0.009	0.03–3.00	0.168–2.939
Magnesium	0.003	0.01–1.00	0.039–0.682
Potassium	0.003	0.01–1.00	0.029–0.499
Sodium	0.003	0.01–2.00	0.105–1.84

1.3 The method detection limit (MDL) is based on single operator precision (2) and may be higher or lower for other operators and laboratories. Many workers have found that this test method is reliable at lower levels than were tested, but the precision and bias data presented are insufficient to justify their use at lower levels.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific warning statements are given in 8.3, 8.7, 12.1.8, and Section 9.