Investigation of differences between field and laboratory pH measurements of national atmospheric deposition program/national trends network precipitation samples

• Published in: Water, air, and soil pollution air, and soil pollution, 2004-05, Vol.154 (1-4), p.249-270
• Main Authors: LATYSH, Natalie, GORDON, John
• Format: Article
• Language: English
• Subjects: Acidity; Analysis methods; Applied sciences; Atmospheric pollution; Comparative analysis; Deposition; Earth, ocean, space; Environmental monitoring; Exact sciences and technology; External geophysics; Hydrogen; Laboratories; Meteorology; Networks; pH effects; Pollution; Precipitation; Shipments; Soil pollution; Studies; Trend analysis; Trends; Water in the atmosphere (humidity, clouds, evaporation, precipitation)
• ISSN: 0049-6979; 1573-2932
• DOI: 10.1023/B:WATE.0000022971.59349.fc

A study was undertaken to investigate differences between laboratoryand field pH measurements for precipitation samples collected from 135 weekly precipitation-monitoring sites in the National Trends Network from 12/30/1986 to 12/28/1999. Differences in pH between field and laboratory measurements occurred for 96% of samples collected during this time period. Differences between the two measurements were evaluated for precipitation samples collected before and after January 1994, when modifications to sample-handling protocol and elimination of the contaminating bucket o-ring used in sample shipment occurred. Median hydrogen-ion and pH differences between field and laboratory measurements declined from 3. 9 μeq L^sup -1^ or 0. 10 pH units before the 1994 protocol change to 1. 4 μeq L^sup -1^ or 0. 04 pH units after the 1994 protocol change. Hydrogen-ion differences between field and laboratory measurements had a high correlation with the sample pH determined in the field. The largest pH differences between the two measurements occurred for high-pH samples (>5. 6), typical of precipitation collected in Western United States; however low-pH samples (