Calibration of collection procedures for the determination of precipitation chemistry

Abstract

Precipitation is currently collected by several methods, including several different designs of collection apparatus. We are investigating these differing methods and designs to determine which gives the most representative sample of precipitation for the analysis of some 25 chemical parameters. The experimental site, located in Ithaca, New York, has 22 collectors of 10 different designs. The designs include bulk (wet and dry deposition collected together), wet only (only rain and snow) and wet/dry (collects wet and dry deposition separately). In every sampling period, which varies from 1 day to 1 mo, depending on the time variable being tested, the following chemical parameters are determined: conductivity, pH, and PCB's.The results of the investigation lead us to conclude that:(1) Precipitation samples must exclude dry deposition if accurate information on the chemical content of precipitation is required.(2) Substantial contamination results when glass and plastic collectors are used to sample precipitation for inorganic and organic components, respectively. (3) The inorganic components of precipitation samples of low pH (3.5 to 4.5), with the exception ofPO 4 and C1, exhibited no significant change in concentration when stored at 4°C for a period of 8 mo.We believe this is due to the stabilizing influence of a large concentration of H ions. (4) If quantitative information on the chemical composition is required, precipitation samples should be collected at no longer than weekly intervals if immediate collection is not possible.

Chemical characteristics and sources of organic acids in precipitation at a semi-urban site in Southwest China

“…Over the last few decades, the increasing SO 2 and NO x emission trends associated with the increasing energy use, coal combustion, and economic growth in China has intensified the acid rain problem (Larssen et al, 2006). Consequently, the South and Southwest China have become the third largest acid rain-prone region in the world (Wang and Wang, 1995) after Northeast America (Galloway and Likens, 1976;Ito et al, 2002) and Central Europe (Menz and Seip, 2004;Smirnioudi and Siskos, 1992). Therefore, the information gathering of the current status of acid deposition in China through monitoring is essential.…”

Hydrogen ion speciation in the acid precipitation of the northeastern United States

“…The samples were collected from February to May, 1975. From the results presented in Table 2, the following points are evident: 1) While the range of free acidities is similar in the rural areas and the semi-urban area, the amount of weak acids is significantly higher in the urban samples.…”

Identification of Ion sources in rainwater of a coastal site impacted by the gas and oil industry in the southeast of Mexico

“…Various proton donors may cause free acidity in precipitation: strong acids (e.g., H 2 SO 4 , HNO 3 ), weak organic acids (e.g., acetic, formic), or metal oxides (e.g., Al, Fe) (Galloway et al, 1976). Since all strong acid anions were measured, we determined the possible contribution of (SO 4 2-) xs and NO 3 -to free acidity by using the equivalent ratios (SO 4 2-) xs /H + and NO 3 -/H +.…”