Evolution of the Concentration of Inorganic Ions during the Initial Stages of Precipitation Events

Abstract

Ion concentrations in relatively low-intensity precipitation were measured in southern Indiana, USA and are presented as a function of their temporal evolution during individual precipitation events with a specific focus on the first 30 min of those events. These data indicate that during individual rain events potassium concentrations in precipitation may decline by up to 70%-80% in the first 30 min of the event. The other ions exhibited less rapid concentration declines during this event which are in rank order (highest to lowest); sodium, chloride, magnesium, nitrate, calcium, sulfate and ammonium. There is some evidence that the initial declines for precipitation accumulations up to 2 mm in the concentration of chloride, calcium and sulfate in precipitation more closely approximate a power-law dependency on precipitation depth than the commonly applied exponential form which, if confirmed, may have implications for efforts to correct flux networks for under-sampling due to delay in sample collection. Scavenging coefficients (b) derived using an exponential relationship over entire events for sodium, chloride, nitrate, calcium, sulfate and ammonium indicate highest values for sodium and lowest for ammonium, but the uncertainty bounds on ion-specific values of b are sufficiently large that they are statistically indistinguishable.

Dissolved organic carbon transformations and microbial community response to variations in recharge waters in a shallow carbonate aquifer

“…The terrestrially sourced organic matter should plot within region A of the graph, FI \ 1.4 and BIX \ 0.6, and the microbial sourced organic matter plot within region B of the graph, FI [ 1.9 and BIX [ 0.8. Where one or both indices fail to provide a conclusive indicator of source, samples plot within region C and composition of cloud condensation nuclei, atmospheric aerosols and gases, the sources of which vary both seasonally and spatially, and are heavily influenced by storm hydrodynamics (Pryor et al 2007). The majority of atmospheric aerosols on North Andros are likely to be derived from either marine or local terrestrial sources, and the variability in the concentration of DOC could depend on meteorological conditions, sample location and the input from these sources.…”

A Comparison of Two Collectors for Monitoring Precipitation Chemistry

“…For example, higher chemical concentrations have been measured in early stages of precipitation events and during light precipitation (Seymour and Stout 1983;Lim et al 1991;Claassen and Halm 1995b;Radojevic and Lim 1995;Khare et al 1996;Iwasaka 1996, 1997;Tanner and Wong 1997;Pryor et al 2007). Thus, automatic precipitation collectors that do not collect early stages of a rain event, or light precipitation, can underestimate concentration and total deposition of important solutes.…”

“…This feature was not available on the AM collector. Concentrations of inorganic ions are often higher during the initial and light stages of precipitation events (Seymour and Stout 1983;Lim et al 1991;Claassen and Halm 1995b;Radojevic and Lim 1995;Khare et al 1996;Minoura and Iwasaka 1996;Pryor et al 2007), which could explain the higher concentrations and volume in the YES samples. The difference between sulfate concentrations from the YES and the AM sampler was higher for low-volume events than high-volume events (Fig.…”