Dissolved organic carbon (DOC) is ubiquitous in atmospheric water, plays an important role in cloud formation processes, and contributes to organic acidity of precipitation. Rain and snow deposited to the landscape is a source of acidity and nutrient enrichment to ecosystems and water bodies. Despite the significance of DOC to a plethora of ecosystem processes, knowledge about its contributions via precipitation remains limited. In this research project, we are quantifying temporal variations in the sources and concentrations of organic carbon in precipitation in the central Pennsylvania. Here, we present results of a study focusing on the dynamic variability of DOC in rainwater, at multiple time scales, at two sites located in the Appalachian Plateau Region. Sequential sampling during stormflow events at the first site, the Shale Hills Critical Zone Observatory, was conducted to address event-scale variability in rainfall DOC concentrations and is explored in the context of the types and the origins of the storms. Weekly sampling over many years at the second site, the Leading Ridge Experimental watershed, was conducted to address relationships among emissions sources, seasonal variability in storm tracks, antecedent atmospheric moisture conditions, and the temporal variability in DOC responses. In addition to DOC, other chemical analyses were conducted on the rainwater samples, including dissolved inorganic carbon, forms of nitrogen, major cations and anions, trace elements, water isotopes, pH and conductivity. These ancillary data, along with meteorological back trajectory analyses, help to identify sources and origins of DOC in the rainwater of central Pennsylvania over short and long time scales.
Iavorivska, L., Boyer, E.W., Grimm, J., Fuentes, J.D. (2012): Dissolved Organic Carbon Dynamics in Precipitation of Central Pennsylvania as Influenced by Climatic Variability. AGU Annual Fall Conference Proceedings.