Rainfall composition, Agoufou, Mali

Precipitation chemical composition including inorganic and organic soluble ions follow the methodologies and guidelines recommended by GAW
(<a href="https://library.wmo.int/records/item/41241-manual-for-the-gaw-prec-data-quality-objectives-and-standard-operating-procedures">GAW-WMO Report n°160, 2004</a>).
Rainwater samples are collected using a wet only precipitation collector designed for the INDAAF network. The first rain droplets order the rain detector to open the lid of the collector. Rainwater samples are collected in polyethylene single-use bags. In order to avoid any contamination, the rain collector remains closed before and after the rain event. Rain samples are immediately collected by a local observer after each rain event. Samples are stored in Greiner tubes of 50 ml in a freezer -18°C. After collection, samples are sent for analysis to the Laboratoire d’Aérologie (LAERO, analytical laboratory code: FR05L) in Toulouse in the strict respect of the cold chain, where they are stored in a freezer (-18°C) until analysis. Rainfall samples are analyzed for pH, conductivity, major inorganic and organic ion concentrations (in μeq/L). Analytical precision is estimated to be 5% or better for all the ions according the LAERO analytical laboratory results to the Quality Assurance/Science Activity Centre – Americas (QA/SAC-Americas), one of five QA/SACs operating to ensure data quality and support science activities in the World Meteorological Organization Global Atmosphere Watch (WMO GAW) ( https://qasac-americas.org).