Rainfall composition, Katigoubou, 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).

降水化学成分（包含无机与有机可溶性离子）的分析流程遵循全球大气监测网（Global Atmosphere Watch, GAW）推荐的方法与指南，具体参照《GAW-WMO第160号报告（2004年）：GAW降水数据质量目标与标准操作程序》（<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>）。

雨水样品采用专为INDAAF监测网络设计的湿沉降专用采样器采集。首个雨滴触发雨量检测器，开启采样器的盖子。雨水样品被收集于聚乙烯一次性采样袋中。为避免任何形式的污染，该采样器在降雨前后均保持闭合状态。每场降雨结束后，由当地观测人员立即完成样品采集。样品被分装至50ml葛莱娜（Greiner）样品管中，置于-18℃冰箱内保存。样品采集完成后，需严格遵循冷链运输要求，送至位于图卢兹的大气实验室（Laboratoire d’Aérologie, LAERO，分析实验室代码：FR05L）进行分析，该实验室会将样品继续保存在-18℃冰箱中直至检测环节。

降雨样品的检测指标包括pH值、电导率，以及主要无机与有机离子浓度（单位：μeq/L）。根据LAERO实验室提交至美洲质量保证与科学活动中心（QA/SAC-Americas）的分析结果，所有离子的分析精密度均达到5%或更佳水平。美洲质量保证与科学活动中心是世界气象组织（World Meteorological Organization, WMO）全球大气监测网（WMO GAW）下设的5个质量保证与科学活动中心之一，负责保障数据质量并支撑相关科学活动（<a href="https://qasac-americas.org">https://qasac-americas.org</a>）。