Trace gases, Bambey, Senegal

Monthly gases concentrations (in ppb) of sulfur dioxide, nitric acid, ammonia, nitrogen dioxide and ozone are measured using INDAAF passive samplers technique. Passive sampling technique uses the property of molecular diffusion of gases into the sampling device where they are collected on an impregnated filter or adsorbent material. The advantages of passive sampling technique is that it is generally easy to carry out and low cost compared to active sampling technique to achieve mean or integrated-time concentrations. The sampling technique is conform to WMO-GAW guidelines (<a href="https://library.wmo.int/records/item/41112-report-on-passive-samplers-for-atmospheric-chemistry-measurements-and-their-role-in-gaw">GAW-WMO Report n°122, 1998</a>).
Samplers are exposed at about 1.5–3m above the ground using duplicates for each gas. The INDAAF passive samplers were developed and prepared at the Laboratoire d’Aérologie (LAERO) and then were sent each two months on measurement sites. Samplers were sent back to Laero for chemical analysis using ionic chromatography (IC). The LAERO analytical lab participates bi-annually to the WMO-GAW quality assurance program for soluble trace compounds measured by Ion Chromatography (IC). The results of these inter-comparisons are available under the reference 700106 at the following address: http://qasac-americas.org/. According to these WMO inter-comparison tests, analytical precision is estimated to be 5% or better for all ions.

本数据集采用INDAAF被动采样器（INDAAF passive samplers）技术，对二氧化硫（sulfur dioxide）、硝酸（nitric acid）、氨（ammonia）、二氧化氮（nitrogen dioxide）及臭氧（ozone）的月均气体浓度（单位为ppb）进行测定。被动采样技术利用气体分子的扩散特性，使待测气体进入采样装置并被捕获于浸渍滤膜或吸附材料之上。相较于主动采样技术，被动采样技术在获取平均浓度或积分时间浓度时，具备操作简便、成本低廉的显著优势。该采样方法符合世界气象组织-全球大气观测计划（World Meteorological Organization-Global Atmosphere Watch, WMO-GAW）的相关指南，详见《GAW-WMO第122号报告（1998年）》<a href="https://library.wmo.int/records/item/41112-report-on-passive-samplers-for-atmospheric-chemistry-measurements-and-their-role-in-gaw">GAW-WMO Report n°122, 1998</a>。
每种气体均设置双份平行采样器，采样器的布设高度距地面约1.5至3米。INDAAF被动采样器由大气实验室（Laboratoire d’Aérologie, LAERO）研发制备，随后每两个月将采样器运送至各监测站点。采样完成后，所有采样器将被送回LAERO实验室，采用离子色谱法（Ion Chromatography, IC）开展化学分析。LAERO分析实验室每年两次参与WMO-GAW针对离子色谱法测定的可溶性痕量化合物的质量保证计划。上述实验室间比对的结果可通过以下地址以编号700106查询：http://qasac-americas.org/。根据该WMO实验室间比对测试结果，所有待测离子的分析精密度可达5%或更高。