PM2.5 Mineral Analysis, Zoétélé, Cameroon

Weekly integrated aerosol samples are collected using two automatic aerosol samplers specifically designed and developed for the INDAAF program (http://indaaf.obs-mip.fr). Each sampler is equipped with two independent air inlets connected with KNF pumps (N89 KNE-K 220V) operating at a flow rate of 9 L/min, Cole palmer ball flow meters with a micrometric valve (flow range adjustable from 0 to 10 L/min and NILU online filter holders. Each air inlet is surmounted with an aerosol cutting head corresponding to aerodynamic particles diameter. Two mini Partisol low air inlets PM2.5 and PM10 (Rupprecht and Patashnick) operates at a flow rate of 5 L/min and the air volume sample is measured with a GALLUS type G4 gas meter (accuracy ±0.01 m-3) (Ouafo-Luembe et al., 2017; Djoussou et al, 2018). Aerosol samples were collected on 47mm diameter filters on a weekly basis. PTFE or teflon filters were used for to determine mineral compounds. PTFE filters are weighed before and after sampling using a SARTORIUS MCS21 microbalance (1 µg resolution for a maximum range of 21 g - Measuring accuracy of ± 5 µg). For each filter batch preparation, field blanks are included with the samplers sent into the field. Before and after collection, samples and blanks filters are conditioned in petri slides boxes and stored at 4°C. From 2005, we performed PM2.5 or PM10 weekly filter samples analysis at the Laboratoire d’Aérologie (Laero) to determine mineral composition (soluble major ions) using Ion Chromatography (IC). Before this date, weekly bulk aerosol sampling on teflon filters was performed (1998-2005).

本研究依托INDAAF计划（http://indaaf.obs-mip.fr）专属定制开发的两台自动气溶胶采样器，采集周积分气溶胶样品。每台采样器配备两个独立进气口，分别连接KNF泵（型号N89 KNE-K 220V，额定流量9 L/min）、带微调阀的科尔帕默（Cole Palmer）球式流量计（流量调节范围0~10 L/min）以及NILU在线滤膜支架。每个进气口上方均安装有对应空气动力学粒径的气溶胶切割头。另有两台小型Partisol型PM2.5及PM10低流量进气口装置（制造商为Rupprecht and Patashnick），工作流量为5 L/min；采样空气体积采用GALLUS G4型气体流量计进行计量，精度为±0.01 m⁻³（Ouafo-Luembe等，2017；Djoussou等，2018）。采样每周开展一次，气溶胶样品采集于直径47 mm的滤膜之上。本研究采用聚四氟乙烯（PTFE）或特氟龙（Teflon）滤膜测定矿物组分。采样前后，均使用赛多利斯（SARTORIUS）MCS21型微量天平对PTFE滤膜进行称重，该天平量程上限为21 g，分辨率1 μg，测量精度±5 μg。每批次滤膜制备过程中，均设置现场空白样品，随采样器一同部署至野外采样场地。采样前后，样品滤膜与空白滤膜均置于培养皿盒中进行温湿度平衡处理，并于4℃条件下储存。2005年起，本研究于大气实验室（Laboratoire d’Aérologie，缩写Laero）对每周采集的PM2.5或PM10滤膜样品开展分析，采用离子色谱（Ion Chromatography, IC）测定其矿物组分（可溶性主要离子）。2005年之前（1998-2005年），则采用特氟龙滤膜开展全粒径气溶胶周采样工作。