Centre for Energy Research and Development, Obafemi Awolowo University, Ile-Ife, Nigeria.
Institute of Ecology and Environmental Studies, Obafemi Awolowo University, Ile-Ife, Nigeria.
Environ Sci Pollut Res Int. 2020 Nov;27(31):39317-39329. doi: 10.1007/s11356-020-10004-x. Epub 2020 Jul 9.
Harmattan dust and traffic-related pollution have been a serious environmental concern in the West African sub-region. In order to further contribute to the understanding of ambient levels of atmospheric pollution and chemical composition in the region, this study monitored harmattan dust and traffic-related particulate matter at four locations across southwestern (Ile-Ife) and north-western (Zaria) geo-political zones of Nigeria. The collected samples were characterized for their chemical composition using Energy-Dispersive X-Ray Fluorescence spectrometer equipped with an optimized secondary target x-ray excitation conditions (Al, CaF, Fe, Ge, Zr, Mo, Ag, AlO). The objectives are to assess spatio-temporal mass concentrations, chemical footprints, enrichment factors, elemental correlations, and ratios at all locations. The X-ray analytical method was validated with a NIST SRM 2783 air particulate standard, and detection limits for each chemical specie were determined. Validation results showed good reproducibility of the certified reference material with relative standard deviations of the elements much lower by about 1-13% than the corresponding reference values. Mass concentrations reached up to 2200 μgm in the north and 1500 μgm in the south. The range of mean concentration of crustal marker elements were Al (5-27 μgm), Si (5-856 μgm), Ca (0.78-13 μgm), and Fe (2-13 μgm), and were most abundant during the harmattan particularly in the southwestern region. Highest mean concentration values of 380, 810, and 420 ngm were recorded for Cr, Cu, and Pb respectively at the traffic corridor which also recorded the highest enrichment factors. Black carbon and elemental concentrations contributed between 1 to 54% and 9 to 94% across the locations respectively. Backward trajectories of atmospheric flow over the locations showed two dominant sources; dust laden source from the Sahara desert and maritime flow over the Gulf of Guinea. This study found that chemical footprints (Al, Si, K, Ca, Ti, and Fe) of harmattan-related dust were more correlated (r between 0.88 and 0.99) than those attributed to dust re-suspension at the traffic location.
哈马丹尘暴和交通相关的污染一直是西非次区域的一个严重环境问题。为了进一步了解该地区的大气污染水平和化学成分，本研究在尼日利亚西南部（伊费）和西北部（扎里亚）两个地理政治区域的四个地点监测了哈马丹尘暴和交通相关的颗粒物。使用配备优化二次靶 X 射线激发条件（Al、CaF、Fe、Ge、Zr、Mo、Ag、AlO）的能量色散 X 射线荧光光谱仪对收集的样品进行化学成分特征分析。目的是评估所有地点的时空质量浓度、化学足迹、富集因子、元素相关性和比值。X 射线分析方法用 NIST SRM 2783 空气颗粒物标准进行了验证，并确定了每种化学物质的检测限。验证结果表明，认证参考物质的重现性良好，元素的相对标准偏差比相应的参考值低约 1-13%。在北部，质量浓度高达 2200μg/m3，在南部，质量浓度高达 1500μg/m3。地壳示踪元素的平均浓度范围为 Al（5-27μg/m3）、Si（5-856μg/m3）、Ca（0.78-13μg/m3）和 Fe（2-13μg/m3），在哈马丹期间尤其在西南部地区最为丰富。在交通走廊处记录到 Cr、Cu 和 Pb 的最高平均浓度值分别为 380、810 和 420ng/m3，同时也记录到最高的富集因子。在各个地点，黑碳和元素浓度分别占 1 至 54%和 9 至 94%。大气流在各地点的后向轨迹显示了两个主要来源；撒哈拉沙漠的尘埃源和几内亚湾的海洋流。本研究发现，与哈马丹相关的尘埃的化学足迹（Al、Si、K、Ca、Ti 和 Fe）比在交通位置归因于尘埃再悬浮的化学足迹更为相关（r 值在 0.88 到 0.99 之间）。
