Measurement report: Statistical modelling of long-term trends of atmospheric inorganic gaseous species within proximity of the pollution hotspot in South Africa

Swartz, Jan-Stefan; van Zyl, Pieter G.; Beukes, Johan P.; Galy-Lacaux, Corinne; Ramandh, Avishkar; Pienaar, Jacobus J.

South Africa is considered an important source region of atmospheric pollutants, which is compounded by high population and industrial growth. However, this region is understudied, especially with regard to evaluating long-term trends of atmospheric pollutants. The aim of this study was to perform statistical modelling of inline-formulaSO2, inline-formulaNO2 and inline-formulaO3 long-term trends based on 21-, 19- and 16-year passive sampling datasets available for three South African INDAAF (International Network to study Deposition and Atmospheric Chemistry in Africa) sites located within proximity of the pollution hotspot in the industrialized north-eastern interior in South Africa. The interdependencies between local, regional and global parameters on variances in inline-formulaSO2, inline-formulaNO2 and inline-formulaO3 levels were investigated in the model. Average monthly inline-formulaSO2 concentrations at Amersfoort (AF), Louis Trichardt (LT) and Skukuza (SK) were 9.91, 1.70 and 2.07 inline-formulaµg minline-formula−3, respectively, while respective mean monthly inline-formulaNO2 concentrations at each of these sites were 6.56, 1.46 and 2.54 inline-formulaµg minline-formula−3. Average monthly inline-formulaO3 concentrations were 50.77, 58.44 and 43.36 inline-formulaµg minline-formula−3 at AF, LT and SK, respectively. Long-term temporal trends indicated seasonal and inter-annual variability at all three sites, which could be ascribed to changes in meteorological conditions and/or variances in source contribution. Local, regional and global parameters contributed to inline-formulaSO2 variability, with total solar irradiation (TSI) being the most significant factor at the regional background site LT. Temperature (inline-formulaT) was the most important factor at SK, located in the Kruger National Park, while population growth (inline-formulaP) made the most substantial contribution at the industrially impacted AF site. Air masses passing over the source region also contributed to inline-formulaSO2 levels at SK and LT. Local and regional factors made more substantial contributions to modelled inline-formulaNO2 levels, with inline-formulaP being the most significant factor explaining inline-formulaNO2 variability at all three sites, while relative humidity (RH) was the most important local and regional meteorological factor. The important contribution of inline-formulaP on modelled inline-formulaSO2 and inline-formulaNO2 concentrations was indicative of the impact of increased anthropogenic activities and energy demand in the north-eastern interior of South Africa. Higher inline-formulaSO2 concentrations, associated with lower temperatures, as well as the negative correlation of inline-formulaNO2 levels to RH, reflected the influence of pollution build-up and increased household combustion during winter. The El Niño–Southern Oscillation (ENSO) made a significant contribution to modelled inline-formulaO3 levels at all three sites, while the influence of local and regional meteorological factors was also evident. Trend lines for inline-formulaSO2 and inline-formulaNO2 at AF indicated an increase in inline-formulaSO2 and inline-formulaNO2 concentrations over the 19-year sampling period, while an upward trend in inline-formulaNO2 levels at SK signified the influence of growing rural communities. Marginal trends were observed for inline-formulaSO2 at SK, as well as inline-formulaSO2 and inline-formulaNO2 at LT, while inline-formulaO3 remained relatively constant at all three sites. inline-formulaSO2 and inline-formulaNO2 concentrations were higher at AF, while the regional inline-formulaO3 problem was evident at all three sites.



Swartz, Jan-Stefan / van Zyl, Pieter G. / Beukes, Johan P. / et al: Measurement report: Statistical modelling of long-term trends of atmospheric inorganic gaseous species within proximity of the pollution hotspot in South Africa. 2020. Copernicus Publications.


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Rechteinhaber: Jan-Stefan Swartz et al.

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