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As in other parts of the world, air pollution over West and Central Africa has major health and meteorological impacts. Air quality assessment and its possible sanitary impact have become essential even in medium-sized towns, therefore amplifying the need for easy-to-implement monitoring methods with low environmental impact. We present here the potential of magnetic methods to monitor air quality at street level in the medium-sized city of Maroua (northern Cameroon) affected by dust-laden desert winds. More than five hundred (544) samples of bark and leaves taken from Neem trees in Maroua were analyzed. Magnetic susceptibility, saturation remanence, and S-ratio were found to determine the concentration and nature of magnetic particles. They are dominated by magnetite-like particle signals as a part of particulate emissions due to urban activities, including both traffic, composed of a substantial proportion of motorcycles, and wood burning for food preparation. We show that both bark and leaves from Neem trees are adequate passive bio-recorders. The use of both enables different times and heights to be sampled, allowing for the high-resolution monitoring, in terms of spatialization, of various urban environments. Particle emissions require assessment and screening that could be carried out rapidly and efficiently by magnetic methods on bio-recorders, even in cities impacted by dust-laden wind.

Atmospheric particulate matter (PM) from multinatural and anthropogenic sources poses serious risk to human health and contaminates soil and water resources as it settles back to ground environment and ecosystem. In this study, dust deposition flux (DDF), pollution load index (PLI) of heavy metals, enrichment factor (EF), and settling flux (SF) of eighteen chemical elements were investigated in comparison with crustal composition to assess the influence of anthropogenic emission on PM in major northern Chinese cities. The annual DDF in Lanzhou, Huhhot, Beijing, Zhengzhou, and Harbin was 134.7, 240.6, 103.7, 124.7, and 196.7 g m, respectively. The annual EF of Zn in Harbin, Cd in Lanzhou, and Cd in Beijing was 736.4, 248.6, and 166.3, respectively. Most of the inspected elements were enriched during winter in Lanzhou. Annual PLI showed that deposited dust in Beijing had the highest concentration of heavy metals. Seasonal PLI exhibited obvious changes in different cities. The annual SF of crustal elements was 1-5 orders higher than that of heavy metals. The highest annual SF of elements was identified mainly in Lanzhou and Huhhot. Sulfur, cadmium, copper, lead, and zinc in the dustfall of most urban areas were from human activities. Fossil fuel burning, metal smelting, mining, construction, and vehicle exhaust are the major sources of enriched elements in dustfall in urban areas of northern China. Toxic pollutants with dustfall are widespread and persistent, which deserves public concern in future sustainable development. [ABSTRACT FROM AUTHOR]

Tree leaves are considered as one of the best biogenic dust collectors due to their ability to trap and retain particulate matter on their surfaces. In this study, the magnetic susceptibility (MS) and the concentration of selected heavy metals of plane tree ( Platanus orientalis L.) leaves and deposited atmospheric dust, sampled by an indirect and a direct method, respectively, were determined to investigate the relationships between leaf magnetic parameters and the concentration of heavy metals in deposited atmospheric dust. The objective was to develop a biomagnetic method as an alternative to the common ones used for determining atmospheric heavy metal contaminations. Plane tree leaves were monthly sampled on the 19th of May to November, 2012 (T 1 –T 7 ), for seven months from 21 different sites in the city of Isfahan, central Iran. Deposited atmospheric dust samples were also collected using flat glass surfaces from the same sites on the same dates, except for T 1 . MS (χ lf , χ hf ) values in washed (WL) and unwashed leaves (UL) as well as Cu, Fe, Mn, Ni, Pb, and Zn concentrations in UL and deposited atmospheric dust samples were determined. The results showed that the MS content with a biogenic source was low with almost no significant change during the sampling period, while an increasing trend was observed in the MS content of UL samples due to the deposition of heavy metals and magnetic particles on leaf surfaces throughout the plant growth. The latter type of MS content could be reduced through washing off by rain. Most heavy metals examined, as well as the Tomlinson pollution load index (PLI) in UL, showed statistically significant correlations with MS values. The correlation between heavy metals content in atmospheric dust deposited on glass surfaces and leaf MS values was significant for Cu, Fe, Pb, and Zn. Moreover, the similarity observed between the spatial distribution maps of leaf MS and deposited atmospheric dust PLI provided convincing evidence regarding the suitability of the biomagnetic approach as a relatively rapid and inexpensive method for identifying highly polluted urban areas with selected heavy metals, especially those subjected to anthropogenic and other traffic related sources. [ABSTRACT FROM AUTHOR]