Magnetic response and bioaccessibility of toxic metal pollution in outdoor dustfall in Shanghai, China

Toxic metal content testing, environmental magnetic monitoring and in vitro bioaccessibility experiments each have their own advantages and are often used independently for environmental monitoring, but there are few studies that combine the three to evaluate the hazards of toxic metals to humans. This paper investigated the total content, magnetic properties and bioaccessibility of nine potentially toxic metal elements (Zn, Sn, Pb, Cu, Fe, Ni, Cr, Sr, Mn) in dustfall from different functional zones in Shanghai, China, and systematically compared the related results. The results show that these nine metal elements have different degrees of contamination and enrichment in outdoor dustfall, and their content distribution shows the following trend: Zn > Sn > Pb > Cu > Fe > Ni > Cr > Sr > Mn. Magnetic characteristics χ_lf and SIRM are mostly positively correlated with the metal elements, indicating that the higher the content of magnetic minerals in the sample, the higher the concentration of metal elements. It was also found that χ_lf, SIRM, and χ_ARM can well reflect the characteristics of dustfall pollution. The magnetic minerals have a certain degree of enrichment, and the particle size of the magnetic minerals is relatively coarse, mainly in the form of coarse multi-domain and pseudo-single-domain particles, which are largely derived from anthropogenic pollution. The χ_lf and PM₁₀ concentrations in the precipitation show relatively similar spatial trends, so χ_lf, SIRM, and χ_ARM can be used as air pollution indices to facilitate the evaluation of metal elements pollution in dustfall. The overall trend in gastric bioaccessibility is Pb > Zn > Mn > Cu > Cr. Due to the increase in the pH of digestive fluid, the bioavailability of toxic metals decreases significantly from the gastric stage to the intestinal stage. χ_lf, SIRM, and χ_ARM/SIRM are all related to the bioaccessibility of toxic metals in the intestinal stage, so they can be used as toxicity indicators to evaluate the bioaccessibility of toxic metals in dustfall.