Past and present emission of metal and metalloids from natural and anthropogenic sources to the environment has led to ongoing research concerning their fate and bioavailability. Sequestration and transport of metal(loids) in the environment are controlled by their interactions with particles in soils, water, and air. This thesis addresses the interaction of carbon-bearing particles with metal(loid)s in organic-rich soils impacted by mining activities and in urban air affected by wildfire smoke and residential and industrial activities. Carbon-bearing particles such as organic matter (OM) in soils and soot particles in the air have in common a high affinity towards metal(loid)s due to the presence of reactive functional groups such as carbonyl, carboxylic and hydroxyl groups. The interaction of the respective particles with metal(loid)s were characterized in this thesis with multi-analytical approaches that included bulk chemical and mineralogical analyses, scanning electron microscopy, X-ray photoelectron spectroscopy, focused ion beam technology, transmission electron microscopy, ion milling, and atom probe tomography. These multi-analytical approaches showed that sequestration and transformation of As- and Ag-bearing ionic species and nanoparticles (NPs) in the organic-rich soils in Cobalt, Ontario, Canada was controlled by the latter functional groups as well as by mineral-OM associations within particulate organic matter (POM). They specifically indicated that I. arsenic is sequestered by mineral-OM associations through either its co-precipitation or adsorption on Fe-(hydr)oxides followed by the transformation of the latter hydroxide into scorodite (FeAsO4·2H2O) or amorphous Fe-arsenate (AFA) II. Ag is sequestered as Ag-NPs in the matrix of POM and as Ag-sulfide (acanthite) NPs on the surface of the Fe-hydroxides and Fe-arsenates. The formation of the Ag-sulfide NPs was the result of either the replacement of earlier Ag-NPs (so-called oxysulfidation process), or the complete dissolution of the latter NPs and the nucleation of acanthite NPs on the surface of the Fe-bearing minerals (so-called oxidative dissolution/precipitation process). Similarly, a multi-analytical approach on the interactions of soot particles with PM and aerosols derived from residential and industrial activities in Barranquilla, Atlántico showed that the most common particles are soot aggregates associated with Fe-, Ti-, and Zn-oxides due to the high surface reactivity of individual soot particles. Other observed particles included pure soot aggregates, carbon allotropes, organics, C-rich coatings, and NPs of silicates, salt minerals associated with soot particles (mainly Na-sulfates). The observations of this thesis show that mineral-carbon associations in soils and air strongly control the sequestration, transportation, and transformation of metal(loid)s in both respective environments.