Plastic litter is on the rise where plastic waste ends up in undesignated areas such as the coastal shorelines, where the plastic is exposed to environmental conditions. As a result, the degradation and decomposition of plastics occur, leading to the formation of smaller fragments of plastics, termed microplastics. Microplastics have recently been considered as an emerging class of contaminants due to their ecotoxicological impact on the aquatic environment as well as soil matrix. Microplastics are of a size less than 5 mm and are produced from either a primary source (such as plastic pellets, and beads in makeup products) or a secondary source (such as the wear and tear of normal-use plastics and washing of clothes and textiles). Microplastic pollution is spread across the hydrosphere, pedosphere, and atmosphere, and these environmental zones are being studied for microplastic accumulation individually. However, there exists a source–sink dynamic between these environmental compartments. This study reviews the available literature on microplastic research and discusses the current state of research on the fate and transport of microplastic in the hydrosphere, pedosphere, and atmosphere, explores the ecotoxicological impact of microplastics on aquatic and soil communities, and provides prospective future research directions and plastic waste management strategies to control microplastic pollution. While the fate of microplastics in the hydrosphere is well-documented and researched, studies on understanding the transport mechanism of microplastics in the pedosphere and atmosphere remain poorly understood.

Calcium- and magnesium-rich alkaline silicate minerals, when applied to soil, can aid in carbon dioxide sequestration via enhanced weathering. The weathering of these silicate minerals is also associated with the release of heavy metals such as Ni and Cr, depending on the composition of the parent rock, and also labile Si. This paper critically analyses the risk associated with the release of Ni, Cr, and Si from alkaline silicate minerals as a result of enhanced weathering to evaluate its potential to be applied as a soil amendment. Based on the available data in the literature, this study evaluates the soil contamination level and quantifies the risk these elements pose to human health as well as the environment. To assess these potential threat levels, the geoaccumulation index was applied, along with the method recommended by the US Environmental Protection Agency for health risk assessment. The main findings of this study indicate the potential release of Ni, Cr, and Si to exceed the soil quality guideline value. The geochemical index suggests that the analyzed samples are in the class 0–3 and represents sites that lie between uncontaminated zones to highly contaminated zones. The hazard index value for Ni and Cr is greater than unity, which suggests that Ni and Cr release poses a non-carcinogenic risk. The probability of labile Si concentration in the soil to exceed the critical value is found to be 75%.

Extreme climate change due to heat-trapping gases, especially carbon dioxide, necessitates its mitigation. In this context, the carbon dioxide sequestration technology of enhanced weathering has for years been investigated, with a possible implementation strategy via alkaline mineral soil amendment being more recently proposed. Candidate materials for enhanced weathering include calcium and magnesium silicates, most notably those belonging to the olivine, pyroxene and serpentine groups of minerals, given their reactivity with CO₂ and global availability. When these finely crushed silicate rocks are applied to the soil, the alkaline earth metal cations released during mineral weathering gradually react with carbonate anions and results in the formation of pedogenic carbonates, which, over time, and under the right conditions, can accumulate in the soil. This review paper critically reviews the available literature on alkaline mineral soil amendments and its potential to sequester enough CO₂ to be considered a climate change ‘stabilization wedge’. Firstly, evidence of how agricultural soil can serve as a carbon sink in discussed, based on the observed accumulation of inorganic carbon in alkaline mineral-amended soils. Secondly, the impact of alkaline minerals on agricultural soil and crops, and the factors determining the rate of the weathering process are assessed. Lastly, the CO₂ sequestration potential via alkaline mineral soil amendment is quantified according to an idealized shrinking core model, which shows that it has the potential to serve as a climate change stabilization wedge.

Wollastonite is a natural silicate mineral that can be used as an agricultural soil amendment. Once in the soil, this mineral undergoes weathering and carbonation reactions, and, under certain soil and field crop conditions, our previous work has shown that this practice leads to accumulation of inorganic carbon (calcium carbonate). Mineral carbonation is the carbon sequestration approach with the greatest potential for sequestration capacity and permanency. Agricultural lands offer vast areas onto which such minerals can be applied, while benefiting crops. This work illustrates a technique to separate wollastonite-containing soils into different fractions. These fractions are characterized separately to determine organic and inorganic content, as well as to determine the chemical and mineral composition. The aim is to detect the fate of wollastonite in agricultural soils, and the fate of weathering/carbonation products in the soil. The soils used in the study were collected from soybean and potato farmlands in Southern Ontario, and from an experimental pilot plot. Soil fractionation was done using sieving, and soil fractions were analyzed by a calcimeter, X-ray diffraction, and loss-on-ignition. Acid digested samples were measured by Inductively Coupled Plasma Mass Spectrometry. Carbonates and wollastonite were enriched by fractionation.