Coal remains a very important source of energy for the global economy. Surface and underground coal mining are the two major methods of coal extraction, and both have benefits and drawbacks. Surface coal mining can have a variety of environmental impacts including ecosystem losses, landscape alteration, soil destruction, and changes to surface and groundwater quality and quantity. In addition, toxic compounds such as heavy metals, radioactive elements, polycyclic aromatic hydrocarbons (PAHs), and other organic contaminants are released in the environment, ultimately affecting the health of ecosystems and the general population. Underground mining has large impacts on underground water supplies and water quality, but generally has less visual surface impacts such as leaving waste and tailings on the surface and subsidence problems. In response to the concern about these environmental issues, many strategies have been developed by scientists and practitioners to minimize land degradation and soil pollution due to mining. Reclamation laws passed in numerous countries during the past 50 years have instituted practices to reduce the impacts of soil pollution including burying toxic materials, saving and replacing topsoil, and vegetating the land surface. While modern mining practices have decreased the environmental impacts, many sites are inadequately reclaimed and present long-lasting soil pollution problems. The current review summarizes progress in comprehending (1) coal mining impacts on soil pollution, (2) the potential risks of soil pollution associated with coal mining, and (3) different types of strategies for remediating these contaminated soils. Research and prospective directions of soil pollution in coal mining regions include refinements in assessing pollutant levels, the use of biochars and other amendments, phytoremediation of contaminated soils, and the release of toxic elements such as mercury and thallium.

Metal mining activities have been major contributors of potentially toxic elements (PTEs) in the environment, leading to substantial soil pollution. One such example is lead–zinc mining around the world. Elevated concentrations of PTEs are commonly detected in nearby areas of both active and abandoned mines. This is primarily attributed to the release and dispersal of untreated waste materials from these mines into the surrounding environment. Mining-related soil pollution with PTEs can pose many different kinds of risks in a variety of contexts such as eco-toxicity, phytotoxicity, human health risk, as well as soil and water pollution. This review summarizes available data in the literature (2000–2023) on PTEs polluted soils originating from lead–zinc mining areas across the world. In this study, an attempt has been taken to evaluate the pollution level of PTEs in soils using collected data. The study shows the most polluted world regions are reported in Asia, followed by Europe and Africa, and only a few studies are reported in north, central and south America. The elements commonly analyzed in conjunction with Pb and Zn were Cd and Cu, whereas those responsible for increased pollution were Cd > As > Cu > Hg–Mn–Tl. Assessment of the pollution and health hazards has shifted to include a variety of quality indexes, including multivariate statistical analyses and microbial diversity.

Soil contamination through heavy metals (HMs) is a serious environmental problem that needs to be addressed. One of the methods of remediating soils contaminated with HMs and reducing the environmental risks associated with them is to immobilize these HMs in the soil using specific amendment(s). The use of biochar as an organic amendment can be an environmentally friendly and practically feasible option, as (i) different types of biomass can be used for biochar production, which contributes to environmental sustainability, and (ii) the functionality of biochar can be improved, enabling efficient immobilization of HMs. Effective use of biochar to immobilize HMs in soil often requires modification of pristine biochar. There are various physical, chemical, and biological methods for modifying biochar that can be used at different stages of pyrolysis, i.e., before pyrolysis, during pyrolysis, and after pyrolysis. Such methods are still being intensively developed by testing different modification approaches in single or hybrid systems and investigating their effects on the immobilization of HMs in the soil and on the properties of the remediated soil. In general, there is more information on biochar modification and its performance in HM immobilization with physical and chemical methods than with microbial methods. This review provides an overview of the main biochar modification strategies related to the pyrolysis process. In addition, recent advances in biochar modification using physical and chemical methods, biochar-based composites, and biochar modified with HM-tolerant microorganisms are presented, including the effects of these methods on biochar properties and the immobilization of HMs in soil. Since modified biochar can have some negative effects, these issues are also addressed. Finally, future directions for modified biochar research are suggested in terms of scope, scale, timeframe, and risk assessment. This review aims to popularize the in situ immobilization of HMs with modified biochar.

In many parts of the world, landfills are the primary method for disposal of municipal solid waste. Waste generation in cities of developing countries is increasing as a result of rapid urbanization, lifestyle changes, and demographic growth. Environmental pollution is getting worse due to the lack of development in implementing advanced waste management and disposal techniques, especially in developing countries such as Iran. Waste generation and disposal are major contributors to the presence of various types of pollutants in soil, such as potentially toxic elements and polycyclic aromatic hydrocarbons, as well as microplastics. It is critical to constantly monitor these pollutants since they are harmful to human health as well as the natural environment, including water, soil, plants, and animals. The primary goal of this study was to examine recent studies on soil contamination near landfills in Iran and comparable instances from other regions of the world. In addition, some potential future study directions have been presented in order to develop and establish sufficient monitoring of contaminants in soils around landfills.