Soil pollution has emerged as a critical global issue, with more than 10 million contaminated sites worldwide. The scale of this problem is staggering, with approximately half of these sites tainted by heavy metals. The economic toll is equally alarming, with heavy metal pollution alone costing over 10 billion USD annually.
The situation is particularly dire in Europe, where soil pollution affects nearly 250,000 locations and shows signs of further increase.
The United States is not immune to this crisis. As of June 6, 2024, the National Priorities List, part of the EPA’s Superfund program , included 1,340 sites deemed the country’s most dangerous polluted areas. This program aims to clean up these hazardous locations, highlighting the urgent need for effective remediation strategies.
Professor Colin Hills from the University of Greenwich, an expert in Environment and Materials Engineering, explained that soil pollution has two main sources: natural processes and human activities. As Director of the Centre for Contaminated Land Remediation, he emphasized that both types can pose significant environmental risks.
Natural contaminants, including metallic, organic, or radio-isotopic substances, can result from geological processes over millennia. Anthropogenic contamination, caused by human industrial activities, can be equally harmful. The key concern, Hills notes, is whether these contaminants are mobile and have a defined pathway to a ‘receptor,’ such as humans.
Soil contamination as a disease trigger
The health impacts of soil contamination are severe and far-reaching. Chronic exposure to pollutants like lead, arsenic, or pesticides is linked to a range of health problems, including cancer and neurological disorders.
A study published in Science of The Total Environment revealed a correlation between high soil chromium levels and increased prevalence of Sjögren’s syndrome in Taiwan. Sjögren’s syndrome (SS) is a chronic autoimmune disease that results in dry eyes and dry mouth. However, this only scratches the surface of what living with Sjögren’s syndrome entails. Affecting millions worldwide, SS can also impact several other organs and systems.
In Europe, a study across nine countries showed that cadmium concentrations in soil often exceeded recommended values, with vegetarians showing 35 percent higher cadmium levels compared to non-vegetarians.
Vegetables such as carrots, potatoes, and onions can accumulate chromium from the soil. Although the study did not prove causation, the correlation between chromium levels and the prevalence of SS is significant.
The study included 11,220 patients diagnosed with Sjögren’s syndrome from 2000 to 2011. According to a study of the Changhua region, Taichung and Nantou have the highest prevalence of Sjögren’s disease—533 cases per 100,000 people. These regions had the highest concentrations of heavy metals. Therefore, according to the study, “chromium is probably a risk factor for Sjögren’s syndrome.”
To combat this global issue, various soil remediation technologies have been developed. These include physical remediation methods like thermal soil desorption and soil replacement, bioremediation techniques such as phytoremediation and microbial remediation, and chemical remediation approaches including chemical leaching, stabilization, permeable reactive barriers, and chemical oxidation/reduction.
Professor Hills highlighted several risk management tools for soil contamination. These include stabilization and solidification, which isolates contaminants in a rock-like product, and cover systems employing impermeable membranes over the contaminants. Other approaches involve chemical reagents, electrical currents, and the selective removal of contamination to landfill.
Iván Sánchez-Castro , researcher at the Estación Experimental del Zaidín (EEZ), which is part of the Spanish National Research Council (CSIC) in Granada, Spain, told IE that microorganisms can be used for our benefit (bioremediation). “It is not a simple matter as it requires a solid scientific basis and many field trials. With the recent creation of “living labs,” the field of bioremediation may experience a rapid and promising evolution in the coming years,” Sanchez-Castro said.
Climate change must be taken into consideration
Climate change adds another layer of complexity to soil remediation efforts. Professor Ravi Naidu , Director of the School of Environmental and Life Sciences, stressed the importance of adapting remediation techniques to climate change.
He explained that increasing temperatures could generate volatiles from organic contaminants, posing risks to humans, while changes in moisture could enhance leaching and plant availability of contaminants.
However, the question is how remediation methods can be adapted to different regions, considering that not all soils are the same and that climate change’s effects vary worldwide. “More often, consulting companies from the US and Europe sell their technologies to other countries- without even once letting people know that regional differences matter, and so one just can’t transfer technologies without some modifications- in short, the need is for innovation here,” Naidu concluded.
Threat to food security and environmental health
The impact of soil contamination on global food production cannot be overstated.
Approximately 78 percent of global per capita calorie consumption comes from crops grown directly in soil. The globalization of food production has further complicated the issue, with pollutants traveling through global trade routes and contaminating soils across continents. Life Cycle Assessment (LCA) has become crucial in understanding the full environmental impact of food production and consumption patterns.
Scott D. Warner , a Principal Hydrogeologist and Regional Leader for BBJ’s California and Western US business, emphasizes the importance of chemistry in soil remediation. He provides an example of reducing hexavalent chromium (Cr(VI)) to the less toxic trivalent chromium (Cr(III)) in soil and groundwater remediation.
Warner sees environmental professionals as “doctors of the earth,” highlighting the critical role they play in healing our planet.
Assessment of soil contamination through remote sensing
Innovative approaches are continually being developed to address soil pollution. Smart technology, such as sensors that measure soil nutrient levels, can optimize fertilizer use and reduce pollution.
Remote sensing technologies, including hyperspectral sensors, and high-resolution satellite imagery, are increasingly used to assess and monitor soil contamination over large areas.
Examples include GeoEye and Pleiades , which increase the spatial detail and precision of soil pollution assessment; hyperspectral sensors that facilitate the identification and characterization of contaminants in the soil; and, for example, LiDAR technology , which provides precise data on terrain elevation and vegetation structure. On the other hand, GIS and ground measurements are increasingly used to improve the assessment of soil pollution.
Organic compounds like PAHs and PCBs, as well as radioactive substances such as radium and uranium, contribute to soil pollution. Remote sensing and geospatial technologies, including gamma-ray spectrometry, enable large-scale monitoring of these contaminants, providing comprehensive overviews and identifying pollution hotspots.
The urgent need for global action on soil pollution
Despite the challenges, there is hope. Environmental protection regulations have increased their standards, although international homogenization is still needed. However, most new environmentally friendly soil remediation methods are still far from applicable in real scenarios, indicating the need for continued research and development.
The urgency of addressing soil pollution cannot be overstated.
Air, water, and soil pollution combined are responsible for at least 9 million deaths annually, with soil pollution alone contributing to over 500,000 premature deaths worldwide. These sobering statistics serve as a powerful call to action. As we continue to develop and implement remediation strategies, it’s crucial to consider regional differences, climate change impacts, and the global nature of our food systems.
The clock is ticking, but with concerted effort and innovative solutions, we can work towards a cleaner, healthier future for our planet and its inhabitants.
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