Digging Deep: Emerging Contaminants in Soil

You might be forgiven for thinking soil is just dirt beneath our feet. Certainly, this writer vastly misjudged its importance to life as we know it.

It’s becoming increasingly obvious that soil could be the unsung hero of our planet, quietly working behind the scenes to keep everything in balance. Sure, it’s crucial for growing our food, but its role goes way beyond that.

Think of soil as one of Earth's most important life support systems. In addition to nurturing crops, soil does some heavy lifting in fighting climate change. It's like nature's sponge, soaking up carbon and helping to regulate our planet's temperature – it's a natural filter, purifying the water and air we depend on for our very existence.

And let's not forget about the bustling community of insects that call soil home. They're the ultimate recyclers, breaking down dead plants and organic matter, and keeping the whole ecosystem ticking. Even in our cities, soil plays a vital role – handling heavy rain, absorbing pollutants and even playing a part in mitigating the urban heat island effect. It's the foundation for our urban gardens, parks and playgrounds – the green spaces that make life in cities that little bit more bearable and greener. However, beneath the earth’s surface, there is a whole hidden world of growing threats to soil from emerging contaminants.

These contaminants, ranging from harmful collations of heavy metals and pesticide derivatives to pharmaceutical residues, biological pathogens and plastic waste, hold an alarming power when left unchecked, posing significant threats to environmental, animal and human wellbeing.

Human practices such as polluting industrial activities, agriculture and urbanization all contribute to ongoing environmental pollution. Their impact on soil not only compromises health, fertility and biodiversity but also has far-reaching implications for food safety and water quality.

Biological pathogens, including bacteria, viruses and parasites, introduced through improper waste disposal and agricultural runoff, are another source of worry. These can lead to the spread of many diseases and require thorough screening to ensure they do not compromise public health. Moreover, the relatively recent and pervasive presence of plastic waste, composed of non-biodegradable materials, further exacerbates environmental degradation.

Microplastics and nanoplastics infiltrate soil and water systems, posing threats to both terrestrial and aquatic ecosystems by entering the food chain ‒ endangering human health from the presence of pathogens carried on their surface. Addressing the multifaceted nature of contaminants is crucial for mitigating their detrimental effects and safeguarding the integrity of our environment and wellbeing now and for our future generations.

“Understanding what soil is comprised of can be extremely challenging,” said Dr. David Hackett, chair of the British Standards Institution’s AW/20 Soils Other Growing Media and Turf Committee. He elaborated on the implications of emerging contaminants in soil ecosystems, shedding light on their potential impacts and challenges in detection. “It's one thing to identify its components, but it's a whole new problem to comprehend their environmental impact. Organic chemicals, for instance, may break down into other harmful substances, making it crucial to assess their effects on the environment.”

So, what challenges do we face in addressing the long-term impacts of contaminants on soil health? And how can we develop effective solutions?

“With the rise of things like micro-, and now, nanoplastics being a relatively recent phenomenon, we're still learning about their long-term impacts after decades of use,” Hackett told Technology Networks. The difficulty lies in understanding the significance of soil contaminants but also in determining effective solutions, especially when they've become ubiquitous. The ultimate solution is stopping the production of contaminants. But addressing historic problems like “forever chemicals” will require a deeper understanding and robust approaches.”

Upon being questioned on the importance of examining the chemical contaminants themselves, Dr. Hackett continued, “We need to consider not just the chemical itself but also how it finds its way back to potentially impact human health. While we can observe its impact on the environment to some extent, understanding its route back to human consumption is crucial. The efficiency and likelihood of contaminants reaching humans are key considerations. This journey from soil to human consumption is dynamic and constantly changing, making it imperative to monitor and understand.”

Analytical conundrums

Understanding this comprehensive microbiome ecosystem cycle is crucial in safeguarding, not only the health of the animals and crops that we consume but also the health of wild species; there is a collective expert recognition that a diverse and resilient soil microbiome is essential for ecosystem health. So how can soil be monitored and studied?  It’s a task that’s challenged scientists for decades.

The complex nature of soil matrices, coupled with the diverse range of contaminants, makes detection and quantification tremendously complex. Traditional analytical methods often fall short in accurately assessing contaminant levels, necessitating the development of cutting-edge techniques.

“Current techniques for analyzing complex matrices like soil must meet rigorous standards before being utilized, especially in legal proceedings where transparency and reliability are paramount,” said Professor Lorna Dawson, head of the Centre for Forensic Soil Science at the James Hutton Institute. “Methodologies must undergo thorough testing, publication, and peer review to ensure their validity, credibility, accuracy and reliability, with rare exceptions only being made for intelligence purposes.”

“While cutting-edge analytical techniques, such as volatile organic compound analysis using gas chromatography-mass spectrometry, show promise in identifying suites of organic compounds to identify sources of decomposition, their reliability in court settings remains unproven,” Dawson warned.

Future directions

Efforts to remediate soil contamination issues are underway, with many countries across Europe making progress on soil remediation measures to more sustainable and regulated models for agricultural practices. These practices aim to provide fairness for farmers, while achieving high sustainability, meeting societal expectations and contributing to climate neutrality.

Looking ahead, innovation in soil analysis holds promise for enhancing our understanding of soil ecosystems and mitigating contamination risks. Innovative solutions such as customized soils and collaborative research endeavors will be instrumental in addressing the current and emerging challenges in both soil management and overall environmental conservation.

“We're witnessing a shift towards understanding the nature of new contaminants and their impacts.” noted Dr. Hackett when asked about the future of soils "The future lies in developing tools to identify these contaminants and determining their effects, whether harmful or not, to devise appropriate treatment methods. Additionally, soil analysis is expanding beyond agriculture to support urban life, such as in the cultivation of street trees and green roofs. From contaminated soil to the physical and chemical properties, comprehensive analysis is essential. Developing analytical tools and resources to assess soil quality and guide its utilization is key to the future of soil analysis."

Professor Dawson spoke on the current analytical limitations and what the future looks like from a technological point of view. “It all hinges on the seamless integration of these technologies, enabling precise decision-making in the field,” she said. “I’d love to imagine a future where physical, chemical and biological sensors work in tandem, allowing for comprehensive soil analysis at a glance. While this vision may seem ambitious, with continued innovation and collaboration, we can pave the way for a more sustainable and resilient future based on the best available evidence.”

Soil analysis: Earth's silent hero?

On reflection, it’s clear that soil analysis is very swiftly emerging as a silent hero in safeguarding environmental health and sustainability.

In 2024 and beyond, as we continue to navigate the complexities of soil management and environmental conservation, advocacy for continued collaboration and research efforts is paramount. It should remain a top priority to develop and implement rigorous standards and innovative solutions to address soil contamination issues effectively. Collaboration among scientists, policymakers and stakeholders is essential to ensure our remaining soil is protected. And, by investing in research, technology and sustainable practices, we can ensure a resilient and healthy soil ecosystem for the wellbeing of all life on Earth.

About the interviewees:

Dr. David Hackett BSc (Hons) MLD PhD MCIEEM CEnv, co-founder of Biora, is a distinguished expert in plant-soil relations and landscape architecture, boasting over three decades of experience in brownfield regeneration. He currently chairs the British Standards Institution’s AW/20 Soils, Other Growing Media and Turf Committee, where he leads efforts to establish industry standards. Dr. Hackett's visionary approach and unwavering commitment to sustainability have made him a prominent figure in the field, driving transformative change in landscape design and environmental conservation.

Prof. Lorna Dawson, CBE, is head of the Centre for Forensic Soil Science at the James Hutton Institute in Aberdeen and an Honorary Professor at RGU, Aberdeen. She is a registered expert with the National Crime Agency and has worked on over 100 forensic cases, presenting evidence in court for over 20 of these. She holds diplomas in civil and criminal law (Cardiff University, 2011, 2012, 2017 and University of Aberdeen, 2021) She is a Commissioner with the Food, Farming and Countryside (FFCC) and authored the RSA Scotland FFCC report (2019) and is co-chair of the devolved Scotland inquiry. She recently served on the Scottish Government Arable Climate Change Advisory Group (ACCG) and is on the scientific advisory panel for the Scottish Government’s Agriculture Reform Implementation Oversight Board (ARIOB). She is treasurer of the IUGS Initiative on Forensic Geology (IFG) and Chair of the Geological Society Forensic Geology Group (FGG) and an affiliate member of the Organisation of Scientific Area Committees (OSAC) for Forensic Science, USA. She was awarded a CBE in the late Queen’s birthday honors list, June 2018, for services to soil and forensic science and was made a Fellow of the Royal Society of Edinburgh (FRSE) in 2019 and awarded Soil Forensic Expert Witness of the Year in the Corporate INTL 2021 Global Awards.