In a groundbreaking study, an international team of scientists has shed light on the presence of toxic metals in mineral phosphate fertilizers worldwide, raising concerns about their potential impact on soil, water resources, and the global food supply. Led by Avner Vengosh, chair of the Earth and Climate Sciences division at Duke University's Nicholas School of the Environment, the research team developed a novel method to identify the sources and impacts of these contaminants.
Mineral phosphate fertilizers play a crucial role in boosting sustainable crop yields and ensuring food security worldwide. However, the study revealed that many of these fertilizers contain high levels of toxic metals, including cadmium, uranium, arsenic, vanadium, and chromium. To uncover the extent of this contamination, the researchers employed a new tool based on strontium isotopes, which act as a unique "fingerprint" to trace the origin of the fertilizers.
Robert Hill, the study's lead author and a PhD student at Duke University, explained the methodology: "We measured strontium isotopes in both phosphate rocks and fertilizers generated from those rocks to show how fertilizers' isotope 'fingerprint' matches their original source." By analyzing the unique mix of strontium isotopes in each fertilizer, the researchers were able to match them with the phosphate rocks from which they were sourced.
The study examined 76 phosphate rocks, the primary source of phosphate fertilizers, and 40 fertilizers from major phosphate rock-producing regions, including the western United States, China, India, North Africa, and the Middle East. Samples were collected from mines, commercial sources, and an experimental field in North Carolina. The findings, published on May 9, 2024, in Environmental Science & Technology Letters, demonstrate that strontium isotopes are a reliable indicator of trace elements in fertilizers worldwide.
The concentrations of toxic metals varied among the fertilizers studied, with higher levels observed in those from the United States and the Middle East compared to those from China and India. Consequently, the researchers conclude that fertilizers from the U.S. and the Middle East are likely to have a greater impact on soil quality due to their higher concentrations of uranium, cadmium, and chromium. In contrast, fertilizers from China and India exhibited higher concentrations of arsenic.
Vengosh emphasized the significance of strontium isotopes as a tool for identifying environmental contamination, stating, "Strontium isotopes essentially are a 'fingerprint' that can reveal contamination in groundwater and soil worldwide." His research team has previously used this method to trace contamination from various sources, including landfill leaching, coal mining, coal ash, fracking fluids, and groundwater extracted alongside oil and natural gas.
The study's findings underscore the importance of monitoring and regulating the toxic metal content in mineral phosphate fertilizers to protect soil quality, water resources, and the safety of the global food supply. Without the use of strontium isotopes as a tracing tool, identifying, containing, and remediating fertilizer-linked contamination would prove challenging.
As the world continues to rely on mineral phosphate fertilizers to support sustainable agriculture and food security, it is crucial to address the potential environmental and health risks associated with toxic metal contamination. This groundbreaking study provides a valuable tool for assessing the impact of fertilizers worldwide and highlights the need for further research and regulatory action to ensure the safety and sustainability of global agricultural practices.
