A research team has identified the metal–oxygen (Me–O) bond length of hydrated cations as a promising indicator of how readily trace elements are absorbed and transported by plants. Across perennial ryegrass, New Zealand pasture species, and Indonesian oil palm, longer Me–O distances generally corresponded to higher plant-to-soil bioaccumulation coefficients, except among lanthanides. The relationship was more consistent than those based on ionic potential or hydrated radius. This simple chemical metric could help researchers predict trace-element movement through soil–plant systems, improve contamination risk assessments, and reduce reliance on costly and time-consuming experiments.
Trace-element contamination threatens agricultural productivity, food quality, and human health because potentially harmful elements can move from soil into crops and ultimately enter the food chain. Researchers commonly evaluate this movement using bioaccumulation coefficients, but these values can differ by several orders of magnitude among soils, climates, plant species, and elements. Models based on soil pH, organic matter, metal oxides, redox conditions, distribution coefficients, and other variables therefore require extensive site-specific measurements. Emerging contaminants associated with modern technologies, including gallium, indium, and lithium, are also comparatively understudied. Consequently, a broadly applicable chemical property that predicts plant uptake across diverse environments is needed.
A study (DOI: 10.48130/newcontam-0026-0014 ) published in New Contaminants on 17 May 2026 by Hayley Jensen's team, Bioeconomy Science Institute–Manaaki Whenua Landcare Research, reports that Me–O bond length was positively and significantly associated with trace-element bioaccumulation across three plant–soil datasets after lanthanide outliers were excluded.
The researchers evaluated three chemical descriptors: Me–O bond length, ionic potential, and hydrated radius. They tested their relationships with plant uptake using three datasets representing contrasting species and environments. The first came from a greenhouse experiment in Christchurch, New Zealand, where perennial ryegrass was grown in a loamy-sand Fluvial Recent Soil. The second included paired soil and pasture samples collected from 39 sites across New Zealand, encompassing Brown, Gley, Recent, and Semiarid soils. The third comprised soil and oil-palm leaf samples from four current, abandoned, or former plantations on Acrisol soils in Sumatra, Indonesia. Soil samples were dried, ground, and sieved, while plant material was washed where appropriate and dried. Samples were digested using nitric acid or aqua regia, and trace-element concentrations were measured through inductively coupled plasma mass spectrometry, inductively coupled plasma optical emission spectrometry, or microwave plasma atomic emission spectrometry. The team calculated each bioaccumulation coefficient by dividing the concentration of an element in above-ground plant biomass by its pseudo-total soil concentration. Chemical-property values were compiled from published sources, and regression analyses were used to test their relationships with bioaccumulation. Me–O distance was positively correlated with bioaccumulation in all three datasets for non-lanthanide elements, with coefficients of determination for fitted relationships ranging from approximately 0.29 to 0.84. Ionic potential was inversely correlated with bioaccumulation but was statistically significant in only two datasets. Hydrated radius was also negatively correlated with uptake—contrary to the researchers' initial hypothesis—but missing values for numerous elements substantially limited its usefulness. Lanthanides behaved differently: despite their long Me–O distances, their uptake remained low and generally decreased as Me–O distance increased. The researchers therefore treated lanthanides as outliers and recommended that future models either assess them separately or include a wider range of large ions.
Overall, the findings show that a fundamental property of hydrated ions may offer a practical shortcut for estimating trace-element mobility and plant uptake. Incorporating Me–O distance into empirical or mechanistic models could reduce the need to measure variables such as distribution coefficients, root surface area, water flux, soil pH, and cation-exchange capacity in every system.
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References
DOI
Original Source URL
https://doi.org/10.48130/newcontam-0026-0014
Funding information
This work was carried out through funding from a University of Canterbury Doctoral Scholarship.
About New Contaminants
New Contaminants (e-ISSN 3069-7603) is a multidisciplinary platform for communicating advances in fundamental and applied research on emerging contaminants. It is dedicated to serving as an innovative, efficient and professional platform for researchers in the field of new contaminants research around the world to deliver findings from this rapidly expanding field of science.
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Simple metrics for complex systems: the Me–O distance in hydrated cations is a potential new metric for predicting element uptake by plants
17-May-2026
The authors declare that they have no competing interests.