Integrated monitoring of phytoremediation through analysis of biomass production and soil recovery on a contaminated site

The transition to a sustainable bio-economy faces a crucial challenge: obtaining raw materials without competing for arable land needed for food production. This problem is particularly urgent in Europe, where around 80% of the land is used for settlements, agricultural and forestry production, and infrastructure. Land scarcity requires innovative approaches to raw material cultivation. Contaminated soils, unsuitable for food crops, offer a promising alternative for industrial cultivation. However, the widespread adoption of industrial crops in these soils is limited by key challenges such as determining how contaminants affect plant growth and yield under stress conditions, as well as the dynamics of those contaminants.

This research addresses these challenges by monitoring, testing and optimizing phytoremediation strategies to improve soil health while producing bio-based products for the textile industry. The proposed approach is demonstrated in an experimental field trial at the former Nitrastur fertilizer plant (Asturias, Spain). For this study, we present an integrated monitoring framework that combines proximal and remote detection techniques with chemical analysis to assess soil contamination through vegetation response, using biomass production as a functional indicator of soil recovery.

Terrestrial Laser Scanning (TLS) was used to acquire high-density 3D point clouds, from which volumes were calculated to subsequently estimate the biomass of birch trees (Betula celtiberica) that were planted on the polluted soils twelve years ago. Structural parameters such as tree height, trunk diameter (using multiple geometric estimation methods) were extracted and indirect biomass measurements to characterize vegetation growth with different levels of soil contamination. Unmanned aerial vehicle (UAV) images also complemented TLS data by supporting plot delineation, site-scale visualization and spatial contextualization.

These structural observations were integrated with soil chemical analyses to quantify contamination levels, as well as spectral indices of vegetation and soil to assess soil health. This novel and integrated monitoring approach made it possible to assess the relationships between contamination levels and biomass production by providing key information on soil health status and its recovery process.

This work was funded by the European Union under the Horizon Europe program through the pHYBi project (Grant Agreement No. 101156439; CBE JU) and the INTERSOIL project (PID2023-147718NB-I00, AEI/Spain, FEDER/EU).