Hyperspectral Monitoring of Pesticide Effects on Scots Pine (Pinus sylvestris L.) Seedlings Irrigated with Model Coal Mine Wastewater

The treatment of coal mine wastewater, as well as the reclamation of depleted coal mines, are serious environmental problems. One of the ways to solve them is phytoremediation using stress-resilient plants such as the common pine (Pinus sylvestris L.). To mitigate the risk of epiphytotics during mass cultivation, treatments with chemical pesticides are necessary. It is important to make sure that the pesticides do not harm plants when using coal mine wastewater containing heavy metals for irrigation. In this regard, mass monitoring of plants by non-invasive methods is highly relevant. In this work, we used direct measurement methods and a non-invasive approach based on hyperspectral imaging to comprehensively monitor the condition of pine seedlings treated with the Actara™ and Previcur Energy™ pesticides in different concentrations (single, double, and quadruple compared to the concentration recommended by the manufacturer) and irrigated with the solutions of mineral salts simulating the wastewater from coal mines. It is shown that, despite some methodological difficulties, it is possible to use hyperspectral images for non-invasive remote monitoring of the condition of coniferous seedlings in vegetation experiments, including in the field. It was found that the pesticide treatments exerted neither acute toxicity nor a pronounced negative effect on the growth rate and pigment composition of the pine seedlings during the two-month observation. At the same time, irrigation of these plants with model Coal mine wastewater also did not produce synergistic toxic effects. Thus, there are no obvious obstacles to the use of the above-mentioned pesticides for treatment of Scots pine seedlings irrigated with Coal mine wastewater containing Fe, Zn, and Mn. The results obtained also support the use of wastewater rich in mineral nutrition elements but lacking highly toxic heavy metals (such as Pb and Cd), when growing plants for phytoremediation of soils from depleted coal mines. However, long-term, preferably multi-year studies are needed to assess long-term risks.