Lipid profile of Siberian larch needles under chronic exposure to aluminum smelter emissions (Eastern Siberia, Russia).

The lipid composition of Larix sibirica needles, a key forest-forming species of boreal forests of Eastern Siberia (Irkutsk region, Russia), exposed to emissions from the Bratsk aluminum smelter, one of the world's largest aluminum producers, was studied. The production emissions of this smelter contain multiple pollutants, with fluoride compounds and polycyclic aromatic hydrocarbons (PAHs) demonstrating the highest phytotoxicity. Lipid profiles of needles were analyzed using thin-layer chromatography across a pollution gradient ranging from background to critical levels. The content of pollutant elements (F, S, metals and metalloids) in the needles was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES) and spectrophotometry. The oxidative stress markers (hydrogen peroxide and malonic dialdehyde (MDA) levels) were also measured using spectrophotometric methods. It was shown that unlimited input of pollutants initiates the development of oxidative stress in larch needles. This is evidenced by a 1.3-4.5 fold increase in H₂O₂ concentration in needles compared to background (unpolluted) tree-stands and a close positive relationship between these parameters (r = 0.69-0.87, P ≤ 0.05, n = 29). Analysis of the lipid profile of L. sibirica needles at different pollution levels revealed a significant effect of pollutant elements on the content of neutral (r = 0.0.87, (r = 0.79, P ≤ 0.05, n = 29) and polar lipids (r = 0.67, P ≤ 0.05, n = 29). In the fraction of neutral lipids, with an increase in the pollution level, the content of higher aliphatic alcohols increased by 2.6 times, hydrocarbons by 3.1 times, esters of sterols by 4.3 times, 1.3-diglycerides by10 times compared to background values. The content of sterols and wax, on the contrary, decreased by 1.6 times. In the polar lipid fraction at low, moderate, and high pollution levels the quantitative content of sphingolipids increased up to 7.3 times, glycolipids - up to 2.3 times, phospholipids - up to 1.9 times, at the critical level the content of all fractions decreased. The revealed changes in the quantitative and qualitative composition of total lipids in needles indicate an increase in membrane microviscosity and a decrease in fluidity at low, moderate and high pollution levels, due to which the flow of pollutants inside cells is reduced. At critical pollution levels, these mechanisms are significantly weakened. The results obtained, revealing the specific mechanism of physiological and biochemical adaptation of L. sibirica to industrial pollution, have important applied value for developing highly sensitive bioindicator methods based on lipid biomarkers; integrated assessment of forest ecosystems sustainability under technogenic impact, and modeling of long-term consequences of anthropogenic load on boreal forests - a key component of the global carbon cycle and a major reservoir of biological diversity.