Investigation of the Sorption of Heavy Metals by Terrestrial Ecosystems in Areas of the City of Chita with Various Anthropogenic Loads

Introduction. Environmental pollution with heavy metals is one of the most pressing environmental problems, as these substances can have a negative impact on ecosystems and living organisms. In particular, the accumulation of heavy metals in plants in urban ecosystems is an issue that has been widely studied, but many aspects of the problem remain unintelligible. For example, existing research does not always consider the influence of different environmental factors on metal sorption processes. This creates gaps in understanding the mechanisms of interaction between plants and pollutants. The current study aims to investigate the dependence of heavy metal sorption by the Scots pine (Pinus sylvestris) on the level of environmental pollution. The goal is to determine how metal accumulation indicators change depending on the growing conditions, allowing for a more accurate assessment of this plant's role in urban ecology.

Materials and Methods. The research was conducted in the city of Chita in the Trans-Baikal Territory. Scots pine is a widespread species of pine in this region, therefore, the bark of the Scots pine, as well as soil samples from sites in Chita that were exposed to high levels of human activity served as the basis for the study. Selection of sites was based, among other factors, on complex air pollution index (API5) in Chita. After collecting samples, they were quartered, dried, and ground into a fine powder. Then, the bark and soil were heated in a muffle furnace at 600°C. The burnt soil and pine bark ash were analyzed using methods commonly used in wood chemistry, including a spectrometric analysis on a Shimadzu AA-6200 atomic absorption spectrometer. The acidity was determined by the potentiometric method in a chloride extract. For this purpose, a 1M KCl solution (pH = 6.0) was used, as well as standard buffer solutions (pH 4.01; 6.86; 9.18) for instrument calibration. Suspensions were prepared by adding 75 ml of extractant to 30 g of soil, stirring for one minute. The pH was then measured after the readings stabilized. In parallel, a control experiment was conducted without a soil sample.

Results. Analysis of the data on seasonal changes in the ash and moisture content of Scots pine bark showed that they slightly increased in the summer and autumn months. During the study, we also obtained data on the distribution of heavy metals in the soil and bark of Scots pine depending on the season of the year. It was found that the highest levels of copper in the soil and bark of Scots pine were observed in Batareinaya Sopka, exceeding the maximum permissible concentration by 11 times, followed by Granitnaya Street, where the maximum permissible concentration was exceeded by 5 times. Zinc levels in the soil were high at three locations: Sosnovy Bor, Memory Park, and Batareinaya Sopka, exceeding the maximum permissible concentration by 1.77, 1.74 and 1.5 times, respectively. Lead levels were within the MPC at all seven locations. There were no seasonal changes in the content of heavy metals in the soil and bark. Thus, the study revealed the dependence of the content of heavy metals in the soil and bark of the Scots pine on the degree of anthropogenic load in the districts of Chita in the Trans-Baikal Territory.

Discussion. The results of the study demonstrated the correlation between the concentration of heavy metals in soil and bark samples of Scots pine and the degree of anthropogenic load. Therefore, the Scots pine can be considered a valuable object for monitoring heavy metal pollution, as it combines high sensitivity to man-made effects, resistance to adverse conditions and long-term ability to accumulate toxic substances. The data obtained support the idea of including the Scots pine in environmental monitoring systems, particularly in areas with developed industrial and transportation infrastructure. Future research could focus on developing standardized methods for using pine in bioindication, as well as studying its phytoremediation potential in conditions of chronic pollution.

Conclusion. The study expands our understanding of the mechanisms behind the migration and accumulation of heavy metals in urban ecosystems, especially in areas with a harsh continental climate. The findings can be used to improve urban planning, reduce the negative impact on public health, and develop sustainable strategies for areas with high levels of anthropogenic load.

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