Diversity and negative effect of PM0.3-10.0 adsorbed by needles of urban trees in Irkutsk, Russia.

The study was performed in natural forests preserved within the Boreal zone city, Irkutsk, Russia. Test sites were selected in the forests in different districts of the city, where samples of Scots pine (Pinus sylvestris L.) and Siberian larch (Larix sibirica Ledeb.) needles were taken to study the adsorption on their surface of aerosol particles of different sizes, in microns: PM0.3, PM0.5, PM1, PM2.5, PM5, PM10. Scanning electron microscopy was used to obtain high-resolution photographs (magnification 800- × 2000, × 16,000) and aerosol particles (particulate matter-PM) were shown to be intensively adsorbed by the surface of needles, with both size and shape of the particles characterized by a wide variety. Pine needles can be covered with particles of solid aerosol by 50-75%, stomata are often completely blocked. Larch needles often show areas, which are completely covered with aerosol particles, there are often found stomata deformed by the penetration of PMx. X-ray spectral microanalysis showed differences in the chemical composition of adsorbed PMx, the particles can be metallic if metals predominate in their composition, carbonaceous-in case of carbon predominance-or polyelemental if the composition is complex and includes significant quantities of other elements besides metals and carbon (calcium, magnesium, potassium, sodium, sulfur, chlorine, fluorine). Since the particles contain a large proportion of technogenic pollutants, accumulation by the needles of some widespread pollutants was investigated. A direct correlation of a highly significant level between the concentration of PMx in the air and the accumulation of many heavy metals in pine and larch needles, as well as sulfur, fluorine, and chlorine, has been revealed, which indicates a high cleaning capacity of urban forests. At the same time, the negative impact of PMx particles on the vital status of trees is great, which shows in intense disturbance of the parameters of photosynthesis and transpiration, leading to a significant decrease in the growth characteristics of trees and reduction in the photosynthetic volume of the crowns. We consider that the results obtained are instrumental in developing an approach to improvement of urban forests status and creating a comfortable urban environment for the population.

Ecological condition of natural forests located within the territory of a large industrial center, Eastern Siberia, Russia.

Forest surveys were conducted in 2015-2018 on 12 sample plots (SPs), located in different districts of the city of Bratsk, a large industrial center of Eastern Siberia. The ecological state of natural forests preserved within the city's territory was estimated by a set parameters of pine (Pinus sylvestris L.) trees, understory vegetation, moss-and-lichen cover, and soil. Significant changes in the parameters caused by technogenic pollution and a high recreational load on the soil cover have been revealed. The high level of technogenic pollution of urban forests is evidenced by the accumulation of pollutants (sulfur, heavy metals, PAH) in the needles of pine trees and soil horizons, changes in the ratios of elements-pollutants and elements-nutrients in plants and soils, shift in the acid-base balance of the soil solution to alkalinity. A high recreational load on urban forest soils is indicated by many negative changes: a decrease in the thickness of the forest litter or its complete destruction; violation of the natural structure of the upper horizons due to increase in physical clay content, stony content, and anthropogenic inclusions; significant increase in soil density, and decrease in humidity, porosity, and aeration. The impact of a complex of negative factors also leads to a decrease in the species diversity of the understory vegetation, mosses, lichens, and an increase in the number of ruderal species in the herbaceous vegetation. The biggest negative changes in the parameters of forest ecosystems have been found in Tsentralny district of the city, located in close proximity (from 2 to 8 km) to a large aluminum smelter and timber industry complex. Less-pronounced negative changes in parameters were found in samples taken in the Padunsky district, located 25 km from the emission source, and the smallest changes in the parameters were found in Pravoberezhny district, 45 km away from the emission sources. The main recommendations for improving the condition of forests in all areas of the city are as follows: planning a road-path network, restoring the fertile soil layer, sodding open areas of soil with herbaceous vegetation, and selecting an assortment of trees and shrub plants that are resistant to industrial pollution and recreational stress.

Contamination of Scots pine forests with polycyclic aromatic hydrocarbons on the territory of industrial city of Siberia, Russia.

Anthropogenic contamination with polycyclic aromatic hydrocarbons (PAH) coming from a powerful aluminum smelter has been estimated by the accumulation of these substances (17 substances: phenanthrene, fluoranthene, pyrene, chrysene, acenaphthylene, acenaphthene, anthracene, fluorene, benz[а]anthracene, benz[b]fluoranthene, benz[k]fluoranthene, benz[а]pyrene, benz[е]pyrene, perylene, indeno[1,2,3-c,d]pyrene, benz[g,h,i]perylene, dibenz[a,h]anthracene) in needles of Scots pine (Pinus sylvestris L.) in the residential areas of Bratsk, East Siberia, Russia. It has been found that the total PAH amount reaches the maximum values (982 ng/g) in the needles of trees growing in a residential zone, remote from the smelter up to 10 km (Central Urban District), where more than half of the city's population lives. On the territory remote up to 25 km (Padunsky District), PAH needle levels decline, but are still 14.5-17.5 times higher than the background ones and at a distance of 45 km (Pravoberezhny District), they still exceed background levels (30 ng/g) by 4.7-8.1 times. Qualitative analysis of PAH showed the prevalence (up to 90% of the total amount) of 3-4 ring PAHs in pine needles on the entire studied territory. PAH concentrations increase when approaching the smelter with the highest values in the Central City District. Within the urban area, the content of PAHs with 5-6 rings (benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene (B[a]P), benz[a]anthracene, dibenz[a,h]anthracene, indeno[1,2,3-c,d]pyrene, benzo[g,h,i]perylene) is also significantly increased. In the Central District, needle concentration of B[a]P, which is a class 1 carcinogen, exceeds the background one by 22 times, the Padunsky District-by 7 times, and the Pravoberezhny District-by 3 times. In the territories of the Central Districts, needle level of perylene, which is a marker of territory pollution by aluminum smelter emissions, is 18 times, the Padunsky District-by 10 times, Pravoberezhny District-by 2.5-3 times higher than in the background, where the perylene level is below the detection limit (< 0.2 ng/g).

Pinus sylvestris as a bio-indicator of territory pollution from aluminum smelter emissions.

The study demonstrates the efficiency of using Pinus sylvestris L. as a bio-indicator of polluting substances that enter the environment with the emission of a large aluminum smelter. Recent research has demonstrated that pollution from aluminum smelter emissions covers a vast territory. The highest content of polluting elements is registered at a distance of 3 km from the smelter, with maximum concentrations found in the industrial zone (0.5 km from the smelter). The farther from the aluminum smelter, the lower the amount of polluting elements in the needles, although the F level still exceeds the background values at a distance of about 60 km from the source, the levels of Zn, Pb, and Cd up to 50 km, S up to 40 km, and Fe and Cu up to 35 km mostly in north-eastern and south-eastern directions correlating with prevailing atmospheric transfer of the emissions. Pollution with polycyclic aromatic hydrocarbons (PAHs) is also most expressed at a distance of 3 km from the smelter, then it gradually decreases to coincide with background concentrations at a distance of more than 60 km. This is confirmed by changes in overall PAH content and in qualitative and quantitative compositions of individual PAHs. The greatest number of components (17 substances) has been found in samples from the territory of the plant area: phenanthrene, fluoranthene, pyrene, chrysene, acenaphthylene, acenaphthene, anthracene, fluorene, benz[а]anthracene, benz[b]fluoranthene, benz[k]fluoranthene, benz[а]pyrene, benz[е]pyrene, perylene, indeno[1,2,3-c,d]pyrene, benz[g,h,i]perylene, and dibenz[a,h]anthracene. The farther away from the plant, the lower the number of components detected in PAH fraction, mainly due to the fact that the concentrations of most toxic PAHs with five or six aromatic rings (benz[b]fluoranthene, benz[k]fluoranthene, benz[а]pyrene, benz[е]pyrene, perylene, indeno[1,2,3-c,d]pyrene, benz[g,h,i]perylene, dibenz[a,h]anthracene) fall below the method detection limit. High concentrations of benz[а]pyrene and perylene in pine needles at the territories adjacent to the aluminum smelter confirm the technogenic character of forest pollution by PAHs.