Composition and Genesis of Polyarenes in Soils of Various Aged Durnt Areas in the Baikal Nature Reserve

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Abstract

The article presents data on the content of eleven polycyclic aromatic hydrocarbons (PAHs) in soils under burnt areas of various ages, single and repeated, in the taiga landscapes of the middle mountains of the Khamar-Daban ridge. Morphological features of soils inherited from the fire were identified, such as: layers of coals (pyr), ashes (Cpyr), charred forest litter (Opyr) and pyrogenic humus horizon (Apyr). The post-fire variability of the soil cover, formed due to the presence of areas inside the burnt area with six degrees of burning of forest litter material, is characterised. A decrease in the content of PAHs has been shown with an increase in the intensity of the fire, as well as in the case of repeated fire on the already burnt area. Background soils have a higher content of PAHs compared to 42-year-old burnt areas and to areas of intense burning in one-year-old burnt areas. By factor analysis, four groups of PAHs were identified, differing in origin: polyarenes of pyrogenic autochthonous origin, formed in situ – naphthalene, tetraphene, pyrene, chrysene, anthracene, naphthalene, and to a lesser extent benzo(a)pyrene, and benzo(ghi)perylene; a group of polyarenes of pyrogenic allochthonous origin that accumulate in soils due to atmospheric transport of ash – benzo(a)pyrene and benzo(ghi)perylene; a group of polyarenes of biochemical origin – fluorene and biphenyl; polyarenes of biochemical and petrogenic origin, accumulating at the depth of the soil – phenanthrene.

About the authors

T. S. Koshovskii

Lomonosov Moscow State University

Author for correspondence.
Email: tkzv@ya.ru
Russian Federation, Moscow

A. N. Gennadiyev

Lomonosov Moscow State University

Email: tkzv@ya.ru
Russian Federation, Moscow

N. S. Gamova

Lomonosov Moscow State University; Baikalsky State Nature Biosphere Reserve

Email: tkzv@ya.ru
Russian Federation, Moscow; Tankhoy

References

Supplementary files

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1. JATS XML
2. Fig. 1. Map of factual material. 1 – location of soil catenas; 2 – points on the river terrace, 3 – soil sections, 4 – area of ​​the 2015 burnt area, 5 – streams and rivers.

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3. Fig. 2. Composition of polyarenes (a) and the sum of PAHs (b) in the background soil (P–0) and in soils of one-year-old burnt areas affected by a ground fire (P–1), crown fire accompanied by a ground fire of medium (P–2) and high (P–3) intensity on the terrace of the Levaya Mishikha River. The values ​​averaged over three measurements are shown for each depth. Polyarenes: Flu – fluorene, Dif – diphenyl, Naph – naphthalene, Phe – phenanthrene, Chr – chrysene, Pyr – pyrene, Ant – anthracene, Tet – tetraphene, BaP – benza(a)pyrene, BghiP – benzo(ghi)perylene, Per – perylene.

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4. Fig. 3. Associations of polyarenes (a) and the sum of PAHs (b) in burnt-out and background soils by depth. Averaged values ​​for all points of the catena are shown. Designation of plots: K-1974 – catena of the hill under the burnt-out area of ​​1974, K-74+15 – catena of the hill under the repeated burnt-out area of ​​1974 and 2015, K-2015 – catena of the hill under the burnt-out area of ​​2015. The designation of individual polyarenes is explained in the captions to Fig. 2.

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5. Fig. 4. Result of factor analysis: (a) – eigenvalues ​​of factors, (b) – factor loadings. PAHs with factor loadings over 0.7 are highlighted in darker color. The designation of individual polyarenes is explained in the captions to Fig. 2.

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6. Fig. 5. 1 – relief line (shown conditionally, out of scale), 2 – punch with diameter indicating factor value, shown at sample collection point taking into account position in catena and sampling depth, factor value is signed; 3 – location of sampling point in catena. Positions in catena: A – hilltop, B – upper part of slope; C – middle part of slope; D – foot.

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7. Fig. 6. Hypothetical scheme of changes in the content of PAH groups of different origin in the upper soil horizons before and after a fire; (a) – background autochthonous PAHs, (b) – allochthonous pyrogenic PAHs, (c) – autochthonous pyrogenic PAHs, (d) – total PAHs; the moment of the fire is shown in red on the time scale.

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