Russian Journal of Applied Chemistry, 2013, Vol. 86, No. 4, pp. 510−514.
Pleiades Publishing, Ltd., 2013.
Original Russian Text © L.V. Nechaev, O.N. Chaikovskaya, I.V. Sokolova, A.V. Savel’eva, N.V. Yudina, E.V. Mal’tseva, 2013, published in Zhurnal Prikladnoi
Khimii, 2013, Vol. 86, No. 4, pp. 547−551.
AND INDUSTRIAL ORGANIC CHEMISTRY
Effect of Simulated Solar Radiation on the Interaction
of Humic Acids with Naphthalene
L. V. Nechaev, O. N. Chaikovskaya, I. V. Sokolova, A. V. Savel’eva,
N. V. Yudina, and E. V. Mal’tseva
Tomsk State University, Tomsk, Russia
Received January 14, 2013
Abstract—The equilibrium constants of binding of naphthalene with a series of humic acids were determined by
the ﬂ uorescence quenching method. The effect of irradiation on the extent of the interaction of naphthalene with
humic acids was examined. Based on the data obtained, preliminary conclusions on the structure of humic acids
of raised bog peat before and after modiﬁ cation were made.
Polycyclic aromatic hydrocarbons (PAHs) are or-
ganic substances whose molecules contain condensed
benzene rings. The best known PAHs are naphthalene,
phenanthrene, anthracene, pyrene, and benz[a]pyrene.
Many PAHs are extremely hazardous toxicants exhibiting
carcinogenic, mutagenic, and teratogenic properties .
Polycyclic aromatic hydrocarbons are released into
the environment on incomplete combustion of coal at
thermal power plants. Also, they are present in automobile
exhaust gases, are wastes from coal-tar chemical industry,
and are formed in incineration of industrial and house-
hold wastes. Because of low solubility in water, PAHs
are accumulated in bottom sediments and in tissues of
bottom-dwelling ﬁ shes .
Humic acids (HAs), a fraction of humus substances,
are natural macromolecules of irregular structure. Humic
acids are present in soils, peat, coal, and natural waters.
These substances are capable to bind heavy metal ions
and organic substances (e.g., herbicides) . Interaction
of HAs with PAHs strongly affects the bioaccumulation of
these toxicants with aquatic living bodies. Some authors
note decreased uptake of PAHs by ﬁ shes and Daphnia,
and also a decrease in the PAH toxicity for these animals
. The direct cause of the observed decrease in the effect
of PAHs in the presence of HAs is the interaction of the
toxicants with HAs, leading to the formation of PAH–HA
complexes. The molecular size of PAH–HA complexes
prevents their penetration into living bodies .
According to modern views, the interaction between
HA and PAH molecules is due to the overlap of the
π-electron systems of the aromatic rings in the structure
of these substances, with the formation of charge-transfer
complexes being also possible . The extent of bind-
ing of PAHs with HAs is the greater, the higher the PAH
Binding of PAHs with humic acids can signiﬁ cantly
alter their properties such as toxicity and capability for
photo- and biodegradation. The energy transfer between
aromatic fragments of HAs and organic molecules bonded
with them can favor photochemical conversion of the
latter molecules. Thus, studies on interaction of HAs
with PAHs will favor the development of processes for
removing these toxicants from natural systems.
The capability of HAs to bind PAHs and exert detoxi-
cating effect changes upon modiﬁ cation of their func-
tional composition and physicochemical properties. The
HA modiﬁ cation can be performed by mechanochemical
treatment of peat (source of HAs) and by irradiation.
This study was aimed to examine the spectral and
luminescence properties of naphthalene in the presence