The novel approach to the biomonitor survey using one- and two-dimensional Kohonen networks

To compare the applicability of the leaves of horse chestnut (Aesculus hippocastanum) and linden (Tilia spp.) as biomonitors of trace element concentrations, a coupled approach of one-and two-dimensional Kohonen networks was applied for the first time. The self-organizing networks (SONs) and the self-organizing maps (SOMs) were applied on the database obtained for the element accumulation (Cr, Fe, Ni, Cu, Zn, Pb, V, As, Cd) and the SOM for the Pb isotopes in the leaves for a multiyear period (2002-2006). A. hippocastanum seems to be a more appropriate biomonitor since it showed more consistent results in the analysis of trace elements and Pb isotopes. The SOM proved to be a suitable and sensitive tool for assessing differences in trace element concentrations and for the Pb isotopic composition in leaves of different species. In addition, the SON provided more clear data on seasonal and temporal accumulation of trace elements in the leaves and could be recommended complementary to the SOM analysis of trace elements in biomonitoring studies

Lead spatio-temporal pattern identification in urban microenvironments using moss bags and the Kohonen self-organizing maps

The first investigation of the use of the Kohonen self-organizing map (SOM) which includes lead concentration and its isotopic composition in moss bags to assess the spatial and temporal patterns of lead in the urban microenvironments is presented in this paper. The moss bags experiment was carried out during 2011 in the city tunnel in Belgrade, as well as in street canyons at different heights (4, 8 and 16 m) and in public garages. The moss bags were exposed for 5 and 10 weeks. The results revealed that the 10 weeks period represents suitable exposure time in screening Pb isotopic composition in active biomonitoring analysis. The obtained results showed that the SOM analysis, by recognizing slight differences among moss samples regarding exposure time, horizontal and vertical spatial distribution, with both, contribution of stable lead isotopes and Pb concentration, could be recommended in biomonitoring analysis of lead distribution in urban microenvironments

Lead isotopic composition in tree leaves as tracers of lead in an urban environment

Biomonitoring has been frequently used as a tool for assessing anthropogenic influences on the environment, and trees have been recognized as efficient ecological indicators of urban air quality. Variations of stable lead isotopic ratios have been suggested as a suitable method for the Pb source identification. Substantial methodological points are yet to be resolved regarding isotopic signatures in environmental studies, and especially within plant biomonitoring. This study has been focused on an assessment of stable lead isotopic ratios (Pb-206/Pb-207 and Pb-208/Pb-207)) for some common urban deciduous tree leaves (Aesculus hippocastanum, Tilia cordata, Acer platanoides and Betula pendula). The study was done in 2009, at the time when the leaded gasoline was still in use in Serbia, although during a time span when an increasing number of vehicles, using non-leaded gasoline, was evident. Thus, a decrease of the Pb emitted from leaded gasoline affected the atmospheric Pb concentrations. The measurements of the Pb isotopes were performed by ICP-MS on both, unwashed samples, and those shortly washed in bidistilled. The percentage of lead removed by applied rinsing was approximately the same in the first three above mentioned species (approximate to 30%), while the exception was B. pendula (22%), indicating the highest retention for fine and coarse particulates due to thick epicuticular wax layer. It may be suggested that leaf washing is useful approach when the aim is an assessment of the isotopic composition in leaves after a certain period of exposure, assuming contribution of possible sources. However, in case of screening for possible sources in particular time sequence, leaves may remain unwashed. The obtained isotopic composition in leaf samples partially corresponded to that used in the lead additive in gasoline, implying also an influence of other Pb sources. The results imply that, among the investigated tree species, B. pendula could be the most efficient indicator in multiple Pb source identification. From the obtained Pb isotopic ratios, A. hippocastanum was confirmed as an appropriate biomonitor for the Pb atmospheric pollution, as previously shown from the Pb leaf concentration analyses

Leaves of common urban tree species (Aesculus hippocastanum, Acer platanoides, Betula pendula and Tilia cordata) as a measure of particle and particle-bound pollution: a 4-year study

Magnetic biomonitoring using tree leaves has been proven as a proxy for airborne particle matter (PM) pollution. Since the leaf entrapment of PM is species-specific, in this study, four tree species common in urban areas of Europe and wider (Aesculus hippocastanum, Acer platanoides, Betula pendula and Tilia cordata) were investigated to evaluate which biomonitor enables consistent 'signal' to particle and particle-bound toxic elements. The tree leaves were sampled in the central urban and suburban parks in Belgrade (Serbia) in May and September from 2011 until 2014. Magnetic PM fractions in the samples were quantified by saturation isothermal remanent magnetization (SIRM) while the concentrations of Al, Cr, Cu, Fe, Ni, Pb and Zn were determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Magnetic and elemental measurements were considered in relation to regulatory PM10 data. Median leaf SIRM values of T. cordata, A. hippocastanum and A. platanoides (174, 140 and 123 x 10(-5) x A m(2) kg(-1), respectively) implied the considerable magnetic enhancement contrary to B. pendula (68 x 10(-5) x A m(2) kg(-1)). However, B. pendula leaves showed the significant correlation between SIRM and PM10 values (r = 0.75) and SIRM and element concentrations and significant spatio-temporal differences in SIRM/element content between the studied parks/years. These results recommend B. pendula as a valuable biomonitor of PM and the associated elements. Nevertheless, both the results (high SIRM values, the significant correlation between SIRM and PM10-r = 0.71) and literature findings (abundance, adaptability, PM removal efficiency) favour A. platanoides over B. pendula in magnetic particle biomonitoring

Silver film on nanocrystalline TiO2 support: Photocatalytic and antimicrobial ability

Nanocrystalline TiO2 films were prepared on glass slides by the dip coating technique using colloidal solutions consisting of 4.5 nm particles as a precursor. Photoirradiation of nanocrystalline TiO2 film modified with alanine that covalently binds to the surface of TiO2 and at the same time chelate silver ions induced formation of metallic silver film. Optical and morphological properties of thin silver films on nanocrystalline TiO2 support were studied by absorption spectroscopy and atomic force microscopy. Improvement of photocatalytic performance of nanocrystalline TiO2 films after deposition of silver was observed in degradation reaction of crystal violet. Antimicrobial ability of deposited silver films on nanocrystalline TiO2 support was tested in dark as a function of time against Escherichia coli, Staphylococcus aureus, and Candida albicans. The silver films ensured maximum cells reduction of both bacteria, while the fungi reduction reached satisfactory 98.45% after 24 h of contact