Karel Němeček

Comparing Different Data Preprocessing Methods for Monitoring Soil Heavy Metals Based on Soil Spectral Features

Gholizadeh A., Borůvka L., Saberioon M.M., Kozak J., Vasat R., Němecek K. (2015): Comparing different data pre processing methods for monitoring soil heavy metals based on soil spectral features. Soil & Water Res., 10: 218–227. The lands near mining industries in the Czech Republic are subjected to soil pollution with heavy metals. Ex cessive heavy metal concentrations in soils not only dramatically impact the soil quality, but also due to their persistent nature and indefinite biological half-lives, potentially toxic metals can accumulate in the food chain and can eventually endanger human health. Monitoring and spatial information of these elements require a large number of samples and cumbersome and time-consuming laboratory measurements. A faster method has been developed based on a multivariate calibration procedure using support vector machine regression (SVMR) with cross-validation, to establish a relationship between reflectance spectra in the visible-near infrared (Vis-NIR) region and concentration of Mn, Cu, Cd, Zn, and Pb in soil . Spectral preprocessing methods, first and second derivatives (FD and SD), standard normal variate (SNV), multiplicative scatter correction (MSC), and continuum removal (CR) were employed after smoothing with Savitzky-Golay to improve the robustness and performance of the calibration models. According to the criteria of maximal coefficient of determination ( R 2 cv ) and minimal root mean square error of prediction in cross-validation ( RMSEP cv ), the SVMR algorithm with FD preprocessing was determined as the best method for predicting Cu, Mn, Pb, and Zn concentration, whereas the SVMR model with CR preprocessing was chosen as the final method for predicting Cd. Overall, this study indicated that the Vis-NIR reflectance spectroscopy technique combined with a continuously enriched soil spectral library as well as a suitable preprocessing method could be a nondestructive alternative for monitoring of the soil environment. The future possibilities of multivariate calibration and preprocessing with real-time remote sensing data have to be explored.

Isotopic Tracing of Thallium Contamination in Soils Affected by Emissions from Coal-Fired Power Plants

Here, for the first time, we report the thallium (Tl) isotope record in moderately contaminated soils with contrasting land management (forest and meadow soils), which have been affected by emissions from coal-fired power plants. Our findings clearly demonstrate that Tl of anthropogenic (high-temperature) origin with light isotope composition was deposited onto the studied soils, where heavier Tl (ε(205)Tl ∼ -1) naturally occurs. The results show a positive linear relationship (R(2) = 0.71) between 1/Tl and the isotope record, as determined for all the soils and bedrocks, also indicative of binary Tl mixing between two dominant reservoirs. We also identified significant Tl isotope variations within the products from coal combustion and thermo-desorption experiments with local Tl-rich coal pyrite. Bottom ash exhibited the heaviest Tl isotope composition (ε(205)Tl ∼ 0), followed by fly ash (ε(205)Tl between -2.5 and -2.8) and volatile Tl fractions (ε(205)Tl between -6.2 and -10.3), suggesting partial Tl isotope fractionations. Despite the evident role of soil processes in the isotope redistributions, we demonstrate that Tl contamination can be traced in soils and propose that the isotope data represent a possible tool to aid our understanding of postdepositional Tl dynamics in surface environments for the future.

Profile distribution and temporal changes of sulphate and nitrate contents and related soil properties under beech and spruce forests

The behaviour of principal inorganic anions in forest soils, originating mainly from acid deposition, strongly influences the forest ecosystem response on acidification. The aim of this study was to describe seasonal and temporal changes of sulphate and nitrate contents and related soil properties under beech and spruce forests in a region heavily impacted by acidification. The Jizera Mountains area (Czech Republic) was chosen as such a representative mountainous soil ecosystem. Soil samples were collected at monthly intervals from April to October during the years 2008-2010 under both beech and spruce stands. Soil samples were collected from surface fermentation (F) and humified (H) organic horizons, humic (A) organo-mineral horizons and subsurface mineral (B) horizons (cambic or spodic). A deionised water extract was applied to unsieved fresh samples and the content of anions in these extracts was determined by ion chromatography (IC). In the studied soil profiles, the lowest amount of SO(4)(2-) was found in the organo-mineral A horizons under both types of vegetation. Under spruce the highest amount of SO(4)(2-) was determined in mineral spodic (B) horizons, where a strong sorption influence of Fe and Al oxy-hydroxides is expected. Under beech the highest amount was observed in the surface organic F horizons (forest floor). The amount of NO(3)(-) is highest in the F horizons and decreases with increasing soil profile depth under both types of vegetation. A significantly higher amount of NO(3)(-) was determined in soils under the beech stand compared to spruce. For both soil environments - under beech and also spruce stands - we have determined a general increase of water-extractable SO(4)(2-) and NO(3)(-) during the whole monitoring period. The behaviour of SO(4)(2-) and NO(3)(-) in the soils is strongly related to the dynamics of soil organic matter and particularly to the DOC.

Using dye tracer for visualizing roots impact on soil structure and soil porous system

Abstract Plants influence the water regime in soil by both water uptake and an uneven distribution of water infiltration at the soil surface. The latter process is more poorly studied, but it is well known that roots modify soil structure by enhancing aggregation and biopore production. This study used a dye tracer to visualize the impact of plants on water flow in the topsoil of a Greyic Phaeozem. Brilliant blue was ponded to 10 cm height in a 1 m × 1 m frame in the field immediately after harvest of winter wheat (Triticum aestivum L.). After complete infiltration, the staining patterns within the vertical and horizontal field-scale sections were studied. In addition, soil thin sections were made and micromorphological images were used to study soil structure and dye distribution at the microscale. The field-scale sections clearly documented uneven dye penetration into the soil surface, which was influenced by plant presence and in some cases by mechanical compaction of the soil surface. The micromorphological images showed that root activities compress soil and increases the bulk density near the roots (which could be also result of root water uptake and consequent soil adhesion). On the other hand in few cases a preferential flow along the roots was observed.

The variations of aluminium species in mountainous forest soils and its implications to soil acidification

Aluminium (Al) speciation is a characteristic that can be used as a tool for describing the soil acidification process. The question that was answered is how tree species (beech vs spruce) and type of soil horizon affect Al speciation. Our hypotesis is that spruce and beech forest vegetation are able to modify the chemical characteristics of organic horizon, hence the content of Al species. Moreover, these characteristics are seasonally dependent. To answer these questions, a detailed chromatographic speciation of Al in forest soils under contrasting tree species was performed. The Jizera Mountains area (Czech Republic) was chosen as a representative mountainous soil ecosystem. A basic forestry survey was performed on the investigated area. Soil and precipitation samples (throughfall, stemflow) were collected under both beech and spruce stands at monthly intervals from April to November during the years 2008–2011. Total aluminium content and Al speciation, pH, and dissolved organic carbon were determined in aqueous soil extracts and in precipitation samples. We found that the most important factors affecting the chemistry of soils, hence content of the Al species, are soil horizons and vegetation cover. pH strongly affects the amount of Al species under both forests. Fermentation (F) and humified (H) organic horizons contain a higher content of water extractable Al and Al3+ compared to organo-mineral (A) and mineral horizons (B). With increasing soil profile depth, the amount of water extractable Al, Al3+ and moisture decreases. The prevailing water-extractable species of Al in all studied soils and profiles under both spruce and beech forests were organically bound monovalent Al species. Distinct seasonal variations in organic and mineral soil horizons were found under both spruce and beech forests. Maximum concentrations of water-extractable Al and Al3+ were determined in the summer, and the lowest in spring.

Behaviour of aluminium in forest soils with different lithology and herb vegetation cover

The aim of this study was to determine the content, distribution and behaviour of Al in soils under beech forest with different parent rock, and to assess the role of herbaceous vegetation on soil Al behaviour. We hypothesize that the contents of elements in the soil sorption complex (Al etc.) are strongly influenced by vegetation cover. Also, low molecular mass organic acids (LMMOA) can be considered as an indicator of soil organic matter (SOM) decomposition and vegetation litter turnover. Speciation of LMMOA, nutrition content (PO43-, Ca2+, K+) and element composition in aqueous extracts were determined by means of ion chromatography and inductively coupled plasma - optical emission spectrometry (ICP-OES) respectively. Active and exchangeable pH, sorption characteristics and exchangeable Al (Alex) were determined in BaCl2 extracts by ICP-OES. Elemental composition of parent rocks was assessed by means of X-ray fluorescence spectroscopy. Herb-poor localities showed lower pH, less nutrients (PO43-, Ca2+, K+), less LMMOA, a larger stock of SOM and greater cation exchange capacity. There was also lower mobilisation of Al in organic horizons, which explains the larger pools of Al. Generally, we can conclude that LMMOA, and thus soil vegetation cover, play an important role in the Al soil cycle.

Degradation of forest soils in the vicinity of an industrial zone.

Forest soils near industrial zones can be endangered by acid deposition and by dust deposition containing potentially toxic elements (PTEs). Soils of the study area are acidified and the surface enrichment with Cd, Cu, Pb, and Zn reflects anthropogenic contamination. Two forms of all PTEs were evaluated: potentially mobilized (2M nitric acid extraction) and mobile (0.01M CaCl 2 extraction) -the most toxic form. Negligible amounts of Cu and Pb were found in the mobile form. Pb mobilization is decreased by co-emitted bases and Cu mobilization is mainly controlled by soil reaction. These elements represent just a potential risk for the ecosystem. The mobile forms of Cd, Zn, and Mn account for approximately 30% of potentially mobilized forms in organic horizons. These elements could pose a problem to ecosystem vitality. Cd is toxic at small concentration and its content in mobilized form approaches the critical load. Cd can be considered the most dangerous element in the study area. Zn concentration is not reaching the limit value. Mobilization of Zn and Pb is mainly controlled by Ca and Mg content. The highest concentrations of Mn were found in the mineral horizons. It predicates a geogenic origin. The lowest percentage of the mobile form is in mineral horizon and its mobilization is controlled mainly by pH. Based on these results, a direct damage of forest by PTE contamination in the Silesian Beskids can be excluded. Lower contamination level along with acid condition and P deficiency could act as a permanent stress factor. Stressed forest is more predisposed e.g. to frost or insect damage.

The impact of the permanent grass cover or conventional tillage on hydraulic properties of Haplic Cambisol developed on paragneiss substrate

Abstract This study is focused on the comparison of soil structure and soil hydraulic properties of a Haplic Cambisol on paragneiss under two different land managements. Soil samples were taken from all diagnostic horizons (A, Bw and C) of the soil profile under the permanent grass cover (grassland) and under the conventional tillage (arable land). Basic soil properties were measured. Aggregate stability was assessed using the WSA index. Soil composition was evaluated using micromorphological images. Tension disk infiltrometers with two diameters of 2.22 and 10.25 cm (and applied pressure head of −2 cm) and Guelph permeameter were used to measure unsaturated and saturated hydraulic conductivities, respectively. Soil hydraulic properties were measured in the laboratory using the multistep outflow experiment, which was performed on the undisturbed 100 cm3 soil samples. Results showed that the unsaturated and saturated hydraulic conductivities measured in all horizons were lower at the arable land than conductivities at the grassland. The shapes of the soil water retention curves for A and Bw horizons were also different, indicating that soil below the grass contained larger fraction of the large capillary pores, which also corresponded to measured hydraulic conductivities and soil structure characteristics. Differences between both locations were caused by a negative impact of tillage (inflicting soil degradation) and positive influence of grass (increasing organic matter content and improving soil aggregation).