Gholizadeh A., Borůvka L., Saberioon M.M., Kozák J., Vašát R., Němeček K. (2015): Comparing different data preprocessing 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. Excessive 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.
The detection of a nonequilibrium water flow and solute transport in structured soil at various scales is essential for better understanding of these phenomena. This study focused on the visualization of preferential flow in a Haplic Luvisol and Haplic Cambisol and their horizons by performing field ponding dye infiltration experiments. In addition, thin soil sections were made and micromorphological images were used to study soil aggregate structure and dye distribution at the microscale. The staining patterns within the vertical and horizontal field‐scale sections documented the different nature of preferential flow in different soil types and also within the soil profiles. While preferential flow in the Haplic Luvisol was caused by soil aggregation and biopores, preferential flow in the Haplic Cambisol was caused only by biopores, large soil fractures, and incorporated straw material. Micromorphological images showed that, in the case of the Haplic Luvisol, the dye was primarily distributed either in the interaggregate pores and then in the pores inside the aggregates or in the isolated large pores connected to the dye source and then into the matrix pores. The dye distribution in the soil matrix was uneven as well. Accumulated organic matter, clay coating, and isolated larger capillary pores, which initially did not contain the dye tracer, behaved as less‐permeable or impermeable barriers. Uneven distribution was caused by hierarchical pore size distribution of the soil matrix. Results indicated a multimodal character of preferential flow in this soil. In the case of the Haplic Cambisol, the dye pattern studied at the microscale was mostly affected by fractures and the size and shape of mineral grains.
Alterations in blood and tissue concentrations of trace elements in patients with chronic renal failure have been extensively investigated. Selenium, zinc and copper are elements which play an important role in biological systems as components of proteins, enzymes and antioxidants. The concentrations of selenium, zinc and copper were determined in the plasma, erythrocytes and whole blood of patients on regular hemodialysis (HD) and continuous ambulatory peritoneal dialysis (CAPD) treatment using the method of inductively coupled plasma mass spectrometry (ICP-MS). Analysis of isotopes 77Se, 66Zn and 65Cu was performed. Methodology presents the major limitation to valid studies on trace element levels in biological materials. One of the widely used contemporary techniques is ICP-MS. It is the most sensitive one and has a high dynamic range. The selenium concentration in the studied compartments (plasma 46.1 ± 3.0 vs. 78.0 ± 3.4 μg/l, p < 0.001; erythrocytes 90.4 ± 6.5 vs. 134.2 ± 7.6 μg/l, p < 0.01; whole blood 67.3 ± 3.1 vs. 106.4 ± 3.4 μg/l, p < 0.001) was significantly lower in HD patients compared to healthy controls. The same result was observed in plasma (63.2 ± 5.8 vs. 78.0 ± 3.4 μg/l, p < 0.05) and whole blood (82.7 ± 7.4 vs. 106.4 ± 3.4 μg/l, p < 0.01) from CAPD patients, but the selenium level of erythrocytes in CAPD patients was the same as in the control group (126.0 ± 8.8 vs. 134.2 ± 7.6 μg/l). The cooper content of erythrocytes was lower in HD patients than in controls (0.55 ± 0.02 vs. 0.66 ± 0.01 mg/l, p < 0.01) and CAPD groups (0.55 ± 0.02 vs. 0.68 ± 0.02 mg/l, p < 0.001). There were no differences in copper content in plasma (HD 1.02 ± 0.06; CAPD 1.11 ± 0.09; controls 1.02 ± 0.05 mg/l) and whole blood (HD 0.87 ± 0.04; CAPD 0.90 ± 0.05; controls 0.85 ± 0.02 mg/l) in HD and CAPD patients and healthy controls. The zinc concentration was increased in the whole blood of CAPD patients (6.68 ± 0.36 vs. 5.52 ± 0.11 mg/l, p < 0.001) and erythrocytes of HD (12.30 ± 0.23 vs. 10.11 ± 0.42 mg/l, p < 0.001), and CAPD groups (13.71 ± 0.56 vs. 10.11 ± 0.42 mg/l, p < 0.001) compared to controls. However, the plasma zinc concentration was lower in HD patients compared to blood donors (0.69 ± 0.03 vs. 0.92 ± 0.03 mg/l, p < 0.001) and CAPD patients (0.69 ± 0.03 vs. 0.95 ± 0.04 mg/l, p < 0.001). We did not find a significant increase in trace elements in whole blood after HD. These results suggest differences between plasma, erythrocytes and whole blood concentrations of the studied trace elements. The levels of trace elements are altered by HD and CAPD. A modern precise method with high accuracy, ICP-MS, which was used in our study, eliminated analytical errors and possible interferences.
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