**2. Material and methods**

Two levels of soil limit values were proposed for the Czech legislation, so-called prevention and indication limit. Their general characterisation is as follows:

Prevention limit was derived from the background values of REs and POPs in Czech agricul‐ tural soils when real data were calculated. The indication limits reflect two kinds of the risks. The first one is focused on increased REs transfer from soil into agricultural plants (POPs transfer was not calculated). The second one calculates direct impact on human health via their inhalation, dermal or oral intake on contaminated land for selected POPs and REs.

#### **2.1. The prevention limits of RE and POPs**

The prevention limit was derived from background values of RE and POPs in Czech agricul‐ tural soils proposed by [4] and [5]. REs background values are depending strongly on geochemical properties of the soil substrates and were proposed for 13 soil-lithological groups originally. The reduction into two groups was realised for pragmatic reasons. The background values are not valid for geochemically anomalous soils (mafic rocks, metallogenic zones of acid rocks, etc.). The RE background values were calculated for pseudototal REs contents (Aqua regia extract, ČSN EN 13346 [17]) finally.

The POPs background values were calculated by [5]. The research of 560 soil samples of agricultural soils from the area of the Czech Republic was utilised. The background values were statistically calculated as two multiples of the standard deviation of geometric means or 90% percentiles—GM.GD<sup>2</sup> ) for both groups (RE and POPs). The background values were set for every individual substance of observed POPs groups. Clearly, the simplification of limit values for legislative process was necessary in result of which summary limits were calculated for some POPs groups.

The sum of PAHs—calculated as the sum of 12 substances concentration (anthracene, ben‐ zo(a)anthracene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, ben‐ zo(ghi)perylene, phenanthrene, fluoranthene, chrysene, indeno(1,2,3-cd)pyrene, naphthalene, pyrene).

The polychlorinated hydrocarbons—limits for sum of seven indication congeners of poly‐ chlorinated biphenyls—PCB7 (28 + 52 + 101 + 118 + 138 + 153 + 180) and sum of DDTs (DDT, DDE, and DDD).

The hexachlorbenzene and hexachlorcyclohexane ((Σ α + β + γ) and polychlorinated dibenzop-dioxines and dibenzofurans (PCDDs/Fs) should be analysed only in the case of suspicion of their contents in soil.

The background value of PCCDs/Fs was calculated separately because of different collection of soil samples. The used statistic was identical and 102 soil samples taken in the areas of the Czech Republic with different source of the load [18] were taken into account. The value of International Toxic Equivalent (I-TEQ PCCDs/Fs) of 17 toxic congeners was calculated [19].

#### **2.2. The indication limit values of food chain contamination and plant growth inhibition**

The separation on phytotoxic and zootoxic REs should be accepted. The limits for plant growth inhibition were proposed for this reason. The limits for food chain contamination regulate the transfer of zootoxic elements from the soil into plant production. The limits were supported by the research of RE transfer from the soil into selected plants (triticale, radish) in experimental conditions and into fodder plants (clover, alfalfa, and grass species) in field conditions [20– 23]) and the dependency of REs mobile contents and selected soil conditions (pH, Cox, soil texture) was evaluated by multidimensional statistical methods (factor analysis). The com‐ parison of the selected RE total contents (As, Cd, Cu, Hg, Ni, Pb, Th, Zn) and the content in the extract of 1 mol/L NH4NO3 (As, Cd, Cu, Ni, Pb, Th, Zn) characterised as RE mobile fraction (ISO DIS 19730 [24]) was the principle of RE indication values assessment. The limit values were referred to RE critical values in eatable and fodder plants (the Decree No. 305/2004 Coll. [25]). The other legislative norms for plant contamination (European legislation) are shown in our practical study focused on the husbandry in fluvial zones.

#### **2.3. The indication limit values of human health protection**

The limit values were derived from the direct risk of increased POPs and RE (As, Cd, Hg, and Pb) contents on human health by their inhalation, dermal, and oral intake on contaminated fields. The calculation corresponds with the US EPA methodology (US EPA 2002) and respects the toxicity of the selected substances or elements and the movement duration of farmers on the contaminated land (standard exposition scenario was applied). It is also supported by the experience following from the activities provided in Czech conditions [26].

#### **2.4. The case study of human health risks assessment from soil pollution in flood affected areas in the Czech Republic**

The evaluation of health risk was realised and verified in the research project focused on soil contamination of flood affected areas in the Czech Republic. The human health risk assessment is becoming relevant when the -proposed indication limit values are exceeded, because they are derived as "effect based" for worst-case scenario. The screening evaluation of exposition by Soil Screening Level (SSL) method was applied (see 3.3 of the chapter). The calculation approach is based on the application of exposition models of chemical substances inputs into human bodies followed by the comparison of this predicted chronical dose with referenced "effect-based" dose. This approach allows to assign individual exposition parameters to every locality and then calculate site-specific SSL values and risks following from the exposition. The calculation of human risk (RISKHUMAN) has been done for individual chemical substances first and there has been calculated total sum of all evaluated substances including the calculation of percentage of individual substances contributions to total sum. The RISKHUMAN values should not be higher than 1. The values higher than 2 indicate the possible risk and in the dependency on detail evaluation of exposition scenarios up to significant. The other cases can be evaluated as non-significant considering selected exposition scenario.

The next step for the evaluation of contamination level in floodplain soils was a rigorous statistical evaluation of the results. The dataset for soil contamination of 100 floodplain soils in the Czech Republic was used to estimate the human health risks by presented methodology (Equations 1–3).1 Relative contributions of each risky element/substance to an overall hazard index (RISKHUMAN) were calculated. A matrix transformation of relative contribution of each analyte to total RISKHUMAN on each locality was undertaken before the statistical analysis. The similarity of the soil pollution profiles in individual floodplain samples was assessed by a hierarchical cluster analysis using the average linkage clustering. The results of hierarchical cluster analyses are presented using technique of heatmap, where the similarity among the objects in a cluster dendrogram is visualised by the colour intensity in a square matrix of coloured pixels (R Core Team, Library Gplot).

<sup>1</sup> There were sampled 100 floodplain soils in various catchments of the Czech Republic. For each sampling site, a mixed sample consisting of 10 individual samples from the area of 100 × 100 m was used. Samples are separated and homogenised by quartation. The sample depth was 0–10 cm for pastures and 0–30 cm for arable land. In the soil samples there was analysed a wide range of risky substances including seven indicator PCBs (28, 52, 101, 118, 138, 153, 180), 7 risky elements (As, Cd, Cu, Hg, Ni, Pb, and Zn), polycyclic aromatic hydrocarbons (29 PAHs compounds), and pesticides (DDT and metabolites; hexachlorcyclohexane isomers, HCHs; pentachlorbenzene, PeCB; hexachlorbenzene, HCB). The basic soil properties (e.g. total organic carbon, soil texture characteristics) were determined.
