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<p>Iron and steel works activities are an important industrial source of pollutants that change soil composition with a wide range of substances containing heavy metals. Determination of the multi-element composition of urban soil contributes to an accurate assessment of the quality of the urban environment. Therefore, concentrations of 15 metals (Ti, V, Cr, Mn, Fe, Co, Ni Cu, Zn, Mo, Ag, Sn, Sb, Pb and W) were measured in Ózd, a former industrial city located at the northern part of Hungary. It has been exposed to contaminants for almost two centuries by different anthropogenic activities such as transportation, coal mining, iron and steel works. In this study, 56 urban soil samples were collected from playgrounds, kindergartens, parks and roadsides, as well as 1 local coal, 1smelter slag and 2 steel slags samples.</p><p>In this study, we determined cluster distribution of the samples using compositional data analysis clr-transformed (clr-biplot), k-means cluster analysis (CA) and calculates enrichment factors (EF). To observe the relationships among the 15 metals, the clr-biplot was performed in CoDaPack software and k-means in R statistics, following recommendation in the literature [1].  The results of k-means were overlapped on the clr-biplot and plot on a map. Enrichment factors were calculated for every cluster with the formula: EF=[M/Fe]sample/[M/Fe] background, where (M) metals concentration and Fe was used for normalization. Background values were taken from brown forest soil.</p><p>The average concentration of 15 elements in (mg kg<sup>-1</sup>) for the 57 samples are Fe(27204), Mn(842), Zn(225), Ti (135),  Pb (81), Cr(41,3), Cu(30.2), V(24.2), Ni(21), Co(7.34), Sn(4.22), Sb(1.41), Mo(1.19), W(0.726) and Ag (0.268), respectively.</p><p>The optimal number of clusters are 4, where the most samples in the first cluster are distributed on the northwest side of the city where agricultural activity is a common occasion. Samples forming the second cluster are characteristic in the area of the former iron and steel factory. Samples of the third cluster are located at the new industrial park (northeast side of the city). The fourth cluster samples are derived from the surrounding area the new industrial area and covers most of the city south side. The results of average enrichment factor (EF)>5, which represent significant or very significant enrichment are 1<sup>st</sup>cluster Ti, 2<sup>nd</sup>cluster W>Ti>Sn>Ag>Cr>Pb>Sb>Zn>Cu, 3<sup>rd</sup>cluster W>Cr>Ti, and 4<sup>th</sup>cluster Ti>W.</p><p>The differences between cluster distributions and enrichment of each metallic element show complexity of the study area, which suggested areas with features associations of elements to natural sources, hybrid (natural and anthropogenic) and industrial areas.</p><p> </p>

<p>The <sup>137</sup>Cs (t<sub>1/2</sub> =30 years) is a principal radioisotope that was artificially introduced into the environment through the atmospheric bomb tests took place from the middle of the 1940s to the 1980s and from the major nuclear accidents (i.e., Chernobyl, 1986 and Fukushima, 2011). From the atmosphere, <sup>137</sup>Cs easily adsorbs to particles and it returns to lithosphere (pedosphere) by wet and dry deposition as a radioactive fallout component. Due to the Chernobyl nuclear accident, the released contaminated air mass, containing Cs-137, largely propagated, deposited, and distributed across several European countries in the ambient environment (Balonov et al., 1996). These particles also reached houses (e.g. through open windows, cracks, and vents) in an urban environment and deposited inside resulting in the exposition of the habitants to <sup>137</sup>Cs, especially in areas that are not accessible for a regular cleaning like attics. Following the nuclear accidents, primary attention was drawn to agricultural areas and less attention was paid to urban environments. Accordingly, the goal of this study is to compare the <sup>137</sup>Cs activity in attic dust as undisturbed samples, and urban soils as disturbed environmental materials to determine the <sup>137</sup>Cs distribution in urban environment. </p><p>Attic dust (AD) samples were collected from 14 houses, which were built between 1900 and 1990 14 urban soil (US) samples were collected nearby the houses at a depth of 0-15 cm in Salgótarján, a former industrial city. To obtain a representative local undisturbed soil sample, a forest soil sample was collected from the upwind direction (NW) of the city. To check the <sup>137</sup>Cs content of the local industrial waste material, we also collected fly-ash slag sample from a waste dump.   AD and US samples were analyzed by a well-type HPGe and with an n-type coaxial HPGe detector in a low background iron chamber, respectively.</p><p>Cs-137 activity in the studied AD ranges from 5.51±0.9 to 165.9±3.6 Bq kg<sup>-1, </sup>with a mean value of 75.4±2.5 Bq kg<sup>-1 </sup>(decay corrected in 2016). In contrast, US samples show <sup>137</sup>Cs activity ranging between 2.3±0.4 and 13.6±0.6 Bq kg<sup>-1</sup>.  The brown forest soil sample has elevated <sup>137</sup>Cs activity concentration (18.5<strong>±</strong>0.6 Bq kg<sup>-1</sup>), compared to the urban soils. The fly-ash slags activity is below the detection limit (0.7±0.5 Bq kg<sup>-1</sup>).</p><p>The average <sup>137</sup>Cs activity in AD is ~15 times higher than that of US. This result clearly indicates that attic area provides a protected (hardly or unchanged) environment, therefore physical condition of the dust remains constant in time, and there is a small chance for chemical reaction. Forest soil proves that US were highly disturbed by anthropogenic activity. This is supported by fly-ash slag activity results.  Whereas, <sup>137</sup>Cs activity concentration of the AD samples shows significantly higher than that of the studied soils in Hungary. This confirms again US cannot show the historical atmospheric <sup>137</sup>Cs pollution such as attic dust. A statistically significant relationship (p=0.003, r<sup>2</sup>=0.05) were found between the AD and US samples. Therefore, it can be considered that attic dust remained undisturbed for decades and preserve past record of components of atmospheric pollution.</p><p> </p><p> </p>