# Biogeochemical State of Salinized Irrigated Soils of Central Fergana (Uzbekistan, Central Asia)
## 3 Results and Discussion
Accumulation of nickel above the clarke occurs in sax soils, it does not occur in takyr soils. Nickel is known as an element which may accumulate on the surface of aluminosilicate chemicals [46] and, especially in soils, enriched by smectite. There is an essential accumulation of arsenic in both sax- and takyr- soils and exceedance of clarke is up to 8-9 times. Recently, a high content of arsenic was reported for Western Siberia [46; 47], but high concentrations are not obligatorily dangerous, cause the  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline \hline \multicolumn{1}{c}{**Soil**} & \multicolumn{1}{c}{**Depth,**} & \multicolumn{1}{c}{**Sc**} & \multicolumn{1}{c}{**Cr**} & \multicolumn{1}{c}{**Co**} & \multicolumn{1}{c}{**Ni**} & \multicolumn{1}{c}{**As**} & \multicolumn{1}{c}{**Br**} & \multicolumn{1}{c}{**Sb**} & \multicolumn{1}{c}{**Cs**} & \multicolumn{1}{c}{**Hf**} & \multicolumn{1}{c}{**Ta**} & \multicolumn{1}{c}{**W**} & \multicolumn{1}{c}{**Au**} \\ \hline \multirow{4}{*}{1} & 0–29 & 7.3 & 43.9 & 9.13 & 20 & 16.7 & 4.1 & 1.67 & 6.5 & 3.63 & 0.71 & 4.19 & 0.0055 \\  & 29–44 & 7.3 & 43.  
bulk forms are higher than water soluble. As for bromide salt concentration which exceed clarke by 2.5 times, it has been reported that this element may be immobilized by calcium carbonate salts [48]. Antimony in soils is very poorly studied; it is assumed that it may be related to iron hydroxides [46; 49; 50], but it is not clear whether correlation of antimony content with iron in alkaline conditions of soils in the Fergana Valley is possible. In any case, the clarke in irrigated soils is exceeded twice or more, which may indicate the role of irrigation in the accumulation of this element. Antimony is considered as an active part of biological food chains [50], thus, exceeding its content in comparison with clarke could be a possible predictor of crop production, planted on irrigated soils. Cesium concentration exceeded clarke in irrigated soils, taking into account the fact that cesium is characterized by its low ability to dissolve in water; its migration and accumulation are affected by suspended particles of clay minerals in toposils which corresponds well with the results of particle size distribution in soil sections. Probably irrigation by water enriched by suspended clays could be a reason for cesium accumulation in both types of soil investigated as was suggested for antimony. Hafratium accumulation normally deals with translocation from parent materials or accumulation in the lowlands form of adjacent uplands [51]. Both these factors could be possible predictors of hafratium accumulation in both types of soils investigated. Hafraium behavior in the soil-plant system is poorly studied, nevertheless it is known that even different grains are characterized by different selectivity in hafraium absorption from soils with different levels of contamination [52]. Hafratium accumulation could be essentially affected by loess type of mineral material in the environment [53]. As for tantalum content its content deals normally with thecnogenic sources [54], thus due to that fact that clarke is not exceeded, the role of thecnogenic factor in soil chemical composition is low. Tantalum is known as a very conservative element in biogeochemical terms but real understanding of its cycle and reactivity would require extensive and meaningful data collection [55]. The content of tungsten and aurum in soil is low and does not exceed the clarke concentration, thus it corresponds with the background level. At the end of this section we conclude that trace elements like nickel, arsenic, bromine, antimony, cesium, and hafratium could be accumulated in irrigated soil during their agrogenic transformation. In opposite, such elements as scandium, chromium, cobalt, tantalum, tungsten, and aurum are supposedly inherited from parent materials and are not incoming with irrigation waters in both types of the soils investigated.