Elemental Composition, Leachability Assessment and Spatial Variability Analysis of Surface Soils in the Mugan Plain in the Republic of Azerbaijan

Abstract

Abstract. The Republic of Azerbaijan has suffered from low agricultural productivity caused by soil salinization and erosion, and limited and insufficient soil data are available for economic and political reasons. In this study, soil elemental composition and heavy metal levels were assessed by comparing the results of XRF and ICP-OES analyses for the first time. Leachability assessment and spatial variability analysis were conducted to understand the soil salinization properties, and 632 surface soil samples categorized as agricultural (Ag) or salt-affected (SA) soils from the Mugan Plain were collected and analyzed. Based on our observations, the elemental concentrations of Ca, Fe, Cl and S were high among 20 elements compared with the median values for world soils. Apatite, calcite, gypsum, quartz, olivine, microcline and jarosite were proposed as possible mineral structures. The heavy metal guidelines suggested by the neighboring country of Georgia would be appropriate for assessing heavy metal contamination, and Ni and Pb were the most concerning elements. Leachability assessment confirmed that 99 % of the cationic ions were cationic salts and Na was the most problematic ion. Analysis of the electrical conductivity and sum of leachates showed that the exchange of interlayer cations, dissolution of minerals with low dissolution rates, transformation of metal (hydr)oxides and additional precipitation would be the reasons for this disparity. More leachable salts were accumulated in the lowland area, which is due to water movement and high evaporation. The spatial analysis results confirmed the reciprocal relationship between total Ca and total Fe and between total Fe and DW-leached Fe. This result indicates that less-stable iron complexes are prevalent in SA soils, while stable iron complexes are found in Ag soils. We believe that this approach can provide a foundation for the international study of Azerbaijani soil by sharing soil and salinization data with researchers worldwide and can help to diminish or solve agricultural problems in both Azerbaijan and neighboring countries suffering from soil salinization.