Integrated Assessment of Soil Quality and Heavy Metal Contamination in Arid Agricultural Soils of Northwestern Uzbekistan
Abstract
Soil contamination by toxic elements is one of the major environmental challenges affecting soil quality and ecosystem sustainability, particularly in arid regions. The accumulation of heavy metals in soils can disrupt nutrient cycling, reduce soil biological activity, and pose potential risks to agricultural productivity and human health. Therefore, assessing soil contamination and ecological condition is essential for sustainable land management. This study aimed to evaluate the ecological condition and soil quality of agricultural soils located in the Mehnatobod and Koklikol massifs of the Qo‘ng‘irot district in the Republic of Karakalpakstan. The mechanical composition, agrochemical properties, salinity level, and heavy metal concentrations of soils were analyzed. In addition, SQI was calculated by integrating physicochemical soil indicators and ecological parameters into a single composite index. The results showed that the studied soils are characterized by relatively low humus content and limited nutrient availability. The analysis of chemical elements revealed that several metals exceeded permissible limits. In particular, arsenic (As) showed the highest contamination level, reaching values up to 40 times higher than the permissible limit. Chromium (Cr), nickel (Ni), and vanadium (V) concentrations exceeded permissible limits approximately twofold, while lead (Pb), cobalt (Co), and molybdenum (Mo) exceeded them by up to threefold. The calculated SQI values ranged from 49 to 55, indicating moderate soil quality levels. Although soil physicochemical properties were relatively stable, ecological indicators reduced the overall soil quality score. These findings highlight the importance of environmental monitoring and sustainable soil management practices to improve soil ecological conditions and maintain long-term agricultural productivity.