INTRODUCTION Waste generation and subsequent accumulation generated by increased urbanization and industrialization, coupled with rising standards of living is one of the major problems confronting our present generations (Dela Cruz et al., 2010). Solid wastes arise from human and animal activities, including the heterogeneous mass of garbage from the urban communities, as well as the more homogeneous accumulations comprising countless different materials (paper, metals, plastic and glass), construction wastes, industrial process wastes, pathological wastes, and hazardous wastes (Mohapatra, 2006). Current global MSW generation levels are approximately 1.30 billion tonnes/year, and are expected to increase to approximately 2.20 billion tonnes/ year by 2025 )Shekdar, 2009). In Riyadh city, the Kingdom of Saudi Arabia (KSA), the total MSW generation has increased to more than 12 million ton per year and the per capita of MSW is about 1.50-1.80 kg /person/ day (Al–Oud and Ghoneim, 2018). MSW produced is disposed on land without taking any specific precaution. There are many open dumps causing soil pollution which makes soil unsuitable for irrigation purposes and reduces crop yield. The common method of MSW disposal in Riyadh city is dumping it into the soils or incineration because these are the cheapest methods. Incineration is a common technique for MSW disposal as it reduces its mass and volume by 70 and 90%, respectively (Klein et al., 2001(. The soils contaminated by municipal solid waste ash (MSWA) application areas causes’ potential groundwater pollution especially with heavy metals (Zhang et al., 2012). Moreover, leachate from MSWA dumpsites affects the distribution and mobilization of potential toxic metals (PTMs) in such soils (Saritha et al., 2014; Mahmoud and Ghoneim, 2016). Heavy metal contamination due to MSW applications has received much attention lately because of concerns regarding uptake by plants. Its accumulation in the soil constitutes a long-term environmental hazard as it could leach from the soils and re- entry the food chain or contaminate the ground and surface water (Ghoneim, 2002; Kaschl et al., 2002). Lead is most commonly found in MSWA (Steinnes, 2013; Elbana et al., 2014). The exhaust gases generated from petrol engines which represent about 80% of the total lead in air are considered the main sources of Pb contamination globally and Pak. J. Agri. Sci., Vol. 56(2), 275-282; 2019 ISSN (Print) 0552-9034, ISSN (Online) 2076-0906 DOI: 10.21162/PAKJAS/19.7538 http://www.pakjas.com.pk MOBILITY AND DISTRIBUTION OF LEAD IN SOILS TREATED WITH MUNICIPAL SOLID WASTE ASH Abdulaziz G Alghamdi * , Adel Ghoneim * and Saud S Al-Oud Department of Soil Sciences, College of Food and Agricultural Sciences, King Saud University, P.O. Box 2460, Riyadh 11451, Kingdom of Saudi Arabia * Corresponding authors e-mail: aghoneim@ksu.edu.sa; agghamdi@ksu.edu.sa Lead (Pb) is an inorganic conservative pollutant poses a risk to soils and water resources. Quantifying the potential hazard impacts of Pb in soils needs further circumstances about its mobility and retention as well. The objective of this study was to evaluate the effects of municipal solid waste ash (MSWA) on mobility and distribution of Pb in two types of soil textures. The extent of Pb mobilization in soils amended with different application rates of MSWA has been quantified by soil columns experiment under steady state conditions. Transport of Pb was studied in soil columns by applying Pb solution of 150 mg/L at the rate of 0.09 cm/min for loamy sand soil and 0.035 cm/min for sandy loam soil. The mathematical model- HYDRUS-2D was used to describe this transport. The results indicated that Pb concentrations were extremely low in the leaching solutions collected from soil columns over time regardless of the application rates of MSWA. Application of MSWA increased the recovery of Pb in both soils achieving superiority in loamy sand soil. The Pb distributed in the soil columns ranged between soil leaching solutions and sorbed phase, of which the greater portion was in the sorbed phase. Lead move slowly through soils columns and the distance of movement was about 5 cm to the soil surface and then the concentrations decreased down the soil columns and later disappeared beyond a depth of to 7 cm. Mass balance calculations of Pb according to the HYDRUS-2D mathematical model resulted in values that were similar to those of the experimental data (error ≤ 5%). A soil quality indicator is considered as a key element of sustainable agriculture and hence soil quality plays an important role in deciding the MSWA methods. Keywords: Alkaline soil, column leaching, municipal solid waste ash, Pb mobility.