Relationship between Heavy Metals and Physicochemical Properties of Soil in the Coast and Valley of Hadhramaut, Yemen

The physicochemical properties of soil, especially heavy metals, have become a serious problem in the degradation of the growth and development of agricultural and food crops in Hadhramaut. Therefore, this study aimed to conduct a preliminary comparative study of the physicochemical properties of soil from two sites representing the valley and coastal environments in Hadhramaut and to assess their impact on crop cultivation. Soil samples were collected randomly using an auger at a depth of 20 cm from two farms, one in the Al-Suwairi area (Tareem) in Wadi Hadhramaut and the other in the Al-Sa'ada area (Ghayl Ba Wazir) on the coast of Hadhramaut, Yemen. The soil samples were analyzed for physicochemical parameters such as pH, electrical conductivity (EC), total dissolved solids (TDS), and moisture content. The results of the physicochemical analysis of the soil depth for both sites showed fluctuations in values and ranges for pH (7.7-7.8), moisture content (5-6%), total dissolved solids (1060-1443 mg/L), and electrical conductivity (213.5-288.5 μS/cm). Heavy metals (Lead Pb, Cadmium Cd, Nickel Ni, Mercury Hg, Copper Cu, and Zinc Zn) were analyzed using atomic absorption spectrometry, and the obtained results were for Nickel (27.1-29.2 ppm), Cadmium (0.81-0.97 ppm), Lead (0.29-0.61 ppm), Mercury (0.06–0.08 ppm), Copper (11.63-13.9 ppm), and Zinc (26.63-32.70 ppm). It is noted that these characteristics are controlled by the type, composition of the soil, and its distance from the coast. The farther from the coast, the lower the salinity level. The results of this preliminary study suggest that the values of all analyzed properties fall within the permissible limits according to the Dutch standards for soil assessment (Netherlands Ministry of Housing, Spatial Planning and Environment (VROM), 2000).