Abstract
Heavy metals contamination of soil is one of the most alarming concerns in the debate about food security and food safety all over the world because it determines the possible composition of food and feeds at the root level of the food chain. Simultaneously, plants are important components of the ecosystem as they transfer elements from abiotic and biotic environments. The primary sources of elements from the environment to plants are air, water, and soil. The aim of this study was to determine the accumulation levels of trace toxic heavy metals in soils and plant samples in the garden of the Al-Nadwa-Riyadh area. Lead and cadmium were measured in the soil and plants by graphite atomic absorption spectrometry, while arsenic and mercury were measured using hydride generation atomic absorption spectrometry. Plant samples were digested by 8 ml of nitric acid followed by 2 ml hydrogen peroxide, while soil samples were digested by 6 ml concentrated nitric acid followed by 2 ml hydrofluoric acid and 2 ml hydrogen peroxide. In soil samples, results presented here showed that levels of lead were within the set of all standards, while cadmium exceeds the limits of FAO and EC standards. Arsenic was found to be above the FAO standard but within the set of all other standards. On the contrary, mercury was investigated far above all the set standards. All levels of the heavy metals in all plant samples were below the maximum permissible limit standard values of FAO/WHO, except mercury. The results demonstrated that mean content of Hg uptake by the plants was higher than the contents of each trace metals under test.