Traceability and Heavy Metal Contamination in Agrosystems of Two Rice-Producing Areas of the Ecuadorian Coast

Rice (Oryza sativa) plays a fundamental role in the Ecuadorian diet. This study evaluated traceability and contamination by heavy metals in two rice-producing areas of Ecuador. Microwave-assisted digestion was used to process samples from rice agrosystems including irrigation water, soil, roots, stems, and leaves. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was employed for elemental analysis. Arsenic (As), cadmium (Cd), lead (Pb), and chromium (Cr) were measured in samples collected in Daule and Ventanas. In soils, the concentrations of As (1.50–2.82 mg/kg) and Cd (1.22–1.45 mg/kg) exceeded the internationally recommended safety thresholds. In irrigation water, the content of As (0.85–1.12 mg/L), Pb (0.25–0.38 mg/L), and Cr (0.37–0.53 mg/L) surpass the international/national permissible limits. However, the limits established by Ecuadorian legislation indicate that As in soils did not exceed contamination thresholds. Additionally, the bioaccumulation of As and Pb in roots from Daule and Ventanas, respectively, was observed, along with the movement of Pb to aerial parts in Daule. Finally, preliminary As found in commercial rice grains suggest a potential health concern to the Ecuadorian population. These findings highlight the need for stricter heavy metal restrictions for rice agrosystems and effective agricultural pollution mitigation.