Density functional theory calculations are carried out to study the adsorption of mercury and arsenic on Pd-n (n=1-6) supported on pyridine-like nitrogen doped graphene (PNG). Owing to the promising sensitivity in trace amounts of atoms or molecules, PNG can be acted as micro-sensor for sensing heavy metals in agriculture soils. Through the analyses of structural and electronic properties of pristine PNG and Pd atom decorated PNG, we find that the most favorable adsorption site for Pd atom is the vacancy site. The analyses of structural and electronic properties reveal that the Pd atom or clusters can enhance the reactivity for Hg and AsH3 adsorption on PNG. The adsorption ability of Hg on Pd-n decorated PNG is found to be related to the d-band center (epsilon(d)) of the Pd, in which the closer epsilon(d) of Pd-n to the Fermi level, the higher adsorption strength for Hg on Pd-n, decorated PNG. Moreover, the charge transfer between Pd and arsenic may constitute arsenic adsorption on Pd-n decorated PNG. Further design of highly efficient carbon based sorbents for heavy metals removal should be focused on tailoring ed of adsorbed metals. (C) 2016 Elsevier B.V. All rights reserved.