Abstarct: Heavy mextals are among the most important environmental contaminant in all three phases of soil, water, and air. The present research aimed at the geochemical investigations on the contaminant elements of groundwater resources in south of Birjand plain, Iran and determining the possible source of contamination with regards to petrology and geochemistry of the region. After collecting the available information, field observations, and selecting the sampling locations, water samples were collected in two periods, 27 samples in May 2010 (end of the wet season), and 30 samples in September 2010 (end of the dry season). The concentrations of cations and anions by using standard methods were determined and the concentrations of elements were measured through ICP-MS techniques. Samples from the sediments and rocks from the region were also collected. 18 thin sections of rock samples were prepared and 25 sediment samples were undergone ICP-MS analyzes. Petrologic studies in the area indicated the presence of ophiolite sequence. The ultramafic rocks and basic lava are widely spread in highlands south of Birjand plain which have the highest effects on the water quality of the region. Listonites are the sources of most elements such as Pb, Cu, Zn, B, As, Au, Ag, Ni, Cr, Fe, Ba, Mg, K, Ca, and Cl in the area. Enrichment factor of the sediments were calculated and indicated high enrichment of Ni, relatively high enrichment of As, Cr, and Cu, and medium enrichment of Zn, Pb, and Mg. The contamination degree of the elements in the sediment showed low contamination of most sediments in the area. The investigation on the water resources quality disclosed that more than 80% of these resources were contaminated by B and Cr and 50% by Mg. Also, concentrations of Na and Cl as well as TDS in some resources exceeded the allowable level. The highest correlations in the water resources were calculated as +0.943 between Pb and B, +0.614 between Mg and Ca, and +0.713 between Na and Cl. MI was greater than one for all water resources except one spring which is an indication of contaminated water. Since the water resources were contaminated with Cr and because of advantages of biological methods in removal of heavy mextals, in this research, for the first time in the world, crushed seed of Ziziphus ziziphus was employed to remove Cr(VI) from the solution. The performance of crushed seed of ziziphus ziziphus was optimized for 5 factors including pH, time, particle size, sorbent to solution ratio, and chromium concentration in the room temperature. The results showed the high performance and strong ability of crushed seed of ziziphus ziziphus in the removal of chromium from the solution (95% to 100%) under the optimized conditions.