Natural conditions and human activities have caused serious quality degradation of the Quaternary aquifer in the north of the United Arab Emirates (UAE). The aquifer within Ajman City is unconfined, receiving limited recharge (12 542 m3/day) from the east and large pollutants flux (4,800 m 3/day) from land surface. Field survey and laboratory analyses revealed anomalies in groundwater salinity (TDS), total hardness (TH), dissolved oxygen (DO), cations (Ca2+, Mg2+, Na+ and K+), anions (HCO3-, (SO4 2-, Cl- and (NO3-) and trace elements (Fe, Pb, Cd and Cr), which can be correlated to point and non-point pollution sources. Concentrations of trace elements are more responsive to anthropogenic sources than natural ones. High Fe and Pb levels were measured close to the untreated sewage disposal site, while high Cd and Cr contents were observed near hospitals and clinics. Iso-concentration maps of salinity and major ions, in addition to hydrochemical profiles were used to define the seawater-groundwater interface in Ajman City. The potentiometric surface map of the Quaternary aquifer within the study area shows that groundwater flows from the east towards the Arabian Gulf in the west. The proposed landfill site is suitable because it lies within a topographic low, receiving groundwater flow from all directions. © 2007 Springer Science+Business Media B.V.