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Based on chloride mass balance approach, we used two tracers (Cl- and NO3-) to study the interstitial water in four profiles of an unsaturated dune sand. The aim was to reconstruct the recharge history and use this to infer the long-term related climate changes and vegetation transitions in a cold-arid desert region of northwestern China. The estimated recharge rate of 0.21 to 0.59 mm year(-1) represented approximately 0.2 to 0.7% of the annual precipitation in the western Badain Jaran desert. The orientation of a megadune’s slopes appeared to greatly affect recharge variability. Below the near-surface peaks, the total cumulative NO3-N inventories ranged from 61 to 121 kg ha(-1). The near-surface peaks in NO3-N, with larger NO3-N/Cl- molar ratios, reflected active modern N-fixation by cyanobacteria, and the nitrate enrichment deeper in the unsaturated moisture zone indicated drier periods with less vegetation, limited nitrate fixation, or a combination of the two. (C) 2012 Elsevier B.V. All rights reserved.