Probing the initial conditions of high mass star formation - I. Deuteration and depletion in high mass pre/protocluster clumps

Aims. UltraCompact HII regions are signposts of high-mass star formation. Since high-mass star formation occurs in clusters, one expects to find even earlier phases of massive star formation in the vicinity of UltraCompact HII regions. Here, we study the amount of deuteration and depletion toward pre/protocluster clumps found in a wide-field ( 10 x 10 arcmin) census of clouds in 32 massive star-forming regions that are known to harbour UCHII regions. Methods. We determine the column density of NH(3), NH(2)D, CO, H(13)CN, and HC(15)N lines. We used the (J, K) = (1, 1) and (2, 2) inversion transitions of NH(3) to constrain the gas temperatures. Results. We find that 65% of the observed sources have strong NH(2)D emission and more than 50% of the sources exhibit a high degree of deuteration, (0.1 <= NH(2)D/ NH(3) <= 0.7), 0.7 being the highest observed deuteration of NH(3) reported to date. Our search for NHD(2) in two sources did not result in a detection. The enhancement in deuteration coincides with moderate CO depletion onto dust grains. There is no evidence of a correlation between the two processes, though an underlying correlation cannot be ruled out as the depletion factor is very likely to be only a lower limit. Based on simultaneously observed H(13)CN and HC(15)N ( J = 1 - 0) lines, we derive a high abundance ratio of H(13)CN to HC(15)N, which might indicate anomalous ratios of C and N isotopes relative to those derived toward the local ISM. Conclusions. We find CO depletion and high deuteration towards cold cores in massive star forming regions. Therefore, these are good candidates for sources at the early phases of massive star formation. While our sensitive upper limits on NHD(2) do not prove the predictions of the gas-phase and grain chemistry models wrong, an enhancement of approximate to 10(4) over the cosmic D/H ratio from NH(2)D warrants explanation.