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Recent water line observations toward several low-mass protostars suggest lowwater gas fractional abundances in the inner warm envelopes. Water destructionby X-rays has been proposed to influence the water abundances in these regions,but the detailed chemistry, including the nature of alternative oxygencarriers, is not yet understood. In this study, we aim to understand the impactof X-rays on the composition of low-mass protostellar envelopes, focusingspecifically on water and related oxygen bearing species. We compute thechemical composition of two low-mass protostellar envelopes using a 1Dgas-grain chemical reaction network, under various X-ray field strengths.According to our calculations, outside the water snowline, the water gasabundance increases with $L_{\mathrm{X}}$. Inside the water snowline, watermaintains a high abundance of $\sim 10^{-4}$ for small $L_{\mathrm{X}}$, withwater and CO being the dominant oxygen carriers. For large $L_{\mathrm{X}}$,the water gas abundances significantly decrease just inside the water snowline(down to $\sim10^{-8}-10^{-7}$) and in the innermost regions ($\sim10^{-6}$).For these cases, the O$_{2}$ and O gas abundances reach $\sim 10^{-4}$ withinthe water snowline, and they become the dominant oxygen carriers. The HCO$^{+}$and CH$_{3}$OH abundances, which have been used as tracers of the watersnowline, significantly increase/decrease within the water snowline,respectively, as the X-ray fluxes become larger. The abundances of some otherdominant molecules, such as CO$_{2}$, OH, CH$_{4}$, HCN, and NH$_{3}$, are alsoaffected by strong X-ray fields, especially within their own snowlines. TheseX-ray effects are larger in lower density envelope models. Future observationsof water and related molecules (using e.g., ALMA and ngVLA) will access theregions around protostars where such X-ray induced chemistry is effective.

X-ray induced chemistry of water and related molecules in low-mass protostellar envelopes