Before revision:  With the aid of the previously obtained error bounds, we reveal a mean-square convergence rate of order one for the positivity preserving schemes  under more relaxed conditions, compared with existing relevant results  in the literature.
After revision:  With the aid of the previously obtained error bounds, we reveal a mean-square convergence rate of order one for the positivity preserving schemes under more relaxed conditions, compared with existing relevant results for first order schemes in the literature.