too much SO2

I have just started a batch of mulberry wine (23L) and accidentally added
10g of PMS instead of the 5g I needed for doing a cold soak. The must has a
definite sulfur smell and even after stirring every morning and night for
the last 3 days to agitate the yeast still won't start. I pitched with
lalvin D47 first and have pitched another 500mL with RC212 to try and get
one going.
How can I reduce the SO2 to get the ferments going ?

thanks in advance

JH