def get_organic_aerosols_keys(chem_opt):
    """
    Return the anthropogenic and biogenic keys
    """

    asoa_keys = None
    bsoa_keys = None
    if chem_opt == 106:
        asoa_keys = ('orgaro1i', 'orgaro1j', 'orgaro2i', 'orgaro2j', 'orgalk1i', 'orgalk1j', 'orgole1i', 'orgole1j')  # SOA Anth
        bsoa_keys = ('orgba4i', 'orgba4j', 'orgba3i', 'orgba3j', 'orgba2i', 'orgba2j', 'orgba1i', 'orgba1j')  # SOA Biog
    elif chem_opt == 108 or chem_opt == 100:
        asoa_keys = 'asoa1j,asoa1i,asoa2j,asoa2i,asoa3j,asoa3i,asoa4j,asoa4i'.split(',')  # SOA Anth
        bsoa_keys = 'bsoa1j,bsoa1i,bsoa2j,bsoa2i,bsoa3j,bsoa3i,bsoa4j,bsoa4i'.split(',')  # SOA Biog
    else:
        print('PP: this chem_opt {} is not implemented, dont know how to combine organics')

    return asoa_keys, bsoa_keys