def alpha0_carbonate(pH):
    """Calculate the fraction of total carbonates in carbonic acid form (H2CO3)

    :param pH: pH of the system
    :type pH: float

    :return: Fraction of carbonates in carbonic acid form (H2CO3)
    :rtype: float

    :Examples:

    >>> from aguaclara.research.environmental_processes_analysis import alpha0_carbonate
    >>> round(alpha0_carbonate(10), 7)
    <Quantity(0.00015, 'dimensionless')>
    """
    alpha0_carbonate = 1/(1+(K1_carbonate/invpH(pH)) *
                            (1+(K2_carbonate/invpH(pH))))
    return alpha0_carbonate