What is the fine-grained topic of the following text: The XANES spectra revealed the 1 M HCl and 0.005 M H₂SO₄ extractants remove calcium (Ca) phosphates from Vertosols, suggesting the latter extractant could be used as an alternative for a rapid and cost-effective measure of Ca phosphates in Vertosols. Only return the topic.
The removal of calcium phosphates from Vertosols using 1 M HCl and 0.005 M H₂SO₄ extractants