Abstract:
Amino(poly)phosphonates (A(P)Ps) are widely used in agriculture, industry, and household products for their herbicidal properties. Glyphosate, a non-selective herbicide, and its main metabolite AMPA are the most prominent examples, while others like ATMP and DTPMP are used for their chelating and scale-inhibiting properties in water treatment and detergents. Although glyphosate and related compounds have been studied for biodegradability, key environmental factors are often overlooked, leaving uncertainty about their behavior in real settings with varying nutrients and mineral content.
This study first examined glyphosate biotransformation under substrate competition, where other A(P)Ps served as additional phosphorus (P)-sources. Batch tests with two bacterial strains showed that glyphosate was the least preferred monophosphonate but was more readily transformed when provided alongside a diphosphonate, indicating that high degradation rates seen in P-limited lab tests may not reflect natural conditions.
In the second part of this study, the biotransformation potential of glyphosate and AMPA in the presence of a mineral sorbent was evaluated. Despite expectations of persistence due to sorption, goethite did not hinder their biotransformation, and degradation rates remained unaffected.
The third part investigated the biodegradability of higher APPs (with three or more C–P bonds) in bacterial media. Earlier studies attributed their transformation to microbial activity, but our experiments showed that ATMP and EDTMP degradation was mainly driven by trace Mn(II)–mediated abiotic oxidation. Together with a literature review, these results reveal major flaws in previous biodegradation studies using Mn(II)-containing media.
Finally, compound-specific isotope analysis (CSIA) was explored to assess isotope effects during glyphosate and AMPA biodegradation. Efficient analyte separation from highly concentrated medium components, especially glutamate, proved challenging. Two cleanup methods were tested: cation exchange caused major analyte loss, while aluminum oxide effectively reduced glutamate and preserved recovery, enabling early isotope measurements. Although later analyses were still affected by residual glutamate and byproducts, this represents an important step toward applying CSIA to glyphosate and AMPA studies.
Overall, this thesis advances our understanding of the biodegradability of APs and APPs under more complex conditions, addressing important gaps related to environmental relevance and methodological challenges. By systematically investigating bacterial degradation in the presence of co-occurring P-sources, mineral sorbents, and under abiotic influences, this work reveals that critical previous assumptions do not necessarily hold in real-world settings and need to be reevaluated.
