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Research output: Thesis › Doctoral Thesis
Research output: Thesis › Doctoral Thesis
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TY - BOOK
T1 - The importance of organic phosphorus sources, transfers and impacts across the agricultural continuum
AU - Gittins, Joshua R.
PY - 2021/8/17
Y1 - 2021/8/17
N2 - This thesis investigates the risks posed by organic phosphorus (P) from agriculture to river and stream chemical water quality and the ecology. Organic P compounds have received limited attention in past research, due to the agronomic focus on inorganic P and the analytical challenges of quantifying organic P in environmental matrices. Through laboratory and field experiments, this thesis aimed to: (i) characterise organic P within fresh and stored livestock slurry; (ii) quantify organic P export within overland flow and leachate from grasslands, including following livestock slurry application; and (iii) determine the benthic microbial responses to organic P compounds in rivers and streams. Finally, a coupled terrestrial-aquatic modelling approach was developed to quantify the impact of diffuse agricultural P mitigation measures on river water quality.The organic P pool in fresh livestock slurry was substantial and dominated by monoesters, including glycerophosphates, other labile monoesters (e.g. ATP) and inositol-6-phosphates. Storage drove significant changes in the chemical and physical fractionation of P within slurry. Organic P was observed in overland flow and leachate from grassland soil. Significant increases in organic P concentrations within leachate followed slurry application, predominantly in the form of glycerophosphates and inositol-6-phosphates. Within streams, heterotrophic responses to glycerophosphates and inositol-6-phosphate were observed, although these varied depending on background stream P concentrations. However, under certain stream conditions, inhibitory effects of organic P on the autotrophic community were observed. Modelling the efficacy of agricultural P mitigation suggested a best-case scenario in which annual river total P loads decreased by 7.5%, yet this increased to 19.4-25.1% when wastewater effluent was addressed alongside agricultural sources of P. The outcomes of this thesis present an opportunity to develop an organic P focus to the P transfer continuum, alongside highlighting a range of future research priorities related to organic P in the environment.
AB - This thesis investigates the risks posed by organic phosphorus (P) from agriculture to river and stream chemical water quality and the ecology. Organic P compounds have received limited attention in past research, due to the agronomic focus on inorganic P and the analytical challenges of quantifying organic P in environmental matrices. Through laboratory and field experiments, this thesis aimed to: (i) characterise organic P within fresh and stored livestock slurry; (ii) quantify organic P export within overland flow and leachate from grasslands, including following livestock slurry application; and (iii) determine the benthic microbial responses to organic P compounds in rivers and streams. Finally, a coupled terrestrial-aquatic modelling approach was developed to quantify the impact of diffuse agricultural P mitigation measures on river water quality.The organic P pool in fresh livestock slurry was substantial and dominated by monoesters, including glycerophosphates, other labile monoesters (e.g. ATP) and inositol-6-phosphates. Storage drove significant changes in the chemical and physical fractionation of P within slurry. Organic P was observed in overland flow and leachate from grassland soil. Significant increases in organic P concentrations within leachate followed slurry application, predominantly in the form of glycerophosphates and inositol-6-phosphates. Within streams, heterotrophic responses to glycerophosphates and inositol-6-phosphate were observed, although these varied depending on background stream P concentrations. However, under certain stream conditions, inhibitory effects of organic P on the autotrophic community were observed. Modelling the efficacy of agricultural P mitigation suggested a best-case scenario in which annual river total P loads decreased by 7.5%, yet this increased to 19.4-25.1% when wastewater effluent was addressed alongside agricultural sources of P. The outcomes of this thesis present an opportunity to develop an organic P focus to the P transfer continuum, alongside highlighting a range of future research priorities related to organic P in the environment.
KW - phosphorus, organic phosphorus, water quality, agriculture, Cumbria
U2 - 10.17635/lancaster/thesis/1397
DO - 10.17635/lancaster/thesis/1397
M3 - Doctoral Thesis
PB - Lancaster University
ER -