| Title | Phosphate adsorption by riverborne clay sediments in a southern-Italy Mediterranean reservoir: Insights from a "natural geo-engineering" experiment |
| Abstract | This paper reports data from a southern-Italy reservoir (Lake Occhito) characterized by a strong riverborne sediment transport. Main hydrochemical, trophic, and nutrient variables were measured (over a twelve-month period) in both lake and tributaries. Lacustrine sediments were subjected to mineralogical characterization and to phosphorus fractioning, while a 6-day long batch experiment was carried out to evaluate the lake sediment orthophosphate adsorption capacity. A set of algal growth potential tests was also undertaken on the lake and its tributaries. Results highlight the presence of a strong gradient in nutrient availability among the inflows. Most of the nutrient loads were from the main tributary (20.3 t P a-1, ~83 %), that showed the highest trophic potential (average: 56.8 mg L-1) and was nitrogen/phosphorus co-limited. The other inflows were phosphorus limited and characterized by a higher sediment transport. The lake showed the lowest nutrient concentrations (average total phosphorus: 21 ?g P L-1) and was strongly phosphorus limited. Clays were the principal minerals in the lake sediments (~51 %), while the main phosphorus fraction was apatite (~78 %). The batch experiment demonstrated the capability of the lake sediments to reduce orthophosphate concentrations in phosphorus-rich waters (initial orthophosphate: 320 ?g P L-1; ~80 % reduction). The lake sediment orthophosphate kinetics of abatement was similar to that of a commercially available phosphorus sorbent (lanthanum modified bentonite), although the stability of phosphorus binding was higher for the commercial product. Theoretical average in-lake total phosphorus, chlorophyll-a, and transparency values, estimated through Vollenweider models, were approximately double of the average values measured in the lake. Therefore, the massive presence of riverborne clay sediments seems to markedly reduce the in-lake orthophosphate concentrations (and light penetration), inducing an overall lowering of the lake trophic state, as if the lake ecosystem were permanently subjected to a geo-engineering phosphorus sorbent treatment. |
| Source | Science of the total environment 856–159225 |
| Keywords | Algal growth testMediterranean reservoirsNutrient limitationPhosphorus adsorptionPhosphorus fractioningRiverborne clay sediments |
| Journal | Science of the total environment |
| Editor | Elsevier, Lausanne ;, Paesi Bassi |
| Year | 2023 |
| Type | Articolo in rivista |
| DOI | 10.1016/j.scitotenv.2022.159225 |
| Authors | Copetti, Diego and Valsecchi, Lucia and Tartari, Gianni and Mingazzini, Marina and Palumbo, Maria Teresa |
| Text | 471883 2023 10.1016/j.scitotenv.2022.159225 Algal growth test Mediterranean reservoirs Nutrient limitation Phosphorus adsorption Phosphorus fractioning Riverborne clay sediments Phosphate adsorption by riverborne clay sediments in a southern Italy Mediterranean reservoir Insights from a natural geo engineering experiment Copetti, Diego and Valsecchi, Lucia and Tartari, Gianni and Mingazzini, Marina and Palumbo, Maria Teresa IRSA CNR This paper reports data from a southern Italy reservoir Lake Occhito characterized by a strong riverborne sediment transport. Main hydrochemical, trophic, and nutrient variables were measured over a twelve month period in both lake and tributaries. Lacustrine sediments were subjected to mineralogical characterization and to phosphorus fractioning, while a 6 day long batch experiment was carried out to evaluate the lake sediment orthophosphate adsorption capacity. A set of algal growth potential tests was also undertaken on the lake and its tributaries. Results highlight the presence of a strong gradient in nutrient availability among the inflows. Most of the nutrient loads were from the main tributary 20.3 t P a 1, 83 % , that showed the highest trophic potential average 56.8 mg L 1 and was nitrogen/phosphorus co limited. The other inflows were phosphorus limited and characterized by a higher sediment transport. The lake showed the lowest nutrient concentrations average total phosphorus 21 g P L 1 and was strongly phosphorus limited. Clays were the principal minerals in the lake sediments 51 % , while the main phosphorus fraction was apatite 78 % . The batch experiment demonstrated the capability of the lake sediments to reduce orthophosphate concentrations in phosphorus rich waters initial orthophosphate 320 g P L 1; 80 % reduction . The lake sediment orthophosphate kinetics of abatement was similar to that of a commercially available phosphorus sorbent lanthanum modified bentonite , although the stability of phosphorus binding was higher for the commercial product. Theoretical average in lake total phosphorus, chlorophyll a, and transparency values, estimated through Vollenweider models, were approximately double of the average values measured in the lake. Therefore, the massive presence of riverborne clay sediments seems to markedly reduce the in lake orthophosphate concentrations and light penetration , inducing an overall lowering of the lake trophic state, as if the lake ecosystem were permanently subjected to a geo engineering phosphorus sorbent treatment. 856 Preprint https //www.sciencedirect.com/science/article/pii/S0048969722063240 Phosphate adsorption by riverborne clay sediments in a southern Italy Mediterranean reservoir Insights from a natural geo engineering experiment Journal Pre Print Copetti_2023_Pre_Proof_OnLine_1 s2.0 S0048969722063240 main.pdf Articolo in rivista Elsevier 0048 9697 Science of the total environment Science of the total environment Sci. total environ. gianni.tartari TARTARI GIANNI mariateresa.palumbo PALUMBO MARIA TERESA diego.copetti COPETTI DIEGO lucia.valsecchi VALSECCHI LUCIA marina.mingazzini MINGAZZINI MARINA |
