Benthic solute fluxes, Phosphorus fractionation such as Temperature and oxygen profiles for Bautzen and Rappbode reservoirs

Benthic fluxes from sediment incubation, General sediment characterization, Phosphorus-fractionation

Trajectories of Sediment-Water Interactions in Reservoirs as a Result of Temperature and Oxygen Conditions

Temperate lakes/reservoirs are warming; this can influence the benthic release of nutrients. They undergo seasonal changes resulting in an array of temperature and oxygen conditions; oxic-low, oxic-high, anoxic-low, and anoxic-high temperature. We sought to understand the interaction of temperature and oxygen conditions on benthic solutes exchange through a two-factorial sediment core incubation experiment by varying either temperature or oxygen conditions of sediment cores from an oligotrophic and eutrophic reservoir. Temperature and oxygen conditions are both important for nutrient release; however, they influence solutes differently; differences in the fluxes of the treatments were explained more by temperature for P, DOC and N, while for Fe, Mn and SO42−, differences were explained more by oxygen conditions. The combination of strongly reducing conditions (due to anoxia) and high temperature (20 °C) led to a significant increase in nutrients concentrations in the overlying water. Under these conditions, SRP flux was 0.04 and 0.5 mmol m−2 d−1; ammonium was 0.9 and 5.6 mmol m−2 d−1 for the oligotrophic and eutrophic reservoir, respectively. We observed a synergistic interaction between temperature and oxygen conditions which resulted in release of solutes from sediments. An increase in nutrients release under increasing temperatures is more likely and so are algal blooms

Trace-element behaviour in sediments of Ugandan part of Lake Victoria: results from sequential extraction and chemometrical evaluation

Lake Victoria is the second largest freshwater lake and the largest tropical lake in the world. The transboundary lake has the fastest growing population in its catchment, which can impact the water and sediment quality. To determine the extent of anthropogenic effects on sediment quality in the Ugandan part of Lake Victoria, the contents and binding behaviour of trace elements were analysed, as well as organic matter and phosphorus in different sediment layers of both deep and coastal sediments near the coastal cities of Entebbe, Kampala and Jinja. The data were assessed using the German LAWA criteria for trace-element pollution, the Geo-Index, Cluster- and Factor analyses. Mostly, no critical trace-element contamination in the sediments of the investigated area was observed. However, changes in element distributions caused by anthropogenic influences from around the lake were detected, like higher contents of Cu, Ti and V in near shore sediments with urban surrounding. Near Jinja, industrial wastewaters caused particularly elevated contents of Cu in the sediments (70–121 mg/kg, 3.5–6 times the geogenic background), exceeding the LAWA criteria and potentially harming the aquatic habitat. In addition, temporally growing organic matter contents in the lake sediments near the estuary of River Nzoia (from 4.2 to 17.6% in around 60 years) due to increased soil erosion in the river’s catchment area and blooms of the water hyacinth became visible. This study demonstrates that the whole catchment area is responsible to ensure a healthy aquatic ecosystem in Lake Victoria.International Foundation for Science (IFS)Organisation for the Prohibition of Chemical Weapons http://dx.doi.org/10.13039/501100004766Helmholtz-Zentrum für Umweltforschung GmbH - UFZ (4215

Trace-element behaviour in sediments of Ugandan part of Lake Victoria: results from sequential extraction and chemometrical evaluation

Lake Victoria is the second largest freshwater lake and the largest tropical lake in the world. The transboundary lake has the fastest growing population in its catchment, which can impact the water and sediment quality. To determine the extent of anthropogenic effects on sediment quality in the Ugandan part of Lake Victoria, the contents and binding behaviour of trace elements were analysed, as well as organic matter and phosphorus in different sediment layers of both deep and coastal sediments near the coastal cities of Entebbe, Kampala and Jinja. The data were assessed using the German LAWA criteria for trace-element pollution, the Geo-Index, Cluster- and Factor analyses. Mostly, no critical trace-element contamination in the sediments of the investigated area was observed. However, changes in element distributions caused by anthropogenic influences from around the lake were detected, like higher contents of Cu, Ti and V in near shore sediments with urban surrounding. Near Jinja, industrial wastewaters caused particularly elevated contents of Cu in the sediments (70–121 mg/kg, 3.5–6 times the geogenic background), exceeding the LAWA criteria and potentially harming the aquatic habitat. In addition, temporally growing organic matter contents in the lake sediments near the estuary of River Nzoia (from 4.2 to 17.6% in around 60 years) due to increased soil erosion in the river’s catchment area and blooms of the water hyacinth became visible. This study demonstrates that the whole catchment area is responsible to ensure a healthy aquatic ecosystem in Lake Victoria

Sediment incubation fluxes in reservoirs

Sediment incubation studies mostly focus on a few target solutes. This approach provides a limited understanding of the interaction of the processes behind the different solutes occurring in sediments. We provide here a comprehensive data set that covers many solutes to enable a better understanding of the important processes in the sediments. The sediment incubation results in this data set were collected from five water bodies; Hassel pre-dam in 2013, Rappbode pre-dam in 2014, Rappbode Reservoir in 2015, Bautzen Reservoir in 2014, and Sau Reservoir in 2015. The data is divided into 5 groups; i. CTD/Sonde profiles (depth, temperature, dissolved oxygen, pH, turbidity, and chlorophyll-a. ii. Sediment incubation fluxes at different in-situ oxygen and conditions; dissolved organic carbon, methane, nitrate, ammonium, sulphate, dissolved iron and dissolved manganese. Sediments were collected using a gravity sampler (Uwitec, Mondsee, Austria). iii. Porewater concentration; dissolved organic carbon, methane, sulphate, dissolved iron and dissolved manganese. Porewater was extracted by centrifugation. iv. Sediment characterization; loss on ignition, water content, total carbon, total organic carbon, and total iron. v. Calculated parameters; Fred (total oxygen required per area to oxidize all reduced compounds released by the sediment), and respiratio