Search results for "Sediment"

Accumulation of low oxygen water in deep waters of ice-covered lakes cooled below 4 °C

2013

We studied vertical distribution of oxygen under the ice of 5 medium-sized, morphologically variable lakes that cooled well below 4 °C before freezing. In the upper part of the water column, dissolved oxygen and dissolved inorganic carbon concentrations generally remained vertically almost uniform, but in the deepest water, concentrations changed rapidly near the bottom. The coincidence of the changes with an increase in deep water temperature shows that they were due to advection of water made heavier by the heat flux from the sediment. Consequently, water with low concentrations of dissolved oxygen and high concentrations of dissolved inorganic carbon accumulated in the deepest part of th…

Particularities of Grey Alder (Alnus incana) Stands in Riparian Galleries Along Streams of the Southern Transylvanian Tableland (Romania)

2019

Abstract Grey Alder (Alnus incana (L.) Moench.) stands are distributed in the Carpathian area on alluvial deposits with sediments of different grain size as galleries along rivers and streams of the sub-montane to the middle montane level. The geological structure (Tertiary sedimentary deposits) in relation to the hydromorphological processes is the base for the structure of the stream valleys, which are in part very deep. Under the special microclimate of these deeper stream stretches with lower temperatures there are favourable conditions for the development of grey alder stands.

Budgeting soil erosion from floodplain sediments of the central Rhenish Slate Mountains (Westerwald), Germany

2011

The distribution, thickness and composition of the floodplain sediments in the valleys of the Gelbach (Lower Westerwald) and Große Nister (Upper Westerwald) depend on the occurrence of loessic periglacial cover beds in their catchments as well as on historical land use. The budget of floodplain sedimentation was derived from a study of the floodloams underlying the monastery garden of Marienstatt, a village in the Große Nister valley. From the study of two occupation levels, pottery shards and radiocarbon dating, 55% of the floodloam can be attributed to the Modern period (younger than c. AD 1450). From the radiocarbon age of a charcoal fragment extracted from the base of the floodloam at …

A new windstorm proxy from lake sediments: A comparison of geological and meteorological data from western Germany for the period 1965–2001

2009

[1] The feasibility of detecting windstorm layers in lake sediments is explored by comparing quartz grain size data from a freeze core obtained from the Schalkenmehrener Maar (Eifel region, western Germany) to recent meteorological wind data. The Schalkenmehrener Maar is appropriate for such a calibration study because the morphological settings of the lake allow the conservation of windstorm layers (in particular, there is no fluvial sediment inflow) and long-term wind measurements are available from nearby stations. The age model for the uppermost 30 cm of the sediment core is based on measurements of 137Cs and 210Pb concentrations. An ultra-high-resolution grain size analysis is performe…

Pumping of epilimnetic water into hypolimnion improves oxygen but not necessarily nutrient conditions in a lake recovering from eutrophication

2014

To mitigate deep water oxygen depletion and its consequences, epilimnetic water was pumped into deep water of a eutrophic, 26 km 2 subbasin of Lake Vesijarvi, Finland. In winter, the mechanical mixing largely eliminated vertical differences in temperature, oxygen, and nutrients. Although ice cover prevented oxygen flux from the atmosphere, the high proportion of shallows in the basin with high oxygen concentration facilitated the avoidance of hypoxia by mixing. Despite the disappearance of anoxia in deep water, the volume-weighted mean concentrations of nutrients were not affected. In summer, the introduction of epilimnetic water into the hypolimnion improved oxygen conditions, but anoxia o…

Effects of temperature and sediment properties on benthic CO2production in an oligotrophic boreal lake

2010

Summary 1. Temperature and many other physical and chemical factors affecting CO2 production in lake sediments vary significantly both seasonally and spatially. The effects of temperature and sediment properties on benthic CO2 production were studied in in situ and in vitro experiments in the boreal oligotrophic Lake Paajarvi, southern Finland. 2. In in situ experiments, temperature of the water overlying the shallow littoral sediment varied seasonally between 0.5 and 15.7 °C, but in deep water (≥20 m) the range was only 1.1–6.6 °C. The same exponential model (r2 = 0.70) described the temperature dependence at 1.2, 10 and 20 m depths. At 2.5 and 5 m depths, however, the slopes of the two re…

MANUAL SAMPLING AND TANK SIZE EFFECTS ON THE CALIBRATION CURVE OF PLOT SEDIMENT STORAGE TANKS

2004

In many experimental soil erosion plots, runoff is collected and carried by a conveyance system to a sequence of storage tanks. If the soil loss is measured by collecting, after mixing, samples of the stored suspension, then a calibration curve between the actual mean concentration (C) and the measured concentration (Cm) in the storage tank occurs. The aim of this article was to evaluate experimentally the factors affecting the relationship between C and Cm. For a sandy loam soil, the replicated measurements of Cm (20 samples) for two values of the actual concentration (C = 5 and 25 g/L) showed that the variability of the measurements of Cm is low and confirmed the reliability of a calibrat…

A Rainfall Simulator Laboratory Approach to Determine the Impact of Ash Depth on Runoff Generation and Soil Losses

2020

Ash cover the forest fire affected soil for some weeks or months and act as a key factor to determine the soil and water losses. Ash depth is researched here to determine how affect the soil detachment and the runoff generation. Seventy rainfall simulation experiments on paired 0.50 m2 plots (five plots with 0, 1, 2, 3, 5, 10, 15- and 30-mm ash depth), and repeated one week later) under thunderstorms of 48 mmh-1 for one hour were carried out under laboratory conditions. In the first experiment, after the bed of ash was applied, the results show that ash depth determines the runoff rates as they reduce the discharge from 23.1% to 13.9%. The sediment concentration increased from 23.8 till 38.…

Nitrogen sedimentation in a lake affected by massive nitrogen inputs: autochthonous versus allochthonous effects

2006

12 pages, and tables statics, and figures

2019

Flooding may damage important transportation infrastructures, such as roads, railways and bridges, which need to be well planned and designed to be able to withstand current and possible future climate-driven increases in flood frequencies and magnitudes. This study develops a novel approach to predictive statistical modelling of the probability of flooding at major road-stream intersection sites, where water, sediment and debris can accumulate and cause failure of drainage facilities and associated road damages. Two areas in south-west Sweden, affected by severe floods in August 2014, are used in representative case studies for this development. A set of physical catchment-descriptors (PCD…