Estimation of uncertainty arising from different soil sampling devices: the use of variogram parameters

In the frame of the international SOILSAMP project, funded and coordinated by the National Environmental Protection Agency of Italy (APAT), uncertainties due to field soil sampling were assessed. Three different sampling devices were applied in an agricultural area using the same sampling protocol. Cr, Sc and Zn mass fractions in the collected soil samples were measured by k(0)-instrumental neutron activation analysis (k(0)-INAA). For each element-device combination the experimental variograms were calculated using geostatistical tools. The variogram parameters were used to estimate the standard uncertainty arising from sampling. The sampling component represents the dominant contribution of the measurement uncertainty with a sampling uncertainty to measurement uncertainty ratio ranging between 0.6 and 0.9. The approach based on the use of variogram parameters leads to uncertainty values of the sampling component in agreement with those estimated by replicate sampling approach.     

Assessment of spatial variation of cesium-137 in small catchments

Surface contamination by bomb-derived and Chernobyl-derived 137Cs has been subject to changes due to physical decay and lateral transport of contaminated soil particles, which have resulted in an on-going transfer of radionuclides from terrestrial ecosystems to surface water, river bed sediments, and flood plains. Knowledge of the different sources of spatial variation of 137Cs is particularly essential for estimating 137Cs transfer to fluvial systems and for successfully applying 137Cs as an environmental tracer in soil erosion studies. This study combined a straightforward sediment redistribution model and geostatistical interpolation of point samples of 137Cs activities in soil to distinguish the effects of sediment erosion and deposition from other sources of variation in 137Cs in the small Mochovce catchment in Slovakia. These other sources of variation could then be interpreted. Besides erosion and deposition processes, the initial pattern of 137Cs deposition, floodplain sedimentation, and short-range spatial variation were identified as the major sources of spatial variation of the 137Cs inventory.     

Review and assessment of models for predicting the migration of radionuclides from catchments

The present paper summarises the results of the review and assessment of models developed for predicting the migration of radionuclides from catchments to water bodies. The models were classified and evaluated according to their main methodological approaches. A retrospective analysis of the principles underpinning the model development in relation to experimental finding and results was carried out. It was demonstrated that most of the various conceptual approaches of different modellers can be integrated in a general, harmonised perspective supported by a variety of experimental evidences. Shortcomings and advantages of the models were discussed.     

Spatial assessment of the economic feasibility of short rotation coppice on radioactively contaminated land in Belarus, Ukraine, and Russia. II. Monte Carlo analysis

A Monte Carlo analysis of two sequential GIS-embedded submodels, which evaluate the economic feasibility of short rotation coppice (SRC) production and energy conversion in areas contaminated by Chernobyl-derived (137)Cs, was performed to allow for variability of environmental conditions that was not contained in the spatial model inputs. The results from this analysis were compared to the results from the deterministic model presented in part I of this paper. It was concluded that, although the variability in the model results due to within-gridcell variability of the model inputs was considerable, the prediction of the areas where SRC and energy conversion is potentially profitable was robust. If the additional variability in the model input that is not contained in the input maps is also taken into account, the SRC production and energy conversion appears to be potentially profitable at more locations for both the small scale and large scale production scenarios than the model predicted using the deterministic model.     

Streambed Sediment Geochemical Controls on In-Stream Phosphorus Concentrations during Baseflow

A spatially extensive geochemical data set of stream water and bed sediment composition across the Tamar catchment in south-west England was analysed to identify the key bed sediment properties that control the in-stream dissolved reactive phosphorus (DRP) concentrations during baseflow conditions. Linear regression analysis of the streamwater DRP concentrations and the distribution coefficient K _d for DRP revealed that the former is positively correlated with total SiO₂ and Al₂O₃, and negatively correlated with K₂O. The primary control on these major element distributions is the dominant bedrock geology. The data suggest that streamwater DRP concentrations are mainly controlled by adsorption to clay minerals. Where P concentrations in streamwater were considerably elevated by inputs from point sources, DRP concentrations are also controlled by precipitation of hydroxyapatite.     

Controls on catchment-scale patterns of phosphorus in soil, streambed sediment, and stream water

Many models of phosphorus (P) transfer at the catchment scale rely on input from generic databases including, amongst others, soil and land use maps. Spatially detailed geochemical data sets have the potential to improve the accuracy of the input parameters of catchment-scale nutrient transfer models. Furthermore, they enable the assessment of the utility of available, generic spatial data sets for the modeling and prediction of soil nutrient status and nutrient transfer at the catchment scale. This study aims to quantify the unique and joint contribution of soil and sediment properties, land cover, and point-source emissions to the spatial variation of P concentrations in soil, streambed sediments, and stream water at the scale of a medium-sized catchment. Soil parent material and soil chemical properties were identified as major factors controlling the catchment-scale spatial variation in soil total P and Olsen P concentrations. Soil type and land cover as derived from the generic spatial database explain 33.7% of the variation in soil total P concentrations and 17.4% of the variation in Olsen P concentrations. Streambed P concentrations are principally related to the major element concentrations in streambed sediment and P delivery from the hillslopes due to sediment erosion. During base flow conditions, the total phosphorus (<0.45 microm) concentrations in stream water are mainly controlled by the concentrations of P and the major elements in the streambed sediment.     

Spatial assessment of the economic feasibility of short rotation coppice on radioactively contaminated land in Belarus, Ukraine, and Russia. I. Model description and scenario analysis

The economic feasibility of short rotation coppice (SRC) production and energy conversion in areas contaminated by Chernobyl-derived (137)Cs was evaluated taking the spatial variability of environmental conditions into account. Two sequential GIS-embedded submodels were developed for a spatial assessment, which allow for spatial variation in soil contamination, soil type, and land use. These models were applied for four SRC production and four energy conversion scenarios for the entire contaminated area of Ukraine, Belarus, and Russia and for a part of the Bragin district, Belarus. It was concluded that in general medium-scale SRC production using local machines is most profitable. The areas near Chernobyl are not suitable for SRC production since the contamination levels in SRC wood exceed the intervention limit. Large scale SRC production is not profitable in areas where dry and sandy soils predominate. If the soil contamination does not exceed the intervention limit and sufficient SRC wood is available, all energy conversion scenarios are profitable.     

Changes in Nutrient Emissions, Fluxes and Retention in a North-Eastern European Lowland Drainage Basin

Despite dramatic reductions in the 1990s of N and P emissions in the drainage basin, Lake Peipsi/Chudskoe (Estonia/Russia) is still suffering from algal blooms, probably caused by low N:P ratios of the lake water. To quantify the sources and changes of N and P inputs to the lake as a result of economic changes, we modelled emissions, transfer and in-stream retention using a GIS model. The model was calibrated using river monitoring data from the 1985–1989 period, and used to simulate emissions and loads for five future scenarios for 2015–2019. During the 1985–1999 period, diffuse P emissions decreased relatively more than N diffuse emissions, but this was not reflected in the loads to the lake. P loads decreased relatively less than N loads, which caused a decrease in the N:P ratio of the rivers. About 30–45% of diffuse N emissions and only 3–10% of diffuse P emissions reaches the river network. In-stream retention reduces N and P loads to the lake by about 62% and 72%, respectively. Point sources contribute negligibly to the N load to the lake, but form about one-third of the P load. A target/fast development scenario is the most likely scenario for the 2015–2019 period, resulting in higher nutrient loads than in recent years. We conclude that effective load reductions can be achieved by focussing on diffuse N and P emissions close ( < 50 km²) to the lake and by upgrading P removal capacity in wastewater treatment plants of towns.