A Comparison of Soil Losses Estimated Using Fallout Radionuclides and the USLE for the Omerli Watershed, Turkey

Soil erosion is a major degradation process in watersheds. Inappropriate land use is the main reason for soil loss by erosion and for the associated sedimentation of lakes and reservoirs in Turkey. Soil erosion rates are usually part of the information to be considered for land evaluation under special conditions and they are generally estimated using empirical or theoretical models. Fallout radionuclides (FRN's) provide a powerful new technique for obtaining empirical information on erosion rates that can be used for predicting the impacts of proposed land management strategies on soil erosion and sediment yield within river basins. The Universal Soil Loss Equation (USLE) is one of the most comprehensive methods for estimating soil erosion, but the USLE does not estimate deposition. The aim of the study reported in this contribution was to compare soil losses estimated using Cs-137 measurements and the USLE at the Pasakoy and Esenceli study sites in the Omerli dam catchment, which supplies drinking water for Istanbul city. Soil losses estimated usin Cs-137 were 9.62 and 3.32 t ha(-1) yr(-1) for upper slopes and 10.34 and 2.19 t ha(-1) yr(-1) for mid-slopes, in Pasakoy and Esenceli, respectively, while those calculated using the USLE were 11.53 and 16.21 t ha(-1) yr(-1) for upper slopes and 19.58 and 14.45 t ha(-1) yr(-1) for mid-slopes, in Pasakoy and Esenceli, respectively

Determination of soil loss by (CS)-C-137 fallout radionuclide in Omerli watershed of Istanbul, Turkey

Soil erosion and sedimentation in watersheds are usually part of the information to be considered for soil and water conservation measures. Soil loss is generally estimated with models or measured with plot studies. Although fallout radionuclides (FRN)(#) methodology provides a powerful technique for predicting the impacts of proposed land management strategies on soil erosion and sediment yield within river basins and estimates erosion based on fallout radioisotopes (Cs-137, Pb-210, Be-7) radioactivity; it is rarely used in Turkey. The aim of this study was to determine soil losses from different land use types with FRN's methodology by using caesium-137 radionuclide in selected study sites around Pasakoy (shrub) and Esenceli (rangeland) villages in the environs of Omerli watershed. Bulk and 2 cm-depth incremental soil core samples were collected from the reference and sloping areas in both study sites. Soil losses varied from 0.49 to 23.22 t ha(-1) yr(-1) for shrub-covered sites and from 0.44 to 7.23 t ha(-1) yr(-1) for rangelands. The data show that soil loss from shrub-covered site was greater than acceptable tolerance limit (10 t ha(-1) yr(-1)) for soils of the sites

Assessment of Po-210 and Pb-210 by moss biomonitoring technique in Thrace region of Turkey

This study presents the first data of Po-210 and Pb-210 activity concentrations using moss species Hypnum cupressiforme from Thrace region, the northwestern part of Turkey. The moss samples were systematically collected from 40 locations in the study area. The average with standard deviation and range of Po-210 and Pb-210 activity concentrations were found to be 409 +/- 128, 188-777 and 494 +/- 183, 178-852 Bq kg(-1) at dry weight, respectively. Comparatively higher radionuclide activities were found in the northeastern Thrace, probably due to Rn-222 daughters attached to aerosols through high rainfall in this part of the region. A significant positive correlation was found between Po-210 and Pb-210, which shows that their source and/or bioaccumulation behavior are similar. The average and range of Po-210/Pb-210 ratio were calculated to be 0.89 and 0.47-2.67, respectively. Those levels were calculated to be mostly lower than unity that addressed the abundance of Pb-210, probably due to predominantly inorganic particles through atmospheric deposition