Using caesium-137 measurements to investigate soil erosion rates in western Istanbul (NW Turkey)

Buyukcekmece Reservoir, located in the western outskirts of Istanbul, is one of the major water resources of Istanbul, and supplies drinking water to about 4 million people. Erosion in the catchment of the reservoir is an important problem in terms of its longer-term sustainability for water supply. There is an urgent need to obtain reliable quantitative data regarding erosion and deposition rates within the catchment to assess the magnitude of the problem and to plan catchment management strategies. In the absence of existing data, attention has focussed on the potential for using ¹³⁷Cs measurements to provide retrospective estimates of medium-term soil erosion rates within the catchment over the past ca. 40 years. To date, the ¹³⁷Cs approach has not been used to document soil redistribution rates in Turkey and this contribution reports an attempt to confirm the viability of the approach and the results of a preliminary investigation of rates of soil loss from uncultivated areas within the catchment. The soil redistribution rates estimated using the profile distribution conversion model varied from − 16.11 (erosion) to 4.59 (deposition) t/ha/year.     

Calibration of caesium-137 measurements to provide quantitative erosion rate data

The caesium-137 technique for investigating rates and patterns of soil loss has now been successfully applied in a wide range of environments. However, some uncertainty still surrounds the ability of the technique to provide quantitative estimates of rates of erosion. The wide range of calibration relationships that have been employed by individual workers to derive erosion rates from estimates of the amount of ¹³⁷Cs (caesium-137) lost from the soil profile, emphasize the uncertainty involved. Existing calibration procedures, involving both empirical relationships and theoretical models and accounting procedures are reviewed and their limitations and inconsistencies are identified. Further research is required in this important area, if the clear potential of the caesium-137 technique is to be fully realized.     

Rates of soil erosion on arable fields in Britain: quantitative data from caesium-137 measurements

Abstract. Despite a growing awareness that erosion on arable land in Britain is a potential hazard to long-term productivity, there is still only limited information on the rates involved, particularly long-term values. Use of the caesium-137 (¹³⁷Cs) technique to study soil erosion within arable fields on various soil types at 13 locations in southern Britain has yielded retrospective measurements of the long-term ( c. 30 years) rates of soil loss and the patterns of soil redistribution within the study fields. The range of long-term rates of net soil loss extends from 0.61 per hectare per year on clay soils in Bedfordshire to 10.5 t per hectare per year on brown sands in Nottinghamshire. The measured rates are compared with other published data for similar soil types and land use, and the implications for long-term productivity and potential environmental impacts are considered.     

Quantification of accelerated soil erosion using the environmental tracer caesium-137

The principal objective of this investigation was to quantify erosion rates for five agricultural fields in three separate study areas in Saskatchewan. The radionuclide tracer caesium-137 (¹³⁷Cs) was used to quantify net erosion and net deposition within the landscape over a 30-year period. Uneroded (native) sites were used to establish the mean background level of ¹³⁷Cs in each of the study areas. The assumption being that agricultural sites with ¹³⁷Cs areal activities greater than the native site were subject to deposition, and sites with ¹³⁷Cs less than the native control site were subject to erosion. A linear proportionality model was used to convert the loss or gain of ¹³⁷Cs to net soil erosion or deposition. Results have indicated that accelerated (anthropogenic) erosion has been commonplace on arable land in Saskatchewan, even on near-level fields (< 1.3 degrees). The net integrated sediment output from the five agricultural fields ranged from — 0.6 t th⁻¹ y⁻¹ to — 6.8 t ha⁻¹ y⁻¹ (where negative values represent erosion). What is more alarming is that between 40 and 75 per cent of all sites sampled within individual fields had erosion rates in excess of the generally accepted rate of soil formation (1.0 t ha⁻¹ y⁻¹). Also, in one highly eroded field (Crystal Springs medium sloping site) 65 per cent of the sites sampled exceeded the upper tolerable erosion rate of 11.0 t ha⁻¹ y⁻¹. These results indicate significant degradation of the non-renewable soil resource has occurred over the past 30 years and is still presently active. Land degradation by accelerated erosion would result in reductions in effective rooting depth, soil moisture holding capacity, essential nutrient stores, and would adversely effect the physical structure of the topsoil. The major reason for accelerated erosion on arable land in Saskatchewan is the practice of summer fallowing, where the field is left in a ‘bare’ state and repeatedly tilled every second or third year. During a fallow period, or prior to crop emergence during a cropping year, fields are subject to wind and water erosion. On near-level fields wind would be the dominant transport agent, while on sloping fields inter-rill and rill erosion would be the primary forces of erosion. It is suggested that the appropriate conservation farming response would be to increase application of surface mulches and possibly to decrease the frequency of summer fallowing. Without such efforts long-term sustainable agricultural production in the Prairies of Canada is considered to be a tenuous land use practice.     

Use of 137Cs measurements to investigate soil erosion on arable fields in the UK: potential applications and limitations

Recent awareness of the potential hazard of soil erosion on arable land in the UK has highlighted the lack of reliable data concerning actual rates of soil loss. This lack of information reflects both a low level of interest, and the lack of a simple and generally applicable method of documenting long-term rates of soil loss. Existing methods involving the use of hazard classification procedures and direct measurement techniques, including erosion plots and field surveys, all possess significant limitations. The use of ¹³⁷Cs measurements to provide information on rates of soil loss and deposition averaged over the past 30 years would appear to offer considerable potential. The results of applying this approach to three arable fields on contrasting soil types in Britain are reported. These results confirm the viability of the technique and its potential for providing information on patterns and rates of erosion and deposition within individual fields and their overall sediment budgets. Limitations include the restricted size of the areas that can be investigated and the need to take account of additional inputs of ¹³⁷Cs derived from the Chernobyl accident.     

利用137Cs估算土壤侵蚀速率的定量模型

A quantitative model was developed to relate the amount of ^137Cs loss from the soil profile to the rate of soil erosion,According th mass balance model,the depth distribution pattern of ^137Cs in the soil profile ,the radioactive decay of ^137Cs,sampling year and the difference of ^137Cs fallout amount among years were taken into consideration.By introducing typical depth distribution functions of ^137Cs into the model ,detailed equations for the model were got for different soil,The model shows that the rate of soil erosion is mainly controlled by the depth distrbution pattern of ^137Cs ,the year of sampling,and the percentage reduction in total ^137Cs,The relationship between the rate of soil loss and ^137Cs depletion i neither linear nor logarithmic,The depth distribution pattern of ^137Cs is a major factor for estimating the rate of soil loss,Soil erosion rate is directly related with the fraction of ^137Cs content near the soil surface. The influences of the radioactive decay of ^137Cs,sampling year and ^137Cs input fraction are not large compared with others.     

Allowable soil erosion rates in Georgia

A procedure was proposed for the determination of the maximum allowable soil disturbance in Georgia in order to develop a strategy of soil conservation and restoration. The allowable soil losses were calculated within the risk limits of 0.01 < r < 0.1. The lower and upper limits of the allowable soil loss were determined for the soils of different thicknesses. To compare the rates of the soil erosion, one uses the erosion index: the ratio between the actual erosion rate and its maximum allowable value. The actual erosion rate is determined from erosion equations, in which the integrated parameters of the soil loss tolerance include the permissible flow velocity and data on the climatic and soil conditions. From the estimated allowable soil erosion rates, criteria of decision making can be formulated for substantiating the strategy of soil conservation or restoration.     

Combining plot measurements and a calibrated RUSLE model to investigate recent changes in soil erosion in upland areas in Southern Italy

Journal of Soils and Sediments - In recent decades, soil erosion has been recognized as a serious environmental problem in many countries of the world and the impacts of climate change have focused...     

利用137Cs示踪技术评价东北黑土侵蚀和沉积过程

Soil and water losses through erosion have been serious in the black soil region of Northeast China. Therefore, a sloping cultivated land in Songnen Plain was selected as a case study to： 1） determine the ^137Cs reference inventory in the study area; 2） calculate erosion and deposition rates of black soil on different slope locations; 3） conduct a sensitivity analysis of some model parameters; and 4） compare overall outputs using four different models. Three transects were set in the field with five slope locations for each transect, including summit, shoulder-slope, back-slope, foot-slope, and toe-slope. Field measurements and model simulation were used to estimate a bomb-derived ^137Cs reference inventory in the study area. Soil erosion and deposition rates were estimated using four ^137Cs models and percentage of ^137Cs loss/gain. The ^137Cs reference value in the study area was 2 232.8 Bq m^-2 with ^137Cs showing a clear topographic pattern, decreasing from the summit to shoulder-slope, then increasing again at the foot-slope and reaching a maximum at the toe-slope, Predicted soil redistribution rates for different slope locations varied. Among models, the Yang Model （YANG-M） overestimated erosion loss but underestimated deposition. However, the standard mass balance model （MBM1） gave predictions similar to a mass balance model incorporating soil movement by tillage （MBM2）. Sensitivity analysis of the proportion factor and distribution pattern of ^137Cs in the surface layer demonstrated the impact of ^137Cs enrichment on calculation of the soil erosion rate. Factors influencing the redistribution of fallout ^137Cs in landscape should be fully considered as calculating soil redistribution rate using ^137Cs technique.     

Throughfall,runoff and soil erosion after prescribed burning in gorse shrubland in Galicia (NW Spain)

The first‐year effect of two different prescribed burning treatments on throughfall, runoff and soil erosion was evaluated in gorse shrubland (Ulex europaeus L.) in Galicia (NW Spain). The treatments compared were: intense burn, light burn and control (no burn). Accumulated annual throughfall represented between the 81 and 87 per cent of total rainfall in intensely burned and lightly burned areas, respectively, whereas in the unburnt areas it was 60 per cent. No significant differences between burning treatments were found for the annual throughfall. However, runoff was significantly greater in intensely burned plots (1·5‐times) than in lightly burned plots. Burning also resulted in a significant increase in runoff (between 2·5 and 1·7‐times, respectively) compared with controls. Total soil losses were small in all treatments, but the intense burn caused significantly greater soil erosion (5·8‐times) compared with the unburned areas. Soil losses after the light burn did not significantly differ from the control although they were higher (2·3‐times). The relationships obtained between erosion and several rainfall parameters were significantly different in burned areas compared to the control. The same response was observed for runoff. Annual erosion losses showed a strong dependence on percentage of bare soil even for small values of this variable. Litter thickness was also a very important variable influencing on erosion rates. This study indicated that by combining ignition techniques and high litter moisture content to maintain the percentage of bare soil below 85 per cent, soil erosion was low. Nevertheless, this result was constrained by the low rainfall that occurred during the study. Copyright © 2005 John Wiley & Sons, Ltd.     

川中丘陵区人工刨地耕作方式下紫色土坡耕地侵蚀速率的137Cs和210Pbex双核素示踪法研究

Purple soils are widely distributed in the Sichuan Hilly Basin and are highly susceptible to erosion, especially on the cultivated slopes. Quantitative assessment of the erosion rates is, however, difficult due to small size of the plots of the manually-tilled land, the complex land use, and steep hillslopes. 137Cs and 210Pbex (excess 210Pb) tracing techniques were used to investigate the spatial pattern of soil erosion rates associated with slope-land under hoe tillage in Neijiang of the Sichuan Hilly Basin. The 137Cs and 210Pbex inventories at the top of the cultivated slope were extremely low, and the highest inventories were found at the bottom of the cultivated slope. By combining the erosion rates estimates provided by both 137Cs and 210Pbex measurements, the weighted mean net soil loss from the study slope was estimated to be 3100 t km-2 year-1, which was significantly less than 6930 t km-2 year-1 reported for runoff plots on a 10°cultivated slope at the Suining Station of soil Erosion. The spatial pattern of soil erosion rates on the steep agricultural land showed that hoe tillage played an important role in soil redistribution along the slope. Also, traditional farming practices had a significant role in reducing soil loss, leading to a lower net erosion rate for the field.     

Plough marks as a tool to assess soil erosion rates: A case study in Axum (Ethiopia)

From the antiquity, the hilly landscape around the city of Axum in northern Ethiopia has been terraced and extensively used for agriculture purposes. Impacts of the “ard” plough on protruding and/or buried boulder at a depth less than the tillage depth produce scratches on their sides or their top. The spatial relationship among plough marks and rock surface orientations gives information on the ploughing direction, whereas the relative height from the present ground surface to the top of the marks and information on the age of cultivation can be used to assess soil loss rates. Parameters to define plough mark orientation were defined and measured in the field on boulders with plough marks within a study terrace located in an archaeological area with an approx of 2040 year age. These parameters are height from the ground, dip, slope and frequency.     

Caesium-137 fallout depth distribution in different soil profiles and significance for estimating soil erosion rate

Caesium-137 (¹³⁷Cs) has been widely used for the determination of soil erosion and sediment transport rate. However, depth distribution patterns of ¹³⁷Cs in the soil profile have not been considered. As a result, the erosion rates may be over-estimated or underestimated. This paper presents the depth distribution of ¹³⁷Cs fallout in different soil profiles using published data. Three types of depth distribution functions of ¹³⁷Cs are given by using statistical regression methods, the exponential type, the peak type and the decreasing type (including uniform distribution). Relationships between ¹³⁷Cs loss and soil erosion rate are given by introducing the regression functions. The influence of depth distribution of ¹³⁷Cs on the estimation of the soil erosion rate was simulated. Simulation results showed that very different soil erosion rates could be deduced for different depth distributions when ¹³⁷Cs loss is the same, which indicates that the depth distribution pattern should be considered when soil erosion is estimated by using ¹³⁷Cs. Simulation results also suggested that it is most important to determine the depth distribution of ¹³⁷Cs near the soil surface and the annual relative loss of ¹³⁷Cs by using the depth distribution of ¹³⁷Cs as a criterion to estimate the soil erosion rate.     

Using Cs‐137 fingerprinting technique to estimate sediment deposition and erosion rates from Yongkang depression in the karst region of Southwest China

Understanding the erosion and deposition rates is very important for designing soil and water conservation measures. However, existing methods of assessing the rates of soil loss present many limitations and are difficult to apply to in karst areas, and there is still very little data in this areas. Karst depressions comprise geomorphologically important sources and sinks for sediments and can provide the long‐term history records of environmental changes. But there have been few similar studies focused on its sediments in the world. In this paper, the Cs‐137 technique was employed to estimate the sediment deposition rate of karst depression to assess the surface erosion. The results indicate that the average deposition rate, deposition amount and specific deposit yield for the Yongkang catchments since 1963 were estimated to be 4·32 mm y⁻¹, 3·16 t y⁻¹and 20·53 t km⁻² y⁻¹, respectively. The results obtained were consistent with the actual monitoring data of local runoff plots, and confirm the validity of the overall approach. So it was suggested that the mean specific sediment yields of 20 t km⁻² y⁻¹ can be representative of the soil loss rates in the regions. Copyright © 2010 John Wiley & Sons, Ltd.     

Tillage effects on soil properties and maize productivity in western Turkey

Information regarding the evaluation of long-term tillage effects on soil properties and summer maize growth after winter vetch in western Turkey is not available. Therefore, this study was conducted for 5 years with three types of tillage including conventional (mouldboard plough) and conservation (rototiller and chisel). Results indicated that tillage had no significant effect on penetration resistance, except at the bottom of 20 cm soil depth where it was higher in mouldboard plough than in rototiller and chisel. Bulk density in the topsoil of 10 cm decreased with the degree of soil manipulation during tillage practices. Rototiller caused significantly higher root, leaf and stems biomass and plant height than the other systems. The root dry weight was higher in the topsoil of 10 cm than at the bottom of this soil depth for all systems. The highest root dry weight was found in fourth year of chisel, but the lowest was recorded in the same year of plough, especially at the bottom of 20 cm due to higher penetration. Rototiller improved soil properties and maize growth compared to other systems in 2 of 5 years. We concluded that using rototiller for maize after winter vetch will be more effective compared with other systems.     

137Cs示踪分析东北黑土坡耕地土壤侵蚀对有机碳组分的影响

研究土壤侵蚀对有机碳不同组分流失的影响,可为科学评估土壤侵蚀在碳循环中的作用和探明农田有机碳变化机制提供理论依据.该研究以典型黑土区一凸型耕地坡面为研究对象,基于137Cs示踪技术,分析了坡面土壤侵蚀特征及强度分布,定量分析了坡面有机碳组分的变化幅度及侵蚀强度与有机碳组分间的关系.结果表明:研究坡面年均侵蚀速率为380...     

Using rainfall simulation and site measurements to predict annual interrill erodibility and phosphorus generation rates from unsealed forest roads: Validation against in-situ erosion measurements

The measurement of soil erosion rates under natural rainfall conditions is costly and time consuming. Data provided by rainfall simulation and static site measurements can be used to predict erosion rates under natural conditions, however the accuracy of this method is largely untested. This is especially true for erosion rates from unsealed forest roads. In this study, the values for a range of erodibility indices calculated from rainfall simulation experiments are compared to observed erodibility index values from 1 year of detailed in-situ erosion monitoring of seven different forest road types. The prediction of phosphorus generation rates from rainfall simulation and/or soil sampling was also evaluated. The results showed that a series of commonly used erodibility indices such as sediment per unit rainfall, sediment per unit runoff, sediment per unit EI₃₀, and sediment per unit rainfall energy were poorly predicted from the rainfall simulation experiments. Five of the six indices tested substantially overpredicted the observed erodibility at one site, a gravel road subjected to minimal traffic. For the other six road sites predictions were poor and highly variable, the coefficient of efficiency ranging from − 13.32 to 0.17 for these erodibility indices. A modified index, the ratio of sediment per unit rainfall energy to the mean rate of rainfall energy input, was able to predict annual erosion rates from six different road surfaces using rainfall simulation data with a coefficient of efficiency of 0.9. The results indicate that existing erodibility indices are not suitable for predicting observed erosion rates on forest roads using rainfall simulation data as collected in this study. It is argued that the modified index is more suited to sites (such as compacted roads) where interrill processes dominate, and erosion rates are less sensitive to peak flows. With respect to nutrient generation rates, rainfall simulation was able to accurately predict the observed proportion by mass of total phosphorus (TP) in runoff with a coefficient of efficiency of 0.96. Direct soil sampling of the road surface could also be used to predict the proportion by mass of TP in runoff. Concentrations of total nitrogen in forest road materials were found to be at the lower detection limit of the laboratory instruments.     

Using the RUSLE to identify factors controlling erosion rates of mine soils

Observable differences in particle size, smoothness and compaction between cap site (slope 2·8 per cent) and batter site (slope 20·7 per cent) surfaces on the waste rock dump at Ranger Uranium Mine were quantified in terms of revised universal soil loss equation (RUSLE) parameter values. Cap site surface material had a K_m (erodibility corrected for sediment density) of 0·030 and batter site surface material had a K_m of 0·0056. Using these K_m values (derived from particle size distributions), slope length and steepness (LS) factors of 0·36 for the cap site and 3·66 for the batter site, and a cover (C) factor of 0·45 for the cap site and 0·16 for the batter site, the RUSLE predicts an erosion rate from the cap site that is 1·9 times greater than erosion from the much steeper batter site. The RUSLE indicates that the finer particle size and blocky soil structure of the cap site (D₅₀ = 0·91 mm) compared with the looser granular structure of the batter site (D₅₀ = 1·74 mm) strongly influence erosion. The predictions are similar to observed soil losses from erosion plots on these sites under rainfall simulation events, for which the measured erosion rate from the cap site was approximately twice that from the batter site. For the RUSLE to predict the observed erosion rates, the support practice (P) factor for the cap site would have to be approximately 30 per cent greater than the P factor for the batter site. The higher cap site P factor probably results from smoothing and compaction caused by vehicle movement across the surface. Compaction is considered to have greatly reduced infiltration capacity, thus increasing the erodibility of the cap site. Vehicles probably also crushed the surface material at the cap site, creating the observed finer particle size distribution and further increasing the erodibility. Compaction, through its effects on erodibility (K_m) and surface roughness (P), is concluded to be the major cause of higher erosion from the cap site, even though the slope steepness is 10 times less. Parameterisation of the RUSLE quantifies the differences between sites and explains the unexpected erosion rates observed. The results highlight the need for careful management of rehabilitated sites to avoid increases in erosion which may arise from compaction by machinery.     

贵州西部山区土壤侵蚀研究

本文通过对影响贵州西部山区土壤侵蚀的自然因素和人为因素的分析研究,认为:该区已成为贵州省内土壤侵蚀最严重的地区之一,它将对乌江、红水河及长江、珠江流域的综合开发带来严重的危害。同时给本区国民经济的发展和人民生命财产的安全带来严重威胁。为此,作者在科学地论述了该区几种主要侵蚀类型、成因、危害等的基础上,指出加强防治这一地区的土壤侵蚀已成为刻不容缓的紧迫任务。