Radon emission fluctuation as a result of biochar application into the soil.

The presented research was focused on the analysis of the impact of biochar application into the soil on the radon exhalation process as a new issue of radiation protection in agriculture. Field measurements of the radon exhalation rate utilizing two methods-active and passive as well as laboratory measurements of the radon emanation coefficient were performed. In laboratory a soil samples with sunflower husk biochar were analysed using the accumulation chamber technique. At the final step the assessment of the effective dose for humans coming from radon exhalation from soil depending on biochar dose applied were evaluated. The doses of biochar applied in the analysed experimental fields were 0, 20, 40, 60, 80, and 100 Mg ha-1. The results show that biochar application into the soil contribute to a decrease in the emanation coefficient from a value around 7% to less than 2% with a simultaneous decrease in the radon exhalation rate from 4.4 to 14.8 mBq m-2 s-1 when the biochar dose increase from 0 to 100 Mg ha-1.

Effect of Fine Size-Fractionated Sunflower Husk Biochar on Water Retention Properties of Arable Sandy Soil.

Biochar application has been reported to improve the physical, chemical, and hydrological properties of soil. However, the information about the size fraction composition of the applied biochar as a factor that may have an impact on the properties of soil-biochar mixtures is often underappreciated. Our research shows how sunflower husk biochar (pyrolyzed at 650 °C) can modify the water retention characteristics of arable sandy soil depending on the biochar dose (up to 9.52 wt.%) and particle size (<50 µm, 50-100 µm, 100-250 µm). For comparison, we used soil samples mixed with biochar passed through 2 mm sieve and an unamended reference. The addition of sieved biochar to the soil caused a 30% increase in the available water content (AWC) in comparing to the soil without biochar. However, the most notable improvement (doubling the reference AWC value from 0.078 m3 m-3 to 0.157 m3 m-3) was observed at the lowest doses of biochar (0.95 and 2.24 wt.%) and for the finest size fractions (below 100 µm). The water retention effects on sandy soil are explained as the interplay between the dose, the size of biochar particles, and the porous properties of biochar fractions.

The SMOS-Derived Soil Water EXtent and equivalent layer thickness facilitate determination of soil water resources.

The assessment of water resources in soil is important in understanding the water cycle in the natural environment and the processes of water exchange between the soil and the atmosphere. The main objective of the study was to assess water resources (in 2010-2013) in the topsoil from satellite (SMOS) and in situ (ground) measurements using the SWEX_PD approach (Soil Water EXtent at Penetration Depth). The SWEX_PD is a result of multiplying soil moisture (SM) and radiation penetration depth (PD) for each pixel derived from the SMOS satellite. The PD, being a manifold of the wavelength λ0 equal to 21 cm, was determined from the weekly SMOS L2 measurement data based on the real and imaginary part of complex dielectric constant. The SWEX_PD data were compared with soil water resources (WR) calculated from the sum of components derived from multiplication of soil moisture (SM) and layer thickness in nine agrometeorological stations located along the eastern border of Poland. Each study site consisted of seven neighbouring Discrete Global Grid pixels (nodes spaced at 15 km) including the central ones with agrometeorological stations. The study area included different types of soils and land covers. The agreement between the water resources obtained from the SWEX_PD and ground measurements (WR) was quantified using classical statistics and Bland-Altman's plots. Calibrated Layer Thickness (CLT = dbias) from 8 to 28 cm was obtained with a low values of bias (close to zero), limits of agreements, and confidence intervals for all the SWEX_PD, depending on the pixel location. The results revealed that the use of the SWEX_PD for assessing soil water resources is the most reliable approach in the study area. Additionally, the data from Bland-Altman plots and the equation proposed in these studies allowed calculation of the Equivalent Layer Thickness (ELT = [Formula: see text]), which corresponds to the water resources derived from the SMOS satellite at the same time as (SM) measurements performed in the agrometeorological stations. The ranges of the mean, standard deviation, minimum, maximum, and coefficient of variation (CV) of ELT among all pixels and stations were 8.28-28.7 cm, 3.27-12.66 cm, 3.03-10.87 cm, 19.23-94.97 cm, and 24.72-98.79%, respectively. The ranges of the characteristics depended on environmental conditions and their means were close to the values of the calibrated layer thickness. The impacts of soil texture, organic matter, vegetation, and their interactive effects on the differentiation and agreement of soil water resources obtained from SWEX_PD vs. data from ground measurements in the study area are discussed. Further studies are required to address the impact of the environmental factors to improve the assessment of soil water resources based on satellite SM products (retrievals).

Impact of soil incorporation of biochar on environmental radioactivity.

Biochar (charcoal made from biomass in the pyrolysis process) has found broad application in agriculture. It helps to improve both the physical and chemical properties of soil through decontamination of heavy metals and pesticides. This work examines the potential for biochar application to improve the radiological condition of soil. We investigated the activity concentration of natural and anthropogenic radionuclides in soil samples collected from fields treated with various doses of biochar (in 1-100 Mg ha-1 ). In addition, we directly measured radon emission rate at the experimental fields. The analyses were performed using gamma spectrometry and an active method for radon emission using an AlphaGUARD instrument equipped with an accumulation box. The results of activity concentration assessments for six radionuclides, five natural and one anthropogenic, show that the only effect of biochar application into the soil is associated with the reduction of soil bulk density by this material. The radon emission rate increased by 6 mBq m-1 s-1 , on average, depending on the biochar dose (from 1 to 100 Mg ha-1 ). Our results demonstrate that application of biochar into soil kept without vegetation had a limited influence on the radioactivity in the environment.

Spatio-Temporal Mapping of L-Band Microwave Emission on a Heterogeneous Area with ELBARA III Passive Radiometer.

Water resources on Earth become one of the main concerns for society. Therefore, remote sensing methods are still under development in order to improve the picture of the global water cycle. In this context, the microwave bands are the most suitable to study land-water resources. The Soil Moisture and Ocean Salinity (SMOS), satellite mission of the European Space Agency (ESA), is dedicated for studies of the water in soil over land and salinity of oceans. The part of calibration/validation activities in order to improve soil moisture retrieval algorithms over land is done with ground-based passive radiometers. The European Space Agency L-band Microwave Radiometer (ELBARA III) located near the Bubnów wetland in Poland is capable of mapping microwave emissivity at the local scale, due to the azimuthal and vertical movement of the horn antenna. In this paper, we present results of the spatio-temporal mapping of the brightness temperatures on the heterogeneous area of the Bubnów test-site consisting of an area with variable organic matter (OM) content and different type of vegetation. The soil moisture (SM) was retrieved with the L-band microwave emission of the biosphere (L-MEB) model with simplified roughness parametrization (SRP) coupling roughness and optical depth parameters. Estimated soil moisture values were compared with in-situ data from the automatic agrometeorological station. The results show that on the areas with a relatively low OM content (4-6%-cultivated field) there was good agreement between measured and estimated SM values. Further increase in OM content, starting from approximately 6% (meadow wetland), caused an increase in bias, root mean square error (RMSE), and unbiased RMSE (ubRMSE) values and a general drop in correlation coefficient (R). Despite a span of obtained R values, we found that time-averaged estimated SM using the L-MEB SRP approach strongly correlated with OM contents.