Models for Predicting Water Retention in Pyrogenic Carbon (Biochar) and Biochar‐Amended Soil at Low Water Contents

Abstract

The dry end of the soil water retention curve (WRC) plays an important role in various hydrologic, solute transport, plant, and microbial processes. Despite increasing application of biochar as a soil amendment, knowledge about water retention in biochars and biochar-amended soils under dry conditions is lacking. Mechanistic models are presented to predict the WRC for biochars and biochar-amended soils at matric potential (ψ) <~−1 MPa. For biochars, the amount of water retained is linked to biochar surficial oxygen content and pore volume and surface area distributions. The WRC for soils at dry conditions is predicted using specific surface area. The WRC model for biochar-amended soils is the sum of the contributions of models for biochar and soil. The model's utility was examined for three natural soils and a uniform sand, a wood-based biochar, and 10 different combinations of these soils and biochar. The accuracy of the model for biochars was further tested for six other pyrogenic carbonaceous materials (PCMs). The models agreed well with experimental data: for the biochar and PCMs, soils, and biochar-amended soils, the root mean square error normalized to the range of water content was almost always <10%. The line of best fit for predicted versus measured gravimetric water content at permanent wilting point had slope of 0.935 ± 0.013 and a coefficient of determination of 0.997. The applicability of these models for different biochars, soils, and their mixtures is discussed.

Abiotic reduction of 3-nitro-1,2,4-triazol-5-one (NTO) and other munitions constituents by wood-derived biochar through its rechargeable electron storage capacity

“…SRB was chosen for this study because it has been field-tested for stormwater treatment 43 and its ESC and reversibility were well-characterized. 31,34,40,44 Rogue was included because its BET surface area (407 ± 9 m 2 g −1 ) and ESC (7.07 ± 0.15 mmol g −1 ) measured with titanium( iii ) citrate and dissolved O 2 (DO) were the highest of all commercial biochars we have tested. 35 These values are roughly two times those of SRB (158 ± 3 m 2 g −1 and 3.54 ± 0.13 mmol g −1 , respectively).…”

Pyrolysis Creates Electron Storage Capacity of Black Carbon (Biochar) from Lignocellulosic Biomass

“…SRB contained a reversible ESC around 2.5 mmol e – /g. SRB has been applied to soil in a greenhouse experiment for 2 years and in a field demonstration site for 3 years for stormwater treatment . When the SRB was retrieved, interestingly, the ESC of aged SRB samples from the greenhouse and the field site still retained ca.…”

“…SRB was included as a reference char because it was used as a model biochar in the development of the CRT method , and its ESC is well characterized. , SRB sifted to the size range of 250–500 μm was used directly or after grinding to <53 μm. In addition, a high-purity graphite powder, five commercial biochars (CB1 to CB5) produced from pine wood at different pyrolysis temperatures (450–950 °C), two aged SRB samples that had been applied to soil in a greenhouse stormwater treatment study for 2 years (″Aged SRB-G″) and soil in a field demonstration study for 3 years (″Aged SRB-F″), and two wood char samples collected from Newbury Park (″Wildfire Char 1″) and Simi Valley (″Wildfire Char 2″) in January, 2020, following the California wildfire in October, 2019, were analyzed for ESC. Aged SRB particles were separated from soils using forceps, rinsed with deionized water at a 1:50 mass ratio for 24 h at 100 rpm to remove soil minerals attached to the SRB particles, and dried in a vacuum oven at 65 °C .…”

Preparing and characterizing repacked columns for experiments in biochar-amended soils

“…These property differences might cause heterogeneous distributions of biochar in the column [7] , which can result in unrealistic transport and chemical or biological transformations by creating heterogeneous flow regimes. Finally, because biochar particles are porous [4 , 9 , 10] , modifications are needed to quantify the porosity of the packed column and to quantify the pore volume within biochar particles.…”