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Abstract Biochar wettability and ability to accumulate moisture inside the porous space are crucial for improving soil fertility, regulating soil water balance, and regulating nutrients. However, a long-term interaction of biochar with agricultural soils may drastically alter the wetting properties and, eventually, influence water holding capacity and the structure of soils. In this work, the structure and wetting properties of biochar samples after 6-year long exposure to a sandy loam Spodosol with a crop rotation and mineral fertilizers application were studied. It was found that the elemental composition of the aged biochars was richer and more "soil-like", which is explained by the presence of the mineral crust on the biochar surface. The temporal evolution of biochar in the soil without any mineral fertilizer application resulted in significant improvement of its surface wettability due to the effects of various environmental factors. The lateral surface of biochar after 6-year interaction with the soil changes into a loose porous layer in a form of grooved base filled with adherent mineral soil and clay particles. Contrary, the application of the mineral fertilizer to the soil resulted in decreased wettability of the biochar lateral surfaces due to a decrease in the polar component of surface energy and the crusting of the surface with fine material, which blocks the pore space of the biochar. As a result, water capacity of the biochar from the treatment with the fertilizer decreased compared to the biochar samples collected from the soil without the fertilizer application. The radial biochar surfaces of both types of samples collected from the soil were open vessels filled with soil particles that slow down complete wetting and water absorption. The treatment of the biochar samples with surfactants drastically increased wettability of lateral surface and water absorption capacity of control samples as compared to the samples collected from the soil. The obtained results support the idea that the hydrophilisation of biochar caused by the adhesion of soil particles and treatment of its pore surface with surfactants, can improve the water-holding capacity of the sandy loam Spodosol in the plant-available range of soil water. Graphical Abstract

Biochar wettability and ability to accumulate moisture inside the porous space are crucial for improving soil fertility, regulating soil water balance, and regulating nutrients. However, a long-term interaction of biochar with agricultural soils may drastically alter the wetting properties and, eventually, influence water holding capacity and the structure of soils. In this work, the structure and wetting properties of biochar samples after 6-year long exposure to a sandy loam Spodosol with a crop rotation and mineral fertilizers application were studied. It was found that the elemental composition of the aged biochars was richer and more "soil-like", which is explained by the presence of the mineral crust on the biochar surface. The temporal evolution of biochar in the soil without any mineral fertilizer application resulted in significant improvement of its surface wettability due to the effects of various environmental factors. The lateral surface of biochar after 6-year interaction with the soil changes into a loose porous layer in a form of grooved base filled with adherent mineral soil and clay particles. Contrary, the application of the mineral fertilizer to the soil resulted in decreased wettability of the biochar lateral surfaces due to a decrease in the polar component of surface energy and the crusting of the surface with fine material, which blocks the pore space of the biochar. As a result, water capacity of the biochar from the treatment with the fertilizer decreased compared to the biochar samples collected from the soil without the fertilizer application. The radial biochar surfaces of both types of samples collected from the soil were open vessels filled with soil particles that slow down complete wetting and water absorption. The treatment of the biochar samples with surfactants drastically increased wettability of lateral surface and water absorption capacity of control samples as compared to the samples collected from the soil. The obtained results support the idea that the hydrophilisation of biochar caused by the adhesion of soil particles and treatment of its pore surface with surfactants, can improve the water-holding capacity of the sandy loam Spodosol in the plant-available range of soil water. Highlights: A six-year exposure of biochar to soil altered surface wettability and water absorption capacity of biochar. Fertilizer application resulted in crust formation on the lateral surface of biochar. The treatment of biochar with surfactant improved its surface wetting properties for both aged in the soil and control samples. [ABSTRACT FROM AUTHOR]

Globally increasing in water demand causes critical valuation of water reuse. Freshwater demand in the various sectors is mostly fulfilled from ground and surface water. Groundwater resources are highly saline, threatening the long-term viability of arable regions. With negative aspects like reduction of soil fertility and crops yields, several processes were described. Among them, the membrane process was documented as a practicable option for irrigation application. This review work aims to provide a consolidated review on the technical maturity of the reverse osmosis system for feasible and sustainable groundwater desalination. The paper deals with basic principles, membrane modules, flow process, design parameters, and overall performance of the reverse osmosis systems. The implementation system for decentralized groundwater desalination is anticipated to be a practical option in ensuring the availability of good quality water regularly.

As características ambientais e edáficas são determinantes no processo de pedogenése e condicionam a capacidade de uso do solo. Na bacia hidrográfica da ribeira do Covões, em Coimbra, avaliaram-se sete variáveis ambientais e as características físico-químicas do solo, as quais determinam a capacidade de uso do solo. Elaborou-se a cartografia da capacidade de uso, estando representadas as classes B, Bh, C, Cs D, Ds e E. A caracterização evidência o predomínio dos solos com baixa capacidade produtiva e aptidão essencialmente florestal ou utilização agrícola pouco intensiva. Sendo um espaço com elevada dinâmica de peri-urbanização, avaliou-se o uso/ocupação do solo nos anos de 1958 e 2002, o que demonstrou a importância da ocupação florestal, a elevada perda de uso agrícola, e o incremento das áreas urbanas e com equipamentos e infra-estruturas. Foi possível relacionar a capacidade de uso do solo com a alteração de uso e ocupação, a qual revelou o aumento da ocupação urbana em solos de classe C e D; a diminuição da ocupação agrícola em solos de classe E, D e C; o aumento da ocupação florestal em áreas de classe E, D e C; e o aumento das zonas descobertas sem ou com pouca vegetação em solos da classe E de capacidade de uso.The environmental and edaphic characteristics and soil conditions are crucial in the process of pedogenesis and the soil use capacity. In the hydrographical basin of the Covões, close to the Coimbra town, were assessed seven environmental variables and soil chemical and physical characteristics that determine the soil use capacity. The article presents the mapping of land use capacity, appearing represented the classes B, Bh, C, Cs, D, Ds and E. The characterization highlights the predominance of soils with low productive capacity and ability essentially for forest or agricultural use rather intensive. The area has been presenting a high peri-urbanization process. The analysis focused on the land use in the years 1958 and 2002, demonstrating the importance of forest occupation, the high loss of agricultural use, together with the increase in urban areas and with equipment and infrastructure. The analysis reveals the increase of urban occupation in soil class C and D; the decrease in agricultural land occupation in classes E, D and C; the increase of forest areas in classes E, D and C and the increase of bare areas with little or no vegetation in E class and of soil capacity.

The role of soil in the existential environmental problems of declining biodiversity, climate change, water and energy security, impacting on food security has highlighted the need to link the soil functions to ecosystem services. We describe and illustrate by a limited example, the concepts and assessment of soil's capacity measured through its capability and condition as contributors to an overall soil security framework. The framework is based on the concepts of genosoils and phenosoils. The links to other notions, such as threats to soil and soil functions are made. The framework can be potentially applied elsewhere to quantify soil changes under natural processes and human activities. [ABSTRACT FROM AUTHOR]

The Green-Ampt equation describing the infiltration of water into soil requires that the rainfall intensity is greater than the infiltration capacity of the soil at all times. The well-known Mein-Larson model modifies the Green-Ampt equation and attempts to avoid this restriction for infiltration of water into a homogeneous soil under rainfall of constant intensity. The rainfall intensity is considered to be less than the infiltration capacity of the soil in the initial phases of a storm. The Mein-Larson model assumes that until the time to ponding of water over the soil surface, the infiltration rate is constant and equals the rainfall intensity. This study shows that the Mein-Larson model underestimates the ponding time and that the cumulative infiltration predicted by the model is always less than the cumulative infiltration potential of the soil. To avoid these drawbacks, an alternative modification of the Green-Ampt equation is presented. In the proposed modification, the ponding time is considered to occur when the cumulative infiltration potential of the soil is fully satisfied. Beyond the ponding time, both the infiltration rate and cumulative infiltration follow the classical Green-Ampt equations. The modification is achieved by using asymptotic matching technique to render the model applicable within a wide range of rainfall rates greater or less than the soil infiltration capacities. This modification will help extend the ability to analyze hydrologic problems related to water infiltration into soil in different environments of high or low rainfall intensities. Case studies are provided to demonstrate the behavior of the proposed model and compare it with the Mein-Larson modification. [ABSTRACT FROM AUTHOR]