A New Type of Cemented Sand-Gravel (CSG) Mixtures for Water-Tightening of Hardfill Dams

This paper aims to achieve a specific type of cemented sand-gravel mixtures with low permeability to implement in the impervious zone of hardfill dams. To this end, various mixtures are prepared by blending two native soils of sand and gravel with different amounts of kaolinite or bentonite additives in presence of various cement content. The compaction properties, uniaxial compressive strength, permeability and scanning electron microscope (SEM) images of mixtures are measured. According to the results, the cemented mixture containing 10% of kaolinite additive regardless of native soil type exhibits the maximum strength. However, the bentonite disturbs the cement hydration in the mixture, and the strength of mixtures especially with high cement content decreases with increasing the bentonite content. The permeability of mixtures is related to the amount of cement and fine additive in the mixture. The permeability of both cemented sand and gravel mixtures decreases with increasing the bentonite additive. However, the kaolinite additive has a limited influence on the permeability of cemented gravel mixtures. The lowest permeability is achieved in the mixture involving the higher amount of bentonite (with a weight ratio of 30%) in presence of adequate cement.

Native soil amendments combined with commercial arbuscular mycorrhizal fungi increase biomass of Panicum amarum

Coastal dune restorations often fail because of poorly performing plants. The addition of beneficial microbes can improve plant performance, though it is unclear if the source of microbes matters. Here, we tested how native soil amendments and commercially available arbuscular mycorrhizal (AM) fungi influenced performance of Panicum amarum, a dominant grass on Texas coastal dunes. In a greenhouse experiment, we manipulated the identity of native soil amendments (from P. amarum, Uniola paniculata, or unvegetated areas), the presence of soil microbes in the native soil amendments (live or sterile), and the presence of the commercial AM fungi (present or absent). Native soils from vegetated areas contained 149% more AM fungal spores than unvegetated areas. The commercial AM fungi, when combined with previously vegetated native soils, increased aboveground biomass of P. amarum by 26%. Effects on belowground biomass were weaker, although the addition of any microbes decreased the root:shoot ratio. The origin of native soil amendments can influence restoration outcomes. In this case soil from areas with vegetation outperformed soil from areas without vegetation. Combining native soils with commercial AM fungi may provide a strategy for increasing plant performance while also maintaining other ecosystem functions provided by native microbes.

Soil Metaproteomics as a Tool for Environmental Monitoring of Minelands

Opencast mining drastically alters the landscape due to complete vegetation suppression and removal of topsoil layers. Precise indicators able to address incremental changes in soil quality are necessary to monitor and evaluate mineland rehabilitation projects. For this purpose, metaproteomics may be a useful tool due to its capacity to shed light on both taxonomic and functional overviews of soil biodiversity, allowing the linkage between proteins found in soil and ecosystem functioning. We investigated bacterial proteins and peptide abundance of three different mineland rehabilitation stages and compared it with a non-rehabilitated site and a native area (evergreen dense forest) in the eastern Amazon. The total amount of identified soil proteins was significantly higher in the rehabilitating and native soils than in the non-rehabilitated site. Regarding soil bacterial composition, the intermediate and advanced sites were shown to be most similar to native soil. Cyanobacteria and Firmicutes phyla are abundant in the early stages of environmental rehabilitation, while Proteobacteria population dominates the later stages. Enzyme abundances and function in the three rehabilitation stages were more similar to those found in the native soil, and the higher accumulation of many hydrolases and oxidoreductases reflects the improvement of soil biological activity in the rehabilitating sites when compared to the non-rehabilitated areas. Moreover, critical ecological processes, such as carbon and nitrogen cycling, seem to return to the soil in short periods after the start of rehabilitation activities (i.e., 4 years). Metaproteomics revealed that the biochemical processes that occur belowground can be followed throughout rehabilitation stages, and the enzymes shown here can be used as targets for environmental monitoring of mineland rehabilitation projects.

Beneficial cyanosphere heterotrophs accelerate establishment of cyanobacterial biocrust

Biological soil crusts (biocrusts) are communities of microbes that inhabit the surface of arid soils and provide essential services to dryland ecosystems. While resistant to extreme environmental conditions, biocrusts are susceptible to anthropogenic disturbances that can deprive ecosystems of these valuable services for decades. Until recently, culture-based efforts to produce inoculum for cyanobacterial biocrust restoration in the Southwestern US focused on producing and inoculating the most abundant primary producers and biocrust pioneers, Microcoleus vaginatus and members of the family Coleofasciculaceae (aka “ Microcoleus streenstrupii complex”). The discovery that a unique microbial community characterized by diazotrophs is intimately associated with M. vaginatus , known as the “cyanosphere”, suggests a symbiotic division of labor in which nutrients are traded between phototrophs and heterotrophs. To probe the potential use of such cyanosphere members in the restoration of biocrusts, we performed co-inoculations of soil substrates with cyanosphere constituents. This resulted in more rapid cyanobacterial growth over inoculations with the cyanobacterium alone. Additionally, we found that the mere addition of beneficial heterotrophs enhanced the formation of a cohesive biocrust without the need of additional phototrophic biomass within native soils that contain trace amounts of biocrust cyanobacteria. Our findings support the hitherto unknown role of beneficial heterotrophic bacteria in the establishment and growth of biocrusts and allow us to make recommendations concerning biocrust restoration efforts based on the presence of remnant biocrust communities in disturbed areas. Future biocrust restoration efforts should consider cyanobacteria and their beneficial heterotrophic community as inoculants. Importance The advancement of biocrust restoration methodologies for cyanobacterial biocrusts has been largely achieved through trial and error. Successes and failures could not always be traced back to particular factors. The investigation and application of foundational microbial interactions existing within biocrust communities is a crucial step toward informed and repeatable biocrust restoration methodologies.

Methodology of green runoff drainage design for urban streets

The main provisions of the methodology for calculating and designing a "green drainage system" of surface runoff from the road network of settlements that are not equipped with an underground drainage and treatment system are given. Requirements for the "green drainage system" of surface runoff from urban streets that are not equipped with an underground drainage system are formulated. The requirements include the treatment degree of surface runoff, filtration rate, comfort of the visual environment, safety and convenience for pedestrians and bicyclists, technologies of winter maintenance. The main pollutants of surface runoff for different categories of Russian streets are identified. The composition and depth of filtration media, its operating life, types of green plants are determined depending on the composition of pollutants, their typical concentrations, the collection area of surface runoff and the composition of native soils. Examples of the most effective design solutions for the "green drainage system" and treatment of surface runoff from the road network are given.

Commercially available garden products as important sources of antibiotic resistance genes—a survey

The dissemination of antibiotic resistance genes (ARGs) in the environment contributes to the global rise in antibiotic resistant infections. Therefore, it is of importance to further research the exposure pathways of these emerging contaminants to humans. This study explores commercially available garden products containing animal manure as a source of ARGs in a survey of 34 garden products, 3 recently landscaped soils, and 5 native soils. DNA was extracted from these soils and quantified for 5 ARGs, intI1, and 16S rRNA. This study found that both absolute and relative gene abundances in garden products ranged from approximately two to greater than four orders of magnitude higher than those observed in native soils. Garden products with Organic Materials Review Institute (OMRI) certification did not have significantly different ARG abundances. Results here indicate that garden products are important sources of ARGs to gardens, lawns, and parks. Graphical abstract

The Pyrogenic Archives of Anthropogenically Transformed Soils in Central Russia

Charred materials (anthracomass) stored within a soil constitute a major part of its pyrogenic archive and could provide evidence of past fire events, both natural and anthropogenic. However, the dynamics of man-made contributions to the total anthracomass of soil at different time scales are insufficiently understood. In this study, we determined the anthracomass concentrations, stocks, and particle-size distribution in anthropogenically transformed soils of different genesis and ages. Materials were collected from the following archaeological sites within Central Russia—3 Upper Paleolithic sites (Avdeevo, Khotylevo-2 and Yudinovo-1), 2 Early Iron Age settlements (Khotylevo-2 and Yaroslavl), and 1 Medieval site (Yaroslavl). Samples from different cultural layers (CLs), plough layers, and native soils (control) were studied. We identified anthracomass accumulation over a wide chronological scale starting from the Upper Paleolithic Period. The high degree of preservation of anthracomass in ancient anthropogenically transformed soils was explained by the presence of large fragments of charred bones, which are more durable in comparison to wood charcoal. The anthracomass concentrations and stocks in the Early Iron Age plough layer were lower than those in the Medieval plough layer. CLs were generally more enriched in the anthracomass than plough layers, due to their sedimentational genesis, which is more favorable for anthracomass preservation than the turbational genesis of plough layers. However, the differences between charred particle sizes in synlithogenic CLs and turbational plough layers were less clear than expected, due to the specific conditions of formation of each particular layer, e.g., burial rate, duration of ploughing, and type of agricultural land use.