Nitrogen is an essential element for life but its excessive release into the environment in the form of reactive nitrogen causes severe damage, including acidification and eutrophication. One of the main sources of nitrogen pollution is the use of fertilizers in agricultural soils. Feammox is a recently described pathway that couples ammonium (NH4+) oxidation with iron (Fe) reduction. In this study, the enrichment and bioaugmentation of anaerobic sludge under conditions that promote Feammox activity were investigated. The first enrichment stage (E1) achieved 28% of ammonium removal after 28 days of incubation, with a production of 30 mg/L of Fe2+. E1 was then used as inoculum for two enrichments at 35 degrees C with different carbon sources: sodium acetate (E2) and sodium bicarbonate (E3). Neither E2 nor E3 showed significant NH4+ removal, but E2 was highly effective in iron reduction, reaching Fe2+ concentrations of 110 mg/L. Additionally, an increase in nitrate (NO3-) concentration was observed, which may indicate the occurrence of this pathway in the Feammox process. The Monod kinetic model, analyzed using AQUASIM software, showed a good fit to the experimental data for NH4+, NO3-, and Fe2+. Sequencing analysis revealed the presence of phyla associated with Feammox activity. Although there was only a slight difference in NH4+ removal between the bioaugmented and non-augmented control sludge, the bioaugmented sludge was statistically superior in nitrate production and iron reduction. This study provides valuable insights into the enrichment and bioaugmentation of the Feammox process potential large-scale wastewater treatment applications.

Herbicide exposure poses a higher risk to reptiles due to their frequent contact with soil. Besides, food restriction is also a common environmental pressure that can seriously affect the survival of reptiles. The adaptive strategies of reptiles in the face of emerging herbicide pollution and food shortage challenges are not yet known. Therefore, Eremias Argus (a kind of small reptile) was selected as the model to simulate the real scenario of food shortage in lizards, aiming to explore the comprehensive impact of glufosinate-ammonium (GLA: an emerging herbicide) and food restriction on lizards. The results revealed that lizards often regulate their physiological and biochemical activities through body thermal selection and tend to choose lower body temperature, reduce digestibility, and actively participate in fat energy mobilization to avoid oxidative damage in the state of hunger, finally in order to achieve homeostasis. However, herbicide GLA disrupted the lizards' efforts to resist the stress of food shortage and interfered with the normal thermoregulation and energy mobilization strategies of lizards facing starvation. The results of this study would improve our understanding of the impacts of Lizards under extreme stresses, help supplement reptile toxicology data and provide scientific basis for the risk assessment of herbicide GLA.

The paper reports new hydrogels based on quaternary ammonium salts of chitosan designed as biocidal products. The chitosan derivative was crosslinked with salicylaldehyde via reversible imine bonds and supramolecular selfassemble to give dynamic hydrogels which respond to environmental stimuli. The crosslinking mechanism was demonstrated by 1H NMR and FTIR spectroscopy, and X-ray diffraction and polarized light microscopy. The hydrogel nature, self-healing and thixotropy were proved by rheological investigation and visual observation, and their morphology was assessed by scanning electron microscopy. The relevant properties for application as biocidal products, such as swelling, dissolution, bioadhesiveness, antimicrobial activity and ex-vivo hemocompatibility and in vivo local toxicity and biocompatibility on experimental mice were measured and analyzed in relationship with the imination degree and the influence of each component. It was found that the hydrogels are superabsorbent, have good adhesivity to skin and various surfaces and antimicrobial activity against relevant gram-positive and gram-negative bacteria, while being hemocompatible and biocompatible. Besides, the hydrogels are easily biodegraded in soil. All these properties recommend the studied hydrogels as ecofriendly biocidal agents for living tissues and surfaces, but also open the perspectives of their use as platform for in vivo applications in tissue engineering, wound healing, or drug delivery systems.

The loss of nitrogen in soil damages the environment. Clarifying the mechanism of ammonium nitrogen (NH4+-N) transport in soil and increasing the fixation of NH4+-N after N application are effective methods for improving N use efficiency. However, the main factors are not easily identified because of the complicated transport and retardation factors in different soils. This study employed machine learning (ML) to identify the main influencing factors that contribute to the retardation factor (Rf) of NH4+-N in soil. First, NH4+-N transport in the soil was investigated using column experiments and a transport model. The Rf (1.29 - 17.42) was calculated and used as a proxy for the efficacy of NH4+-N transport. Second, the physicochemical parameters of the soil were determined and screened using lasso and ridge regressions as inputs for the ML model. Third, six machine learning models were evaluated: Adaptive Boosting, Extreme Gradient Boosting (XGB), Random Forest, Gradient Boosting Regression, Multilayer Perceptron, and Support Vector Regression. The optimal ML model of the XGB model with a low mean absolute error (0.81), mean squared error (0.50), and high test r(2) (0.97) was obtained by random sampling and five-fold cross-validation. Finally, SHapely Additive exPlanations, entropy-based feature importance, and permutation characteristic importance were used for global interpretation. The cation exchange capacity (CEC), total organic carbon (TOC), and Kaolin had the greatest effects on NH4+-N transport in the soil. The accumulated local effect offered a fundamental insight: When CEC > 6 cmol(+) kg(-1), and TOC > 40 g kg(-1), the maximum resistance to NH4+-N transport within the soil was observed. This study provides a novel approach for predicting the impact of the soil environment on NH4+-N transport and guiding the establishment of an early-warning system of nutrient loss.

Currently, soil-borne fungal disease (SBFD) have caused a huge damage in agriculture, and small molecule soil disinfectants have been widely used for the prevention and control of SBFD, which could not only kill the chlamydospore of pathogenic fungi, but also completely destroy the microbial community and its functional diversity in the soil, and is not conducive to subsequent plant planting. Therefore, how to effectively inhibit plant pathogenic fungi while maintaining the general balance of microbial population in the soil to facilitate subsequent plant planting come to be critical problem in the prevention and control of SBFD. In this work, a series of polyacrylamide containing quaternary ammonium salts (PAM-X) were synthesized based on the radical copolymerization of acrylamide (AM) and acrylamide containing different quaternary ammonium salts groups (AMX). Owing to the entanglement between polymer chains and soil, PAM-X could be stably absorbed in the soil, thus effectively delaying the free migration of PAM-X chains in soil, and reducing the probability of being leached from soil, which might be the key to obtain novel polymeric quaternary ammonium salts that have less impact on the environment. Banana Fusarium wilt, also known as banana cancer, caused by Fusarium oxysporum f. sp. cubense (Foc), was chosen as a typical soil-borne pathogen disease to verify the rationality of the above thoughts. The results showed PAM-X had well anti-Foc4 activities in soil, and could maintain the general balance of microbial population in the soil, which are almost non-toxic to earthworms in soil and fish, thus provides a new prevention and control method for SBFD.

Surfactants are used in agriculture as soil conditioners and components of fungicides, pesticides, and fertilizers. These materials are considered contaminants found in the soil. They can be absorbed by plants and animals and can impact human health when consumed. The objective of this study was to evaluate the phytotoxicity of four cationic surfactants: hexadecyl trimethyl ammonium bromide (HDTMA), octadecyl trimethyl ammonium chloride amine and amine in a hydroponic culture system of lettuce in doses of 0 to 10 mg/L. The variables evaluated were water consumption, dry biomass, leaf area, electrical conductivity (EC), and content of NO3-, K+, and Ca2+in the nutrient solution. After 40 days of exposure to DDA, this did not influence the dry biomass of the plant; however, the application of 1 mg/L of HDTMA decreased the biomass by 27 %, 46 % with 4 mg/L of OTAC, and 60 % with 4 mg/L of HDA. The decrease in water consumption by surfactants was 27 % with 1 mg/L of HDTMA, 20 % with OTAC, and 34 % with HDA from 2 mg/L, and the application of DDA did not show a reducing effect. In most of the variables, the DDA surfactant did not affect the response; in addition, the HDA surfactant was the second to cause the least damage to the crop because it does not have a toxic companion ion such as Cl and Br.

In-situ leaching (ISL) has gained prominence as a non-destructive method for rare earth element (REE) extraction, particularly in regions like China. However, concerns over the environmental impact and soil stability due to ISL activities have surfaced following a landslide incident. This article distills the essence of a comprehensive research endeavor that delves into the effects of ammonium sulfate ISL leaching, employing concentrations of 0.05M, 0.1M, and 0.5M, on soil mechanical properties. The study encompasses physicochemical, physical, and mechanical tests, unveiling substantial alterations in shear strength, cohesion, angle of internal friction, zeta potential, liquid limit, plastic limit, and plasticity index following leaching. XRF and XRD analyses reveal the presence of REEs and distinctive mineral phases in the soil samples. Overall, ISL induces a weakening of the soil, raising concerns about potential slope failures and emphasizing the need for a deeper understanding of ISL's impact on soil properties in the context of REE mining.

The largest permafrost area in China is on the Qinghai-Tibetan Plateau (QTP), and the nitrogen biogeochemical cycles in this area have received significant attention. However, there is insufficient knowledge of the available soil nitrogen and microbial biomass nitrogen (MBN) dynamics in this region, which hinders our understanding of the changes in the ecosystem and the effects of climate change on the nitrogen dynamics in the future. In this study, we determined the monthly changes in ammonium nitrogen, nitrate nitrogen, dissolved organic nitrogen (DON), and MBN contents of the topsoil (at depths of 0-20 cm) from April 2016 to March 2017 in the permafrost region on the QTP. The results show that soil NH4+-N and DON contents decreased during the growing season, while soil NO3--N content increased during the growing season and in the middle of the winter. The soil MBN contents increased at the beginning of the growing season and decreased during peak growth period, despite significant variations among the different sites. The soil temperature was positively correlated with soil NO3--N content but it was negatively correlated with the NH4+-N and DON contents. The soil moisture was positively correlated with the soil NO3--N, DON, and MBN contents. The primary factor affecting the seasonal patterns in soil NO3--N and DON contents was soil moisture. Soil moisture and plant growth also affected soil MBN via nutrient competition. The nutrient uptake by plants overwhelmed effect of temperature on the MBN in growing season. These findings improve our understanding of the nitrogen biochemical cycles and their response to future climate change.

Field observations have suggested that particulate nitrate can promote the aging of black carbon (BC), yet the mechanisms of the aging process and its impacts on BC's light absorption are undetermined. Here we performed laboratory simulation of internal mixing of flame-generated BC aggregates with ammonium nitrate. Variations in particle size, mass, coating thickness, effective density, dynamic shape factor, and optical properties were determined online by a suite of instruments. With the development of coatings, the particle size initially decreased until reaching a coating thickness of similar to 10 nm and then started increasing, accompanied by an increase in effective density and a decrease in dynamic shape factor, reflecting the transformation of BC particles from highly fractal to near-spherical morphology. This is partially attributable to the restructuring of BC cores to more compact forms. Exposing coated particles to elevated relative humidity (RH) led to additional BC morphology changes, even after drying. Particle light absorption and scattering were also amplified with ammonium nitrate coating, increasing with coating thickness and RH. For BC particles with a 17.8 nm coating, absorption and scattering were increased by 1.5- and 7.9-fold when cycled through 70% RH (5-70-5% RH), respectively. The irreversible restructuring of the BC core caused by condensation of ammonium nitrate and water altered both absorption and scattering, with a magnitude comparable to or even exceeding the effects of increased coating. Results show that ammonium nitrate is among the most efficient coating materials with respect to modifying BC morphology and optical properties compared with other inorganic and organic species investigated previously. Accordingly, mitigation of nitrate aerosols is necessary for the benefits of both air pollution control and reducing the impacts of BC on visibility impairment and radiative forcing on climate change. Our results also pointed out that the effect of BC core restructuring needs to be considered when evaluating BC's light absorption enhancement. (C) 2020 Elsevier Ltd. All rights reserved.

The fate of permafrost carbon upon thaw will drive feedbacks to climate warming. Here we consider the character and context of dissolved organic carbon (DOC) in yedoma permafrost cores from up to 20m depth in central Alaska. We observed high DOC concentrations (4 to 129mM) and consistent low molecular weight organic acid concentrations in three cores. We estimate a DOC production rate of 12 mu molDOCm(-2)yr(-1) based on model ages of up to similar to 200kyr derived from uranium isotopes. Acetate C accounted for 241% of DOC in all samples. This proportion suggests long-term anaerobiosis and is likely to influence thaw outcomes due to biolability of acetate upon release in many environments. The combination of uranium isotopes, ammonium concentrations, and calcium concentrations explained 86% of the variation in thaw water DOC concentrations, suggesting that DOC production may be related to both reducing conditions and mineral dissolution over time.