The mechanism for enhancing phosphate immobilization on colloids of oxisol, ultisol, hematite, and gibbsite by chitosan

Antibiotics soil-solution chemistry: A review of environmental behavior and uptake and transformation by plants

The increased use of antibiotics by humans for various purposes has left the environment polluted. Antibiotic pollution remediation is challenging because antibiotics exist in trace amounts and only highly sensitive detection techniques could be used to quantify them. Nevertheless, their trace quantity is not a hindrance to their transfer along the food chain, causing sensitization and the development of antibiotic resistance. Despite an increase in the literature on antibiotic pollution and the development and transfer of antibiotic-resistant genes (ARGs), little attention has been given to the behavior of antibiotics at the soil-solution interface and how this affects antibiotic adsorption-desorption interactions and subsequent uptake and transformation by plants. Thus, this review critically examines the interactions and possible degradation mechanisms of antibiotics in soil and the link between antibiotic soil-solution chemistry and uptake by plants. Also, different factors influencing antibiotic mobility in soil and the transfer of ARGs from one organism to another were considered. The mechanistic and critical analyses revealed that: (a) the charge characteristics of antibiotics at the soil-root interface determine whether they are adsorbed to soil or taken up by plants; (b) antibiotics that avoid soil colloids and reach soil pore water can be absorbed by plant roots, but their translocation to the stem and leaves depends on the ionic state of the molecule; (c) few studies have explored how plants adapt to antibiotic pollution and the transformation of antibiotics in plants; and (d) the persistence of antibiotics in cropland soils can be influenced by the content of soil organic matter, coexisting ions, and fertilization practices. Future research should focus on the soil/solution-antibiotic-plant interactions to reveal detailed mechanisms of antibiotic transformation by plants and whether plant-transformed antibiotics could be of environmental risk.

Effect of carbon and nitrogen mineralization of chitosan and its composites with hematite/gibbsite on soil acidification of an Ultisol induced by urea

Chitosan is a biodegradable polymer with a vast range of applications. Along with its metal composites, chitosan has been applied in the remediation of polluted soils as well as a biofertilizer. However, little attention has been given to the degradation of chitosan composites in soil and how they affect soil respiration rate and other physicochemical parameters. In this study, the degradation of chitosan and its composites with gibbsite and hematite in an acidic Ultisol and the effect on urea (200 mg N kg-1) transformation were investigated in a 70-d incubation experiment. The results showed that the change trends of soil pH, N forms, and CO2 emissions were similar for chitosan and its composites when applied at rates <5 g C kg-1. At a rate of 5 g C kg-1, the C and N mineralization trends suggested that the chitosan-gibbsite composite was more stable in soil and this stability was owed to the formation of a new chemical bond (CH-N-Al-Gibb) as observed in the Fourier-transform infrared spectrum at 1644 cm-1. The mineralization of the added materials significantly increased soil pH and decreased soil exchangeable acidity (P < 0.01). This played an important role in decreasing the amount of H+ produced during urea transformation in the soil. The soil's initial pH was an important factor influencing C and N mineralization trends. For instance, increasing the initial soil pH significantly increased the nitrification rate and chitosan decomposition trend (P < 0.01) and thus, the contribution of chitosan and its composites to increase soil pH and inhibit soil acidification during urea transformation was significantly decreased (P < 0.01). These findings suggest that to achieve long-term effects of chitosan in soils, applying it as a chitosan-gibbsite complex is a better option.

Recent perspective of antibiotics remediation: A review of the principles, mechanisms, and chemistry controlling remediation from aqueous media

Antibiotic pollution is an ever-growing concern that affects the growth of plants and the well-being of animals and humans. Research on antibiotics remediation from aqueous media has grown over the years and previous reviews have highlighted recent advances in antibiotics remediation technologies, perspectives on antibiotics ecotoxicity, and the development of antibiotic-resistant genes. Nevertheless, the relationship between antibiotics solution chemistry, remediation technology, and the interactions between antibiotics and adsorbents at the molecular level is still elusive. Thus, this review summarizes recent literature on antibiotics remediation from aqueous media and the adsorption perspective. The review discusses the principles, mechanisms, and solution chemistry of antibiotics and how they affect remediation and the type of adsorbents used for antibiotic adsorption processes. The literature analysis revealed that: (i) Although antibiotics extraction and detection techniques have evolved from single-substrate-oriented to multi-substrates-oriented detection technologies, antibiotics pollution remains a great danger to the environment due to its trace level; (ii) Some of the most effective antibiotic remediation technologies are still at the laboratory scale. Thus, upscaling these technologies to field level will require funding, which brings in more constraints and doubts patterning to whether the technology will achieve the same performance as in the laboratory; and (iii) Adsorption technologies remain the most affordable for antibiotic remediation. However, the recent trends show more focus on developing high-end adsorbents which are expensive and sometimes less efficient compared to existing adsorbents. Thus, more research needs to focus on developing cheaper and less complex adsorbents from readily available raw materials. This review will be beneficial to stakeholders, researchers, and public health professionals for the efficient management of antibiotics for a refined decision.