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A laboratory incubation study was conducted to evaluate the effect of bensulfuron-methyl treatment on soil microbial biomass and N-mineralization of a loamy sand soil. The herbicide was applied at 0 (control), 0.01 (field rate), 0.1, and 1.0 microg g(-1), and soil microbial biomass carbon (C(mb)), soil microbial biomass nitrogen (N(mb)), and N-mineralization rate (k) were measured at different times after herbicide treatment. Compared to the untreated soil, C(mb) and N(mb) decreased significantly (p < or = 0.05) within the first 7 days after herbicide treatment at 0.1 and 1.0 microg g(-1), and the impact was greater for N(mb) than for C(mb). Nitrogen mineralization was significantly suppressed during the first 5 days of incubation when the soil was treated with bensulfuron-methyl at 0.1 and 1.0 microg g(-1). The overall impact of bensulfuron-methyl to the soil microbial communities was closely related to the application rate in the range of 0.01-1.0 microg g(-1). This effect, however, was found to be transitory, and significant impact occurred only at high application rates.

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Batch adsorption experiments were carried out to evaluate the effect of type of crop residues and chemical pretreatment solutions on the removal efficiency of heavy metal ions at different concentrations of synthetic wastewater solutions. Rice straw, cotton stalks, and maize stalks were pretreated with different solutions (i.e., sulfuric acid, oxalic acid, sodium hydroxide, and distilled water as the control treatment) in order to increase their metal-binding capacity. Results indicated that cotton stalks were the best biosorbent material according to their efficiency in removal of heavy metal ions. Sodium hydroxide was the best chemical pretreatment method for stimulating the biosorption capacity of crop residues. Ions of Pb 2+ had the highest biosorption ratio among all competitive ions, whereas Mn 2+ ions had the lowest. The removal efficiency decreased as the concentration of heavy metal ions increased in aqueous solutions. Sorption equilibrium isotherms could be described by the Langmuir model in most cases, whereas an isotherm of S shape was observed in other cases, which did not follow the Langmuir isotherm model. In conclusion, cotton stalks pretreated with sodium hydroxide could be used as an efficient technique for wastewater remediation prior to irrigation due to its low-cost, little processing, and high biosorption capacity.

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Graphical abstract The health sector is critical to the well-being of any country, but developing countries have several obstacles that prevent them from providing adequate health care. This became an even larger concern after the COVID-19 outbreak left millions of people dead worldwide and generated huge amounts of infected or potentially infected wastes. The management and disposal of medical wastes during and post-COVID-19 represent a major challenge in all countries, but this challenge is particularly great for developing countries that do not have robust waste disposal infrastructure. The main problems in developing countries include inefficient treatment procedures, limited capacity of healthcare facilities, and improper waste disposal procedures. The management of medical wastes in most developing countries was primitive prior to the pandemic. The improper treatment and disposal of these wastes in our current situation may further speed COVID-19 spread, creating a serious risk for workers in the medical and sanitation fields, patients, and all of society. Therefore, there is a critical need to discuss emerging challenges in handling, treating, and disposing of medical wastes in developing countries during and after the COVID-19 outbreak. There is a need to determine best disposal techniques given the conditions and limitations under which developing countries operate. Several open questions need to be investigated concerning this global issue, such as to what extent developing countries can control the expected environmental impacts of COVID-19, particularly those related to medical wastes? What are the projected management scenarios for medical wastes under the COVID-19 outbreak? And what are the major environmental risks posed by contaminated wastes related to COVID-19 treatment? Studies directed at the questions above, careful planning, the use of large capacity mobile recycling facilities, and following established guidelines for disposal of medical wastes should reduce risk of COVID-19 spread in developing countries.