Although biochars show promise for soil remediation, their negative impacts have not been systematically assessed. This study investigated the effects of corn cob biochars on ureasemediated urea hydrolysis and attempted to determine the mechanisms underlying those effects. The results showed that biochars inhibited urease activity (indicated by the NH 4 + generation). Released heavy metals and polyaromatic hydrocarbons explained the 20% inhibition of urease activity in biochar supernatants (200 °C) but could not explain the 70% inhibition in particle systems (400 °C). The levels of protein carbonyl and nitrotyrosine, common oxidative damagers of urease, were high in particle systems but very low in biochar supernatants. The electron paramagnetic resonance signal intensity reached its highest level in the 400 °C biochar and decreased in the 500 °C biochar, possibly due to the decomposition of organic molecules. The observed inhibition of urease activity may be the result of oxidative reactions with free radicals on the biochar surface or oxidative reactions with reactive oxygen species promoted by free radicals. We suggest that these potential hazards be evaluated further to gauge the relevance of these findings to field conditions and to assist in the development of safe and sustainable application schemes for biochars.
The spatial interpolation method is of great sign ificance for the spatial distribution of heavy metals in soil and the prevention and control of pollution. However, different interpolation methods are applied to predict the accuracy of different heavy metal pollution distributions in small-scale areas with a single farmland. There is no relevant argument. Taking a farmland (96000m2) in Lanping County, Yunnan Province, Yunnan Province as the research object, 144 surface soil samples were collected and the contents of Pb and Cd in soil were determined by ICP-MS. The deterministic spatial interpolation method and geostatistical Kriskin interpolation method were used to investigate the accuracy of different interpolation methods and the distribution characteristics of Pb and Cd in soil. The results show that the optimal interpolation methods for heavy metals Pb and Cd in polluted farmland are 0-order ordinary Kristen interpolation method, and the content of Pb and Cd in the soil is relatively accurate. This study will provide important basic information for the identification of spatial distribution characteristics of different heavy metals in small-scale areas with a single farmland, which will help to comprehensively evaluate the function of spatial interpolation to identify spatial distribution information of heavy metals.
Carbon Nanotubes(CNTs) are inevitably released into environment due to their wide production and application, their environmental behavior and risks are greatly controlled by their dispersion and aggregation. Polymers and surfactants were found dispersing CNTs well, however their dispersion mechanism is still not clear. Two kinds of polymers and one kind of surfactant were selected to investigate in this study, the adsorption results showed steric hindrance and electrostatic repulsion were the obstruction to adsorption and the electrostatic attraction might be the main contribution to highest adsorption of PVP. Different from adsorption, the electrostatic repulsion and steric hindrance were the essential contribution to dispersion, which in turn the highest dispersion of PSS.
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