Pyrite-induced hydroxyl radical formation and its effect on nucleic acids

BACKGROUND: Pyrite, the most abundant metal sulphide on Earth, is known to spontaneously form hydrogen peroxide when exposed to water. In this study the hypothesis that pyrite-induced hydrogen peroxide is transformed to hydroxyl radicals is tested. RESULTS: Using a combination of electron spin resonance (ESR) spin-trapping techniques and scavenging reactions involving nucleic acids, the formation of hydroxyl radicals in pyrite/aqueous suspensions is demonstrated. The addition of EDTA to pyrite slurries inhibits the hydrogen peroxide-to-hydroxyl radical conversion, but does not inhibit the formation of hydrogen peroxide. Given the stability of EDTA chelation with both ferrous and ferric iron, this suggests that the addition of the EDTA prevents the transformation by chelation of dissolved iron species. CONCLUSION: While the exact mechanism or mechanisms of the hydrogen peroxide-to-hydroxyl radical conversion cannot be resolved on the basis of the experiments reported in this study, it is clear that the pyrite surface promotes the reaction. The formation of hydroxyl radicals is significant because they react nearly instantaneously with most organic molecules. This suggests that the presence of pyrite in natural, engineered, or physiological aqueous systems may induce the transformation of a wide range of organic molecules. This finding has implications for the role pyrite may play in aquatic environments and raises the question whether inhalation of pyrite dust contributes to the development of lung diseases

Control strategies to combat dissemination of antibiotic resistance in urban water systems

The intensive use of antibiotics for medical, veterinary, or agricultural purposes results in the continuous release of antibiotics into the environment, leading to the increasingly widespread occurrence of antibiotic resistance. Although antibiotic resistance has been recognized as a major threat to human health worldwide, the related phenomenon occurring in natural and engineered environments has so far been largely overlooked. The urban (including industrial) water cycle, which connects urban life, agriculture, and the environment, is potentially a hot spot for the spread of antibiotic resistance. Therefore, better understanding of the distribution and transportation of antibiotic-resistant bacteria (ARB) and acquisition of antibiotic resistance genes (ARGs) in the urban water cycle is critically important to improve the control of this emerging environmental and human health challenge. In this book chapter, we comprehensively review the occurrence, transfer, and acquisition mechanisms of ARGs in the urban water cycle. Various methods that are used to monitor ARB and ARGs are compared in terms of their strengths and limitations. Opportunities for the development of real-time monitoring methods are discussed, along with possible control strategies for ARB and ARGs in urban water environments. We recommend that three major barriers should be developed to minimize or halt the spread of ARGs in urban water systems, including more efficient water disinfection, advanced wastewater treatment, and optimized sludge treatment processes