Air disinfection by nanosecond pulsed DBD plasma.

Atmospheric pressure dielectric barrier discharge (DBD) plasma is an emerging and promising technique for air disinfection in public environments. Power supply is a crucial factor but it remains unclear about its impacts on the air disinfection performance of plasmas. In this work, a nanosecond (ns) pulsed power supply was applied to drive an in-duct grating-like DBD array to achieve fast single-pass air disinfection. The influence of pulse parameters and environmental factors on both the discharge characteristics and the single-pass bacterial inactivation efficiency were uncovered. At a close relative humidity (RH) level, the efficiency was dominated by the discharge power, namely, specific input energy could serve as the disinfection dose. A higher frequency, shorter pulse rising time, and suitable pulse width are preferred to obtain a higher Z value. The pulsed source was not notably superior to an alternating current source, or even worse at a low voltage frequency at the same discharge power. Airflow humidity was a predominant factor to improve the efficiency and a single-pass efficiency of ∼ 99% and a Z value of 2.2 L/J were achieved under an optimal RH of 50%-60%. This work provides fundamental knowledge of ns-pulsed DBD on discharge characteristics and air disinfection behaviors.

Persistent pollution of genetic materials in a typical laboratory environment.

From the onset of coronavirus disease (COVID-19) pandemic, there are concerns regarding the disease spread and environmental pollution of biohazard since studies on genetic engineering flourish and numerous genetic materials were used such as the nucleic acid test of the severe acute respiratory syndrome coronavirus (SARS-CoV-2). In this work, we studied genetic material pollution in an institute during a development cycle of plasmid, one of typical genetic materials, with typical laboratory settings. The pollution source, transmission routes, and pollution levels in laboratory environment were examined. The Real-Time quantitative- Polymerase Chain Reaction results of all environmental mediums (surface, aerosol, and liquid) showed that a targeted DNA segment occurred along with routine experimental operations. Among the 79 surface and air samples collected in the genetic material operation, half of the environment samples (38 of 79) are positive for nucleic acid pollution. Persistent nucleic acid contaminations were observed in all tested laboratories and spread in the public area (hallway). The highest concentration for liquid and surface samples were 1.92 × 108 copies/uL and 5.22 × 107 copies/cm2, respectively. Significant amounts of the targeted gene (with a mean value of 74 copies/L) were detected in the indoor air of laboratories utilizing centrifuge devices, shaking tables, and cell homogenizers. Spills and improper disposal of plasmid products were primary sources of pollution. The importance of establishing designated experimental zones, employing advanced biosafety cabinets, and implementing highly efficient cleaning systems in laboratories with lower biosafety levels is underscored. SYNOPSIS: STATEMENT. Persistent environmental pollutions of genetic materials are introduced by typical experiments in laboratories with low biosafety level.