Inactivation of Rhizoctonia solani in fertigation water using regenerative in situ electrochemical hypochlorination.

The capture and re-use of greenhouse fertigation water is an efficient use of fertilizer and limited water resources, although the practice is not without risk. Plant pathogens and chemical contaminants can build up over successive capture and re-use cycles; if not properly managed they can lead to reduced productivity or crop loss. There are numerous established and emerging water treatment technologies available to treat fertigation water. Electrochemical processes are emerging as effective means for controlling pathogens via in situ regenerative hypochlorination; a process that is demonstrated here to achieve pathogen control in fertigation solutions without leading to the accumulation of potentially phytotoxic free chlorine residuals associated with other chlorination processes. An electrochemical flow cell (EFC) outfitted with ruthenium dioxide (RuO2) dimensionally stable anodes (DSA) was characterized and evaluated for free chlorine production and Rhizoctonia solani inactivation in both irrigation and fertigation solutions. Pathogen inactivation was achieved at low current densities and short residence or cell contact times. Effluent free chlorine concentrations were significantly lower than commonly reported phytotoxic threshold values (approximately 2.5 mg/L) when fertilizer (containing ammonium) was present in the test solution; an effect attributable to reactions associated with breakpoint chlorination, including chloramine formation, as well as the presence of other oxidizable compounds in the fertilizer. Chloride concentrations were stable under the test conditions suggesting that the EFC was operating as a regenerative in situ electrochemical hypochlorination system. No significant changes to macronutrient concentrations were found following passage through the EFC.

The effect of electrostatic fingerprint visualization on integrated ballistic identification systems.

Visualization of fingerprint corrosion on spent brass cartridge cases by the application of a high electrical potential and conducting carbon powder is becoming an accepted method of fingerprint enhancement. However, to date, no examination has been made of any effect this technique has on ballistic identification. To resolve this, images of the breech face and firing pin marks were captured on six plated nickel and six brass primer cup spent cartridge cases. Three nickel and three brass cases were then subjected to the application of a potential of +2500 V for a period of 1 min. The remaining cases were additionally subjected to the application of carbon powder. These latter cases were then washed to remove all traces of powder. Each case was recaptured with the same ballistic identification apparatus and imaging procedure. None of the twelve cases showed any visual difference after the application of the potential or conducting powder.