for a method of detecting biological weapon use , the disclosure suggests to apply known technology relating to interfacial films of monolayer - forming substances having molecules that when spread at an air / water interface will immerse into the water a hydrophilic terminal group for each molecule , with a long - chain carbon - containing hydrophobic group extending vertically upward away from the water . such monolayers manifest monitorable properties which are susceptible using known instrumentation means to measurement of changes induced by biological contaminants thus making it possible to determine by appropriate testing what a bioattack signature change would be . given siting of a monolayer coated aqueous body in a reservoir where a biological attack may occur , monitoring the monolayer properties for the signature change can detect whether and when such an attack does occur . one example of enacting the method involves a lake - sized water reservoir coated by a mixed monolayer which changes respecting color absorbance when bacteria and a biocide in the monolayer interact . another example uses an instrumented film balance , ie ., langmuir trough as the reservoir , which is small enough for siting anywhere needed , eg ., inside postal stations or other important buildings .