SPADA Meeting Book

more acceptable moisture content by air drying with frequent mixing in a sterile 569 environment until the moisture content is low enough. Drying a soil is not recommended 570 unless the method or system being evaluated requires dryer soil. Avoid collecting soil 571 samples after a weather event in order to avoid overly moist soil. To add moisture to a 572 soil, sterilized water can be sprayed onto the soil while monitoring the increase in mass 573 by weighing the soil while spraying. Once added, mix the soil well to ensure even 574 distribution of the added moisture. 575 Soils should be kept in the dark and preferably in an incubator. The container lid 576 should be either opened regularly to ensure a consistent atmosphere or placed ajar with 577 sterile cloth over the container opening preventing contamination in a humidity- 578 controlled incubator. 579 If planning a time series experiment, either a large batch experiment or sacrificial 580 replicates can be used. During each sampled time point, the water content of the soil 581 should be measured as well in order to report the data in soil dry weight. 585 multiple environments and under multiple seasonal conditions. Typically, open-air field 586 testing is conducted using a truth box of ca. ½ km 2 in area. Multiple ground truth 587 instrumentation towers are placed within the box and used in conjunction with 588 meteorological instrumentation placed nearby at heights ranging from 1-3 meters. 589 Ground truth data typically include aerodynamic particle size, concentration, and 590 fluorescence. Samples of airborne particles are collected via impinger or dry filtration to 591 582 583 584 10.2 Outdoor Testing Set-up Field testing designed to simulate a biothreat agent release should be carried out in

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