Advection of Liquid Termiticides within Building Foundation Aggregate Fill

Advection of two liquid termiticides was determined within two different building foundation aggregate fills, ODOT Base Type-A Gravel and Class A-#57 Crushed Rock, after over-the-surface applications. Residues within each aggregate were sampled as two composite soil cores taken in two 5.1-cm incremental partitions to a depth of 10.2-cm after 24 hours, and at 6 and 12 months post-application. Half the test plots were compacted and half remained not compacted. Advection was significantly influenced by aggregate type. Residues within compacted compared with not-compacted aggregates were similar for individual termiti-cides. Some termiticide dispersed completely through the aggregates to reach the soil beneath. Advection resulted in decreasing a.i. concentrations as depth increased within ODOT Base Type-A Gravel fill, with the greatest concentration located in the top 5.1-cm partition, likely due to the fine particle component, with almost no termiticide reaching underlying soil. In contrast, termiticides were more evenly distributed within Class A-#57 Crushed Rock fill, as residue amounts were similar throughout the 10.2-cm depth, with some reaching underlying soil.