Agrochemicals increase trematode infections in a declining amphibian species.

Global amphibian declines have often been attributed to disease, but ignorance of the relative importance and mode of action of potential drivers of infection has made it difficult to develop effective remediation. In a field study, here we show that the widely used herbicide, atrazine, was the best predictor (out of more than 240 plausible candidates) of the abundance of larval trematodes (parasitic flatworms) in the declining northern leopard frog Rana pipiens. The effects of atrazine were consistent across trematode taxa. The combination of atrazine and phosphate--principal agrochemicals in global corn and sorghum production--accounted for 74% of the variation in the abundance of these often debilitating larval trematodes (atrazine alone accounted for 51%). Analysis of field data supported a causal mechanism whereby both agrochemicals increase exposure and susceptibility to larval trematodes by augmenting snail intermediate hosts and suppressing amphibian immunity. A mesocosm experiment demonstrated that, relative to control tanks, atrazine tanks had immunosuppressed tadpoles, had significantly more attached algae and snails, and had tadpoles with elevated trematode loads, further supporting a causal relationship between atrazine and elevated trematode infections in amphibians. These results raise concerns about the role of atrazine and phosphate in amphibian declines, and illustrate the value of quantifying the relative importance of several possible drivers of disease risk while determining the mechanisms by which they facilitate disease emergence.

Analysis of new generation explosives in the presence of u.s. EPA method 8330 energetic compounds by high-performance liquid chromatography.

U.S. EPA Method 8330 was evaluated and modified for the analysis of DNAN (2,4-dinitroanisole) and MNA (n-methyl-p-nitroaniline) by high-performance liquid chromatography in various aqueous media in the presence and absence of the 14 energetic compounds currently assigned to the method. DNAN and MNA are two of the four components in PAX-21, a new generation explosive formulation. An optimized method was developed to separate all 14 energetic compounds from DNAN and MNA using a tertiary mobile phase of water-methanol-acetonitrile (68:28:4) in an isocratic run of 35 min. The limit of detection (LOD, 3S(0)) was calculated to be 10 ppb for both MNA and DNAN. The limit of quantitation (LOQ, 10S(0)) was 40 ppb for both compounds. The dynamic ranges for the two compounds were very wide, a nearly 5 orders of magnitude range from 0.02 to 1,000 parts per million (ppm). The spike recoveries of MNA and DNAN in environmental matrix samples were excellent for DNAN, from 87% to 113%. For MNA, the recoveries were slightly high at the low level (60 ppb), probably due to some contamination in the ditch and pond matrices; but they were satisfactory at higher levels ranging from 85% to 121%.

Trace level analysis of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and its biodegradation intermediates in liquid media by solid-phase extraction and high-pressure liquid chromatography analysis.

The use of solid-phase extraction for the analysis of liquid media containing low microg/L levels of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), mononitroso-RDX (MNX), dinitroso-RDX (DNX), and trinitroso-RDX (TNX) is examined. Aqueous samples (100 mL) consisting of water and a microbiological basal medium are spiked with known concentrations of RDX, MNX, DNX, and TNX. The compounds are extracted from the liquid media using a Porapak RDX cartridge and then eluted from the cartridge with 5 mL of acetonitrile. The eluent is concentrated to 1 mL before analysis by high-pressure liquid chromatography (HPLC). The method detection limits for RDX are 0.1 microg/L in water and 0.5 microg/L in the basal medium after a 100-fold concentration. For MNX, DNX, and TNX, the method detection limits are approximately 0.5 microg/L in water and approximately 1 microg/L in the basal medium after a 100-fold concentration. Interferences in the basal medium and a contaminant in the standard made quantitation for MNX and TNX, respectively, is less accurate below the 1 microg/L level. Solid-phase extraction of the liquid media gave good recoveries of nitramines and nitroso intermediates from a microbiological basal medium, allowing HPLC detection of RDX and the nitroso intermediates in the low microg/L (ppb) range.