Toxicity of hexyl toF. candida and E. crypticus

Aim, Scope and BackgroundHexyl is along with TNT a possible pollutant of ammunition contaminated soils. To assess the ecological risk of a pollutant biotests are obligatory to gain information of the effects on the habitat function of the contaminated soil. The effect of Hexyl was investigated using the standardised biotests for the springtailFolsomia Candida and the enchytraeidEnchytraeus crypticus.MethodThe tests with Hexyl were performed in spiked standard soil (Lufa 2.2). The toxic endpoints were mortality (short-term test, exposure time 7 days) and reproduction rate (long-term test, exposure time 28 days). The effect on the reproduction was further investigated by transferring animals from contaminated soil material onto uncontaminated substrate. Then the number of offspring was determined for the collembola and the cocoon- and hatching rates for the enchytraeid. Results. The mortality of the collembola was not influenced by Hexyl, but the number of offspring was significantly reduced. On the bases of these data the influence of the contaminant on the fertility of the adults itself was investigated. Therefore a reproduction test was performed with adult springtails transferred from contaminated onto uncontaminated soil material. It was shown that the fertility of the adults was not affected by Hexyl indicating a strong lethal effect on the juveniles. In case of the enchytraeid the mortality as well as the reproduction was affected. The surviving enchytraeids turned yellow and rigid in the mortality tests. They were also reduced in size compared to individuals in the uncontaminated control soil material. Thus the cocoon and hatching rates of worms transferred from contaminated soil material onto agar-agar was further investigated. Indeed, the reproduction (both cocoon production and juvenile hatching) was affected by the contaminant. However, the effect was not as strong as might have been suggested by their change in colour and size. A rapid recovery of the worms was observed, too.ConclusionHexyl is toxic for the two terrestrial invertebrates, although in comparison to other explosives tested it is less toxic than TNT, but more toxic than the other explosives such as Hexogen (RDX) and Octogen (HMX) or TAT, the end product of the microbial reduction of TNT. So far, all these substances have only been tested with the luminescent bacteriaVibrio fischeri, for which Hexyl and TNT were classified as very toxic to aquatic organisms. With earthworms (Eisenia