Monitoring cadmium concentrations in sediments and aquatic insects (Hydropsychidae: Trichoptera) in a stream near a zinc mining area

Abstract

Aquatic insects can accumulate pollutants such as cadmium from stream sediments. This research aimed to monitor cadmium concentrations in both larvae and adult Hydropsychidae (Trichoptera, Insecta) in Mae Tao (MT1 to MT5) and Mae Ku (MK2 and MK8) watersheds in northern Thailand. Samples were collected twice a month from July 2011 to May 2012 at seven sampling sites. The cadmium concentrations in the stream sediments ranged from 0.12 to 21.5 mg kg-1 wet weight. The highest concentration was recorded from the MT3 sampling site (21.5 mg kg-1), which is also closest to a mining area. The lowest concentration was recorded from the MK2 sampling site (0.12 mg kg-1). Cadmium concentrations in both larvae and adult Hydropsychidae were not significantly different at all sampling sites. However, the cadmium concentrations in Hydropsychidae larvae that ranged from 0.07-1.70 mg kg-1 were higher than the detected cadmium in adult samples (average 0.020 mg kg-1). There was no significant correlation between cadmium concentrations in sediments, and in both larvae and adult Hydropsychidae. Concentrations of cadmium in adult Hydropsychidae in this study were low. Even though the contamination of heavy metals was low in adult Hydropsychidae, long-term exposure to heavy metals could seriously impact terrestrial animals such as birds and bats that consume these insects.