沉积物中六氯苯对摇蚊幼虫的慢性毒性效应

以淡水底栖动物花翅羽摇蚊(Chironomus kiiensis)幼虫为受试生物,研究了沉积物中六氯苯(HCB)对其28 d的慢性毒性效应,观察摇蚊幼虫的存活情况和活动行为,以死亡率、羽化率和羽化时间为受试终点,计算28 d试验后沉积物中HCB对摇蚊的半数致死浓度(lethal concentration 50,LC50)以及50%羽化时间(50%emergence time,EmT50)。结果表明,HCB对摇蚊28 d的LC50为59.8 mg·kg-1,对摇蚊羽化率的半数效应浓度(half maximal effective concentration,EC50)为59.8 mg·kg-1。与大多数污染物不同,HCB有促进摇蚊幼虫筑巢行为和羽化的作用,随着HCB染毒浓度升高,摇蚊幼虫筑巢行为加强,EmT50缩短。暴露于高浓度HCB(21.6 mg·kg-1)时,摇蚊的EmT50与对照相比明显缩短,尤其对雄性摇蚊影响更大。但与对照相比,HCB对羽化摇蚊的性别比没有很大影响。

Chronic Effects of Hexachlorobenzen (HCB) in Sediments to Chironomus kiiensis Larvae

The chronic toxicities of hexachlorobenzen (HCB) in sediments to freshwater benthic organism Chironomus kiiensis were studied by exposing the larvae in HCB-spiked sediments for 28 days. During the experiment, the behavior of larvae was carefully checked. The mortality, emergence rate and emergence time were used as endpoints. The LC₅₀ (lethal concentration 50) and EmT₅₀ (50% emergence time) in 28-d tests were estimated. The results indicated that the survival rate was equal with the emergence rate and the LC₅₀ and EC₅₀ (half maximal effective concentration) of emergence were both 59.8 mg·kg^-1. Different from most of the organic pollutants, HCB could accelerate tube building of larvae in sediments and emergence of adults. The acceleration of tube building of larvae and the emergence of adults were more obvious as the concentration of HCB in sediments increased. When the concentration of HCB in sediments was higher than 21.6 mg·kg^-1, the EmT₅₀ was significantly lower than the control, especially for the male. However, HCB showed no significant effect on the sex ratio of adults.