卵形鲳鲹网箱养殖过程主要生长阶段DDTs残留特征及其来源分析

Bioaccumulation and potential sources of DDTs in Trachinotus ovatus during typical cage cultured periods

为了解卵形鲳鲹养殖过程主要生长阶段DDTs残留特征及其来源途径,针对卵形鲳鲹实际网箱养殖生产条件,在放苗、养殖生产中期和收获3个主要时期,分别采集网箱中养殖水体、养殖鱼体、所用饲料和网箱处海底表层沉积物底泥样品,采用气相色谱法测定样品中DDTs及其同系物含量。结果显示,苗种、成鱼、所用饲料及养殖水体和养殖环境表层沉积物底泥中,均检测出DDTs,其中苗种、养殖成鱼、所用饲料、养殖海水和表层沉积物底泥中DDTs平均含量分别为(3.15±0.42)、(4.49±0.39)、(3.95±0.33)μg/kg干重、(3.76±0.43)ng/L和(4.34±1.18)μg/kg干重。随着养殖过程的进行,鱼体中DDTs含量逐渐增加,收获上市时期鱼体肌肉中含量显著高于苗种时期的含量,但远低于0.5 mg/kg湿重的国家食品安全限量标准。从DDTs同系物种类上看,养殖海水、饲料和鱼体中ο,ρ′-DDT、ρ,ρ′-DDD、ρ,ρ′-DDT和ρ,ρ′-DDE 4种同系物均能检出,但沉积物中仅检测出前3种同系物。4类样品DDTs主要成分均为ο,ρ′-DDT和ρ,ρ′-DDT,其在鱼体中所占比例平均值分别为42.09%和37.07%;在饲料中所占比例平均值分别为44.85%和34.62%;在养殖海水中所占比例平均值分别为40.91%和37.99%;在养殖环境沉积物底泥中所占比例平均值分别为33.03%和51.34%。从鱼体、饲料、养殖海水和沉积物底泥中DDTs同系物组成比例和含量特征判断,饲料是鱼体后续生长中富集DDTs的主要来源途径之一。为保障卵形鲳鲹质量安全,应着重加强饲料中有毒有害物质的控制和管理。

In the 12 th Stockholm Convention, DDTs is one of the nine organic chlorine pesticides, which were proposed to be controlled as persistent organic pollutants（POPs）, because of its harmful effects to the environment and the ecosystem. In China, a large amounts of DDTs have been used in the past few years, and it still can be generally detected in the environment although it was banned for using in agriculture in 1983. Many studies showed that fish consumption is a significant route for human exposure to POPs in the world. China is the largest fishery producer in the world with nearly 60 million metric tons in 2015, accounting for 70.0% of the total global fishery production. Recent study showed that residues of the DDTs have been widely identified and reported in some aquaculture fishes in China, especially in Trachinotus ovatus. To determine the bioaccumulation and the potential input sources of DDTs to cage farmed T. ovatus, samples of seed,feeds, adult fish, seawater and the sediments were collected at the beginning, medium and the end of aquaculture practice. DDTs were detected in all samples analyzed, with mean concentrations（± standard deviations） at（3.15±0.42） μg/kg wet weight in seed,（4.49±0.39） μg/kg wet weight in adult fish,（3.95±0.33） μg/kg dry weight in fish feeds,（3.76±0.43） ng/L in cage water and（4.34±1.18） μg/kg dry weight in sediment. The concentration of DDTs in the fish increased during the culture period and significantly higher when harvesting compared to the beginning and the medium, but well below the 0.5 mg/kg wet weight of national standards for food safety level. In addition, only ο,ρ＇-DDT, ρ,ρ＇-DDD and ρ,ρ＇-DDT were detected in the sediments, but those three and ρ,ρ＇-DDE were detected in the seeds, fish feeds and seawater. ο,ρ＇-DDT and ρ,ρ＇-DDT were the major constituents in all samples, with respectively average percentage at 42.09% and 37.07% in fish, 44.85% and 34.62% in fish feeds, 40.91% and 37.99% in cage water,33.03% and 51.34% in sediment. Finally, statistical analyses suggested that fish feed, as well as pond water at a lesser degree, may have been the major source of DDTs in cage farmed fish of T. ovatus. In order to ensure the quality and safety of T. ovatus, we should focus on strengthening the control and management of toxic and harmful substances in the feed.