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扬子鳄(Alligator sinensis)是中国特有物种。20世纪80年代以来,扬子鳄野生种群数量急剧下降[1-2],国际自然保护联盟(IUCN)已将扬子鳄列为极度濒危物种。然而,扬子鳄的致濒机制尚不十分清楚。研究认为,栖息地的减少及碎片化、全球环境变化及环境污染可能是扬子鳄野生种群数量锐减的主要原因[3-4]。
滴滴涕(DDT)及其代谢产物二氯二苯二氯乙烯(DDE)和二氯二苯二氯乙烷(DDD)等化合物是环境中广泛存在的内分泌干扰物。我国于20世纪50年代开始生产DDT,随后于1983年被禁用。然而,某些农药(如三氯杀螨醇)和防锈漆中仍然含有DDT成分,这些产品中的DDT还将持续释放到环境。这些污染物具有生物富集效应并可以沿食物链产生生物放大效应,从而对生物的内分泌系统和繁殖系统产生毒害作用[5]。鳄类处于食物链的顶端,很容易蓄积这类污染物。研究证实,DDT类污染物暴露可能使鳄类在性别分化过程中产生性别反转,并可导致新生鳄和幼鳄存活率降低[6-7]。此外,这些污染物可以导致成鳄繁殖力下降、血清性激素水平改变和第二性征异形等不利后果[8-12],最终影响野生种群数量[8-9]。
圈养是保护极度濒危物种-扬子鳄的重要手段。我国主要的扬子鳄圈养地(安徽宣城和浙江长兴)位于长江中下游著名的鱼米之乡,历史上该地区DDT曾作为杀虫剂大量使用。我们的初步研究发现,圈养扬子鳄及卵中DDT及其降解产物的含量处于非点源污染地鳄类这些污染物含量报道值的高端,卵中DDE含量高值已接近可能产生性别反转的DDE含量限值[13]。然而,圈养扬子鳄栖息环境中DDT类化合物污染现状尚不清楚。
本研究测试了我国最大的扬子鳄圈养基地水塘沉积物中DDT、DDE、DDD、2,2-二(氯苯基)1-氯乙烯(DDMU)和二氯二苯甲烷(DDM)等DDT相关污染物的含量和组成,评估了这些污染物潜在的生态风险。
圈养扬子鳄栖息水塘沉积物中滴滴涕(DDT)及其降解产物残留
Residues of DDT and its metabolites in the sediments from a captive breeding center for Chinese alligator
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摘要: 圈养是保护极度濒危物种-扬子鳄的重要手段,但圈养环境中滴滴涕(DDT)等污染物可能对扬子鳄产生毒害作用。本研究测试了我国最大的扬子鳄圈养基地水塘沉积物中DDT及其降解产物的含量和组成,并评估了这些污染物的潜在生态风险。沉积物中∑DDXs(DDT及其降解产物含量之和)的含量范围为4.30—11.9 ng·g−1干重;秋季含量显著高于春季。p,p'-DDE是最主要的DDT类污染物,其含量占∑DDXs的73%。DDT的两种高阶降解产物2-氯-1,1-双(4-氯苯基)乙烯(p,p'-DDMU)和1-氯-4-[(4-氯苯基)甲基]苯(p,p'-DDM)也在沉积物中广泛检出,其含量分别占∑DDXs的6.5%和0.5%。DDT类污染物的组成分析结果显示,圈养扬子鳄栖息地没有DDT的新源输入。沉积物中DDE和DDT的含量超过了这些污染物的阈值效应水平,表明圈养扬子鳄栖息水塘中这些化学品存在潜在的生态风险。Abstract: Captive breeding of the Chinese alligator serves as the last resort for ex situ conservation of this critically endangered species. However, this effort may be compromised by the environmental chemicals such as DDT-related compounds which are proposed stressors contributing to the declines in some crocodilian populations. Here, we reported the presence of DDT and its metabolites in the sediments from the largest captive breeding center for the Chinese alligator in China. The concentrations of ∑DDXs (sum of the concentrations of DDT and its metabolites) in the sediments ranged from 4.30 to 11.9 ng·g−1 dry weight, with significantly higher levels in autumn than spring. The most abundant DDT compound in the sediments was p,p'−DDE, comprising approximately 73% of the ∑DDXs. In particular, two high-order metabolites of DDT, p,p'−DDMU and -DDM, were also consistently detected in the sediments, with contributions of 6.5% and 0.5% to the ∑DDXs, respectively. The profiles of DDT isomers and its metabolites indicated that there is no DDT fresh input in the captive breeding center. The concentrations of DDE and DDT in the sediment samples clearly exceeded the threshold effects level set in sediment quality guidelines, suggesting potential ecological risks of these chemicals.
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Key words:
- DDT /
- DDMU /
- Sediment /
- Alligator sinensis /
- Ecological risks
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表 1 圈养扬子鳄栖息水塘沉积物中DDT及其代谢产物的含量(ng·g−1干重)
Table 1. Concentrations (ng·g−1 dry weight) of DDT and its metabolites in the pond sediments collected from a captive breeding center for Chinese alligator
化合物
Compounds春季(Spring)(n = 12) 夏季(Summer)(n = 12) 秋季(Autumn)(n = 12) 均值
Average标准差
Standard error范围
Range均值
Average标准差
Standard error范围
Range均值
Average标准差a
Standard error范围
Rangep,p'-DDT 1.05 0.11 0.02—1.60 1.17 0.13 0.02—1.79 1.30 0.14 0.02—1.99 o,p'-DDT 0.05 0.01 0.01—0.07 0.05 0.01 0.00—0.08 0.13 0.01 0.09—0.19 p,p'-DDE 5.26 0.25 3.79—6.67 5.89 0.28 4.24—7.47 6.53 0.31 4.70—8.28 o,p'-DDE 0.02 0.003 0.01—0.04 0.03 0.003 0.01—0.05 0.03 0.003 0.01–0.05 p,p'-DDD 0.18 0.02 0.07—0.30 0.20 0.03 0.08—0.34 0.23 0.03 0.09—0.37 o,p'-DDD 0.03 0.003 0.01—0.04 0.03 0.003 0.01—0.05 0.04 0.003 0.01—0.06 p,p'-DDMU 0.47 0.03 0.32—0.69 0.53 0.03 0.36—0.78 0.59 0.04 0.40—0.86 p,p'-DDM 0.03 0.002 0.03—0.05 0.04 0.002 0.03—0.05 0.04 0.002 0.03—0.06 ∑DDXs 7.09 0.39 4.30—9.47 7.94 0.44 4.82—10.6 8.88 0.49 5.45—11.9 ∑DDXs,DDT及其代谢产物的含量之和.
∑DDXs, Sum concentrations of DDT and its metabolites examined.表 2 文献报道的沉积物中p,p'-DDMU含量(干重)
Table 2. The concentrations of p,p'-DDMU (dry wt) in the sediments reported in the literature
采样地点
Sampling sites采样时间
Sampling year浓度范围/(ng·g−1)
Concentration range均值/(ng·g−1)
Average concentration参考文献Reference 圈养扬子鳄栖息水塘 2017 0.32—0.86 0.53 本研究 广东省东莞某池塘 2006—2007 ND—0.22 0.04 [20] 广东省顺德某池塘 2006—2007 ND—0.12 0.01 [20] 渤海湾 2002 NCR 0.2 [21] 长江 2010 0.03—3.76 1.16 [22] 海河 2002 0.48—5.8 1.64 [23] 波兰维斯图拉河 1991—1995 NCR 1.9 [24] 美国帕洛斯弗迪斯大陆架 1992 510—956 712 [25] 美国旧金山湾 1993 1.1—190 39.89 [26] ND,未检出;NCR,无明确范围.
ND, not detected; NCR, have not reported the ranges. -
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