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重金属在水生生态系统中有着非常广泛的分布. 其主要来源包括地球化学结构、采矿活动、金属冶炼、工业废物、废物焚烧和城市污水排放[1]. 由于重金属不会自然降解,它们通常沉淀在沉积物中,溶解在天然水中,或富集在生物体中[2]. 值得注意的是,重金属在食物链中富集,一旦达到生物利用度的阈值,就会对生物体造成毒性影响[3].
水体环境的物理化学特征对沉积物积累重金属的行为存在显著影响[4]. 由于湖泊沉积物是水体环境中重要的重金属库,沉积物中积累的重金属成了水体环境重金属污染的一个重要来源,因此对于水生生态系统中沉积物中重金属含量的检测,也是了解水环境重金属污染的重要环节[5]. 湖泊沉积物提供了环境变化的信息,显示了流域内不同重金属浓度的时空差异[6-7]. 通过测定不同深度的沉积物岩芯中重金属的浓度可以推测重金属污染史[8-10]. 然而,重金属生物积累和放大的信息不能只通过测定水体和沉积物中重金属来衡量[11].
随着时间的推移,水生生物会吸收其生存环境中的各种污染物,另外,鱼类在水生环境食物网中占据重要地位. 因此,检测鱼类重金属的富集情况可以作为水体环境重金属污染的生物监测手段[10]. 更重要的是,鱼体内富集的重金属可以通过食物链转移到人体. 一般来说,重金属可以分为有毒元素(如Pb、Cd、Cr)和生物必需元素(如Cu、Zn),但即使是生物必需元素在高浓度条件下也会产生毒性效应[12]. 测定鱼体中的重金属含量,对评估人类食用鱼的潜在健康风险具有重要意义[13-14]. 研究鱼类组织中重金属的含量,将有助于评价水环境中重金属的污染状况. 鱼类的肌肉组织是人类消费的主要部分;肝脏是金属最重要的代谢和储存器官[15];鳃可以直接反映水中的金属含量,因为它们是直接暴露在水环境中的呼吸器官,可以调节酸碱和离子转移[16]. 因此,本研究检测鱼类的肌肉、肝脏、鳃部位的重金属含量,来了解鱼类体内重金属污染情况.
滇池作为水资源保护区以及中国最大的高原淡水湖,同时也是昆明市主要的储备水源. 根据《云南省环境保护厅关于印发云南省地表水水环境功能区划(2010—2020年)的通知(云环发〔2014〕34号)》一般鱼类保护区和游泳区,执行地表水环境质量Ⅲ类标准. 在经济快速发展的几十年中,该湖受到了工业、农业和城市日常生活污水和废物的严重污染. 滇池是一个富营养化程度很高的湖泊,具有弱碱性环境和较高的溶解氧浓度[17]. 在弱碱性条件下,即使存在相当大的物理干扰,沉积物中的重金属也很难释放出来进入水体[18]. 在较高溶解氧条件下,金属氧化物和氢氧化物与可溶性重金属离子结合形成共沉淀.[19]悬浮沉积物从水中吸附重金属污染物,从而降低其在水中的浓度[20],使得沉积物中重金属含量高于地表水. 尽管之前有研究表明,在滇池沉积物中存在大量重金属[21],但它们在水体和沉积物中的空间分布和历史变化,以及随环境条件变化在特有野生鱼类组织中的生物蓄积量知之甚少.
本文对滇池水环境、底泥和3种典型野生鱼类(鲤鱼、鲫鱼和银鱼)中Pb、Zn、Cu、Cd、Cr的含量进行了比较研究. 本研究旨在研究水体和沉积物中重金属的含量及其空间变化,阐明其在鱼类器官中的富集水平,为重金属污染防治提供基础资料. 在此基础上,对滇池重金属污染对周边居民可能造成的危害进行了评价. 这些研究有助于更好地了解重金属在自然水环境中的迁移转化以及在生物体内的富集情况,为合理管理和控制重金属污染提供有效信息.
滇池重金属污染的分布、积累和风险评估
Distribution, accumulation and risk assessment of heavy metal pollution in Dianchi Lake
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摘要: 本文主要研究重金属在滇池水体、沉积物和3种典型野生鱼类(鲤鱼, 鲫鱼和银鱼)中的积累水平, 同时对滇池重金属污染的潜在健康风险进行评估.研究表明, 滇池水体和表层沉积物中5种重金属的浓度大小顺序是一致的(Zn>Cr>Cu>Pb>Cd). 自20世纪70年代以来, 沉积物岩芯中的重金属含量显著增加, 大多数表层沉积物中的重金属含量均高于当地背景土壤值. 但3种典型野生鱼类中积累的重金属均没有超过中国政府部门设定的安全阈值. 鱼类重金属的生物富集因子(BCF)变化很大, 鱼体内肌肉的重金属的BCF的顺序为: Zn>Cd>Pb>Cu>Cr. 此外, 鱼类器官中重金属的平均含量遵循肝脏>腮>肌肉的顺序. 健康风险评估表明, 目前食用鱼对人类是较为安全的, 但在长期食用过程中仍存在潜在的和可预测的健康风险.Abstract: This article mainly discussed the associated migration of heavy metals and their cumulative levels of water, sediments, and three endemic wild fishes (Cyprinus carpio, Carassius auratus, and Anabarilius alburnops) in Dianchi lake. Meanwhile, the possible health risks of heavy metal pollution in Dianchi lake were evaluated. The results revealed that five heavy metals detected in water and surface sediments were consistent with the order of Zn > Cr > Cu > Pb > Cd. Since 1970s, the levels of heavy metals increased significantly with depths in collected sediment cores, and the heavy metals in most surface sediments were greater than those in local background soils. However, the heavy metals accumulated in three endemic wild fishes did not exceed the safety thresholds established by China government departments. The bioconcentration factors of heavy metals in fish species varied from 0.74 to 36.47, and the order of BCF in fish body was in Zn > Cd > Pb > Cu > Cr. In addition, the mean concentration of heavy metals in fish organs followed the order of liver > gill > muscle. Health risk assessment indicated fish’s consumption was safety for human at present, but there would be a potential and predictably health risk in the process of human long-term consumption.
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Key words:
- heavy metals pollution /
- Dianchi lake /
- accumulation /
- bio-enrichment /
- risk assessment
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表 1 滇池地区三种特有野生鱼类的特征
Table 1. Characteristics of three endemic wild fishes in Dianchi Lake area
种类
Species数量
Number体长/cm Body length 体重/g Weight 均值Average 范围Min-Max 均值Average 范围Min-Max 鲤鱼Carp 12 30.9±9.2 14—51 645±485.5 66—1904 鲫鱼Crucian carp 40 16.3±4.7 7—26 113.4±98.1 13—546 银鱼Silvery minnow 38 13.5±3.6 6—20 25.6±16.6 2—66 表 2 滇池8个采样点的水体和沉积物的重金属含量
Table 2. The concentrations of heavy metals in the water and surface sediments at 8 sites in Dianchi lake are listed in below table
采样点 C1 C2 C3 C4 C5 C6 C7 C8 EQS1 水体/
(μg·L−1)Pb 36.58±2.03ab 20.96±1.84c 46.31±2.07d 42.84±1.82bd 44.85±3.50d 33.62±3.13a 14.33±0.60e 21.22±1.62c ≤10 Zn 466.77±4.86a 491.72±3.50b 355.92±3.43c 316.48±3.41d 384.02±4.07e 345.22±4.08f 214.78±1.51g 386.97±1.56e ≤1000 Cu 93.20±1.88a 105.28±5.20b 84.15±1.75c 125.34±3.06d 107.20±1.83b 100.43±4.94ab 100.58±0.88ab 126.36±2.54d ≤1000 Cd 2.78±0.09ab 3.22±0.12b 1.62±0.09c 2.54±0.34a 1.56±0.23c 1.45±0.05cd 1.02±0.22d 1.36±0.13cd ≤5 Cr 105.73±0.85a 127.83±2.90b 115.89±3.46c 113.48±2.75ac 115.26±3.98ac 118.25±2.18bc 86.72±5.28d 115.19±3.87ac ≤50 C1 C2 C3 C4 C5 C6 C7 C8 SBV2 沉积物/
(mg·kg−1)Pb 75.03±4.42A 96.18±3.39B 98.10±4.19B 111.76±7.51BC 112.13±7.05BC 100.90±8.69BC 119.13±6.36CD 135.37±8.01D 26.2 Zn 210.18±6.02A 225.04±3.27A 165.39±5.59B 172.42±6.71B 190.09±9.87C 189.66±5.51C 157.67±8.55B 171.80±5.71B 88.4 Cu 118.26±
2.16AD104.96±
5.00ABC120.73±3.96D 115.46±
5.06ABD193.30±6.12E 102.09±7.10BC 99.97±8.05C 86.59±5.71F 35.1 Cd 2.21±0.09ABC 2.54±0.08BC 2.09±0.14ABD 2.29±0.14ABC 2.33±0.24ABC 2.58±0.08C 1.68±0.31D 1.86±0.09AD 0.28 Cr 134.39±5.16A 148.80±3.68B 132.68±4.06AC 122.62±
5.42ACD127.00±6.08AC 123.78±
4.34ACD110.51±9.45D 119.70±
10.65CD58.6 1中国地表水质量标准二级标准;Chinese surface water quality standard secondary standard;2云南省土壤重金属背景值;Yunnan background values of heavy metals in soil;
abcdef代表不同采样点水中重金属浓度的显著差异,P<0.05; The letters abcdef represent the significant difference in the concentration of heavy metals in water between different sampling points (P<0.05);
ABCDEF代表不同采样点沉积物中重金属含量的显著差异,P<0.001.The letters ABCDEF represent the significant difference in the concentration of heavy metals in sediments between different sampling points (P<0.001).表 3 水体(μg·L−1)与表层沉积物(mg·kg−1·dw)样品(n=8)之间重金属浓度的皮尔逊相关系数(r)
Table 3. Pearson’s correlation coefficient (r) between heavy metals concentration in water (μg·L−1) and sediment (mg·kg−1·dw) samples collected (n=8).
水体 Water Pb Zn Cu Cd Cr 表层沉积物
Sediment surfacePb −0.364 −0.526 0.683 −0.619 −0.155 Zn −0.023 0.873** −0.129 0.778* 0.554 Cu 0.627 −0.114 −0.141 −0.026 0.110 Cd 0.403 0.562 −0.072 0.562 0.759* Cr 0.193 0.872** −0.307 0.800* 0.716* * 相关性在0.05水平上显著;Correlation is significant at the 0.05 level;**相关性在0.001水平上显著. Correlation is significant at the 0.01 level. 表 4 滇池特有野生鱼类的生物富集因子(BCF, L·kg−1)
Table 4. Bioconcentration factors of three wild fishes (BCF, L·kg−1)
鱼类Fish species 组织Organ Pb Zn Cu Cd Cr 鲤鱼Carp 肌肉Muscles 2.15 14.10 1.43 5.88 0.79 肝脏Livers 7.59 36.47 2.71 16.66 1.50 鳃Gills 4.159 29.03 1.98 11.76 1.29 鲫鱼Crucian carp 肌肉Muscles 1.46 16.65 1.21 5.79 0.74 肝脏Livers 6.29 29.24 1.94 13.16 1.35 鳃Gills 3.28 27.48 1.63 7.61 0.94 银鱼Silvery minnow 肌肉Muscles 2.00 17.58 1.22 6.55 0.68 表 5 3种野生鱼类的目标风险指数(THQ)和风险指数(HI)
Table 5. The target risk quotient (THQ) and hazard index (HI) of three wild fish species
鱼类Fish species THQPb THQZn THQCu THQCd THQCr HI 鲤鱼Carp 0.135 0.129 0.030 0.082 0.00044 0.376 鲫鱼Crucian carp 0.091 0.152 0.026 0.080 0.00042 0.350 银鱼Silvery minnow 0.125 0.161 0.026 0.088 0.00039 0.400 -
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