铝盐絮凝剂是国内外最常用的水处理和水环境修复药剂，其主要成分纳米团簇铝（nano-Al₁₃）兼具高絮凝性能和纳米特性。一直以来，对其残余毒性的研究是从传统单体铝（Al_m）角度进行探索。然而，残余铝絮凝剂的生物毒性与其赋存形态具有直接相关性。目前从总量角度探讨铝毒性的研究较多，但从形态角度对不同形态羟基铝尤其是纳米级Al₁₃团簇毒性效应的研究相对缺乏，且已有研究结果存在争议。单体铝在一定条件下可转化为纳米铝团簇，进一步增大残余铝的毒性效应复杂性。底栖水生动物可直接接触沉积絮体或暴露于上覆水中，将污染物质传递至人类，对人体健康、水生态环境安全造成危害。

双壳贝类河蚬对水体中污染物暴露时间长、活动能力差、且易累积环境污染物，已被成功用作环境毒性指示生物。为此，本研究以河蚬为毒性测试对象，明确铝盐絮凝剂不同形态（无机单体离子态Al_m、纳米多核团簇态Al₁₃）在生物体内的富集特征，深入探讨不同理化条件下各形态残余铝对河蚬的致毒机制，并对铝盐絮凝剂两种典型形态的毒性进行量化评价。结果发现：

（1）残余铝在河蚬消化腺、鳃中均有明显富集，但大部分残余铝会随着暴露时间延长被河蚬排出。不同器官对不同形态铝的蓄积和外排能力具有差异性：Al₁₃在消化腺中富集量更大，而Al_m更易残留在鳃组织内。纳米团簇颗粒Al₁₃主要依靠吞咽作用进入河蚬消化腺与金属硫蛋白结合并富集；而单体铝Al_m主要依靠鳃过滤和吸附截留作用累积于体内。

（2）两种形态铝的存在触发河蚬毒理学终点表现为虹吸行为被抑制、氧化应激发生、脂质过氧化程度显著增加、神经递质被干扰、细胞组织出现炎症反应及肠道菌群失调。两种形态铝对不同器官的毒性作用不同：nano-Al₁₃对消化腺的毒性作用更为强烈，而Al_m对鳃的毒性作用更加明显。其致毒机制与两种形态铝进入机体的蓄积途径有关，其累积位点的特异性导致了其在不同脏器中发挥毒性效应的差异。nano-Al₁₃可对细胞膜造成损伤，可能由纳米铝团簇粒子的穿膜过程和强烈的脂质过氧化反应共同导致。RNA-seq验证表明Al₁₃胁迫会导致机体产生更加积极的调控作用。

（3）随铝暴露浓度增大、水体pH降低，残余铝对于河蚬产生的毒性效应有所增大。暴露浓度较高且长期暴露时，Al₁₃较Al_m对河蚬表现出更强的毒性效应，表现为强烈的细胞组织、生物分子及神经系统的损伤。Al_m导致的毒性效应受pH影响大。有机酸可与羟基铝络合形成有机络合态铝降低铝毒，其中草酸、柠檬酸对Al_m形态的解毒效果较好，络合过程中还可释放出OH-，升高暴露体系pH值，进一步降低铝活性，削弱铝毒。而消毒副产物三氯乙酸、腐殖酸将在短时间内加重Al毒。

（4）运用第一代及第二代综合生物标志物响应指数法（IBR、IBRv2）分别对高低浓度不同形态铝胁迫的河蚬毒性效应进行定量评价，发现纳米多聚态Al₁₃和单聚体Al_m的响应指数分别在消化腺、鳃中有最高值，且在低浓度下就具有较高毒性。建议对《生活饮用水卫生标准》中铝的限值进一步收紧和细化，以期保障居民饮用水安全。

The aluminum flocculant is the most commonly used medicament for water treatment process around the world. Its main component, nanometer aluminum (nano-Al₁₃), has both high flocculation performance and the characteristics of nanoparticles. For a long time, the studies on the toxicity of residual aluminum focused on traditional monomeric aluminum (Al_m). Previous researches focused on the total Al, but the biological toxicity and bioavailability of residual Al from flocculant were dependent on the speciation. In addition, residual Al could transform into nanometer polymeric cluster under natural conditions. Thus, the bio-toxicity enhanced. Aquatic animals can directly contact the deposited flocs or be exposed to the overlying water, and can pass toxic substances to the next level of the food chain through accumulation, affecting the safety of the ecosystem and even human health.

Corbicula fluminea has been used as an effective indicator of environmental toxicity in the world, which has the characteristics of long exposure, poor mobility and high accumulation of pollutants. Therefore, Corbicula fluminea was chosed as the toxicity test animal to study the enrichment characteristics of different species of Al flocculants (monomeric Al_m, polymeric nano-Al₁₃), and further explored their toxic effects under different conditions. Finally, the toxicity of two kinds of flocculants were evaluated quantitatively.

The results show that:

(1) The residual Al was enriched in both digestive gland and gill of Corbicula fluminea, and it would be excreted with the time of exposure. The accumulation and excretion capacity of different organs for different species are different: Al₁₃ is more abundant in digestive gland, and Al_m is more likely to remain in gill tissue. Nano-Al₁₃ mainly enter the digestive gland of Corbicula fluminea by swallowing and then combined with metallothionein. Al_m was accumulated in the body mainly through filtration of gill.

(2) The existence of two forms of Al triggers these ends of toxicology in Corbicula fluminea: the inhibition of siphonage, the occurrence of oxidative stress, the significant increase of lipid peroxidation, the interference of neurotransmitters, the occurrence of inflammation in cell tissues and the change of intestinal microbial diversity. The toxic effects of two Al species on different organs are different: nano-Al₁₃ has a stronger toxic effect on digestive gland, while Al_m has a stronger toxic effect on gill. The mechanism related to the accumulation of two forms of Al. The specificity of its accumulation site leads to the difference of its toxic effect in different organs. Besides, nano-Al₁₃ can damage the cell membrane, which might be caused by the process of membrane penetration as well as the strong lipid peroxidation.

(3) The toxic effect of residual Al on Corbicula fluminea increased with the increase of Al concentration and the decrease of water pH. When exposed to high concentration and long-term exposure, the Al₁₃ showed stronger toxic effect than Al_m, which was expressed by strong damage to celles, biomolecule and nervous system. The toxic effect of Al_m is greatly affected by pH. Organic acids can reduce the toxicity of recidual Al by transform hydroxyl Al to organic complexed Al, among which oxalic acid and citric acid have better detoxification effect especially on the form of Al_m. In the process of complexation, OH^- was released and the pH increased, and the aluminum toxicity will be further weakened. However, trichloroacetic acid and humic acid would aggravate Al toxicity in a short time.

(4) The first and second generation Integrated Biomarker Response index (IBR, IBRv2) were used to quantitatively evaluate the toxic effects of Corbicula fluminea under different kinds of Al floocculants. It was found that the response index of nano-Al₁₃ and monomeric Al_m had the highest value in digestive gland and gill respectively. The toxicity was high even at low concentrations. It is suggested that the limit value of Al in the sanitary standard for drinking water need to be further tighten, thus the safety of drinking water for residents can be ensured.