不同pH下碱性磷酸酶对As(Ⅴ)污染的响应

Response of alkaline phosphate to arsenic(Ⅴ)at different pH

【目的】分析不同pH下砷(As(Ⅴ))对碱性磷酸酶活性的影响,为砷污染监测提供理论依据。【方法】采用室内模拟方法,研究不同pH条件下不同状态(游离态、固定态、土壤)碱性磷酸酶活性与砷污染之间的关系。【结果】同一As(Ⅴ)质量浓度下,pH为7.0~10.0时,碱性磷酸酶活性逐渐增大。As(Ⅴ)明显抑制碱性磷酸酶活性,其对游离态碱性磷酸酶的抑制幅度最大,对土壤碱性磷酸酶抑制幅度最小。砷对碱性磷酸酶的毒性随pH升高而增强。砷质量浓度(C)与碱性磷酸酶活性(E)之间的关系可以用模型E=A/(1+B×C)(A,B为系数)较好表征,揭示出在供试pH范围内碱性磷酸酶在一定程度上均可作为砷污染程度评价指标,且砷对碱性磷酸酶的作用机理为完全抑制作用。与游离态碱性磷酸酶相比,固定态及土壤碱性磷酸酶对砷敏感度降低,pH 10.0条件下游离态、固定态及土壤碱性磷酸酶临界生态剂量值分别为2.60,13.48和20.40mg/kg,远低于国家《土壤环境质量标准》(1995年)中砷的三级污染临界值。【结论】碱性磷酸酶可作为砷污染的监测指标,其对砷污染程度的反应更加灵敏;砷污染条件下,酶载体土壤起到了缓冲作用和保护作用,最终改变了砷的生物毒性。

【Objective】Effects of As（Ⅴ）on activity of alkaline phosphatase at different pH were analyzed to provide basis for monitoring arsenic pollution.【Method】In this study,the relationship between arsenic pollution and activities of alkaline phosphatase at different states（F-ALP,M-ALP and S-ALP）at different pH was investigated using indoor simulation method.【Result】At the same concentration of As（Ⅴ）,the activity of ALP gradually increased with the increase of pH during 7.0-10.0.As（Ⅴ）significantly inhibited the activity of ALP with the largest on F-ALP and the smallest on S-ALP.The toxicity of arsenic on ALP increased with the increase of pH.The model E=A/（1＋B×C）（Aand Bare coefficients）fitted well in the relationship between enzymatic activities（E）and arsenic concentration（C）.ALP activity could be a good bioindicator for arsenic pollution within the studied range of pH.The sensitivity of M-ALP and S-ALP to arsenic was lower than F-ALP.The threshold concentration of As pollution at pH 10.0 for F-ALP,M-ALP,S-ALP were 2.60,13.48 and 20.40 mg/kg,respectively,which were lower than the third standard of Environmental Quality Standard for soils（1995）.【Conclusion】Alkaline phosphatase could beused an index to monitor arsenic pollution.Under arsenic pollution,enzyme carriers played a role of buffering and protection,and changed the biological toxicity of arsenic.