沥滤液中低分子量有机酸对小麦种子的急性毒性

Acute Phytotoxicity to Triticum Aestivum of Low Molecular Weight Organic Acids in Leachate

沥滤液来源于生活垃圾焚烧厂贮坑,富含垃圾中的各种有害物质,其处理与再利用过程中可能引起的生态毒性受到人们的关注。采用小麦种子为受试物,通过种子萌发抑制试验对低分子量有机酸(C2-C5)的急性毒性进行评价,并结合液液萃取和减压蒸馏的方法考察低分子量有机酸对沥滤液总体生物毒性的贡献。结果表明,分子态乙酸对小麦种子萌发的急性抑制毒性高于离子态,低分子量有机酸对小麦种子发芽和根伸长的急性抑制毒性,均随低分子量有机酸碳链的增长而增加。5种有机酸贡献了沥滤液稀释液总体急性抑制毒性的20.25%(根)和12.75%(芽);短链有机酸由于具有较低的辛醇-水分配系数(kow),对酸性有机萃取物总体急性抑制毒性的贡献较低;减压蒸馏馏分总体毒性较低,5种低分子量有机酸对其的毒性贡献为24.6%(根)和21.9%(芽)。

Low molecular weight organic acids are main components of leachate from municipal solidwaste incinerator plant which is complex mixture of toxic compounds and may cause great risk to animals and plants, The phytotoxicity of low molecular weight organic acids （C2-C5） was assayed by acute Triticum aestivum assay. For acetic acid, the non-ionized form played a more important role in toxicity than ionized form, The acute toxicity of five kinds of low molecular weight organic acids to roots of Triticum aestivum showed the order： n-valeric acid 〉 iso-butyrie acid ≈ propionic acid〉 n-butyric acid 〉 acetic acid; while, the acute toxicity to sprouts followed the order： n-valeric acid〉iso- butyric acid ≈ n-butyric acid ≈propionic acid 〉 acetic acid. The same acute toxicity assays were carried out on leachate and its liquid-liquid extracted fraction and vacuum distillate to study the percentage of toxicity accounted by single acids in leachate. It was found that 20.3% （based on roots） or 12.8% （based on sprouts） of the observed leachate toxicity could be explained by these five low molecular weight organic acids; the percentages of toxicity in liquid-liquid extraction accounted by short carbon chain organic acids were not prominent since their noctanol/water partition coefficient（kow） were low; 5 low molecular weight organic acids contributed 24,6% （based on roots） or 21.9% （based on sprouts） to the total acute toxicity of vacuum distillate.