酚顿试剂对竹林土壤中酚类化合物的降解作用

Degradation of Phenolic Allelochemicals in Bamboo Soil by Fenton’s Reagent

摘要:

酚类化合物是农业和生态系统中主要的化感物质之一, 大量积累在土壤中，抑制作物和林下植物生长，导致农作物减产、连作障碍和自然生态环境破坏。用过氧化氢(H2O2)与硫酸亚铁（Fe2+）所组成的酚顿试剂研究了化学氧化法对化感物质（对香豆酸、对羟基苯甲酸和胡桃醌）、竹林土壤提取物及竹林土壤中对香豆酸的降解作用。过氧化氢与硫酸亚铁的摩尔比为15:1的酚顿试剂，过氧化氢与酚类物质浓度比为8:1时，对酚类物质的降解效率最高。以8×10-3 mol/L (0.028%) 的H2O2，5.4×10-4 mol/L (0.075%)的FeSO4和10-3 mol/L 的酚类物质组成的反应体系中，反应10 min和30 min后，对香豆酸的降解率分别为55%和74%；对羟基苯甲酸的降解率在10 min时达90%以上；而胡桃醌在10 min时已经完全被降解。酚顿试剂处理土壤酚类提取物时，可使其中主要的化感物质对香豆酸降解75%。用含0.1%和1%H2O2的酚顿试剂处理竹 (Bambusa chungii) 林土壤，土壤对香豆酸的降解率分别为32%和37%。竹林土壤中存在过氧化氢酶和过氧化物酶活性, 但没有检测到超氧化物歧化酶活性。土壤中的过氧化氢酶和过氧化物酶可能迅速分解外加的过氧化氢, 一方面缩短过氧化氢处理的作用时间和降低降解效率，另一方面可分解过剩的过氧化氢。这说明酚顿试剂是降解土壤和培养液中有害化感物质的有效化学氧化剂。

Abstract:

Phenolic compounds are toxic allelochemicals widely distributed in agriculture and natural ecosystems. They accumulate largely in plant soils, inhibit plant growth and pollute environments. Oxidative degradation of phenolic allelochemicals by Fenton’s reagent was studied under natural conditions. In a 1.0 ml reaction solution containing 8×10-3 mol/L (0.028%) of hydrogen peroxide (H2O2), 5.4×10-4 mol/L (0.075%) of FeSO4, and 10-3 mol/L of phenolics or 160 μg ml-1 of soil extracts, p-coumaric acid was oxidized by 55% and 74% in 10 and 30 minutes, respectively; p-hydroxybenzoic acid was oxidized by 90% within 10 minutes; juglone was completely oxidized within 10 minutes. p-Coumaric acid, the main allelochemical in extracts of soil beneath forest of bamboo (Bambusa chungii), was oxidized by 75% in 2 h. Direct application of 0.1% or 1% of H2O2 of Fenton’s reagent to the soil from bamboo forest resulted in a 32% or 37% degradation of p-coumaric acid in the soil. Activities of antioxidant enzymes of catalase and peroxidase, but no superoxide dismutase, were detected in the bamboo soil. These enzymes may decompose H2O2 employed to soil and reduced its function in soil. Meanwhile, they are responsible for decomposition of surplus H2O2 in the soil. Results indicated that Fenton’s reagent might be a potential reagent for degradation of toxic allelochemcials in plant soils and cultural solutions.