Zhang Ping, Sheng Guangyao, Wolf Duane C, Feng Yucheng
Department of Crop, Soil, and Environmental Sciences, University of Arkansas, Fayetteville, AR 72701, USA.
J Environ Qual. 2004 May-Jun;33(3):868-72. doi: 10.2134/jeq2004.0868.
Burning of crop residues is a common agricultural practice that incorporates the resulting particulate matter (ash) of high adsorptivity into soils. To investigate the effect of ash on the biodegradation of pesticides in soils, we measured the sorption, desorption, and biodegradation of benzonitrile in a silt loam in the presence and absence of an ash resulting from burning of wheat (Triticum aestivum L.) residue. Biodegradation experiments were conducted by inoculating sorbent slurries with a pure culture of benzonitrile-degrading bacteria (Nocardia sp.). Both liquid- and sorbed-phase benzonitrile concentrations were quantified over time. The ash was approximately 2000 times more effective per unit mass than the soil in sorbing benzonitrile. Amendment of the soil with 1% ash (by weight) resulted in a 10-fold increase in sorption. Sorption of benzonitrile by the ash significantly decreased the solution-phase concentration in the slurries of ash and ash-amended soil. Desorption of benzonitrile from the ash required approximately 60 min to complete, whereas approximately 20 min were required for desorption from the soil. Benzonitrile in the extracts of various sorbents and soil slurry was completely degraded within 500 min. However, the degradation was substantially reduced in the presence of the ash. At 2000 min, only 20% of benzonitrile in ash slurry and only 44% in ash-amended soil slurry were degraded. An acclimation period of approximately 100 min was observed in extracts and slurries containing the ash. Substantial reduction in the biodegradation of benzonitrile in the presence of wheat ash was apparently due to sorption of benzonitrile by the ash, slow desorption from the ash, and the increased acclimation period. Our results suggest that the presence of crop-residue-derived ash may increase the persistence of pesticides in agricultural soils.
焚烧农作物秸秆是一种常见的农业做法，它会将具有高吸附性的颗粒物（灰烬）融入土壤。为了研究灰烬对土壤中农药生物降解的影响，我们测量了在有和没有小麦（Triticum aestivum L.）秸秆焚烧产生的灰烬存在的情况下，腈在粉质壤土中的吸附、解吸和生物降解情况。通过用腈降解细菌（诺卡氏菌属）的纯培养物接种吸附剂浆液进行生物降解实验。随着时间的推移，对液相和吸附相中的腈浓度进行了定量分析。每单位质量的灰烬对腈的吸附效果比土壤高出约2000倍。用1%（按重量计）的灰烬改良土壤会使吸附量增加10倍。灰烬对腈的吸附显著降低了灰烬和灰烬改良土壤浆液中的溶液相浓度。腈从灰烬中的解吸大约需要60分钟才能完成，而从土壤中解吸则大约需要20分钟。各种吸附剂和土壤浆液提取物中的腈在500分钟内完全降解。然而，在有灰烬存在的情况下，降解大幅减少。在2000分钟时，灰烬浆液中只有20%的腈被降解，灰烬改良土壤浆液中只有44%的腈被降解。在含有灰烬的提取物和浆液中观察到大约100分钟的适应期。在小麦灰烬存在的情况下，腈生物降解的大幅减少显然是由于灰烬对腈的吸附、从灰烬中缓慢解吸以及适应期增加所致。我们的结果表明，农作物秸秆衍生的灰烬的存在可能会增加农药在农业土壤中的持久性。
