Obiectives To study the mineralization of 2,4-D in clay and clay loam Egyptian soils under subtropical conditions over a period of 90 d. Methods Using 14C-ring labelled pesticide, laboratory studies under aerobic and ...Obiectives To study the mineralization of 2,4-D in clay and clay loam Egyptian soils under subtropical conditions over a period of 90 d. Methods Using 14C-ring labelled pesticide, laboratory studies under aerobic and anaerobic conditions were conducted. 14C-activity in solutions was directly determined by liquid scintillation counting. Unextractable soil residues were determined by combustion. The nature of methanolic '4C-residues was determined by thin layer and high performance liquid chromatographic analysis. Results Under aerobic conditions 10%-14% of applied dose was mineralized during 90 d irrespective of soil type. The soil extractable pesticide residues decreased with time and the bound residues gradually increased. The highest binding capacity of about 26%-29% was observed in clay soil under aerobic conditions after 90 d. A good balance sheet was obtained and the percentage recovery was generally between 91% and 100%. Conclusion The mineralization of 2,4-D in clay soil was higher than that in clay loam soil under anaerobic conditions. Under aerobic conditions, the soil type had no influence on mineralizaion capacity of 2,4-D during 90 d. The soil binding increased with time whereby the extractable 14C-residues simultaneously decreased. Chromatographic analysis of the methanol extractable l4C-residues of soils revealed the presence of 2,4-D as a main product together with 2,4-dichlorophenol.展开更多
本文对14 C 绿磺隆在 7种不同类型土壤中形成结合残留 ( 14 C ER)、可提态残留( 14 C ER)以及矿化为14 C CO2 的规律、影响14 C BR的主要因子及其在腐殖质中的分布规律等进行了研究。结果表明 :( 1 ) 14 C 绿磺隆在土壤中形成的14 C ER...本文对14 C 绿磺隆在 7种不同类型土壤中形成结合残留 ( 14 C ER)、可提态残留( 14 C ER)以及矿化为14 C CO2 的规律、影响14 C BR的主要因子及其在腐殖质中的分布规律等进行了研究。结果表明 :( 1 ) 14 C 绿磺隆在土壤中形成的14 C ER含量与土壤pH呈显著正相关 ,与土壤粘粒和有机质含量呈显著负相关 ,14 C ER中的绿磺隆母体化合物的消减满足一级反应动力学方程 ,其在 7种土壤中的半减期分别为 1 3 0～ 1 3 3 3d。pH是影响绿磺隆母体化合物降解的主要因子 ;( 2 ) 14 C 绿磺隆在 7种土壤中的14 C BR含量与土壤pH呈显著负相关 ,并与土壤粘粒含量呈显著正相关 ,土壤pH是14 C 绿磺隆在土壤中形成BR的主要影响因子 ;( 3 ) 14 C 绿磺隆形成的14 C BR主要分布在富啡酸和胡敏素中 ;14 C BR分布在胡敏酸中的相对百分比约为 2 % ,在14 C 绿磺隆BR的形成过程中 ,富啡酸的作用 >胡敏素 胡敏酸 ;( 4) 14 C 绿磺隆在 7种土壤中的14 C BR含量 ,在培养 2 0d内均随时间而快速增加 ,2 0d后变化量较小。 7种土壤中的14 C BR含量最大值分别占引入量的 53 5%、40 9%、3 7 8%、1 6 4%、42 5%、41 0 %和 3 1 3 % ;( 5)培养 90d内 ,14 C 绿磺隆通过三嗪杂环开环矿化为14 CO2 的量约占引入量的 4%～9% ,而土壤 1表明14展开更多
在实验室培养条件下 ,从质量平衡角度 ,研究了14 C 甲磺隆在 7种土壤中形成结合残留 (14 C BR)、可提态残留 (14 C ER)以及矿化为14 CO2 的规律 ;同时对14 C BR的主要影响因子及其在腐殖质中的分布规律进行了研究 .结果表明 :①14 C 甲...在实验室培养条件下 ,从质量平衡角度 ,研究了14 C 甲磺隆在 7种土壤中形成结合残留 (14 C BR)、可提态残留 (14 C ER)以及矿化为14 CO2 的规律 ;同时对14 C BR的主要影响因子及其在腐殖质中的分布规律进行了研究 .结果表明 :①14 C 甲磺隆在土壤中形成的14 C ER ,其含量与土壤pH呈显著正相关 .甲磺隆母体化合物在 7种土壤中的半减期为 1 3 3～ 66 6d ,降解速率常数λ(d- 1)与 pH呈显著负相关 .②14 C 甲磺隆在 7种土壤中形成的14 C BR ,其含量在培养初期的 2 0d内 ,与土壤 pH呈显著负相关且与土壤粘粒含量呈显著正相关 ;而培养 2 0d后 ,14 C BR的含量只与土壤 pH呈显著负相关 .pH是14 C 甲磺隆在土壤中形成BR的主要影响因子 .14 C 甲磺隆在 7种土壤中的14 C BR的最大值约为引入量的 1 9 3 %～ 5 2 6% .③在整个培养试验过程中 ,7种土壤中的14 C BR主要分布在富啡酸和胡敏素中 ,但其分布在胡敏酸中的相对百分比较小 .因此 ,在14 C 甲磺隆形成BR的过程中 ,富啡酸的作用 >胡敏素 胡敏酸 .④在整个培养试验期间 (1 80d) ,14 C 甲磺隆在 7种土壤中通过三嗪杂环开环矿化为14 CO2的量约占引入量的 1 2 9%～ 2 7 0 % ,其在碱性土壤中更难被矿化为14 CO2 .展开更多
基金This work was supported by FAO/IAEA-division for its financial support.
文摘Obiectives To study the mineralization of 2,4-D in clay and clay loam Egyptian soils under subtropical conditions over a period of 90 d. Methods Using 14C-ring labelled pesticide, laboratory studies under aerobic and anaerobic conditions were conducted. 14C-activity in solutions was directly determined by liquid scintillation counting. Unextractable soil residues were determined by combustion. The nature of methanolic '4C-residues was determined by thin layer and high performance liquid chromatographic analysis. Results Under aerobic conditions 10%-14% of applied dose was mineralized during 90 d irrespective of soil type. The soil extractable pesticide residues decreased with time and the bound residues gradually increased. The highest binding capacity of about 26%-29% was observed in clay soil under aerobic conditions after 90 d. A good balance sheet was obtained and the percentage recovery was generally between 91% and 100%. Conclusion The mineralization of 2,4-D in clay soil was higher than that in clay loam soil under anaerobic conditions. Under aerobic conditions, the soil type had no influence on mineralizaion capacity of 2,4-D during 90 d. The soil binding increased with time whereby the extractable 14C-residues simultaneously decreased. Chromatographic analysis of the methanol extractable l4C-residues of soils revealed the presence of 2,4-D as a main product together with 2,4-dichlorophenol.
