碱式碳酸镁为新结合相的薄膜梯度扩散技术原位富集测定富营养水体中的磷

摘要

A technique of diffusive gradients in thin films (DGT) was developed for the in situ measurement of reactive phosphorus species in natural waters, sediments and potentially soils. Polyacrylamide / basic magnesium carbonate was used as the novel binding phase of DGT. Various factors, such as initial concentration, deployment time, pH and ionic strength, which may affect the adsorption of phosphate to the DGT were investigated. H2 SO4(0. 25 mol/ L, 10 mL) was used for elution of phosphate from the binding gel, and an elution efficiency of 85±5% was obtained. The DGT measurement was independent of ionic strength (0. 001-0. 05 mol/ L) and pH (4. 10-9. 15). The results indicated that the maximum adsorption capacities of DGT were limited to 20. 4 μg per disc ( T = 25℃, pH = 7. 00, [ P] = 2 mg / L). Good agreement was obtained between the measurement results of DGT method and molybdenum blue method in the P concentration from 0. 001 to 20 mg / L. The method detection limit (MDL) was 102. 4 ng / L. Field performances of DGT in synthetic seawater, the coastal seawater of Xiamen, Lake Yihai, Lake Chaohu and Nanfei River indicated that the basic magnesium carbonate-DGT method was more reliable than the commonly used ferrihydrite-DGT method.%薄膜扩散梯度技术(Diffusive gradients in thin films technique, DGT)是近年来应用于自然水体、沉积物和土壤中活性磷原位测定的一种新技术。利用含碱式碳酸镁的聚丙烯酰胺凝胶膜为 DGT 新结合相,探讨了初始浓度、放置时间、pH 值及离子强度对组装后 DGT 吸附性能的影响。用10 mL 0.25 mol/ L H2 SO4对结合相进行洗脱,洗脱率为85%±5%。组装后 DGT 对磷的测定不受溶液 pH 值(4.10~9.15)和离子强度(0.001~0.05 mol/ L)的影响。在温度25℃,pH 7.00,磷初始浓度为2 mg/ L 时, DGT 对磷的最大吸附容量为20.4μg。初始磷浓度为0.001~20 mg/ L 时,新 DGT 测定值与磷钼蓝比色法测定值一致。本方法对磷的检出限为102.4 ng/ L。将碱式碳酸镁-DGT 和商品化的 Ferrihydrite-DGT 应用于合成海水、厦门近岸海水、易海、巢湖水和南淝河中的对比检测,结果表明,碱式碳酸镁-DGT 能更准确测定不同水体中磷浓度。