State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, PR China.
Chemosphere. 2012 Jul;88(5):644-9. doi: 10.1016/j.chemosphere.2012.03.050. Epub 2012 Apr 10.
The extensive utilization of β-blockers worldwide led to frequent detection in natural water. In this study the photolysis behavior of atenolol (ATL) and toxicity of its photodegradation products were investigated in the presence of nitrate ions. The results showed that ATL photodegradation followed pseudo-first-order kinetics upon simulated solar irradiation. The photodegradation was found to be dependent on nitrate concentration and increasing the nitrate from 0.5 mML(-1) to 10 mML(-1) led to the enhancement of rate constant from 0.00101 min(-1) to 0.00716 min(-1). Hydroxyl radical was determined to play a key role in the photolysis process by using isopropanol as molecular probe. Increasing the solution pH from 4.8 to 10.4, the photodegradation rate slightly decreased from 0.00246 min(-1) to 0.00195 min(-1), probably due to pH-dependent effect of nitrate-induced .OH formation. Bicarbonate decreased the photodegradation of ATL in the presence of nitrate ions mainly through pH effect, while humic substance inhibited the photodegradation via both attenuating light and competing radicals. Upon irradiation for 240 min, only 10% reduction of total organic carbon (TOC) can be achieved in spite of 72% transformation rate of ATL, implying a majority of ATL transformed into intermediate products rather than complete mineralization. The main photoproducts of ATL were identified by using solid phase extraction-liquid chromatography-mass spectrometry (SPE-LC-MS) techniques and possible nitrate-induced photodegradation pathways were proposed. The toxicity of the phototransformation products was evaluated using aquatic species Daphnia magna, and the results revealed that photodegradation was an effective mechanism for ATL toxicity reduction in natural waters.
β受体阻滞剂在全球范围内的广泛应用导致其在天然水中频繁被检出。本研究考察了在硝酸盐存在下，阿替洛尔（ATL）的光解行为及其光降解产物的毒性。结果表明，在模拟太阳光照射下，ATL 的光降解符合准一级动力学。发现光降解依赖于硝酸盐浓度，当硝酸盐从 0.5 mML(-1)增加到 10 mML(-1)时，速率常数从 0.00101 min(-1)增加到 0.00716 min(-1)。通过使用异丙醇作为分子探针，确定了羟基自由基在光解过程中起关键作用。将溶液 pH 值从 4.8 增加到 10.4，光降解速率从 0.00246 min(-1)略微下降到 0.00195 min(-1)，可能是由于 pH 值依赖于硝酸盐诱导的.OH 形成。在有硝酸盐存在的情况下，碳酸氢盐通过 pH 效应降低 ATL 的光降解，而腐殖质通过衰减光和竞争自由基抑制光降解。尽管 ATL 的转化速率为 72%，但在 240 min 的辐照后，TOC 仅减少 10%，这表明大多数 ATL 转化为中间产物而不是完全矿化。通过固相萃取-液相色谱-质谱（SPE-LC-MS）技术鉴定了 ATL 的主要光产物，并提出了可能的硝酸盐诱导光降解途径。利用水生物种大型溞评价了光转化产物的毒性，结果表明，光降解是降低天然水中 ATL 毒性的有效机制。
