张爽,张蓬,葛林科,董倩倩,王德高.冰中和水中四环素光降解动力学及其影响因素的比较[J].环境科学学报,2020,40(6):2037-2044
冰中和水中四环素光降解动力学及其影响因素的比较
- Comparison of photodegradation for tetracycline in ice and in water: Kinetics, and effects of main water constituents
- 基金项目：国家自然科学基金（No.21976045，21577029，41476084）；国家水体污染控制与治理科技重大专项（No.2017ZX07602-001）
- 张爽
- 1. 大连海事大学环境科学与工程学院, 大连 116026;2. 陕西科技大学环境科学与工程学院, 西安 710021;3. 国家海洋环境监测中心, 国家环境保护近岸海域生态环境重点实验室, 大连 116023
- 张蓬
- 1. 陕西科技大学环境科学与工程学院, 西安 710021;2. 国家海洋环境监测中心, 国家环境保护近岸海域生态环境重点实验室, 大连 116023
- 葛林科
- 1. 陕西科技大学环境科学与工程学院, 西安 710021;2. 国家海洋环境监测中心, 国家环境保护近岸海域生态环境重点实验室, 大连 116023
- 董倩倩
- 1. 大连海事大学环境科学与工程学院, 大连 116026;2. 国家海洋环境监测中心, 国家环境保护近岸海域生态环境重点实验室, 大连 116023
- 王德高
- 大连海事大学环境科学与工程学院, 大连 116026
- 摘要：冰雪是一类重要且普遍的环境介质，而冰雪环境光化学是一门新兴的学科.在相同光照条件下比较冰中和水中有机污染物的光化学行为，有助于揭示冰雪光化学与水环境光化学之间的异同.本文以四环素（TC）为模型化合物，比较了模拟日光（λ>290 nm）照射下不同水体冰相和水相中TC的光降解动力学，研究了不同相中溶解性物质（腐殖酸（HA）、Cl-、NO3-和Fe（III））对光降解的影响及作用机制，以揭示冰雪环境光化学和水环境光化学的异同.结果表明，冰中和水中TC光解遵循准一级反应动力学，纯水冰中表观光解量子产率为4.76×10-3，高于纯水中表观光解量子产率（3.85×10-3）.在不同水体中，冰相TC的光解快慢顺序为海水冰中 > 淡水冰中 > 纯水冰中，而在水相中光解快慢顺序与冰相不同，为淡水中 > 海水中 > 纯水中.通过考察主要溶解性物质对冰/水中TC光降解动力学的影响发现，无论是在冰相还是水相，Cl-、HA、NO3-和Fe（III）均加快了TC的光降解，且促进作用随浓度的升高而增强.但在水相与冰相中每个因素促进的程度却存在差异，相对于水环境，冰中HA、NO3-、Fe（III）敏化作用较大，对TC光降解的促进作用较强；而冰中Cl-对TC光解的促进作用较水相中弱.这些溶解性物质对TC光解的促进作用能够解释海水冰、淡水冰与海水、淡水中TC相对于纯水冰相/水相具有较强的光降解能力.进一步地，将实验数据外推到实际环境，在35°~50°N地区的仲冬季，冰雪表面和水体表层TC光化学降解的半减期分别为15.4~38.9 min和19.0~48.0 min，其不仅依赖于光解发生的纬度与季节，还受到反应基质（冰/水）的影响.以上结果揭示了冰中和水中TC光化学转化行为的异同，这对于准确评价寒冷环境中此类新型污染物的归趋具有重要意义.
- Abstract：Ice and snow are important environmental media, ice/snow photochemistry is therefore an emerging subject in environmental sciences. In order to reveal the differences and similarities between ice and aqueous photochemistry, photochemical behavior of organic pollutants in ice and in water requires comparative studies. In this study, we selected tetracycline (TC) as a case to compare photodegradation kinetics in ices and in waters from different water bodies under the simulated sunlight (λ>290 nm) by considering the effects of dissolved substances (humic acid (HA), Cl-, NO3- and Fe(III)). It was observed that the photodegradation of TC followed pseudo-first-order kinetics with the higher quantum yield (ΦS=4.76×10-3) in pure-water ice than in pure water (ΦS=3.85×10-3). TC underwent the fastest photolysis in seawater ice followed by freshwater ice and pure-water ice; while TC photodegraded faster in freshwater and seawater than in pure water. Further studies found that Cl-, HA, NO3- and Fe(III) accelerated the photodegradation of TC, with higher efficiencies under higher concentrations, in both ice and water phases. However, the promotion degrees for each factors are different, and HA, NO3- and Fe(III) showed stronger sensitization in ice than in water, to promote TC photodegradation. While Cl- in ice promoted less. The positive effects of these constituents on TC photolysis explained most of the stronger photodegradation potential of TC in natural ices/waters than in pure-water ice or pure water. Furthermore, extrapolation of the lab data to the real environment indicated that the photolytic half-lives of TC in mid-winter of 35°~50°N latitude were estimated to be 15.4~38.9 min and 19.0~48.0 min, respectively in ice/snow surface and in surface water. The half-lives depend not only on the latitude and season, but also on the reaction matrixes (ice/water). The differences and similarities of TC photochemical behavior in ice and in water uncovered by this study would better assess the fate and risk of such emerging pollutants in the cold environments.
