Laser-induced breakdown spectroscopy application in environmental monitoring of water quality: a review

Water quality monitoring is a critical part of environmental management and protection, and to be able to qualitatively and quantitatively determine contamination and impurity levels in water is especially important. Compared to the currently available water quality monitoring methods and techniques, laser-induced breakdown spectroscopy (LIBS) has several advantages, including no need for sample pre-preparation, fast and easy operation, and chemical free during the process. Therefore, it is of great importance to understand the fundamentals of aqueous LIBS analysis and effectively apply this technique to environmental monitoring. This article reviews the research conducted on LIBS analysis for liquid samples, and the article content includes LIBS theory, history and applications, quantitative analysis of metallic species in liquids, LIBS signal enhancement methods and data processing, characteristics of plasma generated by laser in water, and the factors affecting accuracy of analysis results. Although there have been many research works focusing on aqueous LIBS analysis, detection limit and stability of this technique still need to be improved to satisfy the requirements of environmental monitoring standard. In addition, determination of nonmetallic species in liquid by LIBS is equally important and needs immediate attention from the community. This comprehensive review will assist the readers to better understand the aqueous LIBS technique and help to identify current research needs for environmental monitoring of water quality.     

Application of portable gas chromatography-photo ionization detector combined with headspace sampling for field analysis of benzene, toluene, ethylbenzene, and xylene in soils

A method based on headspace (HS) sampling coupling with portable gas chromatography (GC) with photo ionization detector (PID) was developed for rapid determination of benzene, toluene, ethylbenzene, and xylenes (BTEX) in soils. Optimal conditions for HS gas sampling procedure were determined, and the influence of soil organic matter on the recovery of BTEX from soil was investigated using five representative Chinese soils. The results showed that the HS-portable-GC-PID method could be effectively operated at ambient temperature, and the addition of 15 ml of saturated NaCl solution in a 40-ml sampling vial and 60 s of shaking time for sample solution were optimum for the HS gas sampling procedure. The recoveries of each BTEX in soils ranged from 87.2 to 105.1 %, with relative standard deviations varying from 5.3 to 7.8 %. Good linearity was obtained for all BTEX compounds, and the detection limits were in the 0.1 to 0.8 μg kg^?1 range. Soil organic matter was identified as one of the principal elements that affect the HS gas sampling of BTEX in soils. The HS-portable-GC-PID method was successfully applied for field determination of benzene and toluene in soils of a former chemical plant in Jilin City, northeast China. Considering its satisfactory repeatability and reproducibility and particular suitability to be operated in ambient environment, HS sampling coupling with portable GC-PID is, therefore, recommended to be a suitable screening tool for rapid on-site determination of BTEX in soils.     

Spatial, temporal, and speciation variations of heavy metals in sediments of Nan'ao Island, a representative mariculture base in Guangdong coast, China

Heavy metals in sediments from Baisha Bay, Nan'ao Island, one of Guangdong Province's largest mariculture bases in Southern China, were investigated. The results display that the concentrations of 6 heavy metals from surface sediments were 0.040-0.220 (Cd), 24.22-39.61 (Pb), 25.30-42.66 (Cr), 10.83-19.54 (Ni), 15.06-39.24 (Cu) and 55.12-141.73 mg kg(-1) (Zn), respectively. The highest concentrations and the greatest increasing rates of heavy metals were found in a sediment core in a fish cage culture area due to receiving sewage discharge, uneaten fish bait, and boat gasoline combustion. Cd was preferentially associated with the acid-soluble fraction and Pb mainly with the reducible fraction in surface sediments. Meanwhile, Cd and Pb displayed greatest labile fractions, indicating anthropogenic origin. A principal component analysis (PCA) revealed three groupings (Cd; Cr, Ni and Cu; Pb and Zn) that mainly result from different distributions of the metals in the various fractions. The ecological risk of the polluted sediments stemmed mainly from Cd, and from Pb and Cu to a lesser degree. It is suggested that the density of fish-stocking be controlled, periodic movement of rafts (cages) be introduced, and the total numbers of net-cages and human activities in the mariculture zones be restricted. in order to facilitate the recovery of the polluted sediment.     

Natural and anthropogenic factors affecting the shallow groundwater quality in a typical irrigation area with reclaimed water,North China Plain

In this study, the hydrochemical characteristics of shallow groundwater were analyzed to get insight into the factors affecting groundwater quality in a typical agricultural dominated area of the North China Plain. Forty-four shallow groundwater samples were collected for chemical analysis. The water type changes from Ca·Na-HCO₃ type in grass land to Ca·Na-Cl (+NO₃) type and Na (Ca)-Cl (+NO₃+SO₄) type in construction and facility agricultural land, indicating the influence of human activities. The factor analysis and geostatistical analysis revealed that the two major factors contributing to the groundwater hydrochemical compositions were the water-rock interaction and contamination from sewage discharge and agricultural fertilizers. The major ions (F, HCO₃) and trace element (As) in the shallow groundwater represented the natural origin, while the nitrate and sulfate concentrations were related to the application of fertilizer and sewage discharge in the facility agricultural area, which was mainly affected by the human activities. The values of pH, total dissolved solids, electric conductivity, and conventional component (K, Ca, Na, Mg, Cl) in shallow groundwater increased from grass land and cultivated land, to construction land and to facility agriculture which were originated from the combination sources of natural processes (e.g., water-rock interaction) and human activities (e.g., domestic effluents). The study indicated that both natural processes and human activities had influences on the groundwater hydrochemical compositions in shallow groundwater, while anthropogenic processes had more contribution, especially in the reclaimed water irrigation area.     

固载型TiO2光催化反应器对富营养水体杀藻作用研究

以泡沫镍作为载体,利用电沉积技术将纳米TiO2负载在泡沫镍上,制成固载型TiO2光催化反应器.研究表明,经过光催化反应器处理的富营养水体,30 h内叶绿素a由96.2 mg/m3降至2.2 mg/m3,下降率达97.6%,而未负载纳米TiO2普通泡沫镍材料,在同样光强的紫外灯照射下,叶绿素a下降率为74.3%,表明紫外光照射虽然也具有一定的杀藻功能,但是光催化反应才是藻类被杀灭的主要原因.利用9.54 m3景观喷水池进行杀藻中试,光催化反应器也同样表现出优异的杀藻性能,12 d内叶绿素a由18.7 mg/m3降至1.9 mg/m3,下降率达到89.8%,水体由浓绿变为清澈见底,这表明光催化反应器具有很强的杀藻能力,通过有效杀灭富营养水体中藻类、控制藻类基数,对应急处理城市景观水、湖泊等富营养水体和突发性藻华,提高生物-生态法处理效率,改善城市水环境具有十分重要的意义.     

壳聚糖接枝共聚物的合成及应用研究

在N2保护下,以浓度为0.8 mmol/L硝酸铈铵为引发剂,控制壳聚糖(CTS)和丙烯酰胺(AM)质量比为mCTS∶mAM=1∶6,于50℃下接枝共聚反应3 h,得改性的壳聚糖衍生物(CAM).用IR对产物进行表征.通过对废水的处理,研究了共聚产物在絮凝、COD去除、脱色上的应用.结果表明:CAM的絮凝效果好于聚丙烯酰胺和壳聚糖,CAM对COD的去除率达到84.7%,并有较好的脱色效果.     

典型SSRIs类抗抑郁药对鱼类的毒性效应研究进展

选择性血清素再摄取抑制剂(selective serotonin reuptake inhibitors,SSRIs)是一类在临床上具有良好治疗效果的抗抑郁药物,由于使用量巨大,在水环境中频繁被检出,其潜在生态毒性效应引起人们的广泛关注.鱼类作为水生脊椎动物,具有和人类相似的神经调控系统,更易受到水体中残留的SSRIs...     

高锰酸钾预氧化后地表水中三氯甲烷生成量的预测模型研究

在饮用水处理中,适当地采用高锰钾预氧化可以降低水中的三氯甲烷生成量。本文研究了影响三氯甲烷生成量的因素,如反应时间,反应温度等,并以这些影响因素为参数通过一元线性回归等数学方法,建立了各影响因素下三氯甲烷生成量折了模型和综合预测模型。     

氯代苯及氯代酚类优先污染物好氧生物降解动力学的研究

利用测定微生物呼吸耗氧量的方法,对氯代苯及氯代酚类中的７种优先污染物,用经它们分别驯化的活性污泥对其好氧生物降解动力学进行了研究。     

水中微量甲基膦酸类化合物的树脂富集与GC／MS分析

本文使用三种阴离子交换树脂（即大孔弱碱型Ｄ－３０１－Ｒ,强碱型Ｄ－２９６,２０１Ｘ７）柱对水中微量甲基膦酸类化合物的富集方法进行了研究。含磷毒剂降解产物的水样用气相色谱／质谱法进行定性定量分析。结果表明,Ｄ－３０１－Ｒ阴离子交换树脂柱对甲基膦酸的富集回收率高于６０％。