清洁取样和痕量金属研究河和河口水域分析
Summary
Special care using “clean techniques” is required to properly collect and process water samples for trace metal studies in aquatic environments. A protocol for sampling, processing, and analytical procedures with the aim of obtaining reliable environmental monitoring data and results with high sensitivity for detailed trace metal studies is presented.
Abstract
Most of the trace metal concentrations in ambient waters obtained a few decades ago have been considered unreliable owing to the lack of contamination control. Developments of some techniques aiming to reduce trace metal contamination in the last couple of decades have resulted in concentrations reported now being orders of magnitude lower than those in the past. These low concentrations often necessitate preconcentration of water samples prior to instrumental analysis of samples. Since contamination can appear in all phases of trace metal analyses, including sample collection (and during preparation of sampling containers), storage and handling, pretreatments, and instrumental analysis, specific care needs to be taken in order to reduce contamination levels at all steps. The effort to develop and utilize “clean techniques” in trace metal studies allows scientists to investigate trace metal distributions and chemical and biological behavior in greater details. This advancement also provides the required accuracy and precision of trace metal data allowing for environmental conditions to be related to trace metal concentrations in aquatic environments.
This protocol that is presented here details needed materials for sample preparation, sample collection, sample pretreatment including preconcentration, and instrumental analysis. By reducing contamination throughout all phases mentioned above for trace metal analysis, much lower detection limits and thus accuracy can be achieved. The effectiveness of “clean techniques” is further demonstrated using low field blanks and good recoveries for standard reference material. The data quality that can be obtained thus enables the assessment of trace metal distributions and their relationships to environmental parameters.
Introduction
人们已经普遍认识到天然水域取得了一些微量金属的结果可能是由于从样本收集，处理和决心1,2过程中应用的技术所产生的不足，文物不准确的。真正的浓度（亚纳米到纳米范围内的地表水3）溶解的微量金属元素是要比以前发表的值低的到现在为止两个数量级。同样的情况在海洋化学凡在大洋水域中溶解的接受微量金属浓度已经超过过去40年减少了数量级左右改进取样和分析方法被引入被发现。已作出努力以改善与“清洁技术”旨在减少或消除微量金属污染的整个痕量金属分析4-8的各个阶段的发展的数据质量。对于重金属含量在环境的决心水平，富集通常需要。离子交换技术的8-12已普遍应用于有效富集。
污染可从容器的壁出现，容器中，取样器，样品处理和存储，以及样品保存和分析7,13的清洗。使用进行了最近的清洁方法，所有的研究表明，在自然水域中重金属含量一般远低于常规方法7检出限。既然承认在90年代初疑微量金属的数据，清洁方法已被纳入美国EPA（环保局）准则痕量金属检测14和美国地质调查局推行清洁方法，为他们的水质监测项目15个 。需要在所有的项目中被采用，以创造一个坚定而准确的数据基础痕量金属研究清洁方法。
<p类=“jove_content”>原则上，用于痕量金属测定水样应该用特殊的材料组成，具有仪器分析之前，存储和处理使用适当的容器和设备正确，适当的采样齿轮进行收集。由于悬浮颗粒物（SPM）可以进行在样本储存期的变化和改变水的成分，从水样SPM的快速分离是在水生环境痕量金属研究一种常见的做法。为在自然水域溶解痕量金属浓度的测定，过滤是必需的，并在在线过滤技术是合适的和有效的。分布和在水生环境中，如地表水和地下水的微量金属的行为可以通过天然（ 例如 ，风化）和人为的影响（ 例如 ，废水流出物）的因素，以及其它环境条件，如重gional地质，形态，土地利用，植被，气候和16-19。然后这会导致诸如悬浮颗粒物浓度（SPM），溶解的有机碳（DOC），人为的配体（ 例如 ，乙二胺四乙酸，EDTA）的盐，氧化还原电位和pH值17-20的物理化学参数的差异。因此，准确和相关的痕量金属研究需要痕量金属分析的样品的适当的收集以及相关因素和参数的确定。
Protocol
Representative Results
Discussion
在自然水域中获取可靠的微量金属数据需要样品的采集，处理，预处理和分析旨在减少污染期间强调呵护备至。跟踪中获得的天然水域重金属含量中发现，该浓度可以比以前报道的低几个数量级过去二十年来使用“清洁技术”。在水中的微量金属水质标准时，微量金属水平准确测量造成有害影响人类和高等生物更好的评估，现在更容易评估。生物利用度和在水生环境痕量金属的毒性需要在较低浓?…
Disclosures
The authors have nothing to disclose.
Acknowledgements
The authors thank Drs. Bobby J. Presley, Robert Tayloy, Paul Boothe, Mr. Bryan Brattin, and Mr. Mike Metcalf for their assistance during the laborious field sampling and lab work for the practical development and application of “clean techniques”.
Materials
| Nitric Acid | Seastar Chemicals | Baseline grade | |
| Ammonium hydroxide | Seastar Chemicals | Baseline grade | |
| Acetic Acid | Seastar Chemicals | Baseline grade | |
| Nitric Acid | J. T. Baker | 9601-05 | Reagent grade |
| Hydrochloric acid | J. T. Baker | 9530-33 | Reagent grade |
| Chromatographic columns | Bio-Rad | 7311550 | Poly-Prep |
| Column stack caps | Bio-Rad | 7311555 | |
| Cap connectors (female luers) | Bio-Rad | 7318223 | |
| 2-way stopcocks | Bio-Rad | 7328102 | |
| Cation exchange resin | Bio-Rad | 1422832 | Chelex-100 |
| Portable sampler (sampling pump) | Cole Palmer | EW-07571-00 | |
| FEP tube | Cole Palmer | EW-06450-07 | 6.4 mm I.D., 9.5 mm O.D. |
| Pumping tube | Cole Palmer | EW-06424-24 | 6.4 mm I.D. C-Flex |
| Capsule filter (0.4 mm) | Fisher Scientific | WP4HY410F0 | polypropylene casing |
| 1 L low density polyethylene bottle | NALGE NUNC INTERNATIONAL | 312088-0032 | |
| 1 L (or 500 ml) FEP bottle | NALGE NUNC INTERNATIONAL | 381600-0032 |
References
- Taylor, H. E., Shiller, A. M. Mississippi River Methods Comparison Study: Implications for water quality monitoring of dissolved trace elements. Environmental Science and Technology. 29, 1313-1317 (1995).
- Windom, H. L., Byrd, J. T., Smith, R. G., Huan, F. Inadequacy of NASQAN data for assessing metal trends in the nation’s rivers. Environmental Science and Technology. 25 (6), 1137-1142 (1991).
- Mason, R. P. . Trace Metals in Aquatic Systems. , (2013).
- Wen, L. -. S., Santschi, P., Gill, G., Paternostro, C. Estuarine trace metal distributions in Galveston Bay: importance of colloidal forms in the speciation of the dissolved phase. Marine Chemistry. 63, 185-212 (1999).
- Wen, L. -. S., Stordal, M. C., Tang, D., Gill, G. A., Santschi, P. H. An ultraclean cross-flow ultrafiltration technique for the study of trace metal phase speciation in seawater. Marine Chemistry. 55, 129-152 (1996).
- Benoit, G. Clean technique measurement of Pb, Ag, and Cd in freshwater: A redefinition of metal pollution. Environmental Science and Technology. 28, 1987-1991 (1994).
- Benoit, G., Hunter, K. S., Rozan, T. F. Sources of trace metal contamination artifacts during collection, handling, and analysis of freshwater. Analytical Chemistry. 69 (6), 1006-1011 (1997).
- Jiann, K. -. T., Presley, B. J. Preservation and determination of trace metal partitioning in river water by a two-column ion exchange method. Analytical Chemistry. 74 (18), 4716-4724 (2002).
- Fardy, J. J., Alfassi, Z. B., Wai, C. M. . Preconcentration Techniques for Trace Elements. , 181-210 (1992).
- Pai, S. -. C. Pre-concentration efficiency of Chelex-100 resin for heavy metals in seawater. Part 2. Distribution of heavy metals on a Chelex-100 column and optimization of the column efficiency by a plate simulation method. Analytica Chimica Acta. 211, 271-280 (1988).
- Pai, S. -. C., Fang, T. -. H., Chen, C. -. T. A., Jeng, K. -. L. A low contamination Chelex-100 technique for shipboard pre-concentration of heavy metals in seawater. Marine Chemistry. 29, 295-306 (1990).
- Pai, S. -. C., Whung, P. -. Y., Lai, R. -. L. Pre-concentration efficiency of Chelex-100 resin for heavy metals in seawater. Part 1. Effects of pH and salts on the distribution ratios of heavy metals. Analytica Chimica Acta. 211, 257-270 (1988).
- Salbu, B., Oughton, D. H., Salbu, B., Steinnes, E. . Trace Elements in Natural Waters. , 41-69 (1995).
- . U.S. Environmental Protection Agency. Method 1669. Sampling ambient water for trace metals at EPA Water Quality criteria levels Available from: https://www3.epa.gov/caddis/pdf/Metals_Sampling_EPA_method_1669.pdf (1996)
- Horowitz, A. J., et al. Problems associated with using filtration to define dissolved trace metal concentrations in natural water samples. Environmental Science and Technology. 30, 954-963 (1996).
- Cortecci, G., et al. Geochemistry of trace elements in surface waters of the Arno River Basin, northern Tuscany, Italy. Applied Geochemistry. 24 (5), 1005-1022 (2009).
- Markich, S. J., Brown, P. L. Relative importance of natural and anthropogenic influences on the fresh surface water chemistry of the Hawkesbury-Nepean River, south-eastern Australia. The Science of the Total Environment. 217, 201-230 (1998).
- Shafer, M. M., Overdier, J. T., Hurley, J. P., Armstrong, D., Webb, D. The influence of dissolved organic carbon, suspended particles, and hydrology on the concentration, partitioning and variability of trace metals in two contrasting Wisconsin watersheds (U.S.A.). Chemical Geology. 136, 71-97 (1997).
- Warren, L. A., Haack, E. A. Biogeochemical controls on metal behaviour in freshwater environments. Earth-Science Reviews. 54, 261-320 (2001).
- Jiann, K. -. T., Santschi, P. H., Presley, B. J. Relationships between geochemical parameters (pH, DOC, SPM, EDTA Concentrations) and trace metal (Cd, Co, Cu, Fe, Mn, Ni, Pb, Zn) concentrations in river waters of Texas (USA). Aquatic Geochemistry. 19 (2), 173-193 (2013).
- Peltzer, E. T., et al. A comparison of methods for the measurement of dissolved organic carbon in natural waters. Marine Chemistry. 54, 85-96 (1996).
- Nowack, B., Kari, F., Hilger, S. U., Sigg, L. Determination of dissolved and adsorbed EDTA species in water and sediments by HPLC. Analytical Chemistry. 68 (3), 561-566 (1996).
- Bergers, P. J. M., de Groot, A. C. The analysis of EDTA in water by HPLC. Water Research. 28 (3), 639-642 (1994).
