Statistical methods, environmental sampling

This paper discusses the role that statistics can play In environmental sampling. The primary difference between an Investigation based on statistical considerations and one that Is not Is the degree of objectivity that can be Incorporated Into the evaluation of the quality and uncertainty of the study results. Statistical methods In the planning stage can also aid In optimizing allocation of resources. 

The most common question posed to statisticians In environmental sampling Is How many samples do I need to take (or "How many replicates, "How many analyses," etc.). The statistical models Introduced previously provide a framework for addressing these questions after the first four steps In a sampling study are completed (l.e. the objectives, populations of Interest, characteristics to be determined, and required precision are stated). The methods In this section are applicable when the objective Is to estimate the average of a characteristic In the population. 

Barnard TE (1995) Environmental Sampling, in The handbook of environmental chemistry (Ed. O. Hutzinger), Vol 2, Part G Chemometrics in environmental chemistry - statistical methods (Vol. Ed. J. Einax), Springer, Berlin Heidelberg New York, 1-47... 

Experimental studies, particularly those involving the metabolism or mode of action of toxic compounds in animals (or, less often, plants), can be conducted either in vivo or in vitro. Because organisms or enzyme preparations are treated with known compounds, the question of random sampling techniques does not arise as it does with environmental samples. Enough replication is needed for statistical verification of significance, and it should always be borne in mind that repeated determinations carried out on aliquots of the same preparation do not represent replication of the experiment at best, they test the reproducibility of the analytical method. 

Green, R.G. Sampling Design and Statistical Methods for Environmental Biologists, Wiley, New York, Chichester, Brisbane, Toronto, 1979... 

The samples which have to be taken must reflect the properties of the investigated subject without distortion in other words, the samples must be representative according to the purpose of the investigation. Specific examples of the statistical examination of sampling representativeness in different environmental media are given in Sections 7.1, 8.1, and 9.1. The amount of data has to be sufficient. A principal method... 

Commonly the compromising conditions of routine environmental monitoring lead to restrictions on the accuracy and the precision of sampling and analysis. The purpose of this section is to show that under these conditions multivariate statistical methods are a useful tool for qualitative extraction of new information about the degree of stress of the investigated areas, and for identification of emission sources and their seasonal variations. The results represented from investigation of the impact of particulate emissions can, in principle, be transferred to other environmental analytical problems, as described in the following case studies. 

By application of multivariate statistical methods for consideration of the overall environmental situation of a river it is possible to optimize the sampling strategy. 

Comparison and ranking of sites according to chemical composition or toxicity is done by multivariate nonparametric or parametric statistical methods however, only descriptive methods, such as multidimensional scaling (MDS), principal component analysis (PCA), and factor analysis (FA), show similarities and distances between different sites. Toxicity can be evaluated by testing the environmental sample (as an undefined complex mixture) against a reference sample and analyzing by inference statistics, for example, t-test or analysis of variance (ANOVA). 

This text is designed for college students majoring in chemistry and fields related to chemistry. It deals with the principles and techniques of quantitative analysis, that is, how to determine how much of a specific substance is contained in a sample. You will learn how to design an analytical method, based on what information is needed, how to obtain a laboratory sample that is representative of the whole, how to prepare it for analysis, what measurement tools are available, and the statistical significance of the analysis. Chapters 24-26 illustrate applications of techniques you have learned to the fields of clinical chemistry, genomics and pro-teomics, and environmental sampling and analysis. 

Roger H. Green, in his book Sampling Designs and Statistical Methods for Environmental Biologists, describes 10 steps for effective statistical analysis (Green, 1979). These steps are applicable to any analysis ... 

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