The analysis of 87 peer-reviewed journal articles reveals that sampling for pharmaceuticals and personal care products (PPCPs) and illicit drugs in sewers and sewage treatment plant influents is mostly carried out according to existing tradition or standard laboratory protocols. Less than 5% of all studies explicitly consider internationally acknowledged guidelines or methods for the experimental design of monitoring campaigns. In the absence of a proper analysis of the system under investigation, the importance of short-term pollutant variations was typically not addressed. Therefore, due to relatively long sampling intervals, potentially inadequate sampling modes, or insufficient documentation, it remains unclear for the majority of reviewed studies whether observed variations can be attributed to "real" variations or if they simply reflect sampling artifacts. Based on results from previous and current work, the present paper demonstrates that sampling errors can lead to overinterpretation of measured data and ultimately, wrong conclusions. Depending on catchment size, sewer type, sampling setup, substance of interest, and accuracy of analytical method, avoidable sampling artifacts can range from "not significant" to "100% or more" for different compounds even within the same study. However, in most situations sampling errors can be reduced greatly, and sampling biases can be eliminated completely, by choosing an appropriate sampling mode and frequency. This is crucial, because proper sampling will help to maximize the value of measured data for the experimental assessment of the fate of PPCPs as well as for the formulation and validation of mathematical models. The trend from reporting presence or absence of a compound in "clean" water samples toward the quantification of PPCPs in raw wastewater requires not only sophisticated analytical methods but also adapted sampling methods. With increasing accuracy of chemical analyses, inappropriate sampling increasingly represents the major source of inaccuracy. A condensed step-by-step Sampling Guide is proposed as a starting point for future studies.

The aim of this study was to assess uncertainties associated with different sampling modes when evaluating loads of pharmaceuticals and personal care products (PPCPs) in sewers and influents to sewage treatment plants (STPs). The study demonstrates that sampling uncertainty can range from "not significant" to "far greater than the uncertainty due to chemical analysis", which is site- and compound-specific and depends on the (in)accuracy of the analytical method. Conventional sampling devices operated in common time- or flow-proportional sampling modes, and applying traditional sampling intervals of 30 min or longer can result in the collection of nonrepresentative samples. At the influent of a STP, wastewater may appear as a continuous stream, but it is actually composed of a number of intermittently discharged, individual wastewater packets from household appliances, industries, or subcatchments in pressurized sewer systems. The resulting heterogeneity can cause significant short-term variations of pollutant loads. We present different experimental results and a modeling approach showing that the magnitude of sampling uncertainty depends mainly on the number of pollutant peaks and the sampling frequency; sampling intervals of 5 min or shorter may be required to properly account for temporal PPCP variations in influents of STPs. A representative sample is a prerequisite for providing meaningful analytical results and cannot be compensated with a large number of samples, accurate chemical analysis, or sophisticated statistical evaluation. This study highlights that generalizing from one case to another is difficult and hence a careful systems analysis of the catchment under investigation, or precautionary choice for a sophisticated sampling mode, is necessary to prove reproducibility.

We present data for the rare earth elements and yttrium (REY) in the National Research Council of Canada natural river water reference material SLRS-4 and 19 natural river waters from small catchments in South-East Queensland, Australia, by a direct ICP-MS method. The 0.22 lm filtered river water samples show a large degree of variability in both the REY concentration, e.g., La varies from 13 to 1157 ppt, and shape of the alluvial-sediment-normalised REY patterns with different samples displaying light, middle or heavy rare earth enrichment. In addition, a spatial study was undertaken along the freshwater section of Beerburrum Creek, which demonstrates that $75% of the total REYs in this waterway are removed prior to estuarine mixing without evidence of fractionation.

[1] In order to determine the total concentration of bioavailable trace metals in seawater, measurement of both the dissolved and labile particulate fractions is necessary. Comparison of labile particulate metal concentrations from various researchers is limited because of differing definitions of the fraction that is potentially available to phytoplankton on a time frame of generations. A comparison experiment was conducted on coastal and riverine suspended particulate matter to determine the difference between several commonly used techniques that operationally define the labile particulate trace metal fraction. Furthermore, we compared two leach techniques for surface transect samples from within the Columbia River plume and water offshore of Oregon and Washington, United States. The particulate trace metal concentration in the leachate was determined by high-resolution inductively coupled plasma-mass spectrometry. From this comparison, one chemical leach was chosen to best define the labile particulate fraction of Al, Fe, and Mn: a weak acid leach (25% acetic acid at pH 2) with a mild reducing agent (0.02 M hydroxylamine hydrochloride) and a short heating step (10 min 90-95°C). This leach was applied to three surface transects within the Columbia River plume. These coastal waters were found to be rich in labile particulate trace metals that are directly delivered from the Columbia River and indirectly supplied via resuspension from upwelling over a broad continental shelf.

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