Sample control, field studies

Comprehensive chemical analyses of samples of water, sediment, and biota were carried out both before and after the spill. This cannot of course be carried out in most cases, and illustrates a serious limitation in field studies, in which lack of background data or difficulty in finding an uncontaminated control locality is frequently encountered. Sum parameters were sparingly employed in Baffin Island Oil Spill (BIOS), and emphasis was placed on the analysis of specific compounds attention was directed not only to PAHs, but also to azaarenes, dibenzothiophenes, and hopanes. Thereby, a clear distinction could be made between the input from the oil deliberately discharged, and that arising from natural biological reactions or mediated by atmospheric transport. 

A market basket survey, however, is unique in that untreated control commodities, as the term is normally used in residue studies, cannot be obtained. In a market basket survey, food commodities are collected at the consumer level and not from controlled field tests. By design, the cultural and treatment details for the collected commodities are expected to differ from sample to sample. This factor enables the collected commodities to represent the spectrum of conditions under which crops are supplied for human consumption. 

Untreated (control) soil is collected to determine the presence of substances that may interfere with the measurement of target analytes. Control soil is also necessary for analytical recovery determinations made using laboratory-fortified samples. Thus, basic field study design divides the test area into one or more treated plots and an untreated control plot. Unlike the treated plots, the untreated control is typically not replicated but must be sufficiently large to provide soil for characterization, analytical method validation, and quality control. To prevent spray drift on to the control area and other potential forms of contamination, the control area is positioned > 15 m away and upwind of the treated plot, relative to prevailing wind patterns. 

Soil Degradation Study. A controlled degradation study will be conducted using soil samples taken from a field that has not been exposed to metolachlor and from a... 

Twenty-five children selected at random received aerosol treatment with RP 6000 vitamin A units per 2 weeks over 3 months being provided. Twenty-five further children served as controls receiving a placebo also aerosol delivered. The aerosol was administered through the mouth during breath inhalation with an adapter. No adverse effects or reactions were observed during inhalation and the children complied well with the treatment. Trained field workers performed the inhalation trials and blood sampling. In the study and control group. Heparin blood samples were collected before and at completion of the study for measurements of vitamin A, RBP, and TTR concentrations. 

As part of this field study, relevant quality assurance/quality control (QA/QC) criteria and guidelines (SETAC, 1993 JAMP, 1998a,b) have to be set to insure the quality of data generated during the assessments. The development of QA/QC criteria for this study involved conducting a series of replicate bioassays with each of the methods. Samples tested included a control sediment, contaminated sediments and reference toxicants. Based on the results of the bioassay replicates, the variability associated with the tests was quantified and we were able to determine what we considered acceptable QA/QC criteria for these methods. 

Several other microanalytical methods in common use potentially have application on soil and sediments section samples. Laser-ablation inductively coupled plasma mass spectrometery (LA-ICP-MS) has been used on soil thin-sections from a controlled field experiment (21) but required special resins in the preparation. There is presently (May 2006) no reported use of this method on archaeological soil samples. Likewise, for extremely fine-resolution studies (i.e. <10 pm) with low minimum detection limits and despite difficult calibration, secondary ion microscopy (SIMS) has a potential role in examining archaeological soil thin sections. At even higher lateral resolutions ( 100 nm) Auger electron spectroscopy (AES) could also be considered for surface (<5 nm deep) analyses. At present however, the use of these methods in soil systems is limited. SIMS has been focused on biochemical applications (22), whereas AES... 

Prior to a field study, enough untreated control material should be provided to allow the lab to develop and validate adequate analytical methods. The control material should match the test samples as closely as possible to minimize the matrix variations which might affect the performance of the method. Development and validation of a method using a matrix which does not closely resemble the actual test matrix frequently results in a method which is not adequate for the actual study samples. The method revisions required in such a case represent a clear waste of... 

The benthic invertebrate study design used at the Provincial Papers site was a Multiple Control/Impact study including near-field (NF) and far-field (FF) areas in both exposure and reference areas. The NF exposure area was located as close as possible to the outfall (Fig. 2) in the area showing elevated conductivity, while the FF exposure area was located approximately 1000 m from the NF area. A petite Ponar was used to collect duplicate samples at six stations in each exposure and reference area. Substrates in the reference and exposure areas were different the exposure area was 100% organic, comprised of wood chips, while the reference area was dominated by silt and clay with small amounts of fine sand at two stations. 

The potential usefulness of any analytical procedure should be assessed by carrying out control experiments in samples comparable to those collected for the field studies. Analytes in environmental samples are often determined at the ppm-ppb levels. While an immunoassay may appear to be specific, sensitive and reliable under the pristine conditions of the laboratory (e.g. when the test substance is in buffer), it may give false results with environmental samples that vary sufficiently (e.g. in pH, ionic strength, viscosity, solubility, humic content, etc.) to alter the antigen-antibody interaction or interfere with the monitoring systems. Samples collected at the point source where the analyte is most concentrated (e.g. at the... 

Biotechnical control systems are beginning to make their appearance in the agrochemical marketplace One potential commercial application of a pheromone insect control agent is that of the grape berry moth pheromone produced by Shin-Etsu Chemical Company and investigated in the field by Dennehy and Roelofs (10,11). Before petitions could be filed, it was necessary that an analytical method for the two components Z-9-dodecen-l-yl acetate and Z-11-tetradecen-l-yl acetate (Z-9-DDA and Z-ll-TDA) in and on grapes be developed, and further, that residue determinations be conducted on samples from the cited field study ... 

From the standpoint of managing resistance to dicofol in spider mite pests of New York apple orchards, our findings for T. urticae are positive. Most populations had fewer than 10% resistant mites, and our laboratory data indicated that the resistant genotypes of T. urticae are substantially less fit than susceptible ones. Field studies of the critical frequency for dicofol resistance (i.e., the frequency at which resistance results in appreciable reductions in control) indicate that frequencies of resistance must be >20% to impair performance of dicofol treatments. Therefore, dicofol treatments would be expected to provide acceptable control of 9-12 of the 15 T, urticae populations we sampled. However, P. ulmi is the dominant spider mite pest of apple in western New York and, as we have demonstrated, the species most likely to exhibit resistance to dicofol. 

A field study conducted in December 1999 (123,124) confirmed the efficacy of this treatment process. The LAA discharges into North Haiwee Reservoir in a channel about 25 m wide, bordered on the eastern side by a small peninsula. Samples of overlying water, sediment, and sediment porewaters were collected in this channel and in a control site on the eastern side of the peninsula. In the channel, an orange-brown floe was visible floating in the water and was observed to settle near the banks, where flow velocity was reduced. In the water sample collected closest to the LAA discharge, the comparison between arsenic and iron concentrations in unfiltered samples (17 pg/L As and 1.9 mg/L Fe) and samples filtered through 0.45-pm membrane filters (3.3 pg/L As and 0.13 mg/L Fe) indicated that both As and Fe were largely associated with the particulate phase. In contrast, at the control site, the concentrations of arsenic in unfiltered and filtered samples were quite similar unfiltered samples contained 5.7 and filtered samples... 

If urine or blood samples are to be used to determine the absorbed dose, it is helpful to have pre-study information which will give the researcher an opportunity to design his sample collection scheme in a manner which will be simplest to achieve and which will provide the most quantitative information. Much has been written with regard to the excretion rates, quantitative nature of the excretion, and other data on the phenoxy herbicides. For other compounds where less is known, if the manufacturer can not provide detailed information on the excretion data, the researcher may be required to conduct a small controlled study, evaluating excretion rate, and other important characteristics of the compound prior to conducting full-scale field study. It is necessary to know if one should analyze for the parent compound or a metabolite. If a metabolite is to be analyzed, it is necessary to know if its amount can be related to the dose of the parent compound. 

---