Practically all portable radiation instruments come from the manufacturer with a graph of photon energy response. However, many of these graphs are in log-log format which can disguise relatively large variations in response, particularly for low-energy photons. Additionally, many only include one specific orientation. Thus, in many cases, it is left up to the user to determine for which orientation and photon energies the instrument will be calibrated and ultimately used in the field. It is known that many instruments can have inconsistent responses below ~300 keV, which may lead to under or over-estimation of exposure rate. However, based on relative response plots, one can derive an instrument correction factor that can be applied to the measured exposure rate to yield a constant response curve and more accurately estimate the exposure rate. Using a combination of irradiator systems, six different types of radiation instrumentation were irradiated with photons with energies from 38 to 1253 keV in various orientations. A calibrated ion chamber, in conjunction with an electrometer, was used to determine the conventionally true exposure rates for various x-ray beam codes and radionuclides contained in the irradiator systems. The conventionally true exposure rates were compared to the measured values for each instrument type and relative response plots were constructed. These plots were used to determine an ideal orientation and correction factors were chosen for responses > ±20 percent. From the relative response plots, instrument correction factors are not necessary for the following; Eberline RO-20, Thermo RadEye B20, and Bicron Micro Rem LE. Correction factors of 0.7 and 1.5 should be applied for photons between 80 – 120 keV for the Eberline Teletector 6112B low and high-range detectors, respectively. A correction factor of 0.8 should be applied for photons below 120 keV for the Eberline RO-7-BM. For the Thermo Mk2 EPD, a correction factor of 1.25 should be applied for photons below 40 keV. The primary causes of under and/or over-responses were found to be window attenuation, varying interaction cross-sections, and the range of secondary electrons. Angular dependence and calibrations for specific applications are also discussed.

Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (PCBs) have been assigned toxic equivalency factors (TEFs). These compounds are today routinely analysed with sophisticated analytical techniques. In a near future, there might be other dioxinlike compounds such as polychlorinated naphthalenes (PCNs), alkyl-polychlorodibenzofurans (R-PCDFs), and polychlorinated dibenzothiophenes (PCDTs) added to this list of toxic dioxin-like compounds. It is therefore important to have a readiness to analyse these new compounds in environmental samples. In this study, a multi-residue non-destructive analytical method for the analyses of these planar dioxin-like compound classes was developed. The use of HPLC PX-21 carbon column fractionation enabled the separation of interfering PCBs from coplanar PCBs and other planar dioxin-like compounds of interest. The obtained planar fraction containing the dioxin-like compounds was analysed using high-resolution GC-MS. Levels of PCNs in surface sediments and settling particulate matter in the northern Baltic Sea were determined. The concentrations of PCNs in background surface sediments were approximately 1 ng/g dw and the estimated PCN fluxes were similar to the pre-industrial levels determined in Europe. The PCN congener patterns in the surface sediments suggest that the PCNs deposited in the Baltic Sea originate from similar sources. Bioaccumulation of PCNs in a benthic food chain (sediment, amphipod, isopod, and four-horned sculpin) from the Gulf of Bothnia was studied. The results indicated that only a few PCN congeners biomagnified. The highest biomagnification factors (BMFs) were found for 2,3,6,7-substituted congeners and those lacking adjacent hydrogen-substituted carbon atoms. The calculated biota to sediment accumulation factors (BSAFs) showed that the tetra- and penta- CNs exhibited BSAF values higher than one, while BSAFs for the more chlorinated PCNs were less than one. A general difference between the northern and southern parts of the Gulf of Bothnia could be seen in the samples, with the lowest PCN and total PCB concentrations being found in the north and the highest in the south. This gradient is related to distance from the more industrialised and populated regions in the southern parts of Sweden and Finland, and central Europe. Analysis of R-PCDFs in crustacean samples from the Swedish west coast was performed using HRGC-MS/MS. The ΣR-PCDFs in these samples were present at concentrations up to 10 times higher than the ΣPCDFs. The relatively high concentrations of R-PCDFs in the crab samples demonstrate that these compounds bioaccumulate. The fate of a pollutant in the environment and the toxicity of a compound are governed by its physicochemical properties. The information found in a data set of properties can predict a compound’s mode of action. The following physicochemical properties for 87 PCDFs were measured: ultra-violetadsorption, relative retention times on two common gas chromatographic stationary phases, and relative mass spectrometric response factors using EI- and NCI- modes.