Assessment of radiation dose to people and wildife inhabiting the Grote Nete catchment in Belgium.

We evaluate the impact of the radiological contamination of the Grote Nete catchment in Belgium to people and non-human biota. This region has received effluents from the phosphate and nuclear industries via tributaries of the Grote Nete river in past decades, resulting in the presence of radionuclides such as 241Am, 60Co, 137Cs, 40K, 210Pb, 238Pu, 239,240Pu, 226Ra, 228Ra, 228Th, 232Th, 234U, 235U and 238U. During the period 2016-2021, we measured these radionuclides in the water column, the bed sediment and riverbanks. Additionally, we carried out radon measurements on the riverbanks in 2022. Based on these measurements, the dose rates to people were calculated for different potential exposure scenarios, using the SCK CEN biosphere tool. We also performed an assessment of exposure of ionising radiation to non-human biota (including 222Rn and its daughters) using the ERICA Tool. We observed three types of areas at the Grote Nete riverbank: (a) a lower category exposure with 226Ra concentrations reflecting purely Belgian background values; (b) a middle category with enhanced 226Ra, mainly adsorbed on clay minerals and (c) an upper category extending to maximum values in the order of 103 Bq kg-1. The main component of the dose rate for terrestrial and aquatic organisms is 226Ra followed by 210Pb (terrestrial) or 228Ra, (aquatic). The anthropogenic vector of the contamination (40K, 60Co, 90Sr, 137Cs, 228Th, 232Th, 234,235,238U, 238,239Pu, 241Am) makes a negligible contribution to dose. Overall, the Grote Nete wildlife is not under significant risk from exposure to soil or water-borne radionuclides and radon emanating from the soil, even if the ERICA benchmark of 10 µGy h-1 is occasionally exceeded for 226Ra, 210Pb or 228Ra, because exposures are below the levels at which effects are known to occur. For people, radon inhalation is the main exposure pathway and exposures can reach 1 mSv y-1 for hypothetical residents living at the riverbanks and remaining most of their time in the area, but it can be expected that exposures are much lower at increasing distances from the river. It is concluded that neither people nor the environment are at any significant radiological risk from this situation.

Impact of medical radionuclide discharges on people and the environment.

We present a novel methodology to dynamically calculate dose rates to people and wildlife from hospital-released radionuclides reaching the environment through water treatment plants (WTPs), using the biokinetic model D-DAT for aquatic wildlife, applied to 18F, 123I, 131I, 153Sm, 99mTc and 201Tl. We have also developed a method to calculate doses to WTP workers and to farmers from agricultural practices. This proof-of-concept study simulates a generic source term of radionuclide levels in the Belgian Molse Nete River during the year 2018, chosen because the river flow was very low during that year, which constitutes a very conservative, bounding case. The dose rates to wildlife calculated for this hypothetical scenario under conservative assumptions, are well below the ERICA predicted no effects dose rate to wildlife of 10 µGy h-1. Human exposures are also very low, in most cases not exceeding 10 µSv y-1. This work identifies important data gaps and areas of uncertainty in the assessment of radiopharmaceutical effluents. The study, which is part of the EC project SINFONIA, paves the way for a dynamic screening assessment methodology able to perform consistently assessments of the impact of radiopharmaceuticals on people and wildlife. This is particularly relevant since discharges of radiopharmaceuticals in rivers are on the increase and it is necessary to explicitly demonstrate that people and the environment are adequately protected.

The impact of extensive agricultural water drainage on the hydrology of the Kleine Nete watershed, Belgium.

Agricultural water drainage can significantly lower groundwater levels and affect catchment hydrology. Therefore, building models with and without these features can indicate an adverse impact on the geohydrological process. Therefore, the standalone Soil Water Assessment Tool (SWAT+) model was initially developed to simulate streamflow at the Kleine Nete catchment outlet. Next, a physically based and spatially distributed groundwater module (gwflow) was integrated into the SWAT+ model and calibrated for stream discharge at the catchment outlet. Finally, the same model was calibrated for both streamflow and groundwater heads. These final model parameters are used to investigate the basin-wide hydrologic fluxes with and without including agricultural drainage systems in the model scheme. The result suggested that the standalone SWAT+ model poorly represented the stream discharge and attained low NSE values of 0.18 and 0.37 during the calibration and validation periods, respectively. Integrating the gwflow module to SWAT+ improved the model representation of stream discharge (NSE = 0.91 and 0.65 for calibration and validation periods, respectively) and groundwater heads. However, calibrating the model for only streamflow resulted in a high root mean square error (above 1 m) for groundwater head, and the seasonality is not captured. On the other hand, calibrating the coupled model for streamflow and hydraulic head reduced the root mean square error (below 0.5 m) and captured the seasonality of groundwater level fluctuations. Finally, drainage application resulted in a 50 % (from 33.04 mm to 16.59 mm) reduction in groundwater saturation excess flow and an 18.4 mm increment in drainage water to streams. To conclude, the new SWAT+gwflow model is more appropriate than the standalone SWAT+ model for the case study. Furthermore, calibrating the SWAT+gwflow model for streamflow and groundwater head has improved the model simulation, with implications for general coupled models where representing surface and groundwater in the calibration strategy is beneficial.

Toxinotyping of Clostridium perfringens Strains Recovered from U.S. Turkeys with Necrotic Enteritis.

Necrotic enteritis (NE) is a serious disease of chickens and turkeys that causes significant economic losses to the poultry industry. On the basis of studies in chickens, Clostridium perfringens type G is considered by many to be the cause of NE in poultry. However, studies on isolates from Finnish and Italian turkeys with NE revealed that the vast majority were C. perfringens type A, and very few were C. perfringens type G. We therefore examined 74 C. perfringens isolates from U.S. turkeys with NE; 98% were type A and only 1% was type G. This result confirms that different C. perfringens types are involved in NE in turkeys when compared with chickens. We also examined the turkey isolates for other toxin genes associated with enteritis in various animal species, namely tpeL, cpb2, cpe, netE, netF, and netG. The tpeL gene, which has been associated with enhanced virulence of C. perfringens in chickens, was only found in 1% of turkey NE isolates. The cpe gene, which encodes C. perfringens enterotoxin (a major cause of food poisoning and non-foodborne C. perfringens-mediated diarrhea in humans) was also found in only 1% of our turkey NE isolates. Although cpb2, which encodes for the beta2 toxin, was found in 73% of our NE isolates, it has also been found in similar percentages of isolates from turkeys with normal intestine. The netE, netF, and netG genes were not detected among our C. perfringens isolates from turkeys.

Reporte de caso- Tipificación de toxinas de cepas de Clostridium perfringens recuperadas de pavos con enteritis necrótica en los Estados Unidos. La enteritis necrótica es una enfermedad severa de los pollos y pavos que provoca importantes pérdidas económicas a la industria avícola. Sobre la base de estudios en pollos, muchos consideran que Clostridium perfringens tipo G es la causa de la enteritis necrótica en las aves comerciales. Sin embargo, los estudios sobre los aislamientos de pavos con enteritis necrótica de Finlandia e Italia revelaron que la gran mayoría de los aislamientos eran C. perfringens tipo A y muy pocos eran C. perfringens tipo G. Por lo tanto, se examinaron 74 aislamientos de C. perfringens de pavos en los Estados Unidos con enteritis necrótica. El 98% eran del tipo A y solo el 1% fueron del tipo G. Este resultado confirma que diferentes tipos de C. perfringens están involucrados en la enteritis necrótica en pavos en comparación con los pollos. También se examinaron los aislamientos de pavo en busca de otros genes de toxinas asociados con la enteritis en varias especies animales, especialmente, tpeL, cpb2, cpe, netE, netF y netG. El gene tpeL, que se ha asociado con una mayor virulencia de C. perfringens en pollos, solo se encontró en el 1 % de los aislamientos de enteritis necrótica de pavo. El gene cpe, que codifica la enterotoxina de C. perfringens (una de las principales causas de intoxicación alimentaria y diarrea no transmitida por los alimentos causada por C. perfringens en humanos) también se encontró en solo el 1 % de los aislamientos de enteritis necrótica de pavo. Aunque cpb2, que codifica para la toxina beta2, se encontró en el 73 % de los aislamientos de enteritis necrótica, también se ha encontrado en porcentajes similares de aislamientos de pavos con intestino normal. Los genes netE, netF y netG no se detectaron entre los aislamientos de C. perfringens de pavos.