Effect Of Depuration Research Articles

Histopathological Changes and Metallothionein Levels in Filopaludina javanica During Depuration

The heavy metal lead has been reported to pollute waters along the Glagah River, Lamongan Regency, Indonesia. Lead contamination in all organs of the Tutut snail (Filopaludina javanica) was detected at 2.92 ± 0.5 ppm. Therefore, lead contamination can cause severe problems because lead can accidentally accumulate in the human body through the food chain. One effort to reduce risks related to food safety is Depuration. The research aimed to analyze the effect of Depuration using a flushing system on histopathological changes and metallothionein levels in all organs of the spotted snail (Filopaludina javanica). The research used a Completely Randomized Design with four treatments and three replications. Treatment includes flushing time (6 hours, 12 hours, 18 and 24 hours). The MT response was tested statistically using One Way Anova, while the histopathological analysis used a descriptive method by comparing before treatment and after flushing treatment for 24 hours, to determine metallothionein levels, the ELISA (Enzyme-Linked Immunosorbent Assay) method was used. The results showed tissue damage in edema, hyperplasia, and vacuolation. Tissue damage before and after Depuration was relatively the same and included in the low category, with damage ranging from (0-6.1%). Meanwhile, metallothionein analysis has not shown a significant decrease in levels. Metallothionein levels increased with the duration of flushing. Further checks showed that the media water used in flushing during Depuration contained Fe and Zn, which resulted in increased MT levels

Investigating the effects of PFOA accumulation and depuration on specific phospholipids in zebrafish through imaging mass spectrometry.

Perfluorooctanoic acid (PFOA) is an emerging persistent organic pollutant. Exposure to PFOA was observed to have a correlation with the expression levels of phospholipids. However, there are currently no studies that directly visualize the effects of PFOA on phospholipids. To this end, matrix-assisted laser desorption/ionization time of flight imaging mass spectrometry (MALDI-TOF-IMS) was used to visualize changes in phospholipids in the different tissues of zebrafish following exposure to PFOA. This study found that the major perturbed phospholipids were phosphatidylcholine (PC), diacylglycerol (DG), phosphatidic acid (PA), phosphatidylglycerol (PG), sphingomyelin (SM), and triacylglycerol (TG). These perturbed phospholipids caused by PFOA were reversible in some tissues (liver, gill, and brain) and irreversible in others (such as the highly exposed intestine). Moreover, the spatial distribution of perturbed phospholipids was mainly located around the edge or center of the tissues, implying that these tissue regions need special attention. This study provides novel insight into the biological toxicity and toxicity mechanisms induced by emerging environmental pollutants.

Effectiveness of depuration with zeolite stone filter to reduce levels of heavy metal lead (Pb) in the feather shell (Anadara antiquata)

Lead toxicity in humans causes neurological disorders, bone metabolism disorders, kidney damage, and impaired liver function. Feather shells that live in marine waters with high Pb heavy metal content can be exposed to these heavy metals, posing a risk to humans who eat shellfish. Depuration is one method that can reduce the Pb content in the body of the feather shell. The depuration process is influenced by several factors, including the length of the depuration and the filter used. This study aims to determine the effective depuration time to reduce the Pb content in feather shells (Anadara antiquata) using zeolite as a filter. This study applied the Latin Square Design (RSBL) method as a research design consisting of four treatments with four replications. The duration of the depuration treatment was 0 hours (P0), 24 hours (P1), 48 hours (P2), and 72 hours (P3). The effectiveness of the depuration of shells using a zeolite filter can be seen in the reduced Pb content in shellfish. The depuration process for 24 hours showed an effective depuration time with a reduction rate of Pb of 1.095 ± 0.05 mg/kg.

Development of a depuration protocol for commercially important edible bivalve molluscs of India: Ensuring microbiological safety

We investigated the effect of depuration of three naturally contaminated commercially important tropical edible bivalve molluscs by varying temperature, salinity and body-size of animals harvested from Ashtamudi and Vembanad estuaries, India using a static depuration system to ensure microbiological food safety. Before depuration, the levels of faecal indicators and pathogens were above the acceptable limits for live consumption. The depuration water temperature had a significant effect on bacterial elimination. Log reduction of faecal coliforms (FC) and E. coli varied between room-temperature (RTDS) and low-temperature depuration system (LTDS) and it was in the range of 1.39–2.44 and 1.88–2.82 log MPN, respectively under RTDS and LTDS. The elimination of bacterial pathogens such as Vibrio and Salmonella spp. was rapid in RTDS compared to LTDS. The highest elimination of FC and E. coli (2.39 and 2.92 log) was at 35 psμ depuration and the lowest (0.87 and 1.65 log) at 15 psμ depuration. The reduction of FC and E. coli was higher in the medium-sized animals compared to the small animals. Based on the results it is recommended that depuration using the static system under room-temperature (30 ± 1 °C); a salinity range of (25–35 psμ) and using medium-size bivalves (clam>30 mm; mussel >45 mm, and oyster >65 mm length) as optimum conditions for producing microbiologically safe bivalves for live consumption within 36 h.

Exposure to enrofloxacin and depuration: Endocrine disrupting effect in juvenile grass carp (Ctenopharyngodon idella)

This study aimed to determine the effects of Enrofloxacin (ENR) exposure and depuration on the disruption of thyroid function and growth of juvenile grass carp (Ctenopharyngodon idella) as well as to assess the risk of ENR exposure to human health. Juvenile grass carp were treated with ENR solutions at different concentration gradients for 21 days and then depurated for 14 days. The results indicated ENR accumulation in the juvenile grass carp muscles, which persisted after depuration. In addition, exposure to ENR could alter growth by regulating the expression of genes associated with growth hormone/insulin-like growth factor (GH)/IGF) axis and the hypothalamic–pituitary–thyroid (HPT) axis. During ENR exposure, no significant changes in growth hormone levels were observed; however, a significant increase in the growth hormone level was noted. GH/IGF axis-related genes were upregulated after ENR exposure, and their expression levels remained high after depuration. Notably, a significant increase in the serum triiodothyronine (T3) and thyroxine (T4) levels coincided with the upregulation of HPT axis-related genes in both exposure and depuration treatments, and their expression levels remained high after depuration. Therefore, juvenile grass carp exposure to ENR induces physiological stress through HPT and GH/IGF axes that cannot be recovered after depuration. ENR accumulates in the muscles of juvenile grass carp and may pose a threat to human health. Therefore, exposure of juvenile grass carp to ENR results in impaired thyroid function and impaired growth. In addition, consumption of ENR-exposed fish poses human health risks.

Depuration effect on the total hemocytes count and heavy metals concentration in freshwater crayfish, Procambarus clarkii

One of the most important aquatic macro-invertebrates is Procambarus clarkii. This study was designed to evaluate the effect of depuration for 21 days on the total hemocytes count and heavy metals (Co, Cr, Pb and Hg) concentrations in the hemolymph and different tissues of P. clarkii. Two hundred crayfish were collected and were divided into two groups; field crayfish (FCF) that were dissected directly and the depurated crayfish (DCF) that were housed for 21 days in glass tanks. Procambarus clarkii were dissected to determine the total hemocytes count and heavy metal concentrations in the hemolymph, abdominal muscles, and hepato-pancreas. The results showed that the depuration has led to a significant decrease in the total count of hemocytes, however, it increased the percentages of semi-granular cells, granulocytes and decreased the percentage of hyalinocytes. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed different protein patterns between FCF and DCF. Not all the selected heavy metals were detected in the collected water samples and in the investigated tissues. Depuration has led to a significant decrease of the heavy metals, if present, in the hemolymph, abdominal muscles, and hepato-pancreas. Collectively, the depuration resulted in significant decreases in the total hemocytes count and eliminated the selected heavy metals from the different tissues of P. clarkii.

Effect of Soaking and Depuration on the Microbial,Heavy Metals and Nutritional Composition of Oyster Harvested from a Contaminated Creek of Rivers, Nigeria

Effect of Soaking and Depuration on the Microbial,Heavy Metals and Nutritional Composition of Oyster Harvested from a Contaminated Creek of Rivers, Nigeria

Effectiveness of depuration of Pacific Oyster (Crassostrea gigas): removal of bioaccumulated Vibrio vulnificus by UV-treatment.

The present study aimed to evaluate the efficacy of a depuration system equipped with UV-irradiation to control Vibrio vulnificus infection such as septicemia (or sepsis) using alive oysters. After 6 h of bioaccumulation of V. vulnificus, Pacific oyster Crassostrea gigas were found to be contaminated by > 8.0 log MPN/g of V. vulnificus cells. After 60 h of depuration, the V. vulnificus cell number significantly decreased to < 4.0 log MPN/g. The present depuration process meets the standard effectiveness in reducing V. vulnificus cells by > 3.52 log and < 30 MPN/g as recommended by the National Shellfish Sanitization Procedure Molluscan Shellfish Control guidelines. Furthermore, no significant changes in pH value and glycogen content indicate that the depuration process did not affect the freshness and quality of the oyster samples. The present study could help control any potential infection associated with the consumption of raw oysters without losing their quality.

Accumulation and depuration of dissolved hexavalent chromium and effects on the antioxidant response in bighead carp (Aristichthys nobilis)

The present study investigated the accumulation and depuration effects of hexavalent chromium (Cr6+) in ten tissues (gills, intestines, liver, kidney, blood, heart, bladder, spleen, skin and muscle) of the bighead carp (Aristichthys nobilis). Fish were exposed to graded levels of waterborne Cr6+ (0.01, 0.1, 1 and 5 mg/L) for 4, 7 and 14 days, and subsequently transferred to Cr6+-free water for 14 days. After 14-day exposure, a dose-dependent increase of Cr6+ has been observed in most tissues. While after 14-day depuration, Cr6+ contents were significantly decreased in various tissues except in kidney and spleen where Cr6+ contents significantly increased at the group of 5 mg/L. Considering that Cr6+ highly accumulated in gills, intestines, liver and kidney, the oxidative damage of Cr6+ on the four tissues were further investigated and found that the antioxidant response to Cr6+ were organ-specific. The results in this study indicated that a 14-day period is effective for accumulation and depuration of Cr6+ in bighead carp and there was no health risk of fish muscle consumption. Additionally, the delayed efflux of Cr6+ in the fish kidney and spleen indicates that high importance should be attached to them when evaluating the toxic effects and risk assessments of Cr6+.

Case study on depuration of RAS-produced pikeperch (Sander lucioperca) for removal of geosmin and other volatile organic compounds (VOCs) and its impact on sensory quality

Effect of depuration on content of geosmin in pikeperch (Sander lucioperca) produced in a commercial RAS farm was examined during a 15-day period. Concentrations of geosmin in the fish were related to geosmin content in the water. For depuration, half of the water volume in a 230 m3 production tank was replaced daily with geosmin-free water. After 8 days of depuration and absence of feeding, content of geosmin in the fish was reduced from 710 ± 245 ng/kg to 165 ± 50 ng/kg (mean ± SD, p < .01). Additional depuration for 7 days only reduced the geosmin content to 135 ± 24 ng/kg. Geosmin concentration in the water was initially 34 ng/L but declined to 10 ng/L after 15 days. Changes in geosmin concentrations in water of the depuration tank indicated that geosmin was released by the fish during the depuration. In addition to removal of geosmin, the depuration also decreased concentrations of 28 different volatile compounds from the fish. Sensory analysis showed decrease in intensity of geosmin flavor upon depuration and improved the overall sensory quality of the fish after 2 weeks of depuration. Our study shows that geosmin and other off-flavors in pikeperch from RAS production can efficiently be removed to be a level that is below the threshold to most consumers.

The Effect of Depuration on Metals, Bacteria, and Nutrition in Venus verrucosa from the Aegean Sea: Benefit and Risk for Consumer Health of Warty Venus

ABSTRACT In this study, the effect of the depuration period on proximate composition, metals, fatty acids, and bacteria in the edible tissue of warty venus (Venus verrucosa) collected from İzmir Bay in the Aegean Sea was investigated. In addition, benefit and risk for human health associated with the consumption of warty venus were determined by atherogenic index (AI), thrombogenic index (TI), polyene index (PI), fish lipid quality (FLQ), target hazard quotient (THQ), and hazard index (HI). The depuration process did not show a significant (P > .05) effect on proximate composition, except for ash. The depuration process was successful in reducing bacteria growth and the concentrations of all metals, except for copper. Total aerobic mesophilic bacteria count of 1.94 log CFU/g in the fresh samples was uncountable at 24 h of depuration. The concentrations of cadmium, lead, copper, iron, and zinc were below the limit values allowed for safe consumption. The analyzed metals were safe for human consumption based on provisional tolerable weekly intake (PTWI), THQ, and HI. Significant variations were also observed in the fatty acid values depending on the depuration periods (P < .05). The n3/n6 and polyunsaturated/saturated fatty acid ratios were greater than those recommended by the FAO/WHO. Moreover, the AI and TI of samples were under established limits.

Impacts of trace metals on African common toad, Amietophrynus regularis (Reuss, 1833) and depuration effects of the toad's enteric parasite, Amplicaecum africanum (Taylor, 1924) sampled within Lagos metropolis, Nigeria

The study aimed at assessing the depuration potentials of endoparasite, Amplicaecum africanum on trace metals in its toad host, Amietophrynus regularis at sites of significant anthropogenic perturbations within the Lagos metropolis, in Nigeria. A total of 120 toads of both sexes, alongside 45 soil samples were collected from each of three (3) stations labeled Dumpsite, Lagoon front and Highrise, using hand nets and by hand-picking between February and October, 2018. The intestinal tissues sections of the toads were examined using a binocular dissecting microscope (American Optical Corporation, Model 570) and hematoxylin and eosin (H&E) stain. Oxidative stress in toad intestine was assessed by estimating the levels of glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase (CAT), and lipid peroxidation (MDA). Trace metals in the water, soil, toad liver, intestine and parasite, Amplicaecum africanum were tested using Atomic Absorption Spectrophotometry (Philips model PU 9100). Lead (Pb), copper (Cu), nickel (Ni), cadmium (Cd), and chromium (Cr) were detected in the toads, with the infected toads having lower concentrations of most trace metals than the uninfected toads, irrespective of the locations and sex. Strong negative correlations between parasitological indices and concentrations of trace metals in the toads suggest that the parasites might have taken up significant amounts of trace metals from the host. The study demonstrated the potentials of parasite, A. africanum to depurate trace metal burden in Amietophrynus regularis. When the dominant factor impacting the toad is the parasitic infection, parasite intensity determines the trade-off between parasitological harm and depuration benefit to the host. Hence, under controlled conditions, parasites may serve as bioremediation agent in the event of pollution. Depuration potential of A. africanum in the study was supported by the mild tissue alterations observed in the intestine of infected toads, compared to the uninfected counterparts, which exhibited severe glandular hyperplasia, increased connective tissue, and severely stunted villi. Consistently lower activities of biochemical biomarkers which characterize the uninfected toads compared to the infected, irrespective of the sex and stations, further corroborate drawn inferences.

The effect of depuration on lead levels of the cockles Anadara sp. by using activated carbon as a filter

Consumption of cockles with high concentrations of lead metal (Pb) will hurt harm humans from health aspects. The concentration of Pb metal in cockles can be reduced through a depuration process. This study aims to determine the efficient time of retention and the rate of decrease in the concentration of Pb in the cockles (Anadara sp.) by using activated carbon as a filter during the depuration process. The treatment of study consists of P0 (no depuration), P1 (depuration 24 Hours), P2 (depuration 48 Hours), and P3 (depuration 72 Hours). The results showed that the process of depuration of the cockles for 24 hours with activated carbon filters was able to reduce the Pb metal content to 0.926 mg/kg and even the depuration process for 72 hours, the efficiency of the depuration process increased to 86.52% so that the Pb content in the cockles became 0.273 mg/kg. Overall, the duration of the process of depuration of the cockles with activated charcoal as a filter can increase the efficiency of Pb metal reduction in the cockles so that it according to SNI 7387: 2009, which is the maximum metal content of Pb in the shellfish 1.5 mg/kg.

Comprehensive evaluation of water quality status for entire stretch of Yamuna River, India.

This study represented the first comprehensive assessment of the physicochemical water quality status of the entire Yamuna River stretch in India. The upper zone had "excellent-to-good" water quality index (WQI) with mean 5-day biochemical oxygen demand (BOD5) values of 2.1 and 2.4mg/L during monsoon and non-monsoon, respectively. The middle region was described by "poor-to-marginal" WQI with average BOD5 values of 13.1mg/L (monsoon) and 32.3mg/L (non-monsoon). The low WQI observations at the midstream region were due to the negative impact of two major drains, namely Najafgarh and Shahdara, that carry partially treated effluents from industrial units. Further, BOD5 decreased to 1.9mg/L (monsoon) and 1.8mg/L (non-monsoon) in the lower zone, and the WQI values improved to "good" and "excellent". The dilution and depuration effects of the Chambal, Sindh, Betwa, and Ken Rivers recovered the environmental conditions in downstream stations. The oxygen sag curve complied with the water quality status along the river stretch. Based on the principal component analysis, the Yamuna River was strongly influenced by dissolved mineral salts originating from atmospheric deposition, weathering of soils and rocks, and application of deicing chemicals and landfills. Moreover, organic and nutrient substances and biological activities resulting from the discharge of sewage, and the utilization of fertilizers in agriculture, were the second contributors to pollution. The statistical techniques employed in this work could be beneficial for decision-makers (government and stakeholders) to identify the pollution sources/factors and to determine the viability of water bodies for domestic applications.

Depuration reduces microplastic content in wild and farmed mussels

Plastic pollution is a pervasive problem to marine life. This study aimed (1) to investigate levels of microplastic in wild and farmed mussels (Perna perna), and (2) to assess the effectiveness of depuration in reducing microplastics. Wild and farmed mussels were sampled from Guanabara Bay (Southwestern Atlantic). Four treatments were compared (N = 10 mussels/treatment): wild non-depurated mussels, wild depurated mussels, farmed non-depurated mussels, and farmed depurated mussels. Up to 31.2 ± 17.8 microplastics/mussel (≥0.45 μm) were detected (means ± SD), and microplastics were present in all 40 individuals analyzed. Nylon fibers were more abundant than polymethyl methacrylate (PMMA) fragments. Blue, transparent, and red nylon fibers were more abundant in both wild and farmed mussels. Although 93 h-depuration significantly reduced microplastics (ANOVA, p = 0.02) in both wild (46.79%) and farmed mussels (28.95%), differences between farmed and wild mussels were not significant (p > 0.05). Depuration was more effective in removing blue fibers. Our results highlight the importance of depuration in reducing microplastic pollution in seafood.

Effect of depuration on microbial load of mangrove oyster (&lt;i&gt;Crassostrea gasar&lt;/i&gt;) from a polluted creek in Rivers State, Nigeria

The efficiency of depuration in the removal of microbial load in mangrove oyster (Crassostrea gasar) from a polluted creek in Rivers State, Nigeria using a flow-through method with high loading density was evaluated in this study. Depuration experiments were conducted with cartridge-filtered and UV-light using seawater in segregated plastic tanks at a salinity of 30 ‰, pH of 8.0 and temperature of 29.0 °C. The oysters in segregated tanks were taken at intervals of 24, 48, 72 and 96 hours of depuration and analyzed for microbial load (total hetrotrophic bacteria, total fungi counts, hydrocarbon utilizing bacteria and fungi and feacal coliform counts). Results from the two-way ANOVA showed that time, method and season had significant effect on the microbial counts. At different locations, there was significant difference (P 0.05) on total fungi counts, feacal coliforms and hetrotrophic bacteria was recorded. This study depuration method at the different time interval is recommended.Keywords: Cleansing, contaminants, poisoning, food safety, Crassostrea gasar

Effect of depuration on heavy metal concentrations in periwinkle (&lt;i&gt;Tympanatonus fuscastus&lt;/i&gt;) from a polluted creek in Rivers State, Nigeria

The efficiency of depuration in the removal of heavy metals in Periwinkle (Tympanatonus fuscastus) was evaluated in this study. Periwinkle in depuration tanks were taken at intervals of 24, 48, 72 and 96 hours of depuration and analyzed for these heavy metals: Lead (Pb), Zinc (Zn), Chromium (Cr) and Cadmium (Cd). Results from the analyses shows that time, method and season has significant effect on heavy metals. At different location, there was significant difference at different time interval of depuration for both seasons. The control for all the locations had the highest count for depuration at both seasons. The concentration of Pb, Cr, Cd and Zn for depurated periwinkle at 24-96 hours was significantly different (P<0.05) from control for both rainy and dry season. Notably, at 96hours of depuration, these metals were reduced. The depuration of these contaminants on the shellfish was faster during rainy season than dry seasons brought about satisfactory results. This study depuration method at the different time intervals is suggested.Keywords: Heavy metals, purification, processing, pollutants, Tympanatonus fuscastus

Nutritional Value of the Egyptian Freshwater Bivalve Spathopsis rubens arcuata Under the Effect of Depuration

On the view of finding a new source of protein, Spathopsis rubens arcuata is one of fresh water bivalves inhabiting Nile River, Egypt. The quality of this clam as a human food was investigated. The herein results showed that S. rubens arcuata is a good source of protein, carbohydrate and with a negligible source of fat when compared with edible fishes. Myristic acid was the most abundant saturated fatty acid (SFA) while Myristoleic acid and Linoleic acid were the two most abundant unsaturated fatty acids. The nonessential amino acid Glutamine is the most dominant amino acid followed by Aspartic, Alanine and Leucine. Studying the safety of consuming the investigated clam was based on: 1) Studying the heavy metal content in relation to the environment and after a depuration period, 2) Studying the associated parasites. The results showed that the initial heavy metals (Cu, Cd and Pb) concentrations detected in soft tissues of the clam were high and exceeded the legal values. But the 8 days of depuration was an excellent strategy to reduce Cu, Cd and Pb to an acceptable level for human consumption. Seasonal study of the clam associated parasite showed that S. rubens arcuata harbors nonpathogenic ciliated protozoa Conchophthirus sp. and an annelid Batracobdelloides tricarinata as commensal organisms and a trematode Aspidogaster conchicola as a parasite. The present work concludes that S. rubens arcuata can be a good source of food for human on condition that arises in the market after a period of depuration reached to 8 days.

Influence of sample preparation on estuarine macrofauna stable isotope signatures in the context of contaminant bioaccumulation studies

The ratios of stable isotopes of carbon and nitrogen provide important information on food sources of aquatic organisms and trophic structure of aquatic food webs. For many studies, trophic position and food source are linked to bioaccumulation and trophic transfer of contaminants from prey to predators. In these cases, it is useful to use measurements on whole organisms to make direct comparisons of contaminant bioaccumulation and food web attributes. There is a great deal of variation in methods used for stable isotope analysis, particularly in the selection of tissue type and sample preparation prior to stable isotope analysis. While there have been aquatic studies that examined methodological differences, few have focused on estuarine organisms. In this study, the effects of depuration and tissue dissection on the stable isotope enrichment of common estuarine invertebrates and fish were examined. Homogenized tissues of non-depurated whole organisms were compared to dissected muscle tissue or depurated whole organisms. A 24h depuration did not change the mean δ15N and δ13C values for most species examined. Additionally, as expected, significant differences in carbon and nitrogen signatures were found when muscle tissues were compared to whole organisms. However, differences were small enough that food source as inferred by δ13C or trophic level as inferred from δ15N would not be inaccurately represented (differences of <1.9‰ for δ13C and <1.2‰ for δ15N). The results of this study suggest that for these common estuarine fish and macroinvertebrates, stable isotopes ratios of samples can be analyzed without depuration in the same way as samples for contaminant analysis, but differences in tissue type must be taken into account when combining data from different sources.

Optimization of exposure and countryside waste management for different accidental radioactive release

Since the Fukushima accident, Japanese scientists have been intensively monitoring ambient radiations in the highly contaminated territories situated within 80 km of the nuclear site. The surveys that were conducted through mainly carborne, airborne and in situ gamma-ray measurement devices, enabled to efficiently characterize the spatial distribution and temporal evolution of air dose rates induced by Caesium-134 and Caesium-137 in the terrestrial systems. These measurements revealed that radiation levels decreased at rates greater than expected from physical decay in 2011-2012 (up to a factor of 2), and dependent on the type of environment (i.e. urban, agricultural or forest). Unlike carborne measurements that may have been strongly influenced by the depuration of road surfaces, no obvious reason can be invoked for airborne measurements, especially above forests that are known to efficiently retain and recycle radiocaesium.The purpose of our research project is to develop a comprehensive understanding of the data acquired by Japanese, and identify the environmental mechanisms or factors that may explain such decays. The methodology relies on the use of a process-based and spatially-distributed dynamic model that predicts radiocaesium transfer and associated air dose rates inside/above a terrestrial environment (e.g., forests, croplands, meadows, bare soils and urban areas).Despite the lack of site-specific data, our numerical study predicts decrease rates that are globally consistent with both aerial and in situ observations. The simulation at a flying altitude of 200 m indicated that ambient radiation levels decreased over the first 12 months by about 45% over dense urban areas, 15% above evergreen coniferous forests and between 2 and 12% above agricultural lands, owing to environmental processes that are identified and discussed. In particular, we demonstrate that the decrease over evergreen coniferous regions might be due the combined effects of canopy depuration (through biological and physical mechanisms) and the shielding of gamma rays emitted from the forest floor by vegetation. Our study finally suggests that airborne surveys might have not reflected dose rates at ground level in forest systems, which were predicted to slightly increase by 5 to 10% during the same period of time.