Temporal Changes In Concentrations Research Articles

Spatial and temporal change patterns of near-surface CO2 and CH4 concentrations in different permafrost regions on the Mongolian Plateau from 2010 to 2017

Greenhouse gases (GHGs) released from permafrost regions may have a positive feedback to climate change, but there is much uncertainty about additional warming from the permafrost carbon cycle. One of the main reasons for this uncertainty is that the observation data of large-scale GHG concentrations are sparse, especially for areas with rapid permafrost degradation. We selected the Mongolian Plateau as the study area. We first analyzed the active layer thickness and ground temperature changes using borehole observations. Based on ground observation data, we assessed the applicability of Greenhouse Gases Observing Satellite (GOSAT) carbon dioxide (CO2) and methane (CH4) datasets. Finally, we analyzed the temporal and spatial changes in near-surface CO2 and CH4 concentrations from 2010 to 2017 and their patterns in different permafrost regions. The results showed that the Mongolian permafrost has been experiencing rapid degradation. The annual average near-surface CO2 concentration increased gradually between 2.19 ppmv/yr and 2.38 ppmv/yr, whereas the near-surface CH4 concentration increased significantly from 7.76 ppbv/yr to 8.49 ppbv/yr. There were significant seasonal variations in near-surface CO2 and CH4 concentrations for continuous, discontinuous, sporadic, and isolated permafrost zones. The continuous and discontinuous permafrost zones had lower near-surface CO2 and CH4 concentrations in summer and autumn, whereas sporadic and isolated permafrost zones had higher near-surface CO2 and CH4 concentrations in winter and spring. Our results indicated that climate warming led to rapid permafrost degradation, and carbon-based GHG concentrations also increased rapidly in Mongolia. Although, GHG concentrations increased at rates similar to the global average and many factors can account for their changes, GHG concentration in the permafrost regions merits more attention in the future because the spatiotemporal distribution has indicated a different driving force for regional warming.

Comparison of spatial and temporal changes in riverine nitrate concentration from terrestrial basins to the sea between the 1980s and the 2000s in Japan: Impact of recent demographic shifts

Nitrogen (N) is an essential nutrient but may become a pollution source in the environment when the N concentration exceeds a certain threshold for humans and nature. Nitrate is a major N species in river water with notable spatial and temporal variations under the influences of natural factors and anthropogenic N inputs. We analyzed the relationship between riverine N (focusing on nitrate) concentration and various factors (land use, climate, basin topography, atmospheric N deposition, agricultural N sources and human-derived N) in 104 rivers located throughout the Japanese Archipelago except small remote islands. We aimed to better understand processes and mechanisms to explain the spatial and temporal changes in riverine nitrate concentration. A publicly available river water quality database observed in the 1980s (1980–1989) and 2000s (2000–2009) was used. This study is the first to evaluate the long-term scale of 20 years in the latter half of Japan's economic growth period at the national level. A geographic information system (GIS) was employed to determine average values of each variable collected from multiple sources of statistical data. We then performed regression analysis and structural equation modeling (SEM) for each period. The forestland area influenced by the basin topography, climate (i.e., air temperature) and other land uses (i.e., farmland and urban area) played a major role in decreasing nitrate concentrations in both the 1980s and 2000s. Atmospheric N deposition (especially N oxides) and agricultural N sources (fertilizer and manure) were also significant variables regarding the spatial variations in riverine nitrate concentrations. The SEM results suggested that human-derived N (via food consumption) intensified by demographic shifts during the 2000s increased riverine nitrate concentrations over other variables within the context of spatial variation. These findings facilitate better decision making regarding land use, agricultural practices, pollution control and individual behaviors toward a sustainable society.

Contributions of Coagulation, Deposition, and Ventilation to the Removal of Airborne Nanoparticles in Indoor Environments.

Airborne nanoparticles are frequently released in occupied spaces due to episodic indoor source activities. Once generated, nanoparticles undergo aerosol transformation processes such as coagulation and deposition. These aerosol processes lead to changes in particle concentration and size distribution over time and accordingly affect human exposure to nanoparticles. The present study establishes a framework for an indoor particle dynamic model that can predict time- and size-dependent particle concentrations after episodic indoor emission events. The model was evaluated with six experimental data sets obtained from previous measurement studies in the literature. The indoor particle dynamic model quantified the relative contributions of three particle loss mechanisms (i.e., coagulation, deposition, and ventilation) to the total reduction in number concentration. The results show that particle coagulation and indoor surface deposition are two dominant processes responsible for temporal changes in particle size and concentration following indoor emission events. The first-order equivalent coagulation loss rate notably varies with indoor emission source and accounts for up to 59% of the total particle loss for burning a candle, 42% for broiling a fish, and 10% for burning incense. The results reveal that while the coagulation loss rate changes markedly with the particle concentration and source type, the deposition loss rate is more dependent on particle size. Compared to coagulation and deposition, the effect of ventilation is marginal for most of the nanoparticle emission events indoors; however, ventilation loss becomes pronounced with the decrease of particle concentration below 5 × 104 cm-3, especially for particles larger than 100 nm in aerodynamic diameter.

Spatial–Temporal Variations of Total Nitrogen and Phosphorus in Poyang, Dongting and Taihu Lakes from Landsat-8 Data

Poyang Lake, Dongting Lake, and Taihu Lake are the largest freshwater lakes in the middle and lower reaches of the Yangtze River, China. In recent years, the eutrophication level of lakes has increased with the development of the social economy and caused many environmental and social problems. The concentrations of total nitrogen (TN) and total phosphorus (TP) are the key indicators of the degree of eutrophication, but the traditional ground monitoring methods are not capable of capturing such parameters in whole lakes with high spatial-temporal resolution. In this paper, empirical models are established and evaluated between the TN and TP and remote sensing spectral factors in the three lakes using Landsat 8 Operational Land Imager (OLI) satellite data and in-situ data. The results show that the inversion accuracy is higher than 75%. The TN and TP concentrations in the three lakes are inversed based on the Google Earth Engine (GEE) platform from 2014 to 2020 and their spatial-temporal variations are analyzed. The results show that the concentrations of TN and TP in Poyang Lake were decreased by 5.99% and 7.13% over 7 years, respectively, and the TN in Dongting Lake was decreased by 5.25% while the TP remained stable. The temporal changes in TN and TP concentrations displayed seasonal variations. A low concentration was observed in summer and high concentrations were in spring and winter. The average concentrations of TN and TP in Taihu Lake were higher than that of the other two lakes. The TP concentration was increased by 17.3% over 7 years, while the TN concentration remained almost stable. The variation in TN in Taihu Lake was the same as the growth cycle of algae, with higher value in spring and winter and lower value in summer, while the concentration of TP was lower in spring and winter and higher in summer. The spatial distribution of TN and TP concentrations in the three major lakes was significantly affected by human activities, and the concentrations of TN and TP were higher in areas near cities and agricultural activities.

Temporal Changes in the MITC Gas Concentration and Mortality of the Pine Sawyer Beetle (<i>Monochamus alternatus</i>) Following Fumigation Treatment of Pine Logs Using the Top Covering and Complete Wrapping Methods

Temporal Changes in the MITC Gas Concentration and Mortality of the Pine Sawyer Beetle (<i>Monochamus alternatus</i>) Following Fumigation Treatment of Pine Logs Using the Top Covering and Complete Wrapping Methods

Proposal of an Effective Indicator of CO2 Concentration in Seawater

Since CO2 is easily soluble in water, when the concentration of CO2 in the atmosphere rises, that in seawater also rises. This causes the surface ocean acidification, which may alter the chemical and biological activities in the surface ocean. Therefore, it is important to know the temporal and spatial changes in CO2 concentration in the surface ocean. However, seawater CO2 concentration has large regional and seasonal variations mainly because of biological activities. In this study, we proposed an effective measure of the seawater CO2 concentration from the relationship between [DIC + kDO] and water temperature. A strong linear correlation was found for this relationship using seawater data off Tomakomai and in Osaka Bay, Japan. Furthermore, we confirmed that correction with salinity improves this correlation, because salinity is known to have a good correlation with alkalinity, which directly affects DIC. It is expected that this measure can also be applicable to judge the possibility of unexpected leakage of CO2 stored in the sub-seabed geological formation.

Spatial trends and temporal declines in tissue metals/metalloids in the context of wild fish health at the St. Clair River Area of Concern

The St. Clair River, which flows from Lake Huron to Lake St Clair, receives discharges and emissions from numerous petroleum refineries, petrochemical facilities, and other sources. We used a multi-factor ANOVA to test for spatial and temporal changes in concentrations of trace metals/metalloids in homogenates of fish from Lake Huron (reference site) and two river sites - an industrialized region (Stag Island) and downstream Walpole Island/Chenal Écarte. In 2002/2003 and in 2014, we sampled 20 adult fish of each sex of the following species: shorthead redhorse (Moxostoma macrolepidotum), yellow perch (Perca flavescens); we added emerald shiner (Notropis atherinoides; unsexed) in 2014. There was a temporal decline of most metals/metalloids in shorthead redhorse at the river sites. Linear Discriminant Analysis separated the 2014 shorthead redhorse by site. Emerald shiners had higher concentrations of metals/metalloids, apart from mercury, than the other species; those concentrations were highest at Chenal Écarte, which warrants further research. Tissue concentrations of mercury, which declined temporally at Stag Island and Walpole Island, were above the protective guidance for wildlife consumers at all sites, but were lower than predicted to affect fish health. Apart from increased liver size (ANCOVA) in shorthead redhorse at Walpole Island (2014), the health variables in the riverine fish were stable or differed slightly from reference, which indicated good health and reproductive potential. In shorthead redhorse, tissue metals correlated inconsistently with health indices. Further research could ascertain if temporal declines in metals/metalloids in riverine SHRH are benefits of remediation actions or fluctuations with other causes.

Monitoring the volatile language of fungi using gas chromatography-ion mobility spectrometry

Fusarium oxysporum is a plant pathogenic fungus leading to severe crop losses in agriculture every year. A sustainable way of combating this pathogen is the application of mycoparasites—fungi parasitizing other fungi. The filamentous fungus Trichoderma atroviride is such a mycoparasite that is able to antagonize phytopathogenic fungi. It is therefore frequently applied as a biological pest control agent in agriculture. Given that volatile metabolites play a crucial role in organismic interactions, the major aim of this study was to establish a method for on-line analysis of headspace microbial volatile organic compounds (MVOCs) during cultivation of different fungi. An ion mobility spectrometer with gas chromatographic pre-separation (GC-IMS) enables almost real-time information of volatile emissions with good selectivity. Here we illustrate the successful use of GC-IMS for monitoring the time- and light-dependent release of MVOCs by F. oxysporum and T. atroviride during axenic and co-cultivation. More than 50 spectral peaks were detected, which could be assigned to 14 volatile compounds with the help of parallel gas chromatography-mass spectrometric (GC-MS) measurements. The majority of identified compounds are alcohols, such as ethanol, 1-propanol, 2-methyl propanol, 2-methyl butanol, 3-methyl-1-butanol and 1-octen-3-ol. In addition to four ketones, namely acetone, 2-pentanone, 2-heptanone, 3-octanone, and 2-octanone; two esters, ethyl acetate and 1-butanol-3-methylacetate; and one aldehyde, 3-methyl butanal, showed characteristic profiles during cultivation depending on axenic or co-cultivation, exposure to light, and fungal species. Interestingly, 2-octanone was produced only in co-cultures of F. oxysporum and T. atroviride, but it was not detected in the headspace of their axenic cultures. The concentrations of the measured volatiles were predominantly in the low ppbv range; however, values above 100 ppbv were detected for several alcohols, including ethanol, 2-methylpropanol, 2-methyl butanol, 1- and 3-methyl butanol, and for the ketone 2-heptanone, depending on the cultivation conditions. Our results highlight that GC-IMS analysis can be used as a valuable analytical tool for identifying specific metabolite patterns for chemotaxonomic and metabolomic applications in near-to-real time and hence easily monitor temporal changes in volatile concentrations that take place in minutes.

Early post-fire changes in properties of Andosols within a Mediterranean area

The increasing frequency and extent of forest fires cause severe temporal effects on soil properties, which knowledge about is controversial or lacking. So, the research aimed to evaluate changes in Mediterranean Andosol properties (pH, water and organic matter contents, C and N concentrations) and total and available Ca, Cu, Fe, K, Mg, Na, Ni and Pb concentrations 1 and 2 years after fire occurrence, comparing them to the pre-fire ones. The results underline that, in the investigated Mediterranean Andosols, fire caused significant decrease in water and organic matter contents, C, Fe and Mg total concentrations as well as significant increase in pH, total Ca, K, Fe, Na concentrations and available Cu and Pb fractions. After fire, temporal changes of soil element concentrations occurred at different speeds, as Ca, Cu, Fe, Mg and Ni total concentrations changed already 1 year after fire occurrence; whereas, K and Na total concentrations changed only after two years. Finally, 2 years after fire none of the investigated soil properties reached the pre-fire values, suggesting a whole worsening of soil conditions. The early responses of soils to fire are useful to predict the evolution of the system, the relationships between below and above ground and to provide useful tools for management practices.

Carbon Fluxes and Microbial Activities From Boreal Peatlands Experiencing Permafrost Thaw

AbstractPermafrost thaw in northern ecosystems may cause large quantities of carbon (C) to move from soil to atmospheric pools. Because soil microbial communities play a critical role in regulating C fluxes from soils, we examined microbial activity and greenhouse gas production soon after permafrost thaw and ground collapse (into collapse‐scar bogs), relative to the permafrost plateau or older thaw features. Using multiple field and laboratory‐based assays at a field site in interior Alaska, we show that the youngest collapse‐scar bog had the highest CH4 production potential from soil incubations, and, based upon temporal changes in porewater concentrations and 13C‐CH4 and 13C‐CO2, had greater summer in situ rates of respiration, methanogenesis, and surface CH4 oxidation. These patterns could be explained by greater C and N availability in the young bog, while alternative terminal electron accepting processes did not play a significant role. Field diffusive CH4 fluxes from the young bog were 4.1 times greater in the shoulder season and 1.7–7.2 times greater in winter relative to older bogs, but not during summer. Greater relative CH4 flux rates in the shoulder season and winter could be due to reduced CH4 oxidation relative to summer, magnifying the importance of differences in production. Both the permafrost plateau and collapse‐scar bogs were sources of C to the atmosphere due in large part to winter C fluxes. In collapse scar bogs, winter is a critical period when differences in thermokarst age translates to differences in surface fluxes.

Geochemical baseline of trace and major elements in sediments in the Rio de Ondas Basin (Bahia, Brazil)

Sediments provide essential information about geochemical processes occurring in aquatic systems and are useful to monitor temporal changes in metals concentrations. In this work, we conducted a geochemical survey in the Rio de Ondas basin, situated in the inland cerrado area from the northeast Brazilian region, to establish environmental reference values to identify metal origins related to anthropogenic and natural sources. Also, we evaluated the temporal dynamics of soil to assess the anthropic pressure over the soil surface and its potential effects on geochemical compositions of sediments. To this end, we combined geochemical and Geographic Information System (GIS) information, including remote sensing imagery, X-ray diffraction analysis, and geochemical analytical tools. We applied multivariate statistical analysis, determination of Geoaccumulation Index (Igeo), and enrichment factors (EF) to interpret the dataset. The results showed that 47.35% of the Brazilian cerrado in this zone was suppressed due to agricultural activity expansion. Mineralogy analysis indicated the presence of quartz silicates, varying from 65.1% (w/w) to 86% (w/w). Overall, the sediments showed low metal contamination levels and moderate levels near urban centers, probably due to domestic sewage discharge. It was also observed in very similar proportions of mineral constituents, obtaining environmental reference data and their associations with the region's geological formation. Thereby, sediment geochemical compositions probably reflect weathering processes, which may accelerate due to landscape modifications induced by economic activities, notably agriculture.

Calcium Imaging of Neuronal Activity under Gradually Changing Odor Stimulation in Caenorhabditis elegans.

Olfactory behavior is among the most fundamental animal behaviors both in the wild and in the laboratory. To elucidate the neural mechanisms underlying olfactory behavior, it is critical to measure neural responses to odorant concentration changes resembling those that animals actually sense during olfactory behavior. However, reproducing the dynamically changing olfactory stimuli to an animal during such measurements of neural activity is technically challenging. Here, we describe technical details and protocols for odor stimulation during calcium imaging of the sensory neurons of the nematode Caenorhabditis elegans. In this system, the neuronal activity of C. elegans is measured using ratiometric calcium imaging during exposure to quantitatively controlled olfactory stimuli over time. Temporal changes in odor concentrations around the animal are precisely controlled according to a predesigned temporal odor gradient to reproduce a realistic odor concentration change during olfactory behavior in a behavioral arena. By monitoring neural activity in response to the realistic olfactory stimulus, it is possible to elucidate the mechanisms by which olfactory input is processed by neural activities and reflected in behavioral output.

Temporal changes in soil oxygen concentration and redox potential under different soil water conditions in barley cultivation of rice-barley double-cropped paddy fields

Temporal changes in soil oxygen concentration and redox potential under different soil water conditions in barley cultivation of rice-barley double-cropped paddy fields

Spatial and Temporal Changes in the Concentration of Nutrients in Urban Water Body (on the Example of Lake Verbne, Kyiv)

Spatial and Temporal Changes in the Concentration of Nutrients in Urban Water Body (on the Example of Lake Verbne, Kyiv)

A comprehensive assessment of multi-system responses to a renal inoculation of uropathogenic E. coli in swine.

The systemic responses to infection and its progression to sepsis remains poorly understood. Progress in the field has been stifled by the shortcomings of experimental models which include poor replication of the human condition. To address these challenges, we developed and piloted a novel large animal model of severe infection that is capable of generating multi-system clinically relevant data. Male swine (n = 5) were anesthetized, mechanically ventilated, and surgically instrumented for continuous hemodynamic monitoring and serial blood sampling. Animals were inoculated with uropathogenic E. coli by direct injection into the renal parenchyma and were maintained until a priori endpoints were met. The natural history of the infection was studied. Animals were not resuscitated. Multi-system data were collected hourly to 6 hours; all animals were euthanized at predetermined physiologic endpoints. Core body temperature progressively increased from mean (SD) 37.9(0.8)°C at baseline to 43.0(1.2)°C at experiment termination (p = 0.006). Mean arterial pressure did not begin to decline until 6h post inoculation, dropping from 86(9) mmHg at baseline to 28(5) mmHg (p = 0.005) at termination. Blood glucose progressively declined but lactate levels did not elevate until the last hours of the experiment. There were also temporal changes in whole blood concentrations of a number of metabolites including increases in the catecholamine precursors, tyrosine (p = 0.005) and phenylalanine (p = 0.005). Lung, liver, and kidney function parameters worsened as infection progressed and at study termination there was histopathological evidence of injury in these end-organs. We demonstrate a versatile, multi-system, longitudinal, swine model of infection that could be used to further our understanding of the mechanisms that underlie infection-induced multi-organ dysfunction and failure, optimize resuscitation protocols and test therapeutic interventions. Such a model could improve translation of findings from the bench to the bedside, circumventing a significant obstacle in sepsis research.

Dual-target gas-phase biosensor (bio-sniffer) for assessment of lipid metabolism from breath acetone and isopropanol

Volatile organic compounds (VOCs) in breath and skin gas are promising samples for non-invasive and simple disease screening and metabolism assessment. In addition, simultaneous measurement of multiple VOCs helps to improve the examination quality and allows for more reliable disease screening and investigation of detailed metabolic pathways. In this study, we have developed a dual-target gas-phase biosensor (bio-sniffer) that allows for measurement of isopropanol (IPA) and acetone vapours, relevant VOCs for lipid metabolisms, by simply exchanging coenzyme solutions. The measurement exploited a reversible redox reaction that was catalysed by secondary alcohol dehydrogenase (S-ADH). IPA/acetone was oxidised/reduced together with reduction/oxidation of a coenzyme, oxidised (NAD+)/reduced (NADH) form of β-nicotinamide adenine dinucleotide, depending on surrounding pH (8.5/7.5). This reaction resulted in producing/consuming NADH which exhibited autofluorescence (λex = 340 nm, λfl = 490 nm), by which IPA/acetone was measured. The characterization of the dual-target bio-sniffer showed the dynamic ranges for IPA and acetone vapour were 3.3–1000 ppb and 13.0–3000 ppb, respectively, which encompasses those in the breath of healthy people (IPA, 10–30 ppb; acetone, 200–900 ppb). Finally, the dual-target bio-sniffer was applied for measurement of IPA and acetone in the breath of healthy people. As with the standard IPA and acetone vapour, intermittent and repeated measurement of both VOCs in the breath was demonstrated. These results indicated that the dual-target bio-sniffer would be a useful tool to assess the lipid metabolism in detail by measuring temporal changes of IPA and acetone concentrations in the breath.

Colonialism and the environment: The pollution legacy of the Southern Hemisphere’s largest copper mine in the 20th century

Mining has been a major contributor to economic development in Australia since British arrival in the late 1700s, with little to no thought regarding the long-term environmental consequences. This study assesses the metal pollution legacy caused by different smelting methods and mining activities during the British colonialism in western Tasmania. This region was the largest copper producer in the Southern Hemisphere during the 20th century. Lake sediments from Basin Lake and Owen Tarn, 12 and 5 km from Queenstown’s mines, respectively, were used to reconstruct historical metal contamination. Temporal changes in metal concentrations (iron, copper, arsenic, selenium and lead) were assessed in relation to the scale of mining activities and the technologies used. Sedimentation rates and metal influxes increased from 1900, reflecting the beginning of copper mining in Mount Lyell. Observed metal concentrations peaked after 1930, coinciding with the introduction of large-scale open-cut operations and an expansion of the mining machinery used. All elements underwent at least minor enrichment (EF 1-3) during the lifespan of the mine, with lead and copper undergoing extremely severe enrichment (EF > 50). Although smelters contributed to metal increases in the lakes, large open-cut large operations in the 1930s contributed most to metal contamination. Local metal deposition from mining-related activities decreased significantly once operations decreased, with selenium and arsenic decreasing nearly to background levels within 50 years. Lead and copper, the elements which underwent major enrichment, have not yet reached background values. The ecological consequences include the current degraded local landscape, poor water quality and disrupted local biota. Knowledge about the environmental impacts of mining in western Tasmania is less known compared to other sites around the world with a similar history. Our results demonstrate the urgent need to develop better policies and remediation programs that can mitigate the consequences of metal pollution from abandoned mines in Australia.

Distributions and temporal changes of benzene, toluene, ethylbenzene, and xylene concentrations in newly decorated rooms in southeastern China, and the health risks posed

Air samples were collected from 227 newly decorated rooms in southeastern China, between November 2014 and July 2017. Benzene, toluene, ethylbenzene, and xylene (BTEX) concentrations in the samples were determined. Temporal changes in the BTEX concentrations during decorating were investigated. Cancer and non-cancer risks posed by BTEX were evaluated. The mean BTEX concentrations decreased in the order xylene (0.476 ± 0.665 mg/m3) > benzene (0.327 ± 0.189 mg/m3) > toluene (0.325 ± 0.449 mg/m3) > ethylbenzene (0.140 ± 0.280 mg/m3). Benzene, toluene, and xylene concentrations in 86.7%, 42.7%, and 51.5%, respectively, exceeded Chinese regulatory standards. The BTEX concentrations positively correlated with temperature and humidity but negatively correlated with air pressure, and the highest concentrations were found in summer. The BTEX concentrations were higher in conference rooms and residences than classrooms and halls. The highest BTEX concentrations were found during painting and carpentry. The hazard quotient limit of 1 and the cancer risk limit of 1 × 10−6 were exceeded in 91.2% and 85.0%, respectively, of the rooms, and benzene and xylene were the dominant contributors. The results suggested that newly decorated rooms should not be used too soon after decoration is completed.

Ultrasound-guided aspiration of dominant follicles (≥25 mm) followed by luteinization and progesterone production during the estrous cycle in mares

The present study was designed to evaluate luteinization rates subsequent to aspiration of dominant follicles (≥25 mm) in the absence of a functional CL (progesterone <1 ng/mL) and characterize the temporal changes in plasma concentrations of progesterone following aspiration-induced luteinization during the estrous cycle in mares. A total of 29 estrous cycles involving 15 mares in a cross-over design were randomly assigned to five groups: 1) ASP-F≥25 mm (n = 6; follicle aspiration 25–29 mm), 2) ASP-F≥30 mm (n = 6; follicle aspiration 30–34 mm), 3) ASP-F≥35 mm (n = 6; follicle aspiration 35–40 mm), 4) ASP-F≥40 (n = 6; follicle aspiration ≥40), and 5) Control (n = 5; spontaneous ovulation or no follicle aspiration). Subsequent to ovulation (Day 0), PGF was administered to all groups on Day 5, blood samples were collected daily and aspiration of the dominant follicle was done using ultrasound-guided transvaginal follicle needle puncture. Among the follicle aspirations groups 25–29, 30–34, 35–39, and ≥40 mm, the luteinization rates were not different (P > 0.05) at 83, 67, 83, and 100%, respectively. Correspondingly, progesterone concentrations increased (>2 ng/mL) by approximately 6, 7, 5, and 4 d after aspiration, respectively, which were delayed (P < 0.05) in the 25–29 and 30–34 mm follicle aspiration groups compared to 2 d after ovulation in the control group. Thereafter, progesterone reached maximal concentrations (10–11 ng/mL) as averaged over all aspiration groups but were lower (P < 0.05) compared to the mean maximal concentration (18 ng/mL) in the control group. Subsequently, there was a decrease in progesterone concentrations (<2 ng/mL) in response to luteolysis, which was delayed (P < 0.05) in the aspiration groups over Days 16–20 compared to Day 15 in the control group. Despite this discrepancy, the mean length of the interovulatory intervals were not different (P > 0.05) among groups on Day 23. Thus, the present study provided novel information that the luteinization rate is relatively high (83%) and consistent following aspiration of dominant follicles (≥25 mm) in the absence of a functional CL and that the increase in progesterone reaches sustainable progestational concentrations (≥2 ng/mL) in accord with the length of the estrous cycle that may potentially support development and maintenance of early pregnancy in recipient mares involved in an embryo transfer program.

Health risk assessment for multimedia exposure of formaldehyde emitted by chemical accident.

This study was conducted to provide basic data for chemical accident response by assessing the health risks of residents living near a chemical accident site due to long-term exposure. The study considered the temporal concentration changes of the leaked chemical (i.e., its behavior in the environment and dilution) until its extinction. A virtual chemical accident was assumed, in which 40 t of formaldehyde was accidentally discharged for 1 h in Ulsan Metropolitan City, Korea. Formaldehyde concentrations over time in each environmental medium after the accident were calculated using a multimedia environmental dynamics model. Exposure subjects divided into four age groups were considered. Carcinogenic risks due to respiration and non-carcinogenic risks due to soil intake were assessed. For all the age groups, the excess cancer risk did not exceed 1.0 × 10-6, indicating that no harmful health impact was caused by inhalation exposure to formaldehyde. The hazard index exceeded 1 for all the age groups, confirming that harmful health impacts were caused by exposure to soil containing the formaldehyde. This study is the first to assess chronic health risks by reflecting long-term residual and temporal concentration changes of a pollutant released in a chemical accident in each environmental medium until its extinction. This work is also significant in that it reflects the exposure characteristics of the toxic chemical.