Temporal Variations In Concentrations Research Articles

Mathematical Modeling of Oxygen Diffusion from Capillary to Tissues during Hypoxia through Multiple Points Using Fractional Balance Equations with Memory.

The diffusion of oxygen through capillary to surrounding tissues through multiple points along the length has been addressed in many clinical studies, largely motivated by disorders including hypoxia. However relatively few analytical or numerical studies have been communicated. In this paper, as a compliment to physiological investigations, a novel mathematical model is developed which incorporates the multiple point diffusion of oxygen from different locations in the capillary to tissues, in the form of a fractional dynamical system of equations using the concept of system of balance equations with memory. Stability analysis of the model has been conducted using the well known Routh-Hurwitz stability criterion. Comprehensive analytical solutions for the differntial equation problem in the new proposed model are obtained using Henkel transformations. Both spatial and temporal variation of concentration of oxygen is visualized graphically for different control parameters. Close correlation with simpler models is achieved. Diffusion is shown to arise from different points of the capillary in decreasing order along the length of the capillary i.e. for the different values of z. The concentration magnitudes at low capillary length far exceed those further along the capillary. Furthermore with progrssive distance along the capillary, the radial distance of diffusion decreases, such that oxygen diffuses only effectively in very close proximity to tissues. The simulations provide a useful benchmark for more generalized mass diffusion computations with commercial finite element and finite volume software including ANSYS FLUENT.

Calcium Signaling and the Response to Heat Shock in Crop Plants.

Climate change and the increasing frequency of high temperature (HT) events are significant threats to global crop yields. To address this, a comprehensive understanding of how plants respond to heat shock (HS) is essential. Signaling pathways involving calcium (Ca2+), a versatile second messenger in plants, encode information through temporal and spatial variations in ion concentration. Ca2+ is detected by Ca2+-sensing effectors, including channels and binding proteins, which trigger specific cellular responses. At elevated temperatures, the cytosolic concentration of Ca2+ in plant cells increases rapidly, making Ca2+ signals the earliest response to HS. In this review, we discuss the crucial role of Ca2+ signaling in raising plant thermotolerance, and we explore its multifaceted contributions to various aspects of the plant HS response (HSR).

Variation in urban snow quality indicated by three seasonal sampling surveys conducted in Luleå (Sweden) within a span of 27 years

Concentrations of total suspended solids (TSS), trace metals (Cu, Cd, Cr, Zn, Cd, Pb), Na and 16 US EPA priority PAHs in urban snow were studied in the City of Luleå in Northern Sweden. Snow was sampled at six central urban and suburban sites with various traffic intensities, in three sampling surveys (1994–95, 2002–03, 2020–21), repeated for three ages of the urban snow cover of 40, 80, and 120 days, respectively. The older data, from the 1994–95 and 2002–03 surveys, were obtained from the existing literature. The concentrations and mass loads of TSS and most trace metals studied (Zn, Cu, Pb, and Cd) varied with time. TSS, Zn, and Cu showed slightly higher concentrations and mass loads in the 2003 (TSS avg = 2300 μg/L, Zn avg = 620 μg/L and Cu avg = 250 μg/L) and 2021 (TSS avg = 1500 μg/L, Zn avg = 530 μg/L and Cu avg = 220 μg/L) sampling surveys, compared to the 1995 survey (TSS avg = 620 μg/L, Zn avg = 240 μg/L and Cu avg = 97 μg/L). However, no evident trend was observed between the 2003 and 2021 sampling surveys. The highest concentrations of Pb and Cd were observed in snow samples from the 1994–95 sampling survey (Pb max = 570 μg/L, Cd max = 4.6 μg/L). Results indicated higher concentrations of the pollutants studied in the city centre, compared to the residential suburbs, and in areas with heavier traffic, where concentrations of metals correlated well with traffic intensity. Fractionation analysis of trace metals indicated that Zn, Cu and Pb occurred mostly in the particulate-bound phase (>0.45 μm) containing the most of Zn, Cu, and Pb mass, at 80, 84 and 94% of the total, respectively. Over 50% of the dissolved phase of Zn and Cu was in the truly dissolved fraction (<3000 MWCO). Concentrations of PAHs also increased with traffic intensity, with pyrene being the most frequently detected PAH, likely because of the strength of sources and various physical processes influencing the snowbanks development and causing spatial and temporal variations in pollutant concentrations.

Connecting thiamine availability to the microbial community composition in Chinook salmon spawning habitats of the Sacramento River basin.

Thiamine deficiency complex (TDC) is a major emerging threat to global populations of culturally and economically important populations of salmonids. Salmonid eggs and embryos can assimilate exogenous thiamine, and evidence suggests that microbial communities in benthic environments can produce substantial amounts of thiamine. We therefore hypothesize that natural dissolved pools of thiamine exist in the surface water and hyporheic zones of riverine habitats where salmonids with TDC migrate, spawn, and begin their lives. To examine the relationship between dissolved thiamine-related compounds (dTRCs) and their microbial source, we determined the concentrations of these metabolites and the compositions of microbial communities in surface and hyporheic waters of the Sacramento River, California and its tributaries. Here we determine that all dTRCs are present in femto-picomolar concentrations in a range of critically important salmon spawning habitats. We observed that thiamine concentrations in the Sacramento River system are orders of magnitude lower than those of marine waters, indicating substantial differences in thiamine cycling between these two environments. Our data suggest that the hyporheic zone is likely the source of thiamine to the overlying surface water. Temporal variations in dTRC concentrations were observed where the highest concentrations existed when Chinook salmon were actively spawning. Significant correlations were seen between the richness of microbial taxa and dTRC concentrations, particularly in the hyporheic zone, which would influence the conditions where embryonic salmon incubate. Together, these results indicate a connection between microbial communities in freshwater habitats and the availability of thiamine to spawning TDC-impacted California Central Valley Chinook salmon.IMPORTANCEPacific salmon are keystone species with considerable economic importance and immeasurable cultural significance to Pacific Northwest indigenous peoples. Thiamine deficiency complex has recently been diagnosed as an emerging threat to the health and stability of multiple populations of salmonids ranging from California to Alaska. Microbial biosynthesis is the major source of thiamine in marine and aquatic environments. Despite this importance, the concentrations of thiamine and the identities of the microbial communities that cycle it are largely unknown. Here we investigate microbial communities and their relationship to thiamine in Chinook salmon spawning habitats in California's Sacramento River system to gain an understanding of how thiamine availability impacts salmonids suffering from thiamine deficiency complex.

Steep declines in radioactive caesium after 30 years of monitoring alpine plants in mountain areas of central Norway

The Chernobyl accident exposed large areas of northern Europe to radiocaesium (137Cs). We investigated temporal and spatial variation in concentrations of radiocaesium among five functional groups of alpine plants at two mountain areas in central Norway over a 31-year period from 1991 to 2022. Average concentrations of radiocaesium were initially high in lichens and bryophytes at around 4600–6400 Bq/kg dry weight during 1991–1994 but then decreased dramatically over three decades to current concentrations of <200 Bq/kg for all plant groups in 2019–2022. The effective half-life of radiocaesium was estimated to be 4–6 years in lichens and mosses, 7–13 years in herbaceous plants, and 22–30 years in woody plants, which were less than the physical half-life of 30.2 years. Concentrations of radiocaesium were greater at the nutrient-poor site than at the nutrient-rich site, probably due to greater deposition levels at higher elevations and the geographical pattern of the deposition. Functional groups of plants differed with higher concentrations among non-vascular than vascular plants. Common heather Calluna vulgaris was unusual among woody plants with high concentration of radiocaesium, especially in the new shoots. Our new estimates of concentrations and dynamics of radiocaesium for alpine plants in natural environments will be useful for modelling herbivore exposure and evaluating potential impacts on wildlife and human health.

Chlorine Decay Simulation in Real Water Distribution System Using Epanet Program

Abstract Deterioration of treated drinking water intended for consumption during distribution may be due to physical, chemical or microbiological changes that occur in the water. In addition, the type of pipe material and disintegration of a disinfectant agent can affect the quality of the water supplied. Therefore, the research approach is to simulate the decay residual Cl2 through potable water distribution networks produced by a desalination plant of Oran city in western Algeria. EPANET 2.0 software was used for estimating and predicting Cl2 concentration at different water network points. The value of bulk flow decay coefficient (Kb) is set to −1,99 day−1 for a 50-year-old steel pipe, value for the wall decay coefficient (Kw) was determined using a trial-and-error procedure and assumed to be −1,2 day−1. An efficient model with an extended simulations period of 72 h can plot spatial and temporal variations of residual Cl2 concentrations at all links and nodes. Cl2 is injected at the El Mactaa desalination plant, with a concentration of 0.6 mg/l permanently. As well, it was observed that 51.33% of the Cl2 loss is due to pipe wall reaction, while 42.34 and 6.33% represent the bulk and tank reactions respectively. The results show that the range of residual Cl2 (0.11-0,45 mg/l) and most of the measured values are less than are below the minimum authorized threshold (0.2 – 0.5 mg/l) WHO standard. Therefore, it is recommended to rehabilitate the old water transfer pipes and re-chlorination stations were necessary to add into network. Statistical analysis shows that the calculated results correspond well to the observed data. EPANET can follow the Cl2 concentration in the drinking water network produced by El Mactaa desalination plant. It is a research tool to improve our understanding of water movement in the distribution system.

Positive Effect Observed on Reducing Criteria Pollutant Emissions Provided by Provisional Local Regulations during the 2022 Winter Olympics

This study examined the impact of temporary air quality control measures on reducing pollutants during the 2022 Winter Olympics in China, utilizing real-time monitoring data from 2017 and 2022 to assess spatial and temporal variations in critical air pollutant concentrations. The results showed that concentrations of PM2.5, PM10, CO, SO2, and NO2 in the Beijing–Tianjin–Hebei region during the Olympic Games showed a marked decrease compared to the historical period, with reductions of 36.59%, 20.35%, 33.95%, 28.90%, and 22.70%, respectively. Significant north–south spatial differences were observed in Beijing, Tianjin, and Hebei Province during the Olympic period. The cities of Zhangjiakou, Chengde, Qinhuangdao, Beijing, and Tangshan showed the most significant pollution reduction. Based on assessments conducted during the Olympic period, it was noted that more than 95% of the daily average concentrations of pollutants are below the maximum values set by the World Health Organization for the interim target. Our research shows that provisional regulations effectively control the emission of air pollutants, providing a solid reference and basis for ensuring air quality during major international events.

Significant inter-annual fluctuation in CO2 and CH4 diffusive fluxes from subtropical aquaculture ponds: Implications for climate change and carbon emission evaluations

Aquaculture ponds are potential hotspots for carbon cycling and emission of greenhouse gases (GHGs) like CO2 and CH4, but they are often poorly assessed in the global GHG budget. This study determined the temporal variations of CO2 and CH4 concentrations and diffusive fluxes and their environmental drivers in coastal aquaculture ponds in southeastern China over a five-year period (2017–2021). The findings indicated that CH4 flux from aquaculture ponds fluctuated markedly year-to-year, and CO2 flux varied between positive and negative between years. The coefficient of inter-annual variation of CO2 and CH4 diffusive fluxes was 168% and 127%, respectively, highlighting the importance of long-term observations to improve GHG assessment from aquaculture ponds. In addition to chlorophyll-a and dissolved oxygen as the common environmental drivers, CO2 was further regulated by total dissolved phosphorus and CH4 by dissolved organic carbon. Feed conversion ratio correlated positively with both CO2 and CH4 concentrations and fluxes, showing that unconsumed feeds fueled microbial GHG production. A linear regression based on binned (averaged) monthly CO2 diffusive flux data, calculated from CO2 concentrations, can be used to estimate CH4 diffusive flux with a fair degree of confidence (r2 = 0.66; p < 0.001). This algorithm provides a simple and practical way to assess the total carbon diffusive flux from aquaculture ponds. Overall, this study provides new insights into mitigating the carbon footprint of aquaculture production and assessing the impact of aquaculture ponds on the regional and global scales.

Trace elements in PM2.5aerosols in East Asian outflow in the spring of 2018: emission, transport, and source apportionment

Abstract. Trace metals in aerosol particles impact Earth's radiative budget, human health, and ocean biogeochemistry. Semi-continuous measurements of the elemental composition of fine-mode (PM2.5) aerosols were conducted using an automated X-ray fluorescence analyzer on a remote island of Japan during the spring of 2018. Temporal variations in mass concentrations of geochemically important elements for this period, such as Pb, Cu, Si, Fe, and Mn, and their relationships with the emission tracers, carbon monoxide (CO) and black carbon (BC), were reported. The Integrated Massively Parallel Atmospheric Chemical Transport (IMPACT) model was used to evaluate the source apportionment of these components and was evaluated in terms of emissions and wet removal processes. Pb and Cu originated mainly from anthropogenic sources (98 % and 93 % on average, respectively) over the East Asian continent. Positive correlations of Pb and Cu with BC and CO and the similarity of their concentration-weighted trajectories indicated that the emission sources of these metals share the region where the large CO (and BC) emission sources are located and that CO can be regarded as a tracer of continental anthropogenic emissions. The air masses with minimized impacts of the wet removal during transport were extracted to elucidate the “top-down” emission ratio of Pb and Cu to CO, which were, for the first time, evaluated as 152.7 and 63.1 µg g−1, respectively, during the spring of 2018 in the East Asian outflow. The analysis of the tagged tracer simulations by the IMPACT model confirmed that BC and Si could be used as tracers for anthropogenic and dust emissions, respectively, during the observation period. The source apportionment of Fe and Mn in PM2.5 aerosols was conducted using Si and BC tracers, which revealed that the anthropogenic contribution was 17 % and 44 % on average, respectively. Based on the air mass origins of Fe and Mn, their anthropogenic fraction varied from 2 % to 29 % and 9 % to 68 %, respectively, during the high-PM2.5-concentration periods. However, despite the non-dominant anthropogenic contributions of Fe, they could adversely affect human health and ocean biogeochemistry, owing to their higher water solubility. The modeled BC, Pb, Cu, and Fe were evaluated by separately diagnosing their emission and transport. Ratios of modeled to observed concentrations for these components were analyzed in terms of the accumulated precipitation along the transport from the East Asian continent. The current model simulations were found to overestimate the emissions (based on the Community Emissions Data System, CEDS v2021-02-05) of BC by 44 % and underestimate Cu by 45 %, anthropogenic Fe by 28 % in East Asia, and the wet deposition rates for BC and Pb. Overall, Cu in East Asia exhibited a different nature from BC and Pb in terms of emission sources and wet removal.

Assessment of toxic trace elements (Cd, Pb, As, and Co) in small, medium, and large individuals of Mytilus galloprovincialis and Perna perna mussel species along the Algerian coast.

This research paper focused on the monitoring of marine sites using mussels, which are highly valuable organisms in assessing environmental health. However, a significant challenge arises when determining the appropriate size of mussels for monitoring purposes. The objective of this study was to examine the levels of Cd, Pb, As, and Co in three different size classes of two mussel species, Mytilus galloprovincialis and Perna perna, collected from three sites along the Algerian coast, each exhibiting varying degrees of pollution.At each of the study sites, a total of thirty individuals from small, medium, and large size classes of mussels were collected during four different time periods. The mussels were then dissected, and the concentrations of Cd, Pb, As, and Co were measured in the entire flesh of the mussels using ICP-MS.Across the various study sites, the concentrations of cadmium, lead, arsenic, and cobalt ranged from 0.06 to 1.32mg/kg, 0.09 to 12.56mg/kg, 4.23 to 18.31mg/kg, and 0.11 to 1.85mg/kg, respectively. Interestingly, the distribution of these metals in the three different size classes of mussels followed a consistent pattern at all the study sites. Large mussels exhibited higher concentrations, while small and medium-sized mussels displayed lower levels. These findings highlight substantial spatial and temporal variations in metal concentrations within the studied sites.

Characterization of naturally occurring radioactive material dynamics in community water systems using groundwater from Ganghwa Island, Republic of Korea

Understanding the temporal behaviors of naturally occurring radioactive materials is important for the maintenance of community water supply systems for drinking groundwater on islands and in mountainous areas. Intensive field sampling in the Republic of Korea to characterize temporal variation in 238U concentration and 222Rn activity was performed for three community water systems on Ganghwa Island for ten years (2012–2022). 222Rn, a dissolved gas in groundwater, tended to decrease in activity as water moved from the source through community water systems, but no such trend was observed in 238U concentration. 238U and 222Rn behaviors in time series data for different CWSs reflected different geochemical processes and were differently classified accordingly. In particular, the 238U and 222Rn at points GJ and YH shows the signature of weathering: accompaniment by variation in pH and dissolved oxygen. In other time series, the 238U and 222Rn behavior shows the signature of cation exchange by seawater intrusion: accompaniment by dramatic variation in electrical conductivity. Random forest regression models developed to estimate the 238U concentration and 222Rn activity in groundwater boreholes exhibited reasonable threshold classification accuracy. The optimized threshold structure for 238U concentration and 222Rn activity variation with respect to the water quality variable of greatest statistical importance in each community water system random forest regression model corresponded to the geochemical process controlling the behavior of 238U and 222Rn in that groundwater borehole. Therefore, more intensive field sampling, covering the full data range that could emerge at each groundwater borehole, can aid in enhancing the accuracy of estimation of 238U concentration and 222Rn activity. Furthermore, the use of an in situ groundwater monitoring system in a random forest regression model facilitates the effective management of community water systems in the face of risk posed by naturally occurring radioactive materials.

Spatial and Temporal Variations in PM1 Concentration and its Correlation with AOD in China from 2014 to 2017

Based on the PM1 mass concentration data from all the air quality monitoring stations in China from 2014 to 2017, the temporal and spatial distribution characteristics of PM1 concentration were studied using the time series statistical and spatial hierarchical clustering methods, and the PM1 spatiotemporal evolution characteristics were revealed. Combined with AOD data of the MODIS remote-sensing satellite, the temporal and spatial variation in PM1-AOD correlation was analyzed on a fine scale. The results showed that, from 2014 to 2017, the annual average PM1 concentration in China decreased yearly, the seasonal PM1 concentration showed the characteristics of "high in winter and low in summer," and the monthly average PM1 concentration showed a "U"-shaped variation. An "M"-shaped PM1 variation pattern was presented before and after the holidays. Weekly variation showed that high PM1 values occurred on Mondays and Fridays, and low ones occurred on Sundays. Based on the spatial clustering method, the national average annual PM1 concentration in China was divided into seven categories, and the overall spatial distribution pattern was "high in the east and low in the west and high in the north and low in the south." The highest and the lowest values of average PM1 concentration occurred in central China(54.59 μg·m-3) and in Xinjiang-Qinghai-Xizang(11.37 μg·m-3), respectively. The PM1-AOD relationship was positively correlated as a whole, the highest correlation coefficient was 0.55 in central China, and the lowest value was 0.36 in central and southern China.

Long term trend analysis and Spatio-temporal variation of air pollutants over Uttar Pradesh, India

Air pollution poses a significant challenge for developing countries like India, particularly in cities where industrial growth and urban development have led to increased levels of air pollutants. Due to limited monitoring resources and a focus on specific variables, there is a lack of comprehensive understanding regarding air quality in Indian urban areas. This study aims to explore the spatial and temporal variations in air pollutant concentrations and identify long-term trends over a seven-year period (2016-2022) in the state of Uttar Pradesh. Data for PM10, SO2, and NO2 were collected from 78 ambient air quality monitoring stations. The study investigates how these pollutants behave in terms of their distribution on different temporal scales (seasonal, yearly) as well as across various locations. The findings reveal that the concentration of PM10 consistently exceeds national and international air quality standards. Using the Inverse Distance Weighting (IDW) technique, air pollutant distribution maps were created to identify specific hotspots. Additionally, the Mann-Kendall Test was applied to analyze trends within the available data. This research can serve as valuable information for local government authorities to formulate effective strategies for mitigating air pollution in the region.

Analysis of spatiotemporal patterns of atmospheric CO2 concentration in the Yellow River Basin over the past decade based on time-series remote sensing data.

Understanding the spatial and temporal variations of CO2 column concentration (CO2-CCs) is crucial for tackling climate change and promoting sustainable human development. This study provides an in-depth analysis of CO2 dynamics in the Yellow River Basin, an area significantly affected by both natural and anthropogenic factors. Using data from the Orbiting Carbon Observatory 2 (OCO-2) and the Fourier transformation spectrometer (FTS) of the GOSAT satellite remote sensing sensors, supplemented with ground station data from the Waliguan station, we scrutinized the CO2 levels in the region from 2013 to 2022. The regional CO2-CC displayed a 12-month cyclical variation and a continuous upward trend, escalating by approximately 4.26% over the 10-year period. Spatiotemporal differences were evident in the monthly variation of CO2-CC, with peak and minimum values occurring in May and August respectively. Geographically, the highest CO2-CC was found in the central part of the basin, while the lowest was in the northern part of Inner Mongolia. This study underscores the increased significance of the region's CO2-CC, which showed an increase from 17.0ppm at the start of the period to 21.0ppm by the end, representing an overall growth of between 4.35 and 5.25%. The findings highlight the urgency of targeted measures to mitigate CO2 emissions and adapt to their consequences in the Yellow River Basin, contributing to the global efforts against climate change and towards sustainable development.

Seasonal variations in source-sink balance of CO2 in subtropical earthen aquaculture ponds: Implications for carbon emission management

Aquaculture ponds serve as focal points for carbon cycling and act as anthropogenic contributors to the emission of carbon dioxide (CO2). To understand the seasonal CO2 dynamics within the ponds, we measured the CO2 concentrations in sediment porewater and the water column in aquaculture ponds in the Shanyutan Wetland in China. Subsequently, the sediment-to-water and water-to-air CO2 fluxes were calculated based on the gas transfer coefficient model. Our results showed that that CO2 flux ranged 0.01–4.58 mmol m−2h−1 across the sediment-to-water interface and −0.08 to 0.45 mmol m−2h−1 across the water-to-air interface throughout the farming period. Photosynthetic activity was the key driver of the temporal variations in water column CO2 concentration and water-to-air CO2 flux, while the change in porewater CO2 concentration and sediment-to-water CO2 flux were governed by sediment temperature which drive the microbial decomposition of organic matter. Based on a simple mass balance approach, the apparent CO2 consumption (ACC) in the water column across all seasons ranged from 0.24 to 2.32 mmol m−2h−1, indicating that the pond water body had a high capacity to “consume” the excess CO2. Our results highlight that the contrasting roles between the sediment compartment and water column compartment in CO2 dynamics, and the possibility to manipulate ACC to reduce the aquaculture carbon footprint.

Risk evaluation and remedial measures for heavy metal contamination in lagoonal sediments of the Negombo Lagoon, Sri Lanka after the X-Press Pearl maritime disaster

Negombo Lagoon is a vital ecological and socio-economic resource in Sri Lanka that has become susceptible to anthropogenic heavy metal contamination. Therefore, short-core sediment samples from the Negombo Lagoon were analyzed to quantify heavy metal contaminants including both metals (Cr, Ni, Co, Cu, Cd, and Pb) and metalloid As; assess their ecological risk; identify critically polluted regions; and to investigate temporal variation in heavy metal concentration. According to the results, Ni is the most abundant heavy metal in lagoonal sediments. Ni, As, and Cr have severely contaminated the sediments as confirmed by their higher geo-accumulation indices (Igeo) and contamination factors (CF). The degree of contamination (Cdeg) indicated an exceedingly high overall heavy metal contamination, and the pollution load index (PLI) exhibited a prominent site quality decline. Individual potential ecological risk factor (Er) values revealed that Ni, As, and Cd pose a substantial ecological risk. Similarly, the potential ecological risk index (PERI) displayed that heavy metal contamination is a significant peril to this ecosystem. Spatial distributions of the heavy metals are governed mainly by the sediment grain size and freshwater influx. Ni concentration in lagoonal sediments has remarkably increased during the last six years (2016–2022) predominantly due to anthropogenic Ni sources, including the recent X-Press Pearl ship accident. In light of the severe heavy metal contamination in lagoonal sediments, the current study recommends a phytoremediation approach for the Negombo Lagoon.

Salting-out assisted liquid–liquid extraction combined with LC–MS/MS for the simultaneous determination of seven organic UV filters in environmental water samples: method development and application

Organic UV filters (OUVFs), the active ingredient in sunscreens, are of environmental concern due to reported ecotoxicological effects in aquatic biota. Determining the environmental concentrations of these chemicals is essential for understanding their fate and potential environmental risk. Salting‐out assisted liquid–liquid extraction (SALLE) coupled with liquid-chromatography tandem mass spectrometry (LC–MS/MS) was developed for simultaneous extraction, separation, and quantification of seven OUVFs (2,4-dihydroxybenzophenone, 2,2′,4,4′-tetrahydroxybenzophenone, 4-methylbenzylidene camphor, butyl-methoxy-dibenzoyl methane, octocrylene, octyl methoxycinnamate, and oxybenzone). Method detection limits (MDLs) ranged from 11 to 45 ng/L and practical quantification limits (PQLs) from 33 to 135 ng/L. Method trueness, evaluated in terms of recovery, was 69–127%. Inter-day and intra-day variability was < 6% RSD. The coefficients of determination were > 0.97. The method was applied to river and seawater samples collected at 19 sites in and near Port Phillip Bay, Australia, and temporal variation in OUVF concentrations was studied at two sites. Concentrations of OUVF were detected at 10 sites; concentrations of individual OUVFs were 51–7968 ng/L, and the maximum total OUVF concentration detected at a site was 8431 ng/L. Recreational activity and water residence time at the site contributed to OUVF’s environmental presence and persistence. The benefits of the SALLE-LC–MS/MS method include its simple operation, good selectivity, precision over a wide linear range, and that obtained extracts can be directly injected into the LC–MS/MS, overall making it an attractive method for the determination of these OUVFs in environmental water matrices. To our knowledge, this is the first report of the occurrence of OUVFs in Port Phillip Bay, Australia.

Effect of typhoons on spatiotemporal patterns of multi-group persistent organic pollutants in sediment of Chinese southeastern coastal estuaries

Estuaries are susceptible to both anthropogenic disturbances and global climate changes. Impacts may be discriminated by pollution patterns of widely quantified persistent organic pollutants (POPs), though data are scarce for extreme climate events. This study quantified four groups of POPs, i.e., polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethanes (DDTs), and hexachlorocyclohexanes (HCHs), in sediments from seven Chinese coastal estuaries across a gradient of socioeconomic development in their watersheds with comparisons among the pre-typhoon, typhoon, and post-typhoon periods during 2016–2019. The maximal average concentrations, up to 1561 μg PAHs kg−1, 235 μg DDTs kg−1, and 38.9 μg HCHs kg−1, were quantified in the Jiulong River estuary and 7.61 μg PCBs kg−1 in the Jiao River estuary. Anthropogenic activities contributed to the distinctive spatial distributions of four groups of POPs in estuaries with non-agricultural gross domestic product (NAGDP) per capita significantly relating to sedimentary concentrations of PAHs and PCBs and agricultural gross domestic product (AGDP) per capita relating to DDTs and HCHs. Seasonality and typhoons led to less temporal variations in sedimentary POPs concentrations, whose spatial heterogeneity was remarkably reduced in the post-typhoon period rather than in the pre-typhoon and typhoon periods. The results of this study suggested that fingerprinting legacy POPs in spatial and temporal distributions contributed to identifying the effects of anthropogenic disturbances and climate changes on estuarine sediment quality.

Measuring Temporal Variation of Concentration of ALD Precursor TEMAZ in Process Chamber Using UV Absorption Method

Atomic layer deposition (ALD) is becoming increasingly important to realize high-accurate atomic-scale deposition processes in semiconductor industry, where device dimensions approach atomic scale with the advances of the miniaturization. Basically, ALD is a process of forming a film using self-limited cyclic reactions, where precursor gas, purging gas, reaction gas, and purging gas are introduced sequentially [1]. To realize high-quality ALD with high-throughput, the reaction cycle should be shortened. However, this may cause incomplete gas replacement due to residual gas, resulting in the degradation in process quality. To develop high-quality ALD, precise control of temporal and spatial distribution of these gases is required. Although the total gas pressure in the chamber was usually measured as process monitor, partial pressure, or concentration of precursor as well as reaction gas was not be measured so far. This makes it impossible to evaluate gas replacement characteristics in the chamber, despite its importance for developing ALD technology.Our group developed a high-sensitivity, real-time, compact gas concentration sensor using UV light absorption method for the supply system of organometallic gases having UV absorption [2]. The gas concentration can be estimated from the UV absorption using Lambert-Beer law. Recently, to develop a new process monitoring tool in ALD, we apply this technique to in-situ measurement of precursor gas in the chamber. In this study, temporal variation of concentration of Tetrakis(ethylmethylamino)zirconium (TEMAZ) in cyclic introduction of TEMAZ and purging Ar gas was evaluated. Here, TEMAZ is widely used as a Zr precursor in ALD for zirconia films deposition, mainly in DRAM fabrication [3].Fig. 1 shows a schematic diagram of the experimental system used in this study. TEMAZ was supplied by a bubbling method. At the downstream of the TEMAZ tank, upstream pressure controller (UPCUS) was equipped to control the pressure in the tank to be constant. An inner diameter of a test chamber was 200 mm, and TEMAZ and purging Ar were supplied using a shower plate installed at the upside of the chamber. A densitometer using UV absorption method consisted of an UV light emitting part and an UV photometer, and these were placed at opposite side of the chamber. UV light with a wavelength of 250 nm, which corresponds to the absorption of TEMAZ, was used. Two densitometers (hereafter denoted as UVH and UVL) were set at 10mm and 60mm below the shower plate, respectively. A pressure gauge was also set at 10mm below the shower plate to measure total pressure in the chamber. In the measurement, the valve operation and data acquisition were conducted by a computer with a sampling period of 10 ms.Fig. 2(a) shows time evolution of chamber pressure and absorbance of UVH (which approximately proportional to TEMAZ partial pressure) in the case that TEMAZ and purging Ar were introduced alternatively every second for 50 times. TEMAZ was supplied to the chamber with diluted Ar (100 sccm) with a TEMAZ concentration of 2000 ppm. Purging Ar flow rate was 1500 sccm. In Fig. 2(b), extended graph of Fig. 2(a) for time range from 90 to 96 s were shown. It is clearly found that behavior of UVH signal and the chamber pressure was different, where UVH absorbance signal increased at TEMAZ introduction, and rapidly decreased when Ar purge started whereas the chamber pressure increased due to the Ar introduction. Such behavior cannot be obtained only from the pressure measurement.Fig. 3 compares UVH and UVL absorbance signals for 1 cycle of TEMAZ and purging Ar introductions. It can be seen that UVH absorbance began to increase at approximately 80.2 s (0.2 s after the TEMAZ introduction), and UHL absorbance began to increase with a delay at approximately 80.6 s (0.6 s after the TEMAZ introduction). This suggested that down flow of TEMAZ could be observed.The results demonstrated validity of the UV absorption method to evaluate temporal and spatial distribution of precursor gas, and this technology will greatly contribute to developing future ALD technology.[1] R. W. Johnson et al., Materials today, 17 (2014) 236.[2] H. Ishii et al., Jpn. J. Appl. Phys., 58 (2019) SBBL04.[3] S. K. Kim and C. S. Hwang, Electrochem. Solid-State Lett., 11 (2008) G9. Figure 1

A benchmark for variably saturated variable-density variable-viscosity flow and solute transport in porous media

In natural environments, fluid density and viscosity can be affected by spatial and temporal variations of solute concentration, for example, due to saltwater intrusion in coastal aquifers, leachate infiltration from waste disposal sites, and upconing of saline water from deep aquifers. Potentially unstable situations may arise in which a dense fluid overlies a less dense fluid. This situation can produce instabilities manifested by dense plume fingers moving vertically downwards counterbalanced by vertical upward flow of the less dense fluid. The resulting free convection increases solute transport rates over large distances and times relative to constant-density flow. Unstable brine flow is further complicated if the porous medium is variably saturated. The results from a laboratory experiment of variably saturated variable-density flow and solute transport from Simmons et al. (2002) are used as the physical basis to define a new mathematical benchmark. This benchmark aims at realistically reproducing the experimental fingering patterns. Random hydraulic conductivity fields were used in the simulations as a numerical perturbation method to realistically mimic the observed dense plume fingering. The HydroGeoSphere code coupled with PEST are used to calibrate the parameter set that defines the benchmark. A grid convergence analysis is performed to obtain the adequate spatial and temporal discretizations. The new mathematical benchmark is useful for model comparison and testing of variably saturated variable-density flow in porous media. Simmons CT, Pierini ML, Hutson JL (2002) Laboratory investigation of variable-density flow and solute transport in unsaturated–saturated porous media. Transp Porous Media. 47(2): 215–244, 10.1023/A:1015568724369.