Temporal Variations In Concentrations Research Articles

Spatial and Temporal Variations of Atmospheric PM10 and Air Pollutants Concentration in Upper Northern Thailand During 2006–2016

Spatial and Temporal Variations of Atmospheric PM10 and Air Pollutants Concentration in Upper Northern Thailand During 2006–2016

Analyzing the spatial and temporal variations in tropospheric NO2 column concentrations over China using multisource satellite remote sensing

We comprehensively considered the spatial resolution and seasonal differences in NO2 column concentration data observed by different satellites to reconstruct an NO2 column concentration dataset in China from 1997 to 2018. On this basis, the spatial and temporal variations in NO2 column concentrations were analyzed over China from 1997 to 2018. The results show that the reconstructed NO2 column concentration dataset with high spatial structure characteristics in China from 1997 to 2018 effectively compensates for the lack of long-term high-resolution monitoring of NO2 pollution in China by a single satellite. (The accuracy of the reconstructed dataset was verified by season: correlation coefficient between GOME and SCIAMACHY, R > 0.87, P 0.91, P < 0.01.) The analysis of the spatial and temporal variations showed that the NO2 column concentrations in China from 1997 to 2018 generally showed high values in the east and low values in the west. The high concentrations of NO2 are mainly concentrated in the northern and eastern coastal areas and the Pearl River Delta. From 1997 to 2010, the NO2 column concentrations continued to increase with a growth rate of ( 0.180 ± 0.011 ) × 1015 molec / ( cm2 a ) over China. From 2011 to 2018, the NO2 column concentrations showed a downward trend, with a decreasing rate of ( 0.144 ± 0.037 ) × 1015 molec / ( cm2 a ) over China. After 2011, NO2 pollution in high pollution regions such as Beijing, Tianjin, Hebei, Shandong, the Yangtze River Delta, and the Pearl River Delta was alleviated. Energy saving and emission reduction measures can reduce nitrogen dioxide pollution while ensuring sustained gross domestic product (GDP) growth.

Efficient removal of indoor particulate matter using water microdroplets generated by a MHz-frequency ultrasonic atomizer

Airborne particulate matter (PM) has emerged as an important global environmental and social issue due to its harmful health effects. Various techniques have been introduced to remove indoor PM. However, an effective and sustainable method has not been established yet because of complex mechanisms and various factors. Here, we propose the use of water microdroplets generated by a MHz-frequency ultrasound, and experimentally examine the effects of the generated microdroplets on PM removal. The PM removal efficiency and PM deposition constant are analyzed by measuring the temporal variation of PM concentration. The measured experimental results are compared with analytical deposition constants. Two collection efficiencies derived in previous studies are employed to substitute a mathematical model used for determining the analytical deposition constants. In addition, the mean diameter and the moving velocity of the microdroplets are experimentally measured via a digital holographic microscopy and particle image velocimetry generated by a MHz-frequency atomizer. The present results demonstrate that water microdroplets generated by the atomizer can be effectively used to remove PM.

Occurrences of 29 pesticides in the Huangpu River, China: Highest ecological risk identified in Shanghai metropolitan area

To investigate the occurrence and risk of pesticides in the Huangpu River basin, spatial and temporal concentration variations of 29 commonly used pesticides and their risk quotient (RQ) values for three different trophic organisms (fish, daphnia, green algae) from 16 sampling sites were conducted in 2018–2019. These 29 pesticides include 4 carbamates, 2 benzimidazoles, 6 neonicotinoids, 2 organophosphates, 9 triazoles, and 6 others. Of the 29 pesticides analyzed, 18 were present in every sample taken from the Huangpu River. The concentration of target pesticides in water samples ranged from < LOQ (for buprofezin in summer, autumn, and winter) to 607.30 ng L−1 (for carbendazim in spring). From the source (i.e., Taihu Lake) to the estuary of the Huangpu River, with the exception of isocarbophos and isoprothiolane (gradual decrease), the spatial variation of target pesticide concentrations firstly exhibited an increasing trend and then a decreasing trend. Peak spatial variation was seen in metropolitan area, which is closely related to the type of land use and the discharge of tributaries. In addition, the total summed concentration of the 29 pesticides during winter (1037.60 ng L−1) was higher than summer (788.82 ng L−1) in rural and metropolitan areas. For the ecological risk assessments of fish, daphnia, and green algae, the triazoles, carbamates, neonicotinoids were risk-dominant pesticides, respectively. Notably, carbendazim had a 100% detection frequency and the highest concentration of the 29 pesticides analyzed, indicating its high consumption in the Huangpu River basin.

Seasonal variations of trace metals from water and sediment samples in the northern Bay of Bengal.

We aimed to determine the temporal variation of trace metals concentrations in surface water and surface sediment samples at Kutubdia Channel, Bangladesh. Trace metals of samples were detected using energy dispersive X-ray fluorescence (Energy-dispersive X-ray spectroscopy) method. The lowest concentration of metals was found in water samples during post-monsoon season and the highest during pre-monsoon season (Cu: 0.030±0.001μg/L in pre-monsoon and 0.026±0.002μg/L in post-monsoon, Zn: 0.087±0.003μg/L in pre-monsoon and 0.073±0.002μg/L in post-monsoon, Fe: 0.080±0.001μg/L in pre-monsoon and 0.055±0.001μg/L in post-monsoon). In contrast, metal concentration in surface sediment samples were higher in post-monsoon than in pre-monsoon season i.e. Cr 11mg/kg in pre-monsoon and 12mg/kg in post-monsoon, Mn 571mg/kg in pre-monsoon and 606mg/kg in post-monsoon, As (8mg/kg in pre-monsoon and 10mg/kg in post-monsoon, Pb (22mg/kg in pre-monsoon and 24mg/kg in post-monsoon, and Fe 2317mg/kg in pre-monsoon and 2435mg/kg in post-monsoon. We found a spatial gradient of high to medium to low in trace metal concentration from river to river mouth to offshore area. Considering the sources of metals, land erosion by waves and tidal action, an influx of water and sediment from the surrounding rivers, agricultural waste, industrial effluent and sewage are the most likely sources of metal pollution in the study area. We conclude that proper management strategies should be adopted to control the pollution and conserve the ecosystem health.

Spatial and Temporal Variations of Atmospheric CO2 Concentration in China and Its Influencing Factors

Over the past few decades, concentrations of carbon dioxide (CO2), a key greenhouse gas, have risen at a global rate of approximately 2 ppm/a. China is the largest CO2 emitter and is the principle contributor to the increase in global CO2 levels. Based on a satellite-retrieved atmospheric carbon dioxide column average dry air mixing ratio (XCO2) dataset, derived from the greenhouse gas observation satellite (GOSAT), this paper evaluates the spatial and temporal variations of XCO2 characteristics in China during 2009–2016. Moreover, the factors influencing changes in XCO2 were investigated. Results showed XCO2 concentrations in China increased at an average rate of 2.28 ppm/a, with significant annual seasonal variations of 6.78 ppm. The rate of change of XCO2 was greater in south China compared to other regions across China, with clear differences in seasonality. Seasonal variations in XCO2 concentrations across China were generally controlled by vegetation dynamics, characterized by the Normalized Difference Vegetation Index (NDVI). However, driving factors exhibited spatial variations. In particular, a distinct belt (northeast–southwest) with a significant negative correlation (r &lt; −0.75) between XCO2 and NDVI was observed. Furthermore, in north China, human emissions were identified as the dominant influencing factor of total XCO2 variations (r &gt; 0.65), with forest fires taking first place in southwest China (r &gt; 0.47). Our results in this study can provide us with a potential way to better understand the spatiotemporal changes of CO2 concentration in China with NDVI, human activity and biomass burning, and could have an enlightening effect on slowing the growth of CO2 concentration in China.

Remote sensing of coastal algal blooms using unmanned aerial vehicles (UAVs)

The explosive growth of phytoplankton under favorable conditions in subtropical coastal waters can lead to water discolouration and massive fish kills. Traditional water quality monitoring relies on manual field sampling and laboratory analysis of chlorophyll-a (Chl-a) concentration, which is resources intensive and time consuming. The cloudy weather of Hong Kong also precludes using satellite images for algal blooms monitoring. This study for the first time demonstrates the use of an Unmanned Aerial Vehicle (UAVs) to quantitatively map surface water Chl-a distribution in coastal waters from a low altitude. An estimation model for Chl-a concentration from visible images taken by a digital camera on a UAV has been developed and validated against one-year field data. The cost-effective and robust technology is able to map the spatial and temporal variations of Chl-a concentration during an algal bloom. The proposed method offers a useful complement to traditional field monitoring for fisheries management.

Land-use controls on nutrient loads in aquifers draining agricultural and mixed-use karstic watersheds.

Agricultural nonpoint source pollution from the upper areas of the Upper Mississippi, Missouri, and Ohio River basins accounts for the majority of the excess nitrogen that leads to the Gulf of Mexico's hypoxic zone. However, agriculture landscapes across the USA, Europe, and China are undergoing major changes related to the proliferation of confined animal feeding operations (CAFOs) that account for a greater proportion of point source contamination. Mitigating long-term nutrient inputs at a large scale (Mississippi River Basin) requires understanding these microscale changes at the small watershed level (less than 100km2). To assess the control of land-use and subsurface hydrological processes on nutrient fate and transport, temporal patterns in nutrient concentrations in a mixed land-use karstic watershed were analyzed. To assess the control of differential land-use sources on total inorganic nitrogen (TIN) loads within the watershed, 4months of weekly water sampling was performed at a spring location and at two underground conduit locations. The observed temporal variations in nutrient concentrations are primarily associated with seasonal changes in land-use associated with corn growth. Data show that land-use sources explain much of the temporal variability of TIN at the spring when weighted against the hydrological factor. End-member-mixing analysis of dissolved organic carbon (DOC) shows a progressive increase in the contribution of DOC-enriched sources and a more labile form of carbon toward the harvest time. Overall, during high flow, nonpoint source infiltration from manure-fertilized croplands in the northern branch (NB) dominate DOC loads. Because conduit-dominated karstic aquifers are more susceptible to contamination from direct and fast (< 7h) subsurface infiltration during late summer rainfall period (July to August), a slight advance in the timing of manure application could substantially reduce nutrient loads to local groundwater. A combined evaluation of subsurface hydrological processes and land-use factors controlling nutrients at the scale of small watersheds is crucial to developing site-specific nutrient management plans and managing the Gulf of Mexico's hypoxic zone.

Patterns of mercury exposure and relationships with isotopes and markers of oxidative status in chicks of a Mediterranean seabird

The Mediterranean basin is a hotspot of mercury (Hg) contamination owing to intense anthropogenic emissions, volcanic activity and oligotrophic conditions. Little work has been done to assess the sources of Hg exposure for seabirds and, particularly, the physiological consequences of Hg bioaccumulation. In this study, we (i) describe the individual and temporal variation in blood concentration of total Hg (THg) over three breeding seasons, (ii) identify the factors that affect the THg exposure and (iii) determine the individual- and population-level connections between THg and blood-based markers of oxidative status in chicks of Scopoli’s shearwaters (Calonectris diomedea) breeding on the island of Linosa in the southern Mediterranean. We carried out the work on chicks near fledging because they are fed with prey captured near the colony, thus their Hg levels reflect local contamination. The concentration of THg in erythrocytes varied from 0.23 to 4.29 μg g−1 dw. Chicks that were fed upon higher trophic level prey (i.e., higher δ15N values) had higher THg levels. Individual variation in THg concentrations was not explained by parental identity, sex nor δ13C values. There was significant variation in THg among chicks born from the same mother in different years. We found significant correlations between THg and markers of oxidative status; however, these correlations were no longer significant when we took into account the annual variation in mean values of all metrics. Males with higher values of body condition index had higher blood THg, while THg and body condition index were not correlated in females. Our data indicate that THg levels were moderate to high if compared to other seabirds. However, there is little evidence for harmful short-term detrimental effects owing to THg exposure.

Temporal variation of 210Pb concentration in the urban aerosols of Shanghai, China

This study monitored 210Pb levels of the atmospheric aerosol in Shanghai from January 2016 to February 2017. 210Pb levels were found to be low in non-haze weather events (1.46 ± 0.76 mBq/m3, n = 8) and high in moderate pollution weather events (2.34 ± 1.43 mBq/m3, n = 12). Similar to those of other East Asian regions, monthly averaged 210Pb concentration showed a U-shaped distribution pattern, indicating that the East Asian monsoon has an impact on atmospheric 210Pb. Particulate matters (PM) had a significant positive correlation with 210Pb, indicating that there might occur an intensified 210Pb scavenging processes. The linear correlation analysis revealed a clear link between 210Pb and some gaseous pollutants, strong positive correlation between CO and 210Pb (210Pb/CO, R = 0.63, P < 0.01), and weak correlation between 210Pb and O3 (R = − 0.35), NO2 (R = 0.42), and SO2 (R = 0.34). This phenomenon demonstrated that in haze weather, not only the general air pollutants concentrations have increased, but also the 210Pb concentration. Radiation dosimetry of daily inhalation of 210Pb through exposure to outdoor air is estimated to be relatively minor; children intake remains higher.

Large contribution of non-aquaculture period fluxes to the annual N2O emissions from aquaculture ponds in Southeast China

Nitrous oxide (N2O) is one of major potent long-lived atmospheric greenhouse gases (GHGs) with a global warming potential of approximately 300 times that of carbon dioxide (CO2) over a 100-year timespan. To date, only several studies have explored the contribution of N2O emission from aquaculture systems to global emission, but with large uncertainty. In this study, the spatiotemporal distribution of dissolved N2O concentrations along the water column within ponds, and the N2O fluxes over the whole annual cycle were determined in the shrimp ponds in the Min River Estuary, Southeast China. Our results showed that N2O concentrations did not differ among sampling depths, but varied significantly among sampling dates. The temporal variation of N2O concentration was significantly correlated with the concentrations of N-NH4+ and total dissolved nitrogen. The one year study found an annual mean N2O emission of 57.63 μg N2O m−2 h−1 that was equivalent to an annual emission of 504.9 mg N2O m−2 yr−1, demonstrating the aquaculture ponds as an important source of atmospheric N2O. The N2O fluxes during the non-aquaculture period were one to three orders larger than those in the aquaculture period, and accounted for approximately 97% of the annual total emissions from aquaculture ponds. Our results showed that the N2O emission during the non-aquaculture period should not be overlooked owing to its marked contribution to the annual N2O budget in mariculture ponds. Further studies on N2O production dynamics including the abundance and activity of nitrifying and denitrifying bacteria in coastal aquaculture ponds are needed to improve our understanding of N2O biogeochemical cycle and facilitate strategies to reduce N2O emission.

Variation of black carbon in Northeast China based on ground observation and MERRA-2 reanalysis data

The temporal variations of black carbon concentration at 7 sites, including Longfengshan, Anshan, Benxi, Dalian, Changchun, Shenyang, and Fushun, in Northeast China was studied based on up to 11 years of ground observations and MERRA-2 reanalysis dataset. Except for Benxi, Changchun and Shenyang, at other four sites, the ground-based black carbon concentrations have decreased generally in the last decade, while changes in the black carbon concentration of MERRA-2 are relatively small. The seasonality of measured black carbon concentration shows a trend of low in May-June and high in January at all sites, and the diurnal cycles present similar pattern with two peaks occurring at 10:00-12:00 UTC and 23:00-24:00 UTC respectively, two troughs occurring at 05:00-07:00 UTC and 19:00-20:00 UTC respectively. The daily mean of MERRA-2 black carbon concentration is 49.3% lower than that of the ground observations at 7 sites averagely. They also show poor consistency in terms of seasonal and daily changes, which perhaps means an inappropriate application of MERRA-2 black carbon concentration at single point in Northeast China.

Temporal Variations of 7Be and 210Pb Activity Concentrations in the Atmosphere and Aerosol Deposition Velocity in Shenzhen, South China

Naturally occurring beryllium-7 (7Be) and lead-210 (210Pb) serve as powerful tracers in atmospheric studies. In this study, 7Be and 210Pb were simultaneously measured in atmospheric aerosols and deposition samples for an entire year (from January to December 2017) in Shenzhen, South China. The activity concentrations of the airborne 7Be and 210Pb ranged from 0.33 to 9.42 mBq m–3 (averaging 3.23 mBq m–3) and from 0.59 to 4.72 mBq m–3 (averaging 1.58 mBq m–3), respectively, and were observed to be high during the winter but low during the summer. Moreover, the relatively high 210Pb concentration was probably due to the elevated level of radon in this region’s soil. The deposition fluxes of the 7Be and 210Pb were found to range from 0.25 to 3.04 Bq m–2 day–1 (averaging 1.57 Bq m–2 day–1) and from 0.34 to 1.31 Bq m–2 day–1 (averaging 0.73 Bq m–2 day–1), respectively. The temporal trends of these fluxes were largely influenced by rainfall and the origin and pathway of air masses, as well as by atmospheric circulation. Based on their concentrations in the aerosols and their deposition fluxes, the average deposition velocities of 7Be and 210Pb were calculated to be 0.83 and 0.62 cm s–1, respectively. The deposition velocities of both radionuclides correlated well with the amount of rainfall, indicating that precipitation plays a crucial role in removing 7Be and 210Pb from the air. The activity size distributions of these nuclides combined with the characteristic meteorological conditions in this region resulted in high deposition velocities during summer and low ones during winter.

Temporal and spatial variability of stream water chemistry on Subantarctic Marion Island

Concentrations of major ions in stream water from the Soft Plume River on Subantarctic Marion Island were measured. During the annual relief voyage, samples were collected daily over a 16-day period (21 April–6 May 2015) from three sites along the stream to better understand temporal and spatial variability of stream water chemistry on the island. The chemical composition of the stream is dominated by the sea salts Na+&nbsp;and Cl−. Mean solute concentrations for Na+&nbsp;and Cl−&nbsp;are 7 ± 0.58 and 12.5 ± 0.84 mg/L, respectively. The mean molar Na:Cl ratio for all samples is 0.86 ± 0.05, with a range from 0.71 to 0.99 (n&nbsp;= 47), and there is a strong, significant positive correlation between Na+&nbsp;and Cl−&nbsp;concentrations (r&nbsp;= 0.80;&nbsp;p&nbsp;&lt; 0.001). These values are consistent with previous studies from Marion Island and other Subantarctic islands. Temporal variation in ion concentrations was small. The largest detected change was a decrease in most solute concentrations that coincided with two precipitation events. This decrease was largest at the highest altitude and the shallowest site, suggesting that there was more rainfall at this location. These findings confirm the dominance of the surrounding ocean as the main source of the island’s stream water chemistry and illustrate spatiotemporal patterns that provide an insight into mechanisms affecting their composition on Subantarctic Marion Island.

Analysis of NOx Pollution Characteristics in the Atmospheric Environment in Changchun City

Nitrogen oxide (NOx) pollution has become one of the most challenging problems in China in the past 20 years. In this study, on the basis of the Jilin Province Atmospheric Environmental Quality Bulletin and hourly NOx data from the Atmospheric Environment Automatic Monitoring Station in Changchun, temporal and spatial variations in NOx concentration in the province and Changchun and their relationships with various pollutants and meteorological factors were analyzed. The results show that Changchun had the highest NOx concentration of all cities in the province, with a high concentration in the center and a low concentration in the east and west. The areas with high NOx concentrations in Changchun were mainly distributed in urban centers, and the concentration in the northern part of the city was higher than that in the south. The seasonal variation and average daily variation in NOx concentration in Changchun had a bimodal distribution, and the NOx concentration in autumn and winter was higher than that in spring and summer. The maximum monthly average concentrations of NOx and nitric oxide (NO) were reached in October, and the maximum monthly average concentration of nitrogen dioxide (NO2) was reached in March. The average daily variation in NOx concentration first peaked at 07:00–08:00 in the morning, and the second peak occurred between 20:00 and 22:00 at night. The NOx concentration in Changchun was positively correlated with NO2, NO, PM2.5 (fine particulate matter), PM10 (particulate matters), CO (carbon monoxide), and pressure, and it showed a significant negative correlation with O3, temperature, wind speed, and humidity.

Longitudinal trends in perfluoroalkyl and polyfluoroalkyl substances among multiethnic midlife women from 1999 to 2011: The Study of Women′s Health Across the Nation

BackgroundLimited information exists regarding longitudinal trends in midlife women’s exposure to perfluoroalkyl and polyfluoroalkyl substances (PFAS). Further, little is known about how patterns of exposure differ by race/ethnicity and reproductive characteristics including parity and menopause. ObjectiveWe aimed to examine temporal variations in serum PFAS concentrations among midlife women from the Study of Women′s Health Across the Nation. MethodsSerum concentrations of 11 PFAS homologues were measured in 75 White, Black and Chinese women with blood samples collected in 1999–2000, 2002–2003, 2005–2006, and 2009–2011. Rates of changes in PFAS concentrations were calculated assuming a first-order elimination model. Associations between PFAS concentrations and race/ethnicity, menstruation and parity were evaluated with linear mixed models, adjusting for age, body mass index and study site. ResultsSerum concentrations of linear-chain perfluorooctanoic acid (n-PFOA), linear- and branched-chain perfluorooctane sulfonic acid (n-PFOS and sm-PFOS) decreased significantly (-6.0%, 95% CI: −8.3%, −3.6% per year for n-PFOA; −14.8%, 95% CI: −17.3%, −12.3% per year for n-PFOS; −16.9%, 95% CI: −19.1%, −14.6% per year for sm-PFOS); whereas perfluorononanoic acid (PFNA) increased (16.0%, 95% CI: 10.6%, 21.6% per year). Detection rates of perfluorodecanoic acid (PFDeA) and perfluoroundecanoic acid (PFUA) doubled. Temporal trends varied significantly by race/ethnicity. Chinese women tended to have consistently higher PFNA concentrations at each follow-up visit, compared with White and Black women. Serum PFHxS concentrations significantly decreased in White and Black women, but not in Chinese. Menstruating women consistently had lower concentrations. Parity was associated with lower concentrations at baseline but the differences between nulliparous and parous women became smaller over time. ConclusionsOur results suggest longitudinal declines in serum concentrations of legacy PFAS and increases in serum concentrations of emerging compounds from 1999 to 2011 in midlife women. Temporal trends in PFAS concentrations are not uniform across race/ethnicity and parity groups.

Spatial and temporal variability in dissolved oxygen content of Asoro stream, in south western Nigeria

This study examined the spatial and temporal variation of dissolved oxygen (DO) concentration in Asoro stream, the self-recovery ability of the stream of the effluent discharges with a view to providing a baseline information on quality of water in Asoro stream. DO is a measure of the ability of water to sustain aquatic life, it is important in water pollution control and waste water treatment process control. Samples were collected from fifteen sampling points along the Asoro stream at 500 m intervals over a 5000 m stretch for twelve-months. The DO, Biochemical Oxygen Demand and some other physico-chemical parameters of water were determined using standard methods. The hydrographic characteristics of the stream were; width (0.8 to 5.8 m), depth (0.1 to 0.55 m), discharge (0.30 to 0.52 ms -1 ), flow rate 0.07 to 0.0.73 m 3 /s. The temporal variation in DO concentration in Asoro stream fluctuated from the first week of sampling to 25th week after with a peak range of concentration (7.46 mg/L to 10.12 mg/L) between 27th week and 39th week of sampling suggesting high level of organic pollution. The mean spatial distribution of DO at each station changed slightly between the point of brewery effluent discharge and 5000 m away. Regression analysis showed that there was no significant relationship (P≥ 0.05) between time (weeks) and DO concentration along Asoro stream. The study concluded that release of organic matter from industrial effluent affects the DO and BOD concentrations of Asoro stream. Keywords: Dissolved oxygen, Temporal, Spatial, Asoro stream, self- recovery

Temporal variation of atmospheric 7Be and 210Pb concentrations and their activity size distributions at Astana, Kazakhstan in Central Asia

Atmospheric concentrations of 7Be and 210Pb obtained by a high-volume air sampler with a cascade impactor were measured from September 2016 to November 2017 in Astana, Kazakhstan. The levels and seasonal variations of atmospheric 7Be and 210Pb concentrations were investigated together with their activity size distributions. Typical seasonal variability was observed with higher concentrations of 7Be occurring in the warm summer and that of 210Pb towards the cold winter. These trends may be attributed to the increased vertical mixing within the troposphere during the warm summer season and the frequent inversion conditions of the surface layers during the cold winter season.

Geochemical options for water security in a coastal urban agglomerate of Lower Bengal Delta, Bangladesh

Khulna– situated in the Lower Bengal Delta of Bangladesh– is one of the most stressed coastal agglomerates globally under the realm of rapid changes in the climate pattern. This research assesses the geochemical options for water security of Khulna City Corporation (KCC) by analysing a total of 47 surface- and 62 groundwater samples collected during both monsoon and winter from stations uniformly distributed over the city following standard methods. The dissolved ions from three possible water sources such as the ponds and lakes, the river Mayur and groundwater generally show a similar relative dissolved ions concentration pattern where the alkali metals (Na+ + K+) exceed the alkaline earths (Ca2+ + Mg2+), and the strong acidic anions (Cl−+ SO42−) and the weak acidic anions (HCO3−) are of equal importance, indicating natural softening and mixing of water from both plagioclase and carbonate weathering, and seawater sources. Although the spatial variation with reference to mean concentrations of dissolved ions among different sampling stations during both monsoon and winter seasons in all the water sources such as the ponds and lakes, the river Mayur and the groundwater is not statistically significant at 5% level, the variation in dissolved ion concentrations among the water sources is statistically significant at 5% level. The temporal variation in concentrations between monsoon and winter seasons for all water sources is statistically significant for most dissolved ions, suggesting active material exchange in the system. The molar ratios among the dissolved ions suggest that both continental/meteoric and seawater (saline water)/oceanic contributions are important in KCC water. The ions in ponds and lakes and in river Mayur might have derived from similar sources; however, the sources are varied in the case of groundwater. The geochemical mechanism controlling the ponds and lakes, and the Mayur water chemistry is commanded by the process of rock weathering, while the winter chemistry of most groundwater is controlled by the process of evaporation and crystallization. Water from the three potential sources of KCC indicates mixed hydrochemical facies where the process of natural softening is active, while certain KCC groundwater indicates reverse softening and up-coning of saline front. An assessment of potable water quality among the three sources suggests that the ponds and lakes, and the river Mayur have the geochemical potential to provide water security to the KCC, particularly the river Mayur during monsoon. Thus, a plan for maintaining especially the Mayur as a freshwater reservoir is necessary for meeting the freshwater challenges in KCC.

Spatial and temporal variations of CO2 emissions from the active fault zones in the capital area of China

The chemical and isotopic composition of 26 soil gas wells and 11 springs along the active fault zones in the capital area of China was determined to investigate the origin of CO2, the spatial and temporal variations of CO2 emission, and their mechanisms. The chemical and isotopic data indicated that biogenic CO2 was the primary source for CO2 from the soil gas wells in both the basin and orogen regions, the crust-derived and mantle-derived CO2 could have ascended through the deep-cut faults and got into the springs, with a few diffusing into the soil gas wells. Minor air could have intruded into the soil gas wells in the orogen region through the faults cutting the surface, owing to the barometric pressure fluctuation. Relatively high He concentration, CO2 concentration, and flux of soil gas from wells were observed in the basin region than those in the orogen region. A significant amount of CO2 is produced during the process of oxidation of organic matter in the basin, where the organic matter accumulates in thick clayey strata. Further amounts of CO2 are produced by interactions between groundwaters and carbonates, which are widely represented in the basin region and by intruded air into the soil gas wells in the orogen region due to barometric pressure fluctuations. Temporal variations of CO2 concentration and CO2 flux were observed in soil gas wells in the basin region, where seismic activity is more frequent compared to those in the orogen, indicating that seismic activity could be responsible for the jumpily temporal variations of CO2 concentration and flux in wells. Monitoring activities of soil gas CO2 concentrations and CO2 fluxes in active fault zones should be carried out.