Lower Values In Winter Research Articles

The Global Spatiotemporal Distribution of the Mid-Tropospheric CO2 Concentration and Analysis of the Controlling Factors

The atmospheric infrared sounder (AIRS) provides a robust and accurate data source to investigate the variability of mid-tropospheric CO2 globally. In this paper, we use the AIRS CO2 product and other auxiliary data to survey the spatiotemporal distribution characteristics of mid-tropospheric CO2 and the controlling factors using linear regression, empirical orthogonal functions (EOFs), geostatistical analysis, and correlation analysis. The results show that areas with low mid-tropospheric CO2 concentrations (20°S–5°N) (384.2 ppm) are formed as a result of subsidence in the atmosphere, the presence of the Amazon rainforest, and the lack of high CO2 emission areas. The areas with high mid-tropospheric CO2 concentrations (30°N–70°N) (382.1 ppm) are formed due to high CO2 emissions. The global mid-tropospheric CO2 concentrations increased gradually (the annual average rate of increase in CO2 concentration is 2.11 ppm/a), with the highest concentration occurring in spring (384.0 ppm) and the lowest value in winter (382.5 ppm). The amplitude of the seasonal variation retrieved from AIRS (average: 1.38 ppm) is consistent with that of comprehensive observation network for trace gases (CONTRAIL), but smaller than the surface ground stations, which is related to altitude and coverage. These results contribute to a comprehensive understanding of the spatiotemporal distribution of mid-tropospheric CO2 and related mechanisms.

Vegetation indices variability in the Pampa grasslands in Brazil and Uruguay

The Pampa Biome is one of the largest and richest grasslands in the world, with a vast diversity of species and an unique coexistence of several C3 and C4 plants in time and space. The object of this study was to characterize the annual and seasonal variability of NDVI and EVI vegetation indices over grassland types and to identify the possible difference between ecological regions. The study area focuses on 13 ecological regions into the Pampa Biome in Brazil (Rio Grande do Sul State), and Uruguay. The temporal and spatial variability of the vegetation vigor was analyzed through NDVI and EVI vegetation indices for a period from 2000 to 2011. The results showed that NDVI and EVI temporal average patterns are similar and reflect, for each region, the vegetation vigor associated to the soil type, and the rainfall. For both vegetation indices, the high values occur during summer and lower values in winter. However, the intra-annual variability of the vegetation indices are higher during summer, when EVI shows more potential to detect changes in vegetation vigor.

Transference of isotopic signal from rainfall to dripwaters and farmed calcite in Mediterranean semi-arid karst

This study was conducted in Ejulve cave (Spain, southwestern Europe) over a period of four years (2013–2016) to identify the factors affecting the isotopic composition of rainfall, dripwaters, and farmed calcite. The results indicate that δ18O of rainfall in the study area was mainly controlled by the temperature effect (r2 = 0.82, p-value < 0.001) with source effect and amount effect being secondary controls. Additionally, it exhibited a seasonal pattern with lower values indicated during winter and higher in summer. The use of effective infiltration to evaluate the recharge of the epikarst is extremely important in semi-arid karst climate conditions. This analysis revealed that while the amount effect exerted a moderate control on the annual δ18O in rainfall, it had a lower influence on the isotopic variability of the rainfall potentially infiltrating the karst aquifer. The sampling of 12 drip locations in Ejulve cave indicated that seepage and seasonal drips featured similar δ18O values in dripwaters. The homogenisation process during the infiltration in the epikarst was not complete, therefore, the δ18O seasonality seen in rainfall was also observed in dripwater δ18O, albeit attenuated and lagged. With the seasonal increase in rainfall in autumn, drip rates of seasonal and seepage groups increased within a few weeks. However, the lower δ18O of autumn–winter rain was observed in dripwaters with a lag as long as 21 weeks. The δ18O in farmed calcite showed a small variation of 0.11‰ while the δ13C varied seasonally with a variation of about 0.22‰ and indicated higher values during summer and autumn and lower values in winter and spring. Seasonal and seepage sites exhibited similar δ18O variability. However, δ13C was more positive in seepage sites and was enhanced by degassing kinetics to produce a variability of up to 0.42‰ in contrast to the 0.29‰ observed in the seasonal sites. The δ18O of calcite showed dependence on the δ18O of dripwater with a weak influence of the drip rate. However, δ13C exhibited a higher correlation with the drip rate and high δ13C was explained by enhanced degassing and low water availability while low δ13C values were in concordance with higher microbial activity, vegetation productivity, and greater water availability. The ventilation of the cave during late autumn through spring favoured the higher calcite deposition rates found during that time.

Spatio-Temporal Characteristics of Tropospheric Ozone and Its Precursors in Guangxi, South China

The temporal and spatial distributions of tropospheric ozone and its precursors (NO2, CO, HCHO) are analyzed over Guangxi (GX) in South China. We used tropospheric column ozone (TCO) from the Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) onboard the Aura satellite (OMI/MLS), NO2 and HCHO from OMI and CO from the Measurements of Pollution in the Troposphere (MOPITT) instrument in the period 2005–2016. The TCO shows strong seasonality, with the highest value in spring and the lowest value observed in the monsoon season. The seasonal variation of HCHO is similar to that of TCO, while NO2 and CO show slightly different patterns with higher values in spring and winter compared to lower values in autumn and summer. The surface ozone, NO2 and CO observed by national air quality monitoring network sites are also compared with satellite-observed TCO, NO2 and CO, showing good agreement for NO2 and CO but a different seasonal pattern for ozone. Unlike TCO, surface ozone has the highest value in autumn and the lowest value in winter. To reveal the difference, the vertical profiles of ozone and CO from the measurement of ozone and water vapor by airbus in-service aircraft (MOZAIC) observations over South China are also examined. The seasonal averaged vertical profiles of ozone and CO show obvious enhancements at 2–6 km altitudes in spring. Furthermore, we investigate the dependence of TCO and surface ozone on meteorology and transport in detail along with the ECMWF reanalysis data, Tropical Rainfall Measuring Mission (TRMM) 3BV42 dataset, OMI ultraviolet index (UV index) dataset, MODIS Fire Radiative Power (FRP) and back trajectory. Our results show that the wind pattern at 800 hPa plays a significant role in determining the seasonality of TCO over GX, especially for the highest value in spring. Trajectory analysis, combined with MODIS FRP suggests that the air masses that passed through the biomass burning (BB) region of Southeast Asia (SEA) induced the enhancement of TCO and CO in the upper-middle troposphere in spring. However, the seasonal cycle of surface ozone is associated with wind patterns at 950 hPa, and the contribution of the photochemical effect is offset by the strong summer monsoon, which results in the maximum surface ozone concentration in post-monsoon September. The variations in the meteorological conditions at different levels and the influence of transport from SEA can account for the vertical distribution of ozone and CO. We conclude that the seasonal distribution of TCO results from the combined impact of meteorology and long-term transport.

Spatial and temporal variations of suspended solid concentrations from 2000 to 2013 in Poyang Lake, China

Concentrations of suspended solids in lakes can affect the latter’s primary productivity and reflect changes in sediment deposition. Determining the temporal and spatial distribution of suspended solid concentrations has important significance in lake water environmental management; this is particularly urgent for Poyang Lake, the largest freshwater lake in China. In this study, suspended solid concentration inversion models for Poyang Lake were created using a semi-empirical method with regression analysis between continuously measured suspended solid concentration data and multi-band moderate-resolution imaging spectroradiometer images for spring, summer, autumn, and winter from 2009 to 2012. The coefficient of determination (R2) is from 0.6 to 0.9 and the average relative error for the accuracy verification was between 10 and 30%. The seasonal distributions of suspended solid concentrations in Poyang Lake from 2000 to 2013 were then obtained using optimal reversal models. The results showed that the seasonal variation in suspended solid concentrations had a “W” shape in which high spring and autumn and low summer and winter values. The suspended solid concentrations increased annually from 2000 to 2013 and were mainly distributed in the northern and central portions of the lake, with lower values along the shorelines. Further analysis indicated that the large difference in water level between the wet and dry seasons is an important factor in explaining these seasonal variations. Moreover, the suspended solid concentrations were poorly correlated with water temperature and chlorophyll-a concentration but more highly correlated with the deferred chlorophyll-a concentration.

Nutrient removal from agricultural run-off in demonstrative full scale tubular photobioreactors for microalgae growth

The objective of this paper is to present the design, construction and operation (during one year) of 3 full scale semi-closed, horizontal tubular photobioreactors (PBR, 11.7 m3 of volume each) used to remove nutrients of a mixture of agricultural run-off (90%) and treated domestic wastewater (10%). PBRs were located outdoor and have 2 paddlewheels (engines of 0.25 kW) to ensure the movement of the mixed liquor. The microalgal biomass produced in the PBRs was harvested in a static lamella settling tank in which a polyaluminium chloride coagulant is applied. Each PBR treated in average 2.3 m3/d, being the actual mean hydraulic retention time 5 d. PBRs were submitted to strong seasonal changes regarding solar radiation and temperature, which had a direct impact in the activity of microalgae and the efficiency of the system. Higher mixed liquor pH values were registered in summer (daily average > 10). These high values were not observed in the effluents because the system was designed to discharge the mixed liquor (effluent) only at the end of night, when pH reached the lowest daily values (around 8.5). Most of the influent and effluent nitrogen content was inorganic (average of 9.0 mg N/L and 3.17 mg N/L, respectively), and in the form of nitrate (62% and 50%, respectively). Average nitrogen removal efficiency was 65%, with values of around 90% in summer, 80% in autumn, 50% in winter and 60% in spring. Most of the influent and effluent phosphorus content was in the form of orthophosphate. Influent average was 0.62 mg P/L, but with great variations and in a considerable number of samples not detected. Removal efficiency (when influent values were detected) was very high during all the study, usually greater than 95%, and there were not clear seasonal trends for efficiency as observed for TIN. Volumetric biomass production greatly changed between seasons with much lower values in winter (7 g VSS (volatile suspended solids)/m3·d) than in summer (43 g VSS/m3·d). Biomass separation efficiency of the settler was very good in either terms of turbidity and total suspended solids, being most of the time lower than 5 UNT and 25 mg/L, respectively. Overall this study demonstrated the reliable and good effectiveness of microalgae based technologies such as the PBR to remove nutrients at a full scale size.

Nutrient removal from agricultural run-off in demonstrative full scale tubular photobioreactors for microalgae growth

The objective of this paper is to present the design, construction and operation of 3 full scale semi-closed, horizontal tubular photobioreactors (PBR) used to remove nutrients of a mixture of agricultural run-off (90%) and treated domestic wastewater (10%). The microalgal biomass produced in the PBRs was harvested in a static lamella settling tank. Each PBR treated in average 2.3 m3/d. PBRs were submitted to strong seasonal changes regarding solar radiation and temperature, which had a direct impact in the activity of microalgae and the efficiency of the system. Higher mixed liquor pH values were registered in summer (daily average> 10). Most of the influent and effluent nitrogen content was inorganic (average of 9.0 mg N/L and 3.17 mg N/L, respectively), and in the form of nitrate (62% and 50%, respectively). Average nitrogen removal efficiency was 65%, with values of around 90% in summer, 80% in autumn, 50 % in winter and 60% in spring. Most of the influent and effluent phosphorus content was in the form of ortophosphate. Influent average was 0.62 mg P/L, but with great variations and in a considerable number of samples not detected. Removal efficiency (when influent values were detected) was very high during all the study, usually greater than 95%, and there were not clear seasonal trends for efficiency as observed for TIN. Volumetric biomass production greatly changed between seasons with much lower values in winter (7 g VSS/m3d) than in summer (43 g VSS/m3d). Biomass separation efficiency of the settler was very good in either terms of turbidity and total suspended solids, being most of the time lower than 5 UNT and 15 mg/L, respectively. Overall this study demonstrated the reliable and good effectiveness of microalgae based technologies such as the PBR to remove nutrients at a full scale size.

Seasonality of the lower tropospheric ozone over China observed by the Ozone Monitoring Instrument

We analyzed the ozone (O3) profile product (PROFOZ) derived from Ozone Monitoring Instrument(OMI) ultraviolet (UV) spectra to reveal spatial and temporal variations in O3 distributions over China. Although discriminating vertical O3 in the lower troposphere is a challenge for satellite-borne measurements, previous research has confirmed the reliability of the lowermost layer O3 of the PROFOZ product, corresponding to 0–3 km, under the high O3 condition over China by comparison with the airborne measurements. In the present study, we focus on the seasonal variation of O3 obtained in the lowermost layer over China. We track the O3 enhancement under polluted conditions by using the ozone anomaly (ΔO3), defined as the difference between the retrieval values and a priori values, because our focus is the temporally high O3 level compared with the background level. We divide the 25–40° N and 100–135° E region into clusters according to the similarity of the seasonal variation in ΔO3 at the lowermost layer corresponding to approximately 0–3 km in altitude. Using this cluster analysis, we distinguish the areas in which ΔO3 has outstanding seasonality with high values in summer, particularly in June, and low values in winter over the North China Plain and Sichuan basin. The areas with these anomalous ΔO3 values correspond to high NO2 emission areas. We compare the results with model simulations from the Meteorological Research Institute–Chemistry Climate Model (MRI-CCM2) and meteorological data. The areas showing outstanding seasonality also correspond to those of high chemical production rates in June. Along the coastal area, ΔO3 values tend to drop to negative in August, which can be attributed to the inflow of clean oceanic air to inland regions. The results presented here again demonstrate the reliability of the lower tropospheric O3 data from the OMI PROFOZ product and suggest good capability of UV satellite sensors for monitoring O3 pollution that will be launched in the near future.

Validation and Spatiotemporal Distribution of GEOS-5–Based Planetary Boundary Layer Height and Relative Humidity in China

Few studies have specifically focused on the validation and spatiotemporal distribution of planetary boundary layer height (PBLH) and relative humidity (RH) data in China. In this analysis, continuous PBLH and surface-level RH data simulated from GEOS-5 between 2004 and 2012, were validated against ground-based observations. Overall, the simulated RH was consistent with the statistical data from meteorological stations, with a correlation coefficient of 0.78 and a slope of 0.9. However, the simulated PBLH was underestimated compared to LIDAR data by a factor of approximately two, which was primarily because of poor simulation in late summer and early autumn. We further examined the spatiotemporal distribution characteristics of two factors in four regions—North China, South China, Northwest China, and the Tibetan Plateau. The results showed that the annual PBLH trends in all regions were fairly moderate but sensitive to solar radiation and precipitation, which explains why the PBLH values were ranked in order from largest to smallest as follows: Tibetan Plateau, Northwest China, North China, and South China. Strong seasonal variation of the PBLH exhibited high values in summer and low values in winter, which was also consistent with the turbulent vertical exchange. Not surprisingly, the highest RH in South China and the lowest RH in desert areas of Northwest China (less than 30%). Seasonally, South China exhibited little variation, whereas Northwest China exhibited its highest humidity in winter and lowest humidity in spring, the maximum values in the other regions were obtained from July to September.

Retrieval Accuracy of HCHO Vertical Column Density from Ground-Based Direct-Sun Measurement and First HCHO Column Measurement Using Pandora

In the present study, we investigate the effects of signal to noise (SNR), slit function (FWHM), and aerosol optical depth (AOD) on the accuracy of formaldehyde (HCHO) vertical column density (HCHOVCD) using the ground-based direct-sun synthetic radiance based on differential optical absorption spectroscopy (DOAS). We found that the effect of SNR on HCHO retrieval accuracy is larger than those of FWHM and AOD. When SNR = 650 (1300), FWHM = 0.6, and AOD = 0.2, the absolute percentage difference (APD) between the true HCHOVCD values and those retrieved ranges from 54 (30%) to 5% (1%) for the HCHOVCD of 5.0 × 1015 and 1.1 × 1017 molecules cm−2, respectively. Interestingly, the maximum AOD effect on the HCHO accuracy was found for the HCHOVCD of 3.0 × 1016 molecules cm−2. In addition, we carried out the first ground-based direct-sun measurements in the ultraviolet (UV) wavelength range to retrieve the HCHOVCD using Pandora in Seoul. The HCHOVCD was low at 12:00 p.m. local time (LT) in all seasons, whereas it was high in the morning (10:00 a.m. LT) and late afternoon (4:00 p.m. LT), except in winter. The maximum HCHOVCD values were 2.68 × 1016, 3.19 × 1016, 2.00 × 1016, and 1.63 × 1016 molecules cm−2 at 10:00 a.m. LT in spring, 10:00 a.m. LT in summer, 1:00 p.m. LT in autumn, and 9:00 a.m. LT in winter, respectively. The minimum values of Pandora HCHOVCD were 1.63 × 1016, 2.23 × 1016, 1.26 × 1016, and 0.82 × 1016 molecules cm−2 at around 1:45 p.m. LT in spring, summer, autumn, and winter, respectively. This seasonal pattern of high values in summer and low values in winter implies that photo-oxidation plays an important role in HCHO production. The correlation coefficient (R) between the monthly HCHOVCD values from Pandora and those from the Ozone Monitoring Instrument (OMI) is 0.61, and the slope is 1.25.

Physical and chemical properties of deposited airborne particulates over the Arabian Red Sea coastal plain

Abstract. Mineral dust is the most abundant aerosol, having a profound impact on the global energy budget. This research continues our previous studies performed on surface soils in the Arabian Peninsula, focusing on the mineralogical, physical and chemical composition of dust deposits from the atmosphere at the Arabian Red Sea coast. For this purpose, aerosols deposited from the atmosphere are collected during 2015 at six sites on the campus of the King Abdullah University of Science and Technology (KAUST) situated on the Red Sea coastal plain of Saudi Arabia and subjected to the same chemical and mineralogical analysis we conducted on soil samples. Frisbee deposition samplers with foam inserts were used to collect dust and other deposits, for the period December 2014 to December 2015. The average deposition rate measured at KAUST for this period was 14 g m−2 per month, with lowest values in winter and increased deposition rates in August to October. The particle size distributions provide assessments of &lt; 10 and &lt; 2.5 µm dust deposition rates, and it is suggested that these represent proxies for PM10 (coarse) and PM2. 5 (fine) particle size fractions in the dust deposits.X-ray diffraction (XRD) analysis of a subset of samples confirms variable amounts of quartz, feldspars, micas, and halite, with lesser amounts of gypsum, calcite, dolomite, hematite, and amphibole. Freeze-dried samples were re-suspended onto the Teflon® filters for elemental analysis by X-ray fluorescence (XRF), while splits from each sample were analyzed for water-soluble cations and anions by ion chromatography. The dust deposits along the Red Sea coast are considered to be a mixture of dust emissions from local soils and soils imported from distal dust sources. Airborne mineral concentrations are greatest at or close to dust sources, compared to those through medium- and long-range transport. It is not possible to identify the exact origin of deposition samples from the mineralogical and chemical results alone. These aerosol data are the first of their kind from the Red Sea region. They will help assess their potential nutrient input into the Red Sea, as well the impact on human health, industry, and solar panel efficiency. These data will also support dust modeling in this important dust belt source area by better quantifying dust mass balance and optical properties of airborne dust particles.

Assessing river water quality using water quality index in Lake Taihu Basin, China

Lake Taihu Basin, one of the most developed regions in China, has received considerable attention due to its severe pollution. Our study provides a clear understanding of the water quality in the rivers of Lake Taihu Basin based on basin-scale monitoring and a water quality index (WQI) method. From September 2014 to January 2016, four samplings across four seasons were conducted at 96 sites along main rivers. Fifteen parameters, including water temperature, pH, dissolved oxygen (DO), conductivity, turbidity (tur), permanganate index (CODMn), total nitrogen, total phosphorus, ammonium (NH4-N), nitrite, nitrate (NO3-N), calcium, magnesium, chloride, and sulfate, were measured to calculate the WQI. The average WQI value during our study period was 59.33; consequently, the water quality was considered as generally “moderate”. Significant differences in WQI values were detected among the 6 river systems, with better water quality in the Tiaoxi and Nanhe systems. The water quality presented distinct seasonal variation, with the highest WQI values in autumn, followed by spring and summer, and the lowest values in winter. The minimum WQI (WQImin), which was developed based on a stepwise linear regression analysis, consisted of five parameters: NH4-N, CODMn, NO3-N, DO, and tur. The model exhibited excellent performance in representing the water quality in Lake Taihu Basin, especially when weights were fully considered. Our results are beneficial for water quality management and could be used for rapid and low-cost water quality evaluation in Lake Taihu Basin. Additionally, we suggest that weights of environmental parameters should be fully considered in water quality assessments when using the WQImin method.

Evaluation of radiosonde, MODIS-NIR-Clear, and AERONET precipitable water vapor using IGS ground-based GPS measurements over China

Water vapor is one of the major greenhouse gases in the atmosphere and also the key parameter affecting the hydrological cycle, aerosol properties, aerosol-cloud interactions, the energy budget, and the climate. This study analyzed the temporal and spatial distribution of precipitable water vapor (PWV) in China using MODerate resolution Imaging Spectroradiometer near-infrared (MODIS-NIR)-Clear PWV products from 2011 to 2013. We then compared the four PWV products (Global Positioning System PWV (GPS-PWV), radiosonde PWV (RS-PWV), MODIS-NIR-Clear PWV, and Aerosol Robotic Network sunphotometer PWV (AERONET-PWV)) at six typical sites in China from 2011 to 2013. The analysis of the temporal and spatial distribution showed that the PWV distribution in China has clear geographical differences, and its basic distribution characteristics gradually change from the coast in the southeast to inland in the northwest. Affected by the East Asian monsoon, the PWV over China showed clear seasonal distribution features, with highest values in the summer, followed by autumn and spring, and the lowest values in winter. Intercomparison results showed that GPS-PWV and RS-PWV had a slightly higher correlation (R2=0.975) at 0000 UTC than that at 1200 UTC (R2=0.967). The mean values of Bias, SD, and RMSE between GPS-PWV and RS-PWV (GPS-RS) were −0.03mm, 2.36mm, and 2.60mm at 0000 UTC, and −0.23mm, 2.76mm, and 2.95mm at 1200 UTC, respectively. This showed that GPS-PWV was slightly lower than RS-PWV, and this difference was more obvious during the nighttime. The MODIS-NIR-Clear PWV product showed a similar correlation coefficient (R2=0.88) with GPS-PWV compared with RS-PWV. In addition, MODIS-NIR-Clear PWV was greater than GPS-PWV and RS-PWV. The MODIS-NIR-Clear PWV showed a larger deviation from GPS-PWV (MODIS-GPS Bias=1.50mm, RMSE=5.76mm) compared with RS PWV (MODIS-RS Bias=0.75mm, RMSE=5.31mm). The correlation coefficients between AERONET-PWV and the PWV from GPS, RS, and MODIS-NIR-Clear were 0.970, 0.963, and 0.923 (with RMSE of 2.53mm, 3.67mm, and 4.39mm), respectively. In the Beijing area, the overall mean bias of the AERONET-PWV product with GPS-PWV, RS-PWV and MODIS-NIR-Clear PWV was −0.09mm, −1.82mm, and −1.54mm, respectively, which shows that the AERONET-PWV product was lower than the other three PWV products.

Characteristics of black carbon in snow from Laohugou No. 12 glacier on the northern Tibetan Plateau

Black carbon (BC) emitted from the incomplete combustion of biomass and fossil fuel impacts the climate system, cryospheric change, and human health. This study documents black carbon deposition in snow from a benchmark glacier on the northern Tibetan Plateau. Significant seasonality of BC concentrations indicates different input or post-depositional processes. BC particles deposited in snow had a mass volume median diameter slightly larger than that of black carbon particles typically found in the atmosphere. Also, unlike black carbon particles in the atmosphere, the particles deposited in snow did not exhibit highly fractal morphology by Scanning Transmission Electron Microscope. Footprint analysis indicated BC deposited on the glacier in summer originated mainly from Central Asia; in winter, the depositing air masses generally originated from Central Asia and Pakistan. Anthropogenic emissions play an important role on black carbon deposition in glacial snow, especially in winter. The mass absorption efficiency of BC in snow at 632nm exhibited significantly seasonality, with higher values in summer and lower values in winter. The information on black carbon deposition in glacial snow provided in this study could be used to help mitigate the impacts of BC on glacier melting on the northern Tibetan Plateau.

The combined effect of reduced fossil fuel consumption and increasing biomass combustion on Athens' air quality, as inferred from long term CO measurements

To evaluate the role of biomass burning emissions, and in particular of residential wood heating, as a result of the economic recession in Greece, carbon monoxide (CO) atmospheric concentrations from five (5) stations of the National Air Pollution Monitoring Network in Athens, spanning the period 2000–2015, in conjunction with black carbon (BC) concentrations from the NOA (National Observatory of Athens) station at Thissio were analysed. The contribution of the different sources to the diurnal cycle of these two pollutants is clear, resulting to a morning peak, mainly due to traffic, and a late evening peak attributed both to fossil fuel (traffic plus central heating) and biomass combustion. Calculated morning and evening integrals of CO peaks, for the investigated period, show consistent seasonal modulations, characterised by low summer and high winter values. The summer and winter morning CO peak integrals demonstrate an almost constant decreasing trend of CO concentrations over time (by almost 50% since 2000), attributed to the renewal of passenger car fleet and to reduced anthropogenic activities during the last years. On the other hand, an increase of 23%–78% (depending on the monitoring site) in the winter evening integrals since 2012, provides evidence of the significant contribution of biomass combustion, which has prevailed over fossil fuel for domestic heating. CO emitted by wood burning was found to contribute almost 50% to the total CO emissions during night time (16:00–5:00), suggesting that emissions from biomass combustion have gained an increasing role in atmospheric pollution levels in Athens.

7Be in soil, deposited dust and atmospheric air and its using to infer soil erosion along Alexandria region, Egypt

This study investigated the radioactivity behavior of 7Be in surface soil, airborne and deposited dust along Alexandria region in Egypt. The results obtained were used to predict scavenging processes of 7Be from surface soil to infer soil erosion and land vulnerable to accelerated sea-level rise. The areal activity concentrations of 7Be in surface soil were investigated in 30 undisturbed sites and 7Be inventories were determined via deposited dust in 10 locations. Results of the former were found to be ranged from 78 Bq/m2 to 104 Bq/m2. High levels were observed in western sites associated with high dust deposition rate. On the other hand, low levels were found in the eastern sites, those may be attributed to scavenging processes such as land erosion toward the direction to the sea. The effective removal rates of 7Be were calculated using the box-model, showing a broad special trend of inventories generally decreasing eastwards. The scavenging rates were ranged between 3.13 yr−1 in western sites to 5.34 yr−1 in eastern ones which denote that the east of the city suffers from rapid soil erosion. The airborne 7Be was monthly monitored along the period from October 2014 to September 2015 through one site located at the mid of the city. The results revealed lower values in winter and autumn than in summer and spring ranged between 6.2 mBq/m3 and 10.5 mBq/m3. These levels are comparable with that in other world regions and the seasonal variations are associated with the prevailing climatic conditions in Alexandria region.

Aerosol optical properties measurements by a CAPS single scattering albedo monitor: Comparisons between summer and winter in Beijing, China

AbstractAerosol optical properties were measured in Beijing in summer and winter using a state‐of‐the‐art cavity attenuated phase shift single scattering albedo monitor (CAPS PMssa) along with aerosol composition measurements by aerosol mass spectrometers and aethalometers. The SSA directly measured by the CAPS PMssa showed overall agreements with those derived from colocated measurements. However, substantial differences were observed during periods with low SSA values in both summer and winter, suggesting that interpretation of low SSA values needs to be cautious. The average (±σ) extinction coefficient (bext) and absorption coefficient (bap) were 336 (±343) Mm−1 and 44 (±41) Mm−1, respectively, during wintertime, which were approximately twice those observed in summer, while the average SSA was relatively similar, 0.86 (±0.06) and 0.85 (±0.04) in summer and winter, respectively. Further analysis showed that the variations in SSA can be approximately parameterized as a function of mass fraction of secondary particulate matter (fSPM), which is SSA = 0.74 + 0.19 × fSPM (fSPM &gt; 0.3, r2 = 0.85). The contributions of aerosol species to extinction coefficients during the two seasons were also estimated. Our results showed that the light extinction was dominantly contributed by ammonium sulfate (30%) and secondary organic aerosol (22%) in summer, while organic aerosol was the largest contributor (51%) in winter. Consistently, SPM played the major role in visibility degradation in both seasons by contributing 70% of the total extinction.

Diurnal, seasonal, and spatial variations and flux of carbon monoxide in Jiaozhou Bay, China

Abstract Four cruises were conducted in Jiaozhou Bay from January to November in 2008 to study carbon monoxide (CO) distribution, diurnal variation, seasonal variation, and sea-to-air flux. Surface water CO concentration exhibited strong diurnal variations at an anchor station in both April and November, with highest CO concentration 3–5 times higher than minimum values. Diurnal variation (sampling time) exerts an overall pattern on CO distribution, spatially distributed factors impose extra influence. High CO concentrations and fluxes were observed in the eastern, northern, and western parts of the bay, which are close to areas of estuaries, dense population, and high industrialization, reflecting the impact of human activities on CO distribution. Both surface water CO concentrations and sea-to-air fluxes showed seasonal variations, with the highest values in summer and the lowest values in winter. Sea-to-air CO flux in Jiaozhou Bay ranged from 0 to 34.66 μmol m − 2 d − 1 with a mean flux of 4.96 μmol m − 2 d − 1 .

Diurnal and Seasonal Variations in the Net Ecosystem CO2 Exchange of a Pasture in the Three-River Source Region of the Qinghai-Tibetan Plateau.

Carbon dioxide (CO2) exchange between the atmosphere and grassland ecosystems is very important for the global carbon balance. To assess the CO2 flux and its relationship to environmental factors, the eddy covariance method was used to evaluate the diurnal cycle and seasonal pattern of the net ecosystem CO2 exchange (NEE) of a cultivated pasture in the Three-River Source Region (TRSR) on the Qinghai−Tibetan Plateau from January 1 to December 31, 2008. The diurnal variations in the NEE and ecosystem respiration (Re) during the growing season exhibited single-peak patterns, the maximum and minimum CO2 uptake observed during the noon hours and night; and the maximum and minimum Re took place in the afternoon and early morning, respectively. The minimum hourly NEE rate and the maximum hourly Re rate were −7.89 and 5.03 μmol CO2 m−2 s−1, respectively. The NEE and Re showed clear seasonal variations, with lower values in winter and higher values in the peak growth period. The highest daily values for C uptake and Re were observed on August 12 (−2.91 g C m−2 d−1) and July 28 (5.04 g C m−2 day−1), respectively. The annual total NEE and Re were −140.01 and 403.57 g C m−2 year−1, respectively. The apparent quantum yield (α) was −0.0275 μmol μmol−1 for the entire growing period, and the α values for the pasture’s light response curve varied with the leaf area index (LAI), air temperature (Ta), soil water content (SWC) and vapor pressure deficit (VPD). Piecewise regression results indicated that the optimum Ta and VPD for the daytime NEE were 14.1°C and 0.65 kPa, respectively. The daytime NEE decreased with increasing SWC, and the temperature sensitivity of respiration (Q10) was 3.0 during the growing season, which was controlled by the SWC conditions. Path analysis suggested that the soil temperature at a depth of 5 cm (Tsoil) was the most important environmental factor affecting daily variations in NEE during the growing season, and the photosynthetic photon flux density (PPFD) was the major limiting factor for this cultivated pasture.

US: Techmer – plastic compounds

The objective of this paper is to present the design, construction and operation (during one year) of 3 full scale semi-closed, horizontal tubular photobioreactors (PBR, 11.7 m3 of volume each) used to remove nutrients of a mixture of agricultural run-off (90%) and treated domestic wastewater (10%). PBRs were located outdoor and have 2 paddlewheels (engines of 0.25 kW) to ensure the movement of the mixed liquor. The microalgal biomass produced in the PBRs was harvested in a static lamella settling tank in which a polyaluminium chloride coagulant is applied. Each PBR treated in average 2.3 m3/d, being the actual mean hydraulic retention time 5 d. PBRs were submitted to strong seasonal changes regarding solar radiation and temperature, which had a direct impact in the activity of microalgae and the efficiency of the system. Higher mixed liquor pH values were registered in summer (daily average > 10). These high values were not observed in the effluents because the system was designed to discharge the mixed liquor (effluent) only at the end of night, when pH reached the lowest daily values (around 8.5). Most of the influent and effluent nitrogen content was inorganic (average of 9.0 mg N/L and 3.17 mg N/L, respectively), and in the form of nitrate (62% and 50%, respectively). Average nitrogen removal efficiency was 65%, with values of around 90% in summer, 80% in autumn, 50% in winter and 60% in spring. Most of the influent and effluent phosphorus content was in the form of orthophosphate. Influent average was 0.62 mg P/L, but with great variations and in a considerable number of samples not detected. Removal efficiency (when influent values were detected) was very high during all the study, usually greater than 95%, and there were not clear seasonal trends for efficiency as observed for TIN. Volumetric biomass production greatly changed between seasons with much lower values in winter (7 g VSS (volatile suspended solids)/m3·d) than in summer (43 g VSS/m3·d). Biomass separation efficiency of the settler was very good in either terms of turbidity and total suspended solids, being most of the time lower than 5 UNT and 25 mg/L, respectively. Overall this study demonstrated the reliable and good effectiveness of microalgae based technologies such as the PBR to remove nutrients at a full scale size.