Diurnal and seasonal variation of short-lived radon progeny concentration and atmospheric temporal variations of 210Pb and 7Be in Egypt

During a one-year period, from November 1998 upto October 1999, the atmospheric activity concentrations of the short-lived (²²²Rn)-progeny (²¹⁸Po, ²¹⁴Pb, ²¹⁴Po) were measured every 4 h in the open air, using α-spectrometry. The concentration data of short-lived radon progeny together with meteorological variables (relative humidity, air temperature, and wind speed) were used for a comprehensive regression analysis of daily time variation of radioactivity in the air. The seasonal concentration pattern of all short-lived radon progeny shows the same trend for diurnal variation with higher values at night and early morning hours compared with lower values at noon and in afternoon. The activity concentrations were observed to be higher during the winter months (November–January) than in other seasons. The mean activity concentrations of ²¹⁸Po, ²¹⁴Pb and ²¹⁴Po within the whole year were found to be 6.7±0.8, 4.9±0.5 and 4.4±0.3 Bq m⁻³, respectively.Also, within that time period, approximately 120 samples were analysed to determine the concentrations of the long-lived radon decay product ²¹⁰Pb and the cosmogenic radionuclide ⁷Be using a single-filter technique. The course of ²¹⁰Pb air concentration is characterized by higher values in autumn/winter season and lower values in spring/summer season. The seasonal concentration pattern of ⁷Be reaches regular maximum values in the spring to early summer months. The annual average concentration values of ²¹⁰Pb and ⁷Be have been found to be 0.37±0.06 and 2.0±0.09 mBq m⁻³, respectively. A mean aerosol mass concentration of 36.6±6.2 μg m⁻³ was also determined during the measurements of the long-lived radionuclides. The majority of attached ²¹⁰Pb and ⁷Be were observed at lower aerosol mass concentrations while small fractions of attached activities were found to be associated with the higher mass concentrations.     

Use of principal component analysis to profile temporal and spatial variations of chlorinated solvent concentration in groundwater

This work aims at evaluating spatial distribution patterns of concentration variations for chlorinated solvents in groundwater, based on principal component analysis and geographic information system (GIS) tools. The study investigates long-time series of chlorinated solvent concentrations in groundwater measured for 18 contaminated industrial sites. The characterization of contaminant plumes and delineation of pollutant sources are essential for choosing appropriate monitoring and remediation strategies, as contaminated groundwaters are characterized by complex patterns of spatial and temporal concentration variability, with wide unpredictable fluctuations over time. The present work describes the results of a new exploratory statistical method called the Variability Index Method (VIM) applied to environmental data to assess the performance of using concentration variations as molecular tracers to reveal aquifer dynamics, industrial impacts, and point sources for contamination plumes. The application of this method provides a useful assessment of controls over contaminant concentration variations as well as support for remediation techniques.     

Smoke concentration in the greater Cairo atmosphere

A study of smoke content of the atmosphere over the Greater Cairo area was conducted during the 12 months from June 1977 to May 1978. Smoke samples were taken continuously over two-hour periods at two sites, one in Shubra El-Kheima industrial sector on the northern boundary of the study area and the other in a purely residential district about 15 km south-south-west of the first site.A comparison was made between the averaged concentrations at both sites. It was found that the industrial area was considerably higher in smoke contamination and that industrial activity is the principal source of smoke in the Cairo atmosphere.Daily and yearly cycles of smoke concentration were also studied and discussed in terms of man-made source activities and meteorological conditions. Concentrations were found to be much higher in the cold months. The daily cycle rhythm was the same at the two sites, having two well developed maxima in the morning and late evening and a pronounced minimum in the mid-afternoon. Daily maxima were almost of the same order of magnitude in each site. The morning maximum seemed to be formed by fumigation just after sunrise in the industrial sector and appeared two hours later in the downwind residential district.No significant difference was found between smoke concentrations during weekdays and weekends.     

Spatial and temporal variations of nitrous oxide flux between coastal marsh and the atmosphere in the Yellow River estuary of China

To investigate the spatial and seasonal variations of nitrous oxide (N₂O) fluxes and understand the key controlling factors, we explored N₂O fluxes and environmental variables in high marsh (HM), middle marsh (MM), low marsh (LM), and mudflat (MF) in the Yellow River estuary throughout a year. Fluxes of N₂O differed significantly between sampling periods as well as between sampling positions. During all times of day and the seasons measured, N₂O fluxes ranged from ?0.0051 to 0.0805 mg N₂O m^?2 h^?1, and high N₂O emissions occurred during spring (0.0278 mg N₂O m^?2 h^?1) and winter (0.0139 mg N₂O m^?2 h^?1) while low fluxes were observed during summer (0.0065 mg N₂O m^?2 h^?1) and autumn (0.0060 mg N₂O m^?2 h^?1). The annual average N₂O flux from the intertidal zone was 0.0117 mg N₂O m^?2 h^?1, and the cumulative N₂O emission throughout a year was 113.03 mg N₂O m^?2, indicating that coastal marsh acted as N₂O source. Over all seasons, N₂O fluxes from the four marshes were significantly different (p?<?0.05), in the order of HM (0.0256?±?0.0040 mg N₂O m^?2 h^?1)?>?MF (0.0107?±?0.0027 mg N₂O m^?2 h^?1)?>?LM (0.0073?±?0.0020 mg N₂O m^?2 h^?1)?>?MM (0.0026?±?0.0011 mg N₂O m^?2 h^?1). Temporal variations of N₂O emissions were related to the vegetations (Suaeda salsa, Phragmites australis, and Tamarix chinensis) and the limited C and mineral N in soils during summer and autumn and the frequent freeze/thaw cycles in soils during spring and winter, while spatial variations were mainly affected by tidal fluctuation and plant composition at spatial scale. This study indicated the importance of seasonal N₂O contributions (particularly during non-growing season) to the estimation of local N₂O inventory, and highlighted both the large spatial variation of N₂O fluxes across the coastal marsh (CV?=?158.31 %) and the potential effect of exogenous nitrogen loading to the Yellow River estuary on N₂O emission should be considered before the annual or local N₂O inventory was evaluated accurately.     

长江三角洲PM_(10)质量浓度遥感估算与时空分布特征

卫星遥感反演气溶胶光学厚度(AOT)已被广泛地应用于地面PM10遥感监测。为遥感监测长江三角洲地区PM10,利用2013年的MODIS/Terra AOT产品,考虑研究区36个空气质量监测站点的风速、温度、湿度和边界层高度等气象条件,构建了基于MODIS AOT产品估算PM10的模型。利用17个空气质量监测站点数据对模型进行散点拟合验证,结果表明,模型估算精度较高,春夏秋冬4个季节PM10质量浓度的模型估算值与地面监测值的相关系数R2值分别为0.72、0.76、0.69和0.72。利用模型估算的长时间序列PM10时空分布数据进行时空变化特征分析,结果表明:2000—2013年研究区PM10质量浓度呈增长趋势,月均增长量为0.077μg/m3,最大值出现在2月,为(107.2±22.0)μg/m3,最小值出现在8月,为(40.5±12.0)μg/m3;研究区PM10质量浓度空间分布差异显著,南部低,北部高,高值主要出现在由上海、杭州和南京构成的三角形区域的城市群中,而低值主要出现在南部远离城市的森林区域。结果表明,基于MODIS/Terra AOT产品和地面观测气象数据估算PM10的多元线性回归模型能较好地应用于区域PM10监测。     

Elemental background concentration in the atmosphere of an industrialized country

Concentrations of heavy elements in air were determined at a rural site in Belgium during periods of very low pollution levels. These low levels were appraised by means of a sensitive SO₂ monitor. Observed mean background concentrations are high or very high as compared with levels observed in remote or very remote areas of continental zones. However, extrapolating the observed concentrations to very low sulfur levels gives results comparable to those observed in remote areas.     

Modelling temporal variations in the global tropospheric arsenic burden

The response of the troposphere to anthropogenic mobilization of arsenic has been examined by inclusion of the troposphere in a seven reservoir global cycling model for arsenic. Mobilization was simulated from a steady-state condition by increasing the land efflux of arsenic with time according to present day observed arsenic concentrations in the troposphere. Simulations involved separation of low and high temperature pollutant processes, and restrictions in the magnitude of the low temperature source. The sensitivity of the model was also tested by subdividing the troposphere into marine and continental airmasses. The tropospheric burden of arsenic showed increases by factors from 2 to 10 over time scales varying from 8000 to 16,000 years. The elevation of the tropospheric burden was enhanced using the two airmass model, and these elevated levels were more persistent than for a single well-mixed troposphere.     

The characteristics of ozone and related compounds in the boundary layer of the South China coast: temporal and vertical variations during autumn season

We present measurements of several trace gases made at a subtropical coastal site in Hong Kong in October and November 1997. The gases include O₃, CO, SO₂, and NO_x. The surface measurement data are compared with those from an aircraft study [Kok et al. J. Geophys. Res. 102 (D15) (1997) 19043–19057], and a subset of the latter is used to show the vertical distribution of the trace gases in the boundary layer. During the study period, averaged concentrations at the surface site for O₃, CO, NO_x, and SO₂ were 50, 298, 2.75, and 1.65 ppbv, respectively. Their atmospheric abundance and diurnal pattern are similar to those found in the “polluted” rural areas in North America. The measured trace gases are fairly well mixed in the coastal boundary layer in the warm South China region. Large variability is indicated from the data. Examination of 10-day, isentropic back trajectories shows that the measured trace gases are influenced by maritime air masses, outflow of pollution-laden continental air, and the mixing of the two. The trajectories capture the contrasting chemical features of the large-scale air masses impacting on the study area. CO, NO_x and SO₂ all show higher concentrations in the strong outflow of continental air, as expected, than those in the marine category. Compared with previously reported values for the western Pacific, the much higher levels found in the marine trajectories in our study suggest the impacts of regional and/or sub-regional emissions on the measured trace gases at the study site. The presence of abundant O₃ and other chemically active trace gases in the autumn season, coupled with high solar radiation and warm weather, suggests that the South China Sea is a photochemically active region important for studying the chemical transformation of pollutants emitted from the Asian continent.     

A passive air sampler for characterizing the vertical concentration profile of gaseous phase polycyclic aromatic hydrocarbons in near soil surface air

Air-soil exchange is an important process governing the fate of polycyclic aromatic hydrocarbons (PAHs). A novel passive air sampler was designed and tested for measuring the vertical concentration profile of 4 low molecular weight PAHs in gaseous phase (PAH_LMW4) in near soil surface air. Air at various heights from 5 to 520 mm above the ground was sampled by polyurethane foam disks held in down-faced cartridges. The samplers were tested at three sites: A: an extremely contaminated site, B: a site near A, and C: a background site on a university campus. Vertical concentration gradients were revealed for PAH_LMW4 within a thin layer close to soil surface at the three sites. PAH concentrations either decreased (Site A) or increased (Sites B and C) with height, suggesting either deposition to or evaporation from soils. The sampler is a useful tool for investigating air-soil exchange of gaseous phase semi-volatile organic chemicals.     

Occurrence and temporal variations of TMDD in the river Rhine,Germany

Background, aim, and scope

The chemical substance 2,4,7,9-tetramethyl-5-decyne-4,7-diol (TMDD) is a non-ionic surfactant used as an industrial defoaming agent and in various other applications. Its commercial name is Surynol 104® and the related ethoxylates are also available as Surfynol® 420, 440, 465 and 485 which are characterized by different grades of ethoxylation of TMDD at both hydroxyl functional groups. TMDD and its ethoxylates offer several advantages in waterborne industrial applications in coatings, inks, adhesives as well as in paper industries. TMDD and its ethoxylates can be expected to reach the aquatic environment due its widespread use and its physico-chemical properties. TMDD has previously been detected in several rivers of Germany with concentrations up to 2.5?µg/L. In the United States, TMDD was also detected in drinking water. However, detailed studies about its presence and distribution in the aquatic environment have not been carried out so far. The aim of the present study was the analysis of the spatial and temporal concentration variations of TMDD in the river Rhine at the Rheingütestation Worms (443.3 km). Moreover, the transported load in the Rhine was investigated during two entire days and 7 weeks between November 2007 and January 2008.

Materials and methods

The sampling was carried out at three different sampling points across the river. Sampling point MWL1 is located in the left part of the river, MWL2 in the middle part, and MWL4 in the right part. One more sampling site (MWL3) was run by the monitoring station until the end of 2006, but was put out of service due to financial constrains. The water at the left side of the river Rhine (MWL1) is influenced by sewage from a big chemical plant in Ludwigshafen and by the sewage water from this city. The water at the right side of the river Rhine (MWL4) is largely composed of the water inflow from river Neckar, discharging into Rhine 14.9 km upstream from the sampling point and of communal and industrial wastewater from the city Mannheim. The water from the middle of the river (MWL2) is largely composed of water from the upper Rhine. Water samples were collected in 1-L bottles by an automatic sampler. The water samples were concentrated by use of solid-phase extraction (SPE) using Bond Elut PPL cartridges and quantified by use of gas chromatography-mass spectrometry (GC-MS). The quantification was carried out with the internal standard method. Based on these results, concentration variations were determined for the day profiles and week profiles. The total number of analyzed samples was 219.

Results

The results of this study provide information on the temporal concentration variability of TMDD in river Rhine in a cross section at one particular sampling point (443.3 km). TMDD was detected in all analyzed water samples at high concentrations. The mean concentrations during the 2 days were 314 ng/L in MWL1, 246 ng/L in MWL2, and 286 ng/L in MWL4. The variation of concentrations was low in the day profiles. In the week profiles, a trend of increasing TMDD concentrations was detected particularly in January 2008, when TMDD concentrations reached values up to 1,330 ng/L in MWL1. The mean TMDD concentrations during the week profiles were 540 ng/L in MWL1, 484 ng/L in MWL2, and 576 ng/L in MWL4. The loads of TMDD were also determined and revealed to be comparable in all three sections of the river. The chemical plant located at the left side of the Rhine is not contributing additional TMDD to the river. The load of TMDD has been determined to be 62.8 kg/d on average during the entire period. By extrapolation of data obtained from seven week profiles the annual load was calculated to 23 t/a.

Discussion

The permanent high TMDD concentrations during the investigation period indicate an almost constant discharge of TMDD into the river. This observation argues for effluents of municipal wastewater treatment plants as the most likely source of TMDD in the river. Another possible source might be the degradation of ethoxylates of TMDD (Surfynol® series 400), in the WWTPs under formation of TMDD followed by discharge into the river. TMDD has to be considered as a high-production-volume (HPV) chemical based on the high concentrations found in this study. In the United States, TMDD is already in the list of HPV chemicals from the Environmental Protection Agency (EPA). However, the amount of TMDD production in Europe is unknown so far and also the biodegradation rates of TMDD in WWTPs have not been investigated.

Conclusions

TMDD was found in high concentrations during the entire sampling period in the Rhine river at the three sampling points. During the sampling period, TMDD concentrations remained constant in each part of the river. These results show that TMDD is uniformly distributed in the water collected at three sampling points located across the river. ‘Waves’ of exceptionally high concentrations of TMDD could not be detected during the sampling period. These results indicate that the effluents of WWTPs have to be considered as the most important sources of TMDD in river Rhine.

Recommendations and perspectives

Based also on the occurrence of TMDD in different surface waters of Germany with concentrations up to 2,500 ng/L and its presence in drinking water in the USA, more detailed investigations regarding its sources and distribution in the aquatic environment are required. Moreover, the knowledge with respect to its ecotoxicity and its biodegradation pathway is scarce and has to be gained in more detail. Further research is necessary to investigate the rate of elimination of TMDD in municipal and industrial wastewater treatment plants in order to clarify the degradation rate of TMDD and to determine to which extent effluents of WWTPs contribute to the input of TMDD into surface waters. Supplementary studies are needed to clarify whether the ethoxylates of TMDD (known as Surfynol 400® series) are hydrolyzed in the aquatic environment resulting in formation of TMDD similar to the well known cleavage of nonylphenol ethoxylates into nonylphenols. The stability of TMDD under anaerobic conditions in groundwater is also unknown and should be studied.

     

Determining temporal and spatial variations in ozone air quality

Unless the change in emissions is substantial, the resulting improvement in ozone air quality can be easily masked by the meteorological variability. Therefore, the meteorological and chemical signals must be separated in examining ozone trends. In this paper, we discuss the use of the Kolmogorov-Zurbenko filter in evaluating the temporal and spatial variations in ozone air quality utilizing ozone concentration data from several monitoring locations in the northeastern United States. The results indicate a downward trend in the ozone concentrations during the period 1983-1992 at most locations in the northeastern United States. The results also reveal that ozone is a regional-scale problem in the Northeast.     

Temporal variations of concentrations of currently used pesticides in the atmosphere of Strasbourg, France

Atmospheric samples have been collected in Strasbourg between April 18 and May 29, 2007 and were analyzed for 71 current-use pesticides, of which 38 were detected. Average concentrations ranged from 0.09 ng m⁻³ for Fenarimol to 110.42 ng  m⁻³ for Dimethachlor, which was slightly higher than the concentrations reported from other, comparable agricultural regions.Significant temporal variations were observed for 30 pesticides, and for most of them it could be shown that these were linked to time, temperature or atmospheric pressure. In several cases this helped to identify pesticide application just before or at the beginning of the sampling period, or ongoing treatment. Humidity, in contrast to previous reports, could not be linked to these variations. For the other 8 pesticides, only very little temporal variations were observed. Generally, these concentrations were low (less than 1 ng m⁻³), and it was assumed that they are not in use in Alsace at present.     

Modeling variations of medium porosity in rotating drum biofilter

Rotating drum biofilters (RDBs) mounted with reticulated polyurethane sponge media has showed high removal efficiencies over a long period of time when used for volatile organic compound (VOC) removal. Due to the accumulation of biomass within the sponge medium, the porosity of a filter bed usually changes dynamically, which makes it difficult to predict and to control. In this paper, the porosity of a multi-layer RDB bed was investigated by a diffusion-reaction model in which biofilm growth and decay were taken into account at the pore scale of the sponge medium. Temporal and spatial changes of porosity were studied under various organic loadings and gas empty bed contact times (EBCTs). The porosity of the biofilter bed was assumed to be a function of biofilm thickness, and all the pores were assumed to be uniform. Toluene was selected as the model VOC. The model was solved using numerical methods through the MATLAB software. Results show that the porosity decreased with increased time of operation, increased toluene loading, or decreased gas EBCT value. The porosity in the outermost medium layer was less than that in the inner medium layers. Toluene removal efficiencies and porosities calculated from this model correlated with the experimental data well. Porosity variation was proposed to be an indicator for prediction of biofilter performance in biofilters as a consequence.     

Spatial and temporal variations in San Joaquin Valley fog chemistry

Fog was sampled at four locations in California’s San Joaquin Valley (SJV) during December 1995 and January 1996 as part of the 1995 Integrated Monitoring Study (IMS95). The fog sampling campaign was conducted in two phases. During the first phase, fog was sampled at three southern SJV surface locations, two urban (Fresno and Bakersfield) and one rural (near the Kern Wildlife Refuge). Both bulk samples (representative of the entire fog drop spectrum) and size-fractionated samples were collected. During the second phase, bulk fog samples were collected at three elevations on a 430 m television transmission tower in the northern SJV, representing some of the first observations of vertical variations in fog composition. SJV fog was observed to be consistently alkaline. The median pH measured in the southern SJV was 6.49, with a range from 4.97 to 7.43. Dominant species in the fog water were ammonium (median southern SJV concentration of 1008 microequivalents/l (μN)), nitrate (483 μN), sulfate (117 μN), acetate (117 μN), formate (63 μN), and formaldehyde (46 μM). Concentrations of the inorganic ions were similar in the urban and rural fogs, although occasionally much higher spikes of S(IV) and sulfate were observed in Bakersfield fog. Acetate, formaldehyde, and total organic carbon, by contrast, were observed to be present in greater concentration in the urban fogs. Bakersfield IMS95 fog concentrations of most species were similar to those measured there in the early 1980s, although concentrations of S(IV) and sulfate were much lower in IMS95 fogs. Significant differences were found between the composition of large and small fog drops, with pH differences at times exceeding one pH unit. The chemical heterogeneity present among SJV fog drop populations is likely to result in significant enhancement of aqueous sulfate production rates over those expected from average fog properties. Significant vertical variations were also observed in fog composition. Liquid water content was observed to increase strongly with elevation, while major ion aqueous concentrations in fog drops decreased with altitude. The total amount of solute contained within the fog (per unit volume of air) was observed to increase with altitude. These observations form a unique data set to be used for model evaluation and for further analysis of aerosol processing by fogs.     

Influence of nuclei concentration and humidity upon the attachment rate of atoms in the atmosphere

The attachment rate of atoms and ions to the atmospheric aerosol indoors and outdoors was studied by means of the Tn(²²⁰Rn) decay products, which have a diffusion coefficient D = 0.068 cm²s⁻¹ and a sticking probability S = 1. In a nuclei concentration range between 0.6–7 × 10⁴ particles cm⁻³ the attachment rates were 0.009–0.05 s⁻¹ (relative humidity : 30–50%) corresponding to a half-life of attachment 77 to 14 seconds. The change of the average nuclei size with humidity could be determined by measuring the attachment rate for different water vapour concentrations. By changing the humidity from 20% to about 100%, the average particle size increases up to a factor of 2.1.     

Spatial and temporal variations in the trace elemental data over the northeastern United States

Time series of trace elemental concentrations (14 species) of atmospheric fine particles measured in the northeastern United States between 1988 and 1998 are analyzed for spatial and temporal variations. The influence of synoptic-scale systems to the transport and accumulation of pollutants can be investigated successfully if the short-term fluctuations (i.e. weather-induced variations) embedded in the time series of pollutant concentrations are separated from the original time series. The spatial short-term correlation coefficients for Al, Br, Fe, Se, and Zn permit good predictions of pollutant concentrations up to distances of about 350 km from a given monitor. The species correlation matrices for individual sites reveal that As, Br, Se, and Zn are highly correlated in New York State, while Fe, Mn, and V show also strong correlations, suggesting the commonality of source regions for these industrial and urban pollutants impacting New York.