Numerical integration of chemical ODE problems arising in air pollution models

The numerical treatment of a regional air pollution model (such models are, as a rule, described mathematically by systems of partial differential equations) leads to the solution of very large computational problems. The chemical submodel of an air pollution model is normally the most timeconsuming part of the computational work. The application of appropriate discretization and splitting procedures reduces the chemical submodel to a large number of relatively small ODE systems (one such system per gridpoint). In the process of searching for efficient numerical algorithms for the chemical submodels one can carry out experiments by using only one such ODE system in order to facilitate the work. This approach has been used in connection with a particular chemical scheme, the condensed CBM IV scheme, which is used in several large air pollution models. Six integration algorithms have been tested on a set of typical scenarios (consisting of different starting concentrations and/or of different values of the emissions). The advantages and the disadvantages of the algorithms tested are discussed. The final decision about the most efficient algorithm, among the algorithms tested, should be made after a second series of experiments. The coupling of the chemical process with the transport of air pollution (on, at least, a twodimensional domain) together with the application of highspeed computers has to be studied in the second series of experiments, which will be performed in a subsequent paper.     

Total mercury determination in sand boxes from Montreal

Direct mercury analysis was successfully applied to determine trace levels of total mercury in samples from sand boxes in Montréal (Québec, Canada). Twenty sand boxes were sampled from across the city and divided into two size fractions, a fine fraction (<100 microm) and a whole fraction. The concentrations of mercury ranged from 1.6 to 35 microg Hg kg(-1) dry soil for the fine fraction and from 0.7 to 6 microg Hg kg(-1) dry soil for the whole fraction. The mercury concentrations correlated with the soil organic carbon content (R2= 0.67) in the sand. The ratio of the concentration of mercury in the fine over the whole fraction varied from 2.2 to 18. Using published soil ingestion rates for children, the calculated daily intake values varied from 0 to 0.5 ng Hg kg(-1) bw d(-1) with an estimated oral ingestion of 200 mg of sand and from 0.2 to 4.7 ng Hg kg(-1) bw d(-1) with an ingestion of 1750 mg of sand. None of the sand boxes contain sufficient amounts of mercury so as to exceed the currently accepted daily intake threshold of 0.105 microg Hg kg(-1) bw d(-1) established by Health Canada.     

Secondary desertification due to salinization of intensively irrigated lands: The Israeli experience

Secondary salinization of intensively irrigated lands is an increasingly alarming redesertification process experienced in many irrigated regions of the developed countries. The major cause is a profound interference in the geochemical/salt balances of irrigated regions. A case-in-point is the recent salinization of the Yizre'el Valley, a 20,000 ha intensively irrigated region in Israel. The extremely intensive and advanced agroecosystem developed in the region since the 1940s included pumping and importing irrigation water by the National Water Carrier, large-scale reclamation and reuse of municipal sewage water, winter flood impoundment in reservoirs for summer irrigation, and cloud seeding to enhance rainfall. Modern irrigation methods were applied, including sprinkler, trickle, moving-line, and center-pivot systems. Water use efficiency at any level was very high. Nevertheless, large-scale salinization of regional water resources and many fields had developed in the mid-1980s. Reconstructing and evaluating the water and salt balances of the Yizre'el Valley (using Cl as the representative salt constituent) shows that as water use in the valley increased to about 60 million m³ per year, the importing of soluble salts by water totaled 15,000 tons of Cl per year. Recirculated salt — salt picked up by impounded surface water and applied to fields — increased significantly and in the late 1980s amounted to more than 9,000 tons Cl per year. The source of recirculated salts was the accumulated salts in soils and in the shallow aquifer in the valley, which were leached by floodwater or drained or infiltrated into reservoirs, grossly and adversely affecting water quality. Analysis of the Yizre'el Valley's case points to the utmost importance of maintaining the geochemical balances in addition to increasing irrigation efficiency. An irrigated region may achieve geochemical balance by the following means: limiting the extent of irrigated areas, developing a well-maintained drainage system that drains tail-water and salinized shallow-aquifer water, and devoting a significant portion of water for regional leaching. The sustained long-term productivity of irrigated lands in arid zones crucially depends on correctly managing water and soil resources. Regional management of irrigated lands to prevent secondary desertification will be aimed at carefully balancing the undisputed benefits of irrigation with the long-term (on time scales of 10 to 100 years) detrimental processes set in motion when irrigation is introduced to arid and semiarid zone soils.     

Identification and observation of desertification processes with the aid of measurements from space: Results from the European Field Experiment in Desertification-threatened Areas (EFEDA)

The ECHIVAL Field Experiment in Desertification-threatened Areas (EFEDA) addresses the question of desertification from the viewpoint of changing interactions between the land surface and the atmosphere under varying climatic conditions. The basic tool to improve our understandin of these processes are Soil-Vegetation-Atmosphere-Transfer (SVAT) and climate models. In testing techniques for deriving the needed input data from observations from space, EFEDA requires high-precision data sets that can be used to aggregate desertification-related land-surface characteristics into the scale up to the grid width of global climate models (10⁴–10⁵ km²). In this context schemes have been developed to infer from satellite measurements fluxes at the surface. To validate the information inferred from observations in space, ground measurements have been performed on 2500 km² of Castilla-La Mancha, Spain, during the drying periods of the summers of 1991 and 1994. Ultimately EFEDA aims to determine cumulative fluxes over longer periods to allow discrimination between natural variability and trends over large areas, such as the land around the Mediterranean. To recalibrate and adjust the algorithms used to infer information about the land surfaces from satellite measurements, anchor stations are proposed for critical areas to provide collateral information and continuous quality control of inferred information.     

The relative role of climate change and human activities in the desertification process in Yulin region of northwest China

To overcome the shortcoming of existing studies, this paper put forward a statistical vegetation–climate relationship model with integrated temporal and spatial characteristics. Based on this model, we quantitatively discriminated on the grid scale the relative role of climate change and human activities in the desertification dynamics from 1986 to 2000 in Yulin region. Yulin region’s desertification development occurred mainly in the southern hilly and gully area and its reverse in the northwest sand and marsh area. This spatial pattern was especially evident and has never changed thoroughly. From the first time section (1986–1990) to the second (1991–1995), the desertification was developing as a whole, and either in the desertification development district or in the reverse district human activities’ role was always occupying an overwhelmingly dominant position (they were 98.7% and 101.4%, respectively), the role of climate change was extremely slight. From the second time section (1991–1995) to the third (1996–2000), the desertification process was reaching a state of stability, in the desertification development district the role of climate change was nearly equivalent to that of human activities (they were 46.2% and 53.8% separately), and yet in the desertification reverse district, the role of human activities came up to 119.0%, the role of climate change amounted to ?19.0%. In addition, the relative role of climate change and human activities possessed great spatial heterogeneity. The above conclusion rather coincides with the qualitative analysis in many literatures, which indicates that this method has certain rationality and can be utilized as a reference for the monitoring and studying of desertification in other areas.     

An evaluation of improvements in the air quality of Beijing arising from the use of new vehicle emission standards

An innovative approach of mean emission by vehicle type was used in this paper to assess the impact of new vehicle emission standards in Beijing, China during the period of 2000–2005. It was found that CO and NO_x emissions decreased by 48% and 23%, respectively, from Type O (before 2000) to Type I (year 2000) vehicles. The reductions from Type O to Type II (year 2002) vehicles were 85% and 73% for CO and NO_x, respectively. When all three types of vehicles (Types O, I and II) are combined, the annual per vehicle CO emissions decreased from 586 kg per vehicle per year in 2000 to 324 kg per vehicle per year in 2005, while that of NO_x decreased from 66.9 to 43.4 kg per vehicle per year, which was mainly resulted from the impact of stringent new vehicle emission standards implemented in years 2000 and 2002. However, the vehicle population increased by 70% during the same time period, which offset the impact of cleaner vehicles. Thus, the total vehicle emission decreased little for CO (885,000 tons in 2000, 837,000 tons in 2005) and even increased slightly for NO_x (101,000 and 112,000 tons in 2000 and 2005, respectively). The ambient concentrations of CO decreased significantly throughout 2000–2005, the same trend was not observed for NO₂. Correlation analysis (grey correlation and Pearson correlation) between the annual vehicle emissions and annual concentrations of CO, the annual NO_x emission and annual NO₂ concentration indicated that the implementation of new vehicle emission standards was associated with the abatement of ambient CO and NO₂ concentrations in Beijing.     

Geo-morphological changes of the Wanpingkou tidal system arising from the building of a sailing boat station in Rizhao of China

This paper examines a small tidal system in Wanpingkou, Rizhao of China. The tidal system was originally maintained by a balance of the natural interaction between tidal currents and waves. But this tidal system was diminishing by reclamation processes since the 1980s, especially in 2003 when a sailing boat station was built in the study area. To investigate the stability and development mechanism of the tidal system, its feasibility was evaluated before the sailing boat station was built. The erosion and deposition in and out of the tidal system was analyzed, forecasted and compared with the data from field monitoring. The results show that the tidal system would remain relatively stable, although its adjacent shoreline might change somewhat after the newly built sailing boat station. This change would also affect the coastal water and wetland environment in the study area. Further field monitoring in the area is still necessary.     

The effects of season and sand mining activities on thermal regime and water quality in a large shallow tropical lake

Thermal structure and water quality in a large and shallow lake in Malaysia were studied between January 2012 and June 2013 in order to understand variations in relation to water level fluctuations and in-stream mining activities. Environmental variables, namely temperature, turbidity, dissolved oxygen, pH, electrical conductivity, chlorophyll-A and transparency, were measured using a multi-parameter probe and a Secchi disk. Measurements of environmental variables were performed at 0.1 m intervals from the surface to the bottom of the lake during the dry and wet seasons. High water level and strong solar radiation increased temperature stratification. River discharges during the wet season, and unsustainable sand mining activities led to an increased turbidity exceeding 100 NTU, and reduced transparency, which changed the temperature variation and subsequently altered the water quality pattern.     

乌鲁木齐市餐饮业油烟污染的调查及防治初探

通过对乌鲁木齐市20家餐饮业油烟污染的调查分析,结果表明,乌鲁木齐市餐饮业油烟污染严重,并提出了防治措施。     

Geochemical characterisation of pyrite oxidation and environmental problems related to release and transport of metals from a coal washing low-grade waste dump, Shahrood, northeast Iran

Pyrite oxidation and release of the oxidation products from a low-grade coal waste dump to stream, groundwater and soil was investigated by geochemical and hydrogeochemical techniques at Alborz Sharghi coal washing plant, Shahrood, northeast Iran. Hydrogeochemical analysis of water samples indicates that the metal concentrations in the stream waters were low. Moreover, the pH of the water showed no considerable change. The analysis of the stream water samples shows that except the physical changes, pyrite oxidation process within the coal washing waste dump has not affected the quality of the stream water. Water type was determined to be calcium sulphate. The results of the analysis of groundwater samples indicate that the pH varies from 7.41 to 7.51. The concentrations of the toxic metals were low. The concentration of SO4 is slightly above than its standard concentration in potable water. It seems that the groundwater less affected by the coal washing operation in the study area. Geochemical analysis of the sediment samples shows that Fe concentration decreases gradually downstream the waste dump with pH rising. SO(4) decreases rapidly downstream direction. Copper, Zn and Co concentrations decrease with distance from the waste dump due to a dilution effect by the mixing of uncontaminated sediments. These elements, in particular, Zn are considerably elevated in sediment sample collected at the nearest distance to the waste dump. There is no doubt that such investigations can help to develop an appropriate water remediation plan.     

The Effect of Smoke from Charcoal Kilns on Soil Respiration

The objective of the work was a laboratory examination of the effect of a water-soluble fraction of the smoke, emitted during charcoaling by dry distillation, on soil metabolism. The experimental soil was exposed to smoke for ten years and the control soil was taken from a site not exposed to smoke. Oxygen uptake and carbondioxide evolution were measured in soil samples by using the method of volumetric respirometry. When an aqueous smoke solution was added to the soil, the rate of oxygen metabolism increased by a factor 15 for the experimental soil and by a factor 5 for the control soil. A similar increase was observed in carbondioxide evaluation. RQ was clearly higher for the experimental soil. Also after the addition of an aqueous smoke solution to the soil, differences were observed in changes of RQ between the experimental and control soils. These differences suggest that respiratory metabolism is changed in the soils permanently exposed to smoke, and RQ value can be an indicator of the initial stages of soil degradation.     

The Importance of Leaching from Litter Collected in Litterfall Traps

Litterfall (LF) is usually collected by means of opentraps. However, this litter will be subject toleaching by the throughfall which passes through theaccumulated litter in the traps. The nutrients lostduring this leaching are not taken into account in thecalculation of LF nutrient fluxes. We report theresults from a 2-month (August–September) studycarried out in 8 northern coniferous forest stands toassess the possible importance of leaching from litterin LF traps. Compared to throughfall (TF), thelitterfall leachate (LFL_gross), which includes athroughfall component, had significantly (p < 0.05)higher concentrations and fluxes of Ca, Mg, Na and S.The average net LFL (i.e., LFL_net = LFL_gross-TF) fluxes were 21 (Ca), 7 (Mg), 57 (K), 10 (Na), 10 (N), and 19 (S) mg m^-2 mo^-1. LFL_net accounted for 42%, 37% and 50% of the LFL_gross flux, and for 91%, 51% and 49% of the total litterfall flux (i.e.,LF + LFL_net) of Na, S and K, respectively. ForCa, Mg and N, the LFL_net flux accounted for 64%,58% and 29% of the LFL_gross flux, and for< 14% of the total litterfall flux. Compared to TF,LF was the dominant return pathway for Ca, Mg and N tothe forest floor regardless of whether LFL_net wasincluded or not. However, for K and S, takingLFL_net into account determined whether TF or LFwas the dominant pathway. TF remained the dominantpathway for Na even when LFL_net was included.     

The interaction between concrete pavement and corrosion-induced copper runoff from buildings

Changes in chemical speciation of copper and the capacity of concrete pavement to retain copper in runoff water from external buildings have been investigated at urban field conditions, and in parallel laboratory experiments simulating outdoor scenarios. The research study showed the concrete surface to form a copper rich surface layer (≈50 μm thick) upon exposure, and a high capacity to significantly reduce the bioavailable fraction of released copper (20–95%). The retention capacity of copper varied between 5 and 20% during single runoff events in the laboratory, and between 10 and 40% of the total copper release during single natural runoff events. The capacity to retain and reduce the bioavailable fraction of non-retained copper increased with increasing wetness of the concrete surfaces, increasing pH of the runoff water and decreasing flow rates. Bioassay testing with bacterial and yeast bioreporters showed the bioavailable fraction of non-retained copper to be significantly lower than the total copper concentration in the runoff water, between 22 and 40% for bacteria and between 8 and 31% for yeast. The application of generated data to simulate a fictive outdoor scenario, suggests a significant reduction of bioavailable and total copper to background values during environmental entry as a result of dilution, and the interaction with solid surfaces, organic matter and complexing agents already in the drainage system.     

The determination of the extractability of selected elements from agricultural soil

Concentrations of Ag, Al, Ba, Cd, Co, Cr, Cu, Fe, K, Mn, Na, Ni, Pb, Sr, and Zn—isolated by sequential extraction steps from apple orchard soil—were analyzed by inductively coupled plasma-atomic emission spectroscopy and compared to the total amount of metal in soil determined by XRF. The extractable amount of each metal was calculated by the extraction yields of the four steps. The LODs of the different elements in all extracts ware below 3 μg/L except for Ba (steps 1 and 2), Cu (step 1), Fe (all steps), K (steps 1–3), Mn (step 2), Na (steps 1–3), Ni (step 1), Pb (steps 1 and 4), and Zn (steps 1 and 2). The highest LOD (>10 μg/L) was found for Fe, K, and Na (step 1). The recovery of all metals after four sequential extraction steps was 90–112%. The repeatability (<1.1%), the intermediate precision (<5.3%), the day-to-day reproducibility (<6.2%), and the overall uncertainty of measurement (approximately 4–8.5%) for all analyzed metals supports the choice of the method used.     

Factor analysis of trace-element data from tree-bark samples in The Netherlands

Monte Carlo-assisted factor analysis has been applied to a data set of 20 trace-element concentrations in tree-bark samples obtained from 123 locations in The Netherlands, with the aim to investigate the suitability of bark as a biomonitor for air pollution. A Monte Carlo approach was used to give more insight to the uncertainties and significance levels of the factor analysis results. Notwith-standing a rather strong influence of soil material on the concentration levels, factor analysis enabled the identification of five significant pollution source types, all of which corresponded with source types found in an earlier biomonitoring study in The Netherlands using epiphytic lichens. A more detailed comparison with the lichen results showed a remarkable difference in lead concentrations between bark and lichen. It was concluded that bark can be successfully employed as a biomonitor for air pollution. The power of factor analysis to adequately determine the soil contribution may render extensive sample washing procedures superfluous.     

The distribution of octachlorostyrene (OCS) in environmental samples from Europe

Although octachlorostyrene (OCS) was never used as a commercial product, it may be produced during incineration and combustion processes involving chlorinated compounds. Its environmental spreading was evaluated through the analysis of several representative samples. OCS could not be measured in soil samples collected from urban and rural areas or sediments, but was present (up to 5.41 ng/g dry weight) in industrial soil collected near chemically polluted areas. For aquatic biota samples, the OCS concentrations in freshwater mussels ranged from <0.01 ng/g wet weight (ww) to 0.18 ng/g ww (mean 0.06 ng/g ww) and similar levels could be measured in 11 freshwater fish species from Belgium and Romania. A higher OCS contamination level was found in shrimps (mean 0.08 ng/g ww) compared to marine fish (mean 0.02 ng/g ww for bib and 0.01 ng/g ww for sole and whiting, respectively). OCS could also be measured in 19 harbour porpoise (Phocoena phocoena) liver samples with a mean value of 1.90 ng/g ww. According to these data, it could be computed that the biomagnification factor for OCS was one order of magnitude lower than that of HCB in the fish-porpoise food chain. The mean OCS concentrations in blue tits (Parus caeruleus) eggs and great tits (Parus major) adipose tissue were 1.24 ng/g ww and 3.24 ng/g ww, respectively. OCS could be measured in different tissues of hedgehog (Erinaceus europaeus), with the highest concentrations found in adipose tissue (mean 0.34 ng/g ww) and liver (mean 0.39 ng/g ww). In contrast, only low concentrations of OCS could be measured in human adipose tissue (up to 0.38 ng/g ww) and liver (up to 0.05 ng/g ww), while it could not be detected in human brain or lung. The relationship between the concentrations of OCS and HCB was also discussed for each species.     

The effect of temperature on PAHs emission from incineration of acrylic waste

Incineration of acrylic waste solution in a lab scale quartz tube vertical incinerator showed the presence of 12–15 polycyclic aromatic hydrocarbons (PAHs) from a list of 16 priority pollutants at 700–1100^˚C after an interval of 50^˚C. The amount of total 16 PAHs at 900 and 1100^˚C was about 8.5 and 1.25 times higher than those at 700^˚C (739.48 μg g⁻¹) respectively. The amount of total probable (2A) and possible (2B) human carcinogenic PAHs was minimum at 700^˚C.     

The potential of biogas production from municipal solid waste in a tropical climate

The objective of this study was to estimate the potential of organic municipal solid waste generated in an urban setting in a tropical climate to produce biogas. Five different categories of wastes were considered: fruit waste, food waste, yard waste, paper waste, and mixed waste. These fractions were assessed for their efficiency for biogas production in a laboratory-scale batch digester for a total period of 8 weeks at a temperature of 15–30 °C. During this period, fruit waste, food waste, yard waste, paper waste, and mixed waste were observed to produce 0.15, 0.17, 0.10, 0.08, and 0.15 m³ of biogas per kilogram of volatile solids, respectively. The biogas produced and caloric value of each feedstock was in the range of 1.25?×?10^?3 m³ (17 kWh)/cap/day (paper waste) to 15?×?10^?3 m³ (170 kWh)/cap/day (mixed waste). Paper waste produced the least (<1×10^?3(<17.8 kWh)/cap/day), and mixed waste produced the highest methane yield (10?×?10^?3 m³ (178 kWh)/cap/day). Thus, mixed waste was found to be more efficient than other feedstocks for biogas and methane production; this was mainly related to the better C/N ratio in mixed waste. Taking the total waste production in Jimma into account, the total mixed organic solid waste could produce 865?×?10³ m³ (5.4 m³/capita) of biogas or 537?×?10³ m³ (3.4 m³/capita) of methane per year. The total caloric value of methane production potential from mixed organic municipal solid waste was many times higher than the total energy requirement of the area.     

The Characteristics of Tropospheric Ozone Seasonality Observed from Ozone Soundings at Pohang, Korea

This paper presents the first analysis of vertical ozone sounding measurements over Pohang, Korea. The main focus is to analyze the seasonal variation of vertical ozone profiles and determine the mechanisms controlling ozone seasonality. The maxima ozone at the surface and in the free troposphere are observed in May and June, respectively. In comparison with the ozone seasonality at Oki (near sea level) and Happo (altitude of 1840 m) in Japan, which are located at the same latitude as of Pohang, we have found that the time of the ozone maximum at the Japanese sites is always a month earlier than at Pohang. Analysis of the wind flow at the surface shows that the wind shifts from westerly to southerly in May over Japan, but in June over Pohang. However, this wind shift above boundary layer occurs a month later. This wind shift results in significantly smaller amounts of ozone because the southerly wind brings clean wet tropical air. It has been suggested that the spring ozone maximum in the lower troposphere is due to polluted air transported from China. However, an enhanced ozone amount over the free troposphere in June appears to have a different origin. A tongue-like structure in the time-height cross-section of ozone concentrations, which starts from the stratosphere and extends to the middle troposphere, suggests that the ozone enhancement occurs due to a gradual migration of ozone from the stratosphere. The high frequency of dry air with elevated ozone concentrations in the upper troposphere in June suggests that the air is transported from the stratosphere. HYSPLIT trajectory analysis supports the hypothesis that enhanced ozone in the free troposphere is not likely due to transport from sources of anthropogenic activity.     

The simultaneous stripping of arsenic and selenium from wastewaters using hollow-fibre supported liquid membranes

The extraction of total arsenic and selenium using hollow-fibre supported liquid membranes (HFSLMs), with specific interest in the optimal conditions for the extraction in wastewater, is reported. The extraction time, type of liquid membrane, sample and donor pH and stirring rate were optimised, and thereafter, the developed method was tested in real wastewater samples. The optimal HFSLMs adopted, after optimisation tests, comprised of Aliquat 336, 0.8 M NaOH, 200 rpm and 80 min as the extractant, stripping phase, stirring rate and reaction time, respectively. The developed method had reasonable-to-high extraction efficiencies in real wastewater samples with the final effluent recording as high as 73 and 78 % removal efficiencies for Se and As, respectively. Considering the initial concentrations found in the samples, use of this developed method could bring down the concentrations to levels admissible by the United States Environmental Protection Agency (US-EPA) and World Health Organisation (WHO).