Modeling of non-point source pollution in a Mediterranean drainage basin

SWAT ver. 2000 was used to predict hydrographs, and sediment, nitrate and total phosphorus loadings from a 1349 km² mountainous/agricultural watershed in Northern Greece. The model was calibrated and verified using continuous meteorological data from eight stations within the drainage area, and runoff, sediment and nutrient concentrations measured at nine stations located within the main tributaries of the watershed, for the time period from May 1st, 1998 to January 31st, 2000. Model validation methodology and resulting input parameters appropriate for Mediterranean drainage basins are presented. Predicted by the model hydrographs, sedimentographs and pollutographs are plotted against observed values and show good agreement. Model performance is evaluated using the root mean square error computation and scattergrams of predicted versus observed data. The validated model is also used to test the effectiveness of three alternative cropping scenarios in reducing nutrient loadings from the agricultural part of the watershed. The study showed that this model, if properly validated, can be used effectively in testing management scenarios in Mediterranean drainage basins.     

Cost-effectiveness and cost-benefit analysis of BMPs in controlling agricultural nonpoint source pollution in China based on the SWAT model

Best management practices (BMPs) have been widely used in managing agricultural nonpoint source pollution (ANSP) at the watershed level. Most BMPs are related to land use, tillage management, and fertilizer levels. In total, seven BMP scenarios (Reforest1, Reforest2, No Tillage, Contour tillage, and fertilizer level 1–4) that are related to these three factors were estimated in this study. The objectives were to investigate the effectiveness and cost-benefit of these BMPs on ANSP reduction in a large tributary of the Three Gorges Reservoir (TGR) in China, which are based on the simulation results of the Soil and Water Assessment Tool (SWAT) model. The results indicated that reforestation was the most economically efficient of all BMPs, and its net benefits were up to CNY 4.36×10⁷ years^?1 (about USD 7.08×10⁶ years^?1). Regarding tillage practices, no tillage practice was more environmentally friendly than other tillage practices, and contour tillage was more economically efficient. Reducing the local fertilizer level to 0.8-fold less than that of 2010 can yield a satisfactory environmental and economic efficiency. Reforestation and fertilizer management were more effective in reducing total phosphorus (TP), whereas tillage management was more effective in reducing total nitrogen (TN). When CNY 10,000 (about USD 162) was applied to reforestation, no tillage, contour tillage, and an 0.8-fold reduction in the fertilizer level, then annual TN load can be reduced by 0.08, 0.16, 0.11, and 0.04 t and annual TP load can be reduced by 0.04, 0.02, 0.01 and 0.03 t, respectively. The cost-benefit (CB) ratios of the BMPs were as follows: reforestation (207 %) > contour tillage (129 %) > no tillage (114 %) > fertilizer management (96 and 89 %). The most economical and effective BMPs can be designated as follows: BMP1 (returning arable land with slopes greater than 25° to forests and those lands with slopes of 15–25° to orchards), BMP2 (implementing no tillage on arable land with slopes less than 15°), and BMP5 (0.8-fold less than that of 2010).     

Performance evaluation of a full-scale natural treatment system for nonpoint source and point source pollution removal

This study presents a full-scale performance of a natural treatment system (NTS) facility in Taiwan with nearly 2 years of observations. The study site, composed of several treatment ponds in series, was designed primarily to reduce polluted stormwater runoff from tea gardens and partially to untreated domestic wastewater from nearby villages. Thus, both nonpoint source and point source pollution are treated in this system. From 28 field samplings in 2006-2007, the NTS site shows satisfactory treatment performance and the effluent water quality is significantly improved. Seven of the 28 sampling events are storm events (nonpoint source pollution) and the remainder are from regular monitoring (point source pollution). The average volume of influent and effluent is 533 CMD and 196 CMD, respectively. In order to determine the removal efficiency, several assessment measures are employed in an attempt to obtain unbiased conclusions. They are removal rate (RR), efficiency rate (ER), summation of loads (SOL), flux rate (FR), and effluent probability method (EPM). The average percent removal efficiency of NH(3)-N is 53.5-75.2% and of TP is 59.0-84.7%, in which the highest result is calculated by SOL method and the lowest rate is obtained from RR. In FR evaluation, larger treatment capacity for NH(3)-N than for TP is provided in the site and the average FR is respectively 0.230 g/m(2) day and 0.017 g/m(2) day. Of the methods examined, EPM is the only method capable of illustrating data distribution. Finally, recommendations on the usefulness of these measures are summarized to facilitate the understandings of NTS performance evaluations.     

Effect of land use land cover change on soil erosion potential in an agricultural watershed

Universal soil loss equation (USLE) was used in conjunction with a geographic information system to determine the influence of land use and land cover change (LUCC) on soil erosion potential of a reservoir catchment during the period 1989 to 2004. Results showed that the mean soil erosion potential of the watershed was increased slightly from 12.11 t ha^???1 year^???1 in the year 1989 to 13.21 t ha^???1 year^???1 in the year 2004. Spatial analysis revealed that the disappearance of forest patches from relatively flat areas, increased in wasteland in steep slope, and intensification of cultivation practice in relatively more erosion-prone soil were the main factors contributing toward the increased soil erosion potential of the watershed during the study period. Results indicated that transition of other land use land cover (LUC) categories to cropland was the most detrimental to watershed in terms of soil loss while forest acted as the most effective barrier to soil loss. A p value of 0.5503 obtained for two-tailed paired t test between the mean erosion potential of microwatersheds in 1989 and 2004 also indicated towards a moderate change in soil erosion potential of the watershed over the studied period. This study revealed that the spatial location of LUC parcels with respect to terrain and associated soil properties should be an important consideration in soil erosion assessment process.     

Statistical analysis of effects of measures against agricultural pollution

The Norwegian Government has initiated a plan to reduce agricultural pollution. One of the projects in this plan is aimed at investigating the effects of different measures in order to evaluate their effects and costs.A set of experiments has been designed to estimate the effects of measures to reduce or control the use of fertilizers and erosion. The project started in 1985. It comprises continuous measurements in two water courses in each of four counties: one test drainage area where the relevant measures were implemented at the end of 1986, and one reference area where no specific measures are carried out. A series of chemical parameters are measured together with runoff and other hydrological and meteorogical data.The paper provides a preliminary analysis of the data collected in one of the counties during the period June 1985 to April 1988. It contains examples of analysis of covariance to show possible effects of the measures carried out in the test area.Natural variations in precipitation and pollution are large, making it difficult to see the effects of the measures without using statistical techniques to take the multivariability of the problem into account. Some effects can be shown with analysis of covariance. However, the relatively short measurement period makes it neccessary to be careful when interpreting the results.     

Geochemical position of Pb,Zn and Cd in soils near the Olkusz mine/smelter,South Poland: effects of land use,type of contamination and distance from pollution source

The soils adjacent to an area of historical mining, ore processing and smelting activities reflects the historical background and a mixing of recent contamination sources. The main anthropogenic sources of metals can be connected with historical and recent mine wastes, direct atmospheric deposition from mining and smelting processes and dust particles originating from open tailings ponds. Contaminated agriculture and forest soil samples with mining and smelting related pollutants were collected at different distances from the source of emission in the Pb–Zn–Ag mining area near Olkusz, Upper Silesia to (a) compare the chemical speciation of metals in agriculture and forest soils situated at the same distance from the point source of pollution (paired sampling design), (b) to evaluate the relationship between the distance from the polluter and the retention of the metals in the soil, (c) to describe mineralogy transformation of anthropogenic soil particles in the soils, and (d) to assess the effect of deposited fly ash vs. dumped mining/smelting waste on the mobility and bioavailability of metals in the soil. Forest soils are much more affected with smelting processes than agriculture soils. However, agriculture soils suffer from the downward metal migration more than the forest soils. The maximum concentrations of Pb, Zn, and Cd were detected in a forest soil profile near the smelter and reached about 25 g kg^− 1, 20 g kg^− 1 and 200 mg kg^− 1 for Pb, Zn and Cd, respectively. The metal pollutants from smelting processes are less stable under slightly alkaline soil pH then acidic due to the metal carbonates precipitation. Metal mobility ranges in the studied forest soils are as follows: Pb > Zn ≈ Cd for relatively circum-neutral soil pH (near the smelter), Cd > Zn > Pb for acidic soils (further from the smelter). Under relatively comparable pH conditions, the main soil properties influencing metal migration are total organic carbon and cation exchange capacity. The mobilization of Pb, Zn and Cd in soils depends on the persistence of the metal-containing particles in the atmosphere; the longer the time, the more abundant the stable forms. The dumped mining/smelting waste is less risk of easily mobilizable metal forms, however, downward metal migration especially due to the periodical leaching of the waste was observed.     

Status of heavy metals in agricultural soils as affected by different patterns of land use

This study was conducted to determine status of heavy metals in agricultural soils under different patterns of land use. A total of 38, 40 and 45 soil samples for bare vegetable field, greenhouse vegetable field, and grain crop field were respectively taken from surface layer (0–20 cm) from selected experimental areas away from suburbs of ten counties (or districts or cities) in four provinces or municipalities of Huabei plain in north China. Information of crop production history, including varieties, rotation systems and fertilizer use, at the corresponding sampling sites was surveyed. Soil total Cu, Zn, Cd, Pb, Cr, As and Hg were measured. The results showed that the contents of total Cu, Zn, Cd, Pb, Cr, As, and Hg in the soil samples, especially soil total Cu and Zn contents, were higher in the bare vegetable field and the greenhouse vegetable field than that in the grain crop field. Long-term use of excessive chemical fertilizers and organic manures in the bare vegetable field and the greenhouse vegetable field contributed to the accumulation of Cu, Zn, and other heavy metals in the soils. The contents of total Cu, Zn, and other heavy metals in soils increased with increasing vegetable production history of the research areas. In comparison with the grain crop field, the comprehensive pollution indices of the seven soil heavy metals and the single-factor pollution indices of soil Zn, Cu, Cd, Cr, and Hg based on the second criterion of Environmental Quality Standard for Soils were significantly higher in the bare vegetable field and the greenhouse vegetable field. Soils from the greenhouse vegetable field were slightly contaminated according to the comprehensive pollution index, and soils from the bare vegetable field and the grain crop field were at the warning heavy metal pollution level. The soils were contaminated with Cd according to the single-factor pollution index. The Cd pollution was relatively more serious in the bare vegetable field and the greenhouse vegetable field than that in the grain crop field. The soils selected with different land use patterns were not contaminated with Zn, Cu, Pb, Cr, As and Hg.     

Air pollution in Athens basin and health risk assessment

An inventory of air pollution sources within the Athens basin is carried out for the years 1989, 1992 and 1998 and the results areinputted in a climatological model for predicting ambient concentrations. Despite of the significant growth in the numberof road vehicles and the deteriorating traffic, the emissions andambient concentrations of fine particulates, CO, NO_x and VOCappear to remain reasonably constant over for the period 1989 to 1998, while these of SO₂ and Pb are reduced, mainly due to the renewal of vehicle fleet, the use of catalytic technologies and the improved quality of the used fuel. The results further indicate that for CO, NO_x and VOC the major source is road traffic, while for PM_2.5 and SO₂ both space heating andtraffic share responsibility. The air pollutant concentrations monitored by the network of 11 stations are reviewed and statistics related to air quality guidelines are presented. As fine particulate levels are not monitored, approximate PM_2.5and PM₁₀ concentrations are derived from black smoke ones on basis of experimentally determined conversion factors. The computed and monitored air pollution levels are compared and found in reasonable agreement. The results of the above analysisshow that the levels of all `classical' pollutants, with the exception of SO₂ and Pb, exceed significantly the WHO guidelines and are thus expected to exert a significant healthimpact. The latter could be quantified in relation to the PM_2.5 or PM₁₀ levels on the basis of risk assessment information developed by the World Health Organization (WHO). The results show that the existing levels of fine particle concentrations in Athens increase significantly the mortality and morbidity, and reduce the average longevity of the entirepopulation from 1.3 to 1.7 years.     

Using Multiple Antibiotic Resistance and land use characteristics to determine sources of fecal coliform bacterial pollution

Multiple Antibiotic Resistance (MAR) analysis and regression modeling techniques were used to identify surface water areas impacted by fecal pollution from human sources, and to determine the effects of land use on fecal pollution in Murrells Inlet, a small, urbanized, high-salinity estuary located between Myrtle Beach and Georgetown, South Carolina. MAR analysis was performed to identify areas in the estuary that are impacted by human-source fecal pollution. Additionally, regression analysis was performed to determine if an association exists between land use and fecal coliform densities over the ten-year period from 1989 to 1998. Land-use variables were derived using Geographic Information System (GIS) techniques and were used in the regression analysis.MAR analyses were conducted by comparing the frequency and patterns of antibiotic resistance found in Escherichia coli isolates derived from surface water samples and from sewage sources in the Murrells Inlet sewage collection system. The MAR results suggest that the majority of the fecal pollution detected in the Murrells Inlet estuary may be from non-human sources, including fecal coliforms isolated from areas in close proximity to high densities of active septic tanks.A MAR Index, which measures the frequency of antibiotic resistance, was calculated for each of twenty-three water samples and nine sewage samples. The antibiotic resistance pattern comparisons were performed using cluster analysis. Although the MAR indices indicated that several surface water sites had potential human-source contamination, the cluster analysis suggests that only one sampling site had MAR patterns that were similar to those found in the sewage samples. This site was in close proximity to several large pleasure boats as well as a sewage collection system lift station, but was not near areas with active septic tanks. The results of the regression analysis also suggest that sewage sources and rainfall runoff from urbanized areas may contribute to fecal pollution in the estuary.     

Groundwater quality and its suitability for domestic and agricultural use in Tondiar river basin,Tamil Nadu,India

Assessment of suitability of groundwater for domestic and agricultural purposes was carried out in Tondiar river basin, Tamil Nadu, India. The study area covers an area of 315 km² and lies in a semiarid region. Groundwater is the major source for domestic and agricultural activity in this area. Groundwater samples were collected from 45 wells during pre-monsoon and post-monsoon period in the year 2006. The water samples were analysed for physical and chemical characteristics. Suitability of groundwater for irrigation was evaluated based on salinity hazard, sodium percent, sodium adsorption ratio, residual sodium carbonate, US salinity diagram, Wilcox’s diagram, Kelly’s ratio and permeability index. Ca-HCO₃, mixed Ca–Mg–Cl and Na–Cl were the dominant groundwater types. High hardness and electrical conductivity in this area makes the groundwater unsuitable for drinking and agricultural purposes. Concentration of trace elements (Mn, Cu, Zn, Pb and Ni) did not exceed the permissible limit for drinking and agricultural purposes. Majority of the groundwater samples were unsuitable for domestic and agricultural purposes except for 31% and 36%, which were suitable for drinking and irrigation purposes, respectively.     

Assessing the effects of land use changes on soil sensitivity to erosion in a highland ecosystem of semi-arid Turkey

There has been increasing concern in highlands of semiarid Turkey that conversion of these systems results in excessive soil erosion, ecosystem degradation, and loss of sustainable resources. An increasing rate of land use/cover changes especially in semiarid mountainous areas has resulted in important effects on physical and ecological processes, causing many regions to undergo accelerated environmental degradation in terms of soil erosion, mass movement and reservoir sedimentation. This paper, therefore, explores the impact of land use changes on land degradation in a linkage to the soil erodibility, RUSLE-K, in Cankiri–Indagi Mountain Pass, Turkey. The characterization of soil erodibility in this ecosystem is important from the standpoint of conserving fragile ecosystems and planning management practices. Five adjacent land uses (cropland, grassland, woodland, plantation, and recreational land) were selected for this research. Analysis of variance showed that soil properties and RUSLE-K statistically changed with land use changes and soils of the recreational land and cropland were more sensitive to water erosion than those of the woodland, grassland, and plantation. This was mainly due to the significant decreases in soil organic matter (SOM) and hydraulic conductivity (HC) in those lands. Additionally, soil samples randomly collected from the depths of 0–10 cm (D ₁) and 10–20 cm (D ₂) with irregular intervals in an area of 1,200 by 4,200 m sufficiently characterized not only the spatial distribution of soil organic matter (SOM), hydraulic conductivity (HC), clay (C), silt (Si), sand (S) and silt plus very fine sand (Si + VFS) but also the spatial distribution of RUSLE-K as an algebraically estimate of these parameters together with field assessment of soil structure to assess the dynamic relationships between soil properties and land use types. In this study, in order to perform the spatial analyses, the mean sampling intervals were 43, 50, 64, 78, 85 m for woodland, plantation, grassland, recreation, and cropland with the sample numbers of 56, 79, 72, 13, and 69, respectively, resulting in an average interval of 64 m for whole study area. Although nugget effect and nugget effect–sill ratio gave an idea about the sampling design adequacy, the better results are undoubtedly likely by both equi-probable spatial sampling and random sampling representative of all land uses.     

Evaluation of land use and water quality in an agricultural watershed in the USA indicates multiple sources of bacterial impairment

Pathogens are the number one cause of impairments of assessed rivers and streams in the USA and pose a significant human health hazard. The Dry Run Creek Watershed in Northeast Iowa has been designated as impaired by the State of Iowa because of high levels of Escherichia coli bacteria. To investigate the nature of this impairment, land use and stream bank assessments were coupled with comprehensive water quality monitoring. Physical, chemical, and biological parameters were measured at 13 different sites in the watershed, including pH, temperature, conductivity, dissolved oxygen, turbidity, total Kjeldahl nitrogen, ammonia-N, nitrate?+?nitrite-N, total phosphorus, and E. coli. In addition, benthic macroinvertebrate communities were analyzed at seven sites, and optical brightener tests were performed late in the season. Results identified segments of the watershed that were more prominent contributors of E. coli, and correlations were observed between levels of E. coli and several chemical parameters, including ammonia-N, total Kjeldahl nitrogen, and total phosphorus. Interestingly, distinct sites emerged as more prominent contributors of these elements during rain vs. non-rain events, suggesting different types of sources. Both the amount of rainfall and the time elapsed between the rain event and the sampling influenced E. coli levels during wet weather conditions. Nitrate?+?nitrite-N displayed a unique response to rain events compared with the other parameters, suggesting a different delivery route. Analyses of benthic macroinvertebrate communities were consistent with pollution trends. Collectively, these data suggest distinct agriculturally related E. coli contributions, as well as specific areas and practices for water quality improvement strategies. This study can serve as a resource for evaluating agricultural watersheds that are impaired for bacteria.     

Assessing the changes in land use and ecosystem services in an oasis agricultural region of Yanqi Basin,Northwest China

The Yanqi Basin, one of the most productive agricultural areas, has a high population density in Xinjiang, Northwest China. Land use changes, mainly driven by oasis expansion, significantly impact ecosystem services and functions, but these effects are difficult to quantify. The valuation of ecosystem services is important to clarify the ecological and environmental changes caused by agriculturalization of oasis. This study aimed to investigate variations in ecosystem services in response to land use changes during oasis agricultural expansion activities in the Yanqi Basin from 1964 to 2009. The methods used were based on formula of ecosystem service value (ESV) and ESV coefficients. Satellite data were combined with the ESV coefficients to quantify land use changes and ecosystem service changes in the study area. Sensitivity analysis determined the effect of manipulating the coefficients on the estimated values. The results show that the total ESVs in the Yanqi Basin were $1,674, $1,692, $1,471, $1,732, and $1,603 million in 1964, 1973, 1989, 1999, and 2009, respectively. The net deline in ESV was $71 million in the past 46 years, but the ESVs of each types of landscape changed significantly. The aggregated ESVs of water areas and wetlands were approximately 80 % of the total ESV. Water supply and waste treatment were the two largest service functions and contributed approximately 65 % of the total ESV. The estimated ESVs in this study were elastic with respect to the value coefficients. Therefore, the estimations were robust in spite of uncertainties on the value coefficients. These significant changes in land use occur within the entire basin over the study period. These changes cause environmental problems, such as land degradation, vegetation degeneracy, and changes in aquatic environment.     

Application of processed organic municipal solid waste on agricultural land – a scenario analysis

Source separation, composting and anaerobic digestion, with associated land application, are increasingly being considered as alternative waste management strategies to landfilling and incineration of municipal solid waste (MSW). Environmental life cycle assessments are a useful tool in political decision-making about waste management strategies. However, due to the diversity of processed organic MSW and the situations in which it can be applied, the environmental impacts of land application are very hard to determine by experimental means. In the current study, we used the agroecosystem model Daisy to simulate a range of different scenarios representing different geographical areas, farm and soil types under Danish conditions and legislation. Generally, the application of processed organic MSW resulted in increased emissions compared with the corresponding standard scenarios, but with large differences between scenarios. Emission coefficients for nitrogen leaching to the groundwater ranged from 0.03 to 0.87, while those for nitrogen lost to surface waters through tile drains ranged from 0 to 0.30. Emission coefficients for N₂O formation ranged from 0.013 to 0.022 and for ammonia volatilization from 0.016 to 0.11. These estimates are within reasonable range of observed values under similar conditions. Furthermore, a sensitivity analysis showed that the estimates were not very sensitive to the mineralization dynamics of the processed organic MSW. The results show that agroecosystem models can be powerful tools to estimate the environmental impacts of land application of processed MSW under different conditions. Despite this, agroecosystem models have only been used to a very limited degree for this purpose.     

Load estimation and source apportionment of nonpoint source nitrogen and phosphorus based on integrated application of SLURP model, ECM, and RUSLE: a case study in the Jinjiang River, China

The nonpoint source (NPS) pollution is difficult to manage and control due to its complicated generation and formation. Load estimation and source apportionment are an important and necessary process for efficient NPS control. Here, an integrated application of semi-distributed land use-based runoff process (SLURP) model, export coefficients model (ECM), and revise universal soil loss equation (RUSLE) for the load estimation and source apportionment of nitrogen and phosphorus was proposed. The Jinjiang River (China) was chosen for the evaluation of the method proposed here. The chosen watershed was divided into 27 subbasins. After which, the SLURP model was used to calculate land use runoff and to estimate loads of dissolved nitrogen and phosphorus, and ECM was applied to estimate dissolved loads from livestock and rural domestic sewage. Next, the RUSLE was employed for load estimation of adsorbed nitrogen and phosphorus. The results showed that the 12,029.06 t?a^?1 pollution loads of total NPS nitrogen (TN) mainly originated from dissolved nitrogen (96.24 %). The major sources of TN were land use runoff, which accounted for 45.97 % of the total, followed by livestock (32.43 %) and rural domestic sewage (17.83 %). For total NPS phosphorous (TP), its pollution loads were 570.82 t?a^?1 and made up of dissolved and adsorbed phosphorous with 66.29 and 33.71 % respectively. Soil erosion, land use runoff, rural domestic sewage, and livestock were the main sources of phosphorus with contribution ratios of 33.71, 45.73, 14.32, and 6.24 % respectively. Therefore, land use runoff, livestock, and soil erosion were identified as the main pollution sources to influence loads of NPS nitrogen and phosphorus in the Jinjiang River and should be controlled first. The method developed here provided a helpful guideline for conducting NPS pollution management in similar watershed.     

Modeling the effect of land use/land cover on nitrogen,phosphorous and dissolved oxygen loads in the Velhas River using the concept of exclusive contribution area

Non-point source water pollution is a major problem in most parts of the world, but is also very difficult to quantify and control since it is not easily separated from point sources and can theoretically originate from the whole watershed. In this article, we evaluate the relationship between land use and land cover and four water pollution parameters in a watershed in Southeast Brazil. The four parameters are nitrate, total ammonia nitrogen, total phosphorous, and dissolved oxygen. To help concentrate on non-point source pollution, only data from the wet seasons of the time period (2001–2013) were analysed, based on the fact that precipitation causes runoff which is the main cause of diffuse pollution. The parameters measured were transformed into loads, which were in turn associated with an exclusive contribution area, so that every measuring station could be considered independent. Analyses were also performed on riparian zones of different widths to verify if the effect of the land cover on the water quality of the stream decreases with the increased distance. Pearson correlation coefficients indicate that urban areas and agriculture/pasture tend to worsen water quality (source). Conversely, forest and riparian areas have a reducing effect on pollution (sink). The best results were obtained for total ammonia nitrogen and dissolved oxygen using the whole exclusive contribution areas with determination coefficients better than R²≈0.8. Nitrate and total phosphorous did not produce valid models. We suspect that the transformation delay from total ammonia nitrogen to nitrate might be an important factor for the poor result for this parameter. For phosphorous, we think that the phosphorous sink in the bottom sediment might be the most limiting factor explaining the failure of our models.     

Air quality of Prague: traffic as a main pollution source

Political and economical transition in the Central and Eastern Europe at the end of eighties significantly influenced all aspects of life as well as technological infrastructure. Collapse of outdated energy demanding industry and adoption of environmental legislation resulted in seeming improvements of urban environmental quality. Hand in hand with modernization the newly adopted regulations also helped to phase out low quality coal frequently used for domestic heating. However, at the same time, the number of vehicles registered in the city increased. The two processes interestingly acted as parallel but antagonistic forces. To interpret the trends in urban air quality of Prague, Czech capital, monthly averages of PM(10), SO(2), NO(2), NO, O(3) and CO concentrations from the national network of automated monitoring stations were analyzed together with long term trends in fuel consumption and number of vehicles registered in Prague within a period of 1992-2005. The results showed that concentrations of SO(2) (a pollutant strongly related to fossil fuel burning) dropped significantly during the period of concern. Similarly NO(X) and PM(10) concentrations decreased significantly in the first half of the nineties (as a result of solid fuel use drop), but remained rather stable or increased after 2000, presumably reflecting rapid increase of traffic density. In conclusion, infrastructural changes in early nineties had a strong positive effect on Prague air quality namely in the first half of the period studied, nevertheless, the current trend in concentrations of automotive exhaust related pollutants (such as PM(10), NO(X)) needs adoption of stricter measures.