An Exploration of Future Patterns of the Contributions to OpenStreetMap and Development of a Contribution Index

OpenStreetMap (OSM) represents one of the most well‐known examples of a collaborative mapping project. Major research efforts have so far dealt with data quality analysis but the modality of OSM's evolution across space and time has barely been noted. This study aims to analyze spatio‐temporal patterns of contributions in OSM by proposing a contribution index (CI) in order to investigate the dynamism of OSM. The CI is based on a per cell analysis of the node quantity, interactivity, semantics, and attractivity (the ability to attract contributors). Additionally this research explores whether OSM has been constantly attracting new users and contributions or if OSM has experienced a decline in its ability to attract continued contributions. Using the Stuttgart region of Germany as a case study the empirical findings of the CI over time confirm that since 2007, OSM has been constantly attracting new users, who create new features, edit the existing spatial objects, and enrich them with attributes. This rate has been dramatically growing since 2011. The utilization of a Cellular Automata‐Markov (CA‐Markov) model provides evidence that by the end of 2016 and 2020, the rise of CI will spread out over the study area and only a few cells without OSM features will remain.     

Aquifer porosity in the Pan-African semi-arid context

Water scarcity is one of the major concerns that people are facing worldwide. Although the liquid is absolutely abundant through the globe, its availability poses too much problems specifically to each region. Those problems can result in one or a combination of three basic situations: declining water (drought), overabundance of surface water (floods) or degradation of the quality of water (pollution). All these situations are reflected in the scarcity of good quality water. Arid regions are particularly concerned. In such areas where groundwater contained in aquifers is usually perceived as providence, any project of groundwater exploration and exploitation must be preceded by prior careful and meticulous investigation, in order to avoid early and premature drying. This investigation is likely to predict the future behaviour of aquifers and to improve the groundwater resources management. Beside fundamental properties as hydraulic conductivity, the present paper that addresses the water sector in the semi-arid region of northern Cameroon emphasizes the importance of porosity on aquifer productivity and consequently on the groundwater resources management. The porosity of the local aquifer has then been determined using the Waxman and Smits model which establishes a reliable relationship between the apparent and corrected formation factors, F _a and F _c , taking the clay effects into consideration. This approach can be applied in other similar semi-arid regions through the world.     

Observations and Modeling of B[e] Stars

We give a short definition of B[e] star and we show spectrocopicvariabilities obtained for the peculiar star HD 45677 especialy for the strong He I line at 5876 Å. We present also some photometric observations for this type of stars that show a important excess in thenear and mid infrared due to the presence of circumstellar dust. The modelingof these stars shows that a simple model with a spherical dust shell fits well the observations. High spatial resolution gives an additional constraint on the modeling.     

Competitive heavy metals adsorption on natural bed sediments of Jajrood River,Iran

The presence of heavy metal concentrations was examined in natural sediments from four sites along the Jajrood river in northeast of Tehran, the capital of Iran. Besides determination of elemental concentrations (Pb, Cu, Zn, Cd, Ni and Cr), X-ray fluorescence and X-ray diffraction tests were carried out to determine other chemical components in these adsorbents. Also the ability of sediments to adsorb these heavy metal ions from aqueous solutions was investigated. Results show that the extent of adsorption increases with increase in adsorbent concentration. The amount of adsorbed Pb, Cu and Zn in sediments was much greater than that of the other metals, and Cr was adsorbed much less than others. The adsorbabilities of sediments to heavy metals increased in the order of Pb > Cu > Zn > Cd > Ni > Cr. Based on the adsorption data, equilibrium isotherms were determined at selected areas to characterize the adsorption process. The adsorption data followed Freundlich and Langmuir isotherms in most cases. Correlation and cluster analysis was performed on heavy metals adsorption and sediment components at each site to evaluate main adsorbing compounds in sediments for each metal. Results demonstrated that heavy metals sorption is mostly related to load of organic matter in the Jajrood river sediments.     

Shoreline spatial and temporal response to natural and human effects in Boujagh National Park,Iran

Shoreline variation and river deltas are among the most dynamic systems in marine environments. The related different variations in spatial and temporal scales play significant roles in land planning and different management applications. Modeling the dynamics of seashore of Boujagh National Park (BNP) which is located on the southern coast of the Caspian Sea in the Sefidrud Delta (SD), considering natural and anthropogenic factors, was the main objective of the current study. To achieve this goal, a combination of remote sensing data, historical data, and numerical simulations was utilized. The BNP covers an area of 3,270 ha and includes two international wetlands, Boujagh and Kiashahr. In earlier periods, this area faced severe morphological changes whereas recently its shoreline has experienced gradual variations. Accordingly, at the first stage, the shoreline variation from 2006 to 2017 was extracted by processing and classifying Operational Land Imager (OLI) and Thematic Mapper (TM) images from Landsat satellites using the Maximum Likelihood approach. In the second stage, the two dimensional MIKE21 model was utilized to identify wave and coastal current patterns and parameters for the year 2015. Morphologically, the results showed that, the shoreline of the BNP is affected by several natural and anthropogenic factors. Seaward advancement of the shoreline occurred in zones A (east zone) and C (west zone) due to Caspian Sea Level drop and sedimentation while retreating occurred at Zone B (north zone) influenced by wave and current patterns and reduction of the Sefidrud River flows. Also, the results imply that maintaining the existing conditions results in the disappearance of a considerable part of the ecological area in the BNP. Hence, to manage and preserve the coastline of the BNP complying with the current anthropogenic and natural factors, it is vital to take necessary management measures.     

Impact of fertilizer application and urban wastes on the quality of groundwater in the Cambrai Chalk aquifer,Northern France

Since 1975, Europe sets up its policy to limit the degradation and the pollution of the aquatic environments through 30 directives and regulations. In the north of France, the nitrate concentrations measured in the groundwater exceed the water drinking limit fixed at 50 mg/L by the European framework directive in the field of water (2000/60/EC). This high concentration is due to intensive agriculture, industrialization and demographic growth. Several programs were launched in order to resolve this situation: “Ferti-better” or the use of fertilizer in moderation and installation and amelioration of wastewater collect and treatment systems. In order to estimate the influence of the anthropic activities on the quality of groundwater in the “Artois-Picardy” basin, a preliminary validation on parcel and district scale were necessary. The impact of these programs in the “Cambrai district” was evaluated using an integrated approach, which is based on the use of four numerical models: AgriFlux, VS2DT, Modflow and MT3D. The results illustrate an improvement due to the “Ferti-Better” program initiated in 1990 and punctual degradation under urbanized areas. Predictions (2015) show a spatial evolution of nitrates concentration varying with the thickness of unsaturated layer. The integrated model constitutes an efficient tool for predicting the evolution of the groundwater quality. This approach is important to control the application of the new European laws in the water field.     

A new pan-sharpening method using multiobjective particle swarm optimization and the shiftable contourlet transform

In this paper, a novel approach based on multiobjective particle swarm optimization (MOPSO) is presented for panchromatic (Pan) sharpening of a multispectral (MS) image. This new method could transfer spatial details of the pan image into a high-resolution version of the MS image, while color information from the low-resolution MS image is well preserved. The pan and MS images are locally different because of different resolutions, and therefore we cannot directly combine them in the spatial domain. For this reason, we generate two initial results, which are more appropriate for a weighted combination. First, the pan and the MS images are histogram matched. Then we use the shiftable contourlet transform (SCT) to decompose the histogram-matched pan and MS images. The SCT is a new shiftable and modified version of the contourlet transform. In this step, an algorithm based on the SCT is used to generate two initial results of the high-resolution MS images. Our objective is to produce two modified high-resolution MS images, in which one has high spatial similarity to the pan image and the other one has high radiometric quality in each band. Therefore, we have used two different fusion rules to integrate the high-frequency contourlet coefficients of the pan and MS images to generate two initial results of high-resolution MS image or the pan-sharpened (PS) image. Finally, we can find the optimal PS image by applying the MOPSO algorithm and using the two initial PS results. Specifically, the PS image is obtained via a weighted combination of the two initial results, in which the weights are locally estimated via a multiobjective particle swarm optimization algorithm to generate a PS image with high spatial and radiometric qualities. Based on experimental results obtained, the produced pan-sharpened image also has good spectral quality. The efficiency of the proposed method is tested by performing pan-sharpening of high-resolution (Quickbird and Wordview2) and medium-resolution (Landsat-7 ETM +) datasets. Extensive comparisons with the state-of-the-art pan-sharpening algorithms indicate that our new method provides improved subjective and objective results.     

Effect of organic matter and selected heavy metals on sorption of acenaphthene,fluorene and fluoranthene onto various clays and clay minerals

The effects of organic matter (80% humic and 15% fulvic acid) and coexistence of heavy metals (Ni, Pb and Zn) on sorption of three polycyclic aromatic hydrocarbons (PAHs)—acenaphthene, fluorene and fluoranthene—were examined for kaolinite, 60% kaolinite?+?40% sand, and 43% kaolinite?+?42% sand?+?15% bentonite. In total 108 batch sorption tests of PAHs were conducted for three types of clay mineral mixtures in six possible combinations of soil organic matter and heavy metal contents from no heavy metals and organic matter added to maximum organic matter added with spiked heavy metals. Results showed that the existence of metals increased the sorption of PAHs onto kaolinite from 4.7% for acenaphthene to 17.9% for fluoranthene. Organic matter in a kaolinite-sand-bentonite matrix could increase PAH sorption by up to 140% for fluoranthene. In all cases, increases were greater for fluoranthene, a larger PAH molecule. Heavy metals coexisting with organic matter led to enhanced sorption of PAHs compared to clay minerals without organic matter. Synergistic effects of organic matter and heavy metals on PAH sorption increments in the mixtures studied were such that the overall sorption could be 10–41% higher than that based on summation of the separate effects of metals and organics.     

Spatial patterns and temporal trends of daily precipitation indices in Iran

Spatial patterns of daily precipitation indices and their temporal trends over Iran are investigated using the APHRODITE gridded daily precipitation dataset for the period 1961–2004. The performance and limitations of the gridded dataset are checked against observations at ten rain-gauge stations that are representative of different climates in Iran. Results suggest that the spatial patterns of the indices reflect the role of orography and sea neighborhoods in differentiating central-southern arid and semi-arid regions from northern and western mountainous humid areas. It is also found that western Iran is impacted by the most extreme daily precipitation events occurring in the country, though the number of rainy days has its maximum in the Caspian Sea region. The time series of precipitation indices is checked for long-term trends using the least squares method and Mann-Kendall test. The maximum daily precipitation per year shows upward trends in most of Iran, though being statistically significant only in western regions. In the same regions, upward trends are also observed in the number of wet days and in the accumulated precipitation and intensity during wet days. Conversely, the contribution of precipitation events below the 75th percentile to the annual total precipitation is decreasing with time, suggesting that extreme events are responsible for the upward trend observed in the total annual precipitation and in the other indices. This tendency towards more severe/extreme precipitation events, if confirmed by other datasets and further analyses with longer records, would require the implementation of adequate water resources management plans in western Iran aimed at mitigating the increasing risk of intense precipitation and associated flash floods and soil erosion.