No abstract

[1] The source of air pollution must be identified to select the appropriate monitoring activities and remedial measures. The present case study illustrates how analyses of (1) regional-scale synoptics and air mass trajectories, (2) local-scale atmospheric measurements (wind direction and speed, air temperature, dust load, sulfur and nitrogen oxide concentrations in the air, rain amount, and intensity) and (3) chemical and isotopic compositions of rainwater from 46 rain events, collected in the coastal city of Ashdod, Israel, were used to identify the various sources contributing to rainwater salts and contaminants and their timing. Rainwater affected by the Mediterranean Sea was characterized by a large marine fraction of salts, high chloride concentrations, and low values of d18 O and dD. These rain events were associated with the Cyprus Low system, which typically prevails in midwinter. Rainwater affected by continental sources had a small contribution of marine salts, high bicarbonate and calcium concentrations, and high values of d 18 O and dD. These rains were related to continental trajectories from the Red Sea and north African coast prevailing during the fall and spring. Rainwater affected by anthropogenic sources was characterized by low marine fraction, high sulfate concentrations, and low values of d 34 S. Whereas remote anthropogenic source was associated with the Red Sea trough system and were characterized by high nitrate concentrations (representing desert dust), the local anthropogenic source was characterized by high air concentrations of sulfur oxides at the local monitoring stations and high potassium and low nitrate concentrations. The identification of local anthropogenic source suggests that measures taken to reduce emissions from local oil refineries and power stations are likely to reduce the overall air pollution in the study area.

Levels of inorganic nitrogen species (ammonia, nitrite, and nitrate), ammonia oxidation potential (AOP), and diversity of ammonia-oxidizing bacteria (AOB) were studied in the sediments of a 50-km-long segment of an ephemeral stream in the Negev desert, receiving untreated wastewater. Water analysis in downstream sampling points showed reductions of 91.7% in biological oxygen demand, 87.7% in chemical oxygen demand, 73.9% in total nitrogen, and 72.8% in total ammonia nitrogen. Significant AOP levels in the sediment were detected mainly in the fall and spring seasons. Denaturing gradient gel electrophoresis of AOB 16S rRNA gene fragments showed that in most sampling points, the streambed was dominated by Nitrosospira cluster 3 strains similar to those dominating the stream bank's soils and sediments in nearby springs. Nitrosomonas strains introduced by discharged wastewater and others dominated some sections of the stream characterized by high organic carbon levels. The results suggest that climatic conditions in the Negev desert select for AOB belonging to Nitrosospira cluster 3, and these conditions dominate the aquatic environment effect along most of the stream sections. In addition, the nitrification-denitrification processes were not sufficient to reduce nitrogen levels in the sediment and prevent the eutrophication of some sections of the stream ecosystem. Thus, the discharge of high nitrogen wastewater into desert streams should be done carefully as it may endanger the already fragile ecosystem.

This paper describes the relationship between urban road network density and urban runoff coefficient in the coastal plain of Israel. The study assessed 30 years of recorded changes in rainfall-runoff coefficient in an urban catchment in the coastal plain of Israel. Rain and runoff were measured and sampled at measurement stations. Insight into the factors affecting urban runoff was gained by applying GIS and remote-sensing analysis, including street network density assessment and urban impermeable area recognition. Street network density was found to be a reliable indicator for both urban impermeability (R 2 ¼ 0.83) and runoff (R 2 ¼ 0.92) change dynamics, showing a strong linear correlation. Thus the urban street drainage network can help explain the dynamics of change in urban runoff. To prevent urban flooding hazards, and to help conserve water resources, regional planners should take into consideration road network density in built-up areas.