جستجوی مقالات مرتبط با کلیدواژه "urban runoff" در نشریات گروه "عمران"

Urban runoff as one of the most important emission sources of heavy metal to the environment has potential environmental and health risks. This study aimed to evaluate the content of ten heavy metals in runoff of Sorkheh Hesar catchment, Tehran for this purpose, Runoff samples were taken from the outlet of Sorkheh Hesar catchment during three flood events in 2018- 19 and the total concentration of heavy metals was determined by ICP-MS. Fe, Mn, Zn, Pb, Cu, Cr, Ni, As, Mo and Cd had the highest abundance in all samples, respectively. The results of Spearman's rank correlation coefficient showed strong correlation between most metals, especially Fe, Mn, Zn, Pb, Ni, Cd and Cu, which indicating the same input sources and similar geochemical behavior. Also the mean values of Contamination Index, Heavy Metal Evaluation Index and Heavy Metal Pollution Index were 24.7, 30.1 and 130.2, respectively which indicated most of the samples were in contaminated and high contaminated level, due to high concentration of three elements including Fe, Mn and Pb in compare to standard permissible values.

Heavy metals are considered as one of the most important environmental threats, especially for aquatic ecosystems, due to their toxicity, stability, widespread distribution and bioaccumulation in the food chains. Urban runoff is the main non-point source of heavy metal emissions to receiving environments, which its quality and evaluation is particular importance. The major part of Tehran’s surface runoff, especially the northern and eastern catchment, is transferred to the southern areas by drainage network and affects receiving environment including surface water, groundwater and sensitive ecosystems such as Band- e- Alikhan wetland. The aim of this study was to investigate the content of heavy metals in urban runoff and compare the efficiency of the index of Iran’s surface water resources quality toxic parameters with the Contamination Index, heavy metal evaluation index and Heavy metal pollution index. For this purpose, sampling was performed from the outlet of Tehran’s Sorkheh – Hesar catchment during three flood events in 2018- 19 and the concentration of Arsenic, Iron, Lead, Zinc, Cadmium, Chromium, Copper, Manganese, Molybdenum and Nickel were measured by ICP-MS. Iron, Manganese, Zinc, Lead, Copper, Chromium, Nickel, Arsenic, Molybdenum and Cadmium had the highest abundance in all samples, respectively The values of the index of Iran’s surface water resources quality toxic parameters, Contamination Index, heavy metal evaluation index and Heavy metal pollution index were in the range of 5.5 to 68.2, 9.6 to 74.4, 83.2 to 192.7 and 8.8 to 23.7, respectively. The contamination index indicated that all samples were in the highly contaminated class, while according to the and heavy metal evaluation index and Heavy metal pollution index indices, 67 and 86 percent of the samples were highly contaminated, respectively. Also, the index of Iran’s surface water resources quality toxic parameters values showed that 70 percent of the samples are in very bad quality class, and the other samples are in bad quality class. In general, a comparison of the results of the studied indices indicate that most of the samples were polluted. The results of the present study showed that the studied indices presented similar results in determining the contamination status of most samples. The results of Spearmanchr(chr(chr('39')39chr('39'))39chr(chr('39')39chr('39')))s rank correlation coefficient showed strong correlation (0.775-0.999) between all of four indices in runoff, which confirmed the similar behavior of the indices in determining the contamination status of the samples. In more detail, comparing the values of the indices with each other showed that their response to a significant increase in the concentration of elements is different. So that, the changes in the value of the Iran’s surface water resources quality toxic parameters gradually decrease with increasing the concentration of elements and its value is fixed in very high levels of pollution, but the values of the other three indices increase linearly with increasing the concentration of elements. Comparison of the results of the indices for the runoff quality assessment, showed that index of Iran’s surface water resources quality toxic parameters had the highest affinity with the pollution index, Heavy metal pollution index and heavy metal evaluation index, respectively, which shows the appropriate efficiency for evaluating these streams. Thus, the index is suitable for evaluation of heavy metal contamination in urban storm-water runoff due to high separation of pollution degree and less susceptibility to very high concentrations. It is recommended that, more elements in a wide range of concentrations should be considered in order to performance evaluation of the indices in future researches.

The use of porous concrete system in urban areas as a modern and applied management approach during rainfall can prevent the problems by rapid outflow of the surface runoff. In this research, effect of replacing dolomite minerals in two modes of fine-grained and powder, as part of the aggregates or part of the cement, respectively, is investigated on the structural properties of porous concrete. In order to use porous concrete in urban runoff management system, the compressive strength and porosity should be considered. Two series of samples were made for structural experiments. The 15×15×15 cm samples were designed to test the compressive strength and the 10×10×10 cm samples were made to determine the porosity percentage. Statistical analyses of the laboratory results were performed using SPSS software. According to the results, replacement of dolomite powder for cement did not have significant effect on compressive strength and porosity. On the other hand, fine-grained dolomite has greatly improved the compressive strength. In addition to increasing the compressive strength, the porosity was increased due to the mechanism of particle placement in samples receiving 10% fine aggregates. Also adding 30% fine grained, increased compressive strength by 162%. This is while the porosity percentage has fallen sharply.

By adding perlite and leca to porous concrete, its physical characteristics were studied. Compression strength, hydraulic conductivity and porosity of two porous concretes (without fine grains and with 20% fine grains) were measured. Results showed that adding 20% fine grains to porous concrete highly decreases hydraulic conductivity and porosity and increases compression strength. The highest compression strength (20.5 MPa) was seen in without-fine-grains samples (L10-0 treatment) and in with-fine-grains samples (34.85 MPa) in L15-20 treatment. The L5-0 treatment in both cases of with/without additives, had the highest hydraulic conductivity and porosity. Leca had better performance than perlite.

Urban development is always associated with infrastructure surfaces icreasment such as road and building construction and other impermeable surfaces that lead to precipitations runoff. Urban runoff contains heavy contaminants such as nutrients, heavy metals and organic substances including hydrocarbons and polycyclic aromatic hydrocarbons (PAHs). This pollutants can infect water and soil resources by road surface washing and discharging into the receiving waters or infiltrating into surrounding area soils. Stormwater management has recently shifted towards a focus on site level low impact development (LID) techniques that aim to reduce the total stormwater runoff volumes in addition to attenuating peak flows and removing pollutants at or near the source of runoff. Permeable pavement systems (PPS) are a subset of LID stormwater best management practices (BMPs) of particular interest in dense urban areas because they can be installed in parking lots and low traffic roadways where the availability of land space for more traditional BMPs is not available. Such information is necessary to improve the selection of BMP/LIDs for stormwater management. Previous concrete pavement are subset of PPS and able to reduce the volume of urban runoff significantly which leads to hydraulic differentia reduction and its specific side effects urban utilities in addition to providing requirements for treatment processes and in-situ urban pollution management. In this study, porous concrete pavement performance has been surveyed in terms of quantitative and qualitative reduction of synthetic runoff. The effect of porosity and rainfall intensity were investigated. To investigate the effect of concrete porosity, four levels including 15%, 20%, 25% and 30% have studed and for evaluating rainfall intensity effect, a range of precipitation between 25 to 250 mm/h concidered according the recent studies considered. The pilot used for this study consisted of a tank made of galvanized steel that simulated PCP was replaced layer by layer at the bottom of tank. Synthetic runoff sprinkled on the previous concrete surface with specified flow rate. Effluent is collected from the orifice that embedded under the tank then effluent quality parameters were evaluated. Befor run the pilot Previous concrete mixed designs calculated and prosity, percolation rate and Compressive strength were verified. The parameters examined in this study including COD, TDS, TSS, turbidity and EC of pervious concrete pavement system was compared to synthetic runoff. According to study outcomes, the system efficiency in TSS removal was between 75.7% to 88.6%, highest COD removal detected was 15% in case the porosity was 22.9%. Effluent quality analysis demonstrated that PCPS had little ability in TDS and EC removal. However PCPS was able to remove turbidity from syntetic runoff. The maximum efficiency of turbidty removal was detected 70.3% at rainfall intensity of 37 mm/h and the porosity of 22.9%. By comparing the results of the above parameters, it was determined that porosity has almost no effect on runoff quality. Results showed the rainfall intensity dose not have significant effect on PCPS efficency although the systems overall removal efficiency was drastically deacrased due to rainfall intensity increase even in cases with low emissions gradients.

Porous concrete pavement reduces surface runoff volume, prevents flood and reinforces groundwater resources. In this research, effects of replacing concrete aggregates (25, 50, 75 and 100%) by pumice, scoria and zeolite lightweight aggregates in porous concrete on physical properties including compressive strength and porosity were investigated. Preparation of concrete samples and testing was performed in the Concrete Technology Laboratory of Semnan University. Statistical analysis of the results was performed by using SAS 9.4 software. Results showed that by replacing lightweight aggregates in the porous concrete and removing the course aggregates, certain trend was observed among the samples. As the porosity increases, the compressive strength of the samples is reduced. The highest average compressive strength in porous concrete samples was observed in substitution of 50 and 25 percent scoria with aggregates (11.08 and 10.76 Mpa, respectively). The highest average porosity was observed in the sample containing 100% pumice as aggregates, which was 55.95% more than the control sample. Based on the obtained empirical relationship (R2=0.9), the compressive strength of porous concrete can be estimated for different porosities of porous concrete samples. Due to the abundance, economical values, high porosity and reduction of urban runoff, the proposed lightweight natural aggregates of this study have great potential to be used in pavements, especially in areas with low traffic.