CHEMODYNAMICS OF TRACE POLLUTANTS DURING SNOWMELT ON ROOF AND STREET SURFACES
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In order to investigate the concentration levels and chemodynamic behaviour of organic micropollutants and heavy metals in snowmelt runoff from urban sealed surfaces, meltwater was sampled from one street :and four different roof catchments. Apart from peak concentrations of suspended solids during short intense street runoff from rain, concentrations of suspended solids in snowmelt runoff are two to fivefold higher than in rain runoff. However, the specific metal concentrations in suspended solids of snowmelt (except Zn) are lower than in suspended solids of rainwater runoff. This partly compensates the higher concentration of suspended solids. There are no distinct differences in concentrations of heavy metals between rain and meltwater runoff willi the exception of dissolved Cd; its concentrations are increased when high concentrations of macro ions are present. We explain high concentrations of PAH with a molecular weight of 202 or less in snowmelt with longer equilibration times available during melting than during rain runoff. An enhancement of solubility by DOC seems to be likely. The physical and chemical properties of various roof surfaces greatly influence the temporal variation of PAH concentrations during snowmelt runoff.Keywords:
Snowmelt
Meltwater
First flush
Total suspended solids
Total suspended solids
First flush
Indicator bacteria
Urban runoff
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Snowmelt in early spring is one cause of slope failure and landslides in snowy regions. The infiltration of meltwater into a cut slope along an expressway plays a critical role in reducing resistance to sliding. Despite its significant impact on snowmelt-induced slope failure, snowmelt runoff process has not been addressed in most specifications. This paper examines the case of a recent cut slope failure in the Hokkaido Expressway in the snowmelt season, and describes how snow melts and how meltwater infiltrates the ground to destabilize the cut slope. Snowmelt runoff tests were conducted both inside and outside of the laboratory and these tests focused on the fact that when a small snow block melts, meltwater drips only from the lowest part of the block. As part of the tests, snow blocks were placed on two slopes made of sandy soil. While one slope was completely covered with snow blocks, the other slope was covered on the upper part. As the result of the tests in the former case, meltwater moved downslope and flowed out from the snow layer, leaving the soil slope in a sound condition. In the latter case, meltwater flowing out of the lowest part of the snow layer infiltrated into sandy soil, resulting in a failure. The paper discusses how snowmelt processes similar to those observed in the laboratory tests can be seen on natural slopes. Since the site of the expressway cut-slope failure is located at the lower end of a snow-covered area of an expressway cut slope, it can be inferred that phenomena similar to those observed in the laboratory occurred at the slope failure site.
Meltwater
Snowmelt
Snowpack
Slope failure
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In order to investigate the concentration levels and chemodynamic behaviour of organic micropollutants and heavy metals in snowmelt runoff from urban sealed surfaces, meltwater was sampled from one street :and four different roof catchments. Apart from peak concentrations of suspended solids during short intense street runoff from rain, concentrations of suspended solids in snowmelt runoff are two to fivefold higher than in rain runoff. However, the specific metal concentrations in suspended solids of snowmelt (except Zn) are lower than in suspended solids of rainwater runoff. This partly compensates the higher concentration of suspended solids. There are no distinct differences in concentrations of heavy metals between rain and meltwater runoff willi the exception of dissolved Cd; its concentrations are increased when high concentrations of macro ions are present. We explain high concentrations of PAH with a molecular weight of 202 or less in snowmelt with longer equilibration times available during melting than during rain runoff. An enhancement of solubility by DOC seems to be likely. The physical and chemical properties of various roof surfaces greatly influence the temporal variation of PAH concentrations during snowmelt runoff.
Snowmelt
Meltwater
First flush
Total suspended solids
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Urban storm water runoff carries particulate matter and other pollutants to water bodies, causing environmental problems. Removing suspended solids from runoff through geotextile filtration is a storm water control measure currently under investigation, which could help lessen the negative impacts of storm water on aquatic ecosystems. In this study, three geotextiles were tested in a laboratory setup with influent suspensions having hydraulic loading rates, total suspended solids (TSS) concentration, and particle-size distributions similar to those reported for urban highway storm water runoff. The results indicated that after a short priming period, all three geotextiles can effectively remove suspended solids to below a target concentration of 30 mg/L. The results also showed that influent hydraulic loading rate and TSS concentration have minimal effects on the total mass of solids captured by the filter, whereas particle-size distribution does affect the total mass of solids captured by the filters. The retention criteria for choosing the appropriate geotextile for storm water treatment established in recent literature were evaluated by using the laboratory results. The geotextiles and sand filters were directly compared by using the results of the laboratory column testing of sand filters performed for this study. The results indicate that a geotextile will outlast a sand filter in terms of total solids loading under similar conditions.
Total suspended solids
Geotextile
First flush
Turbidity
Filtration (mathematics)
Retention basin
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In June 2003, a proprietary stormwater filtration device (SFD) was installed at an employee parking lot in downtown Madison, Wisconsin. A total of 26 filter cartridges were used to treat stormwater runoff from the 0.91 acre asphalt parking lot. Automated equipment was installed to measure flow and collect water-quality samples during storms at the inlet, outlet, and bypass pipes of the SFD. Thirty-three organic and inorganic constituents or physical properties plus particle-size distributions were analyzed for in samples from the inlet and outlet, 18 of which were polycyclic aromatic hydrocarbons (PAHs). Water-quality samples were collected for 51 runoff events from November 2005 to August 2007. Samples from all runoff events were analyzed for suspended sediment concentrations, whereas samples from 31 of the runoff events were analyzed for 15 of the constituents. Samples from 15 runoff events were analyzed for PAHs, and samples from 36 events were analyzed for particle size. The treatment efficiency of the SFD was calculated using the summation of loads (SOL) and the efficiency ratio methods. Constituents for which the concentrations and (or) loads were significantly decreased by the SFD include total suspended solids (TSS), suspended sediment, volatile suspended solids, total phosphorous (TP), total copper, total zinc, and PAHs. The efficiency ratios for these constituents were 44, 43, 38, 55, 22, 5, and 45 percent, respectively. The SOLs for these constituents were 32, 39, 28, 36, 23, 8, and 48 percent, respectively. Both the SOL and efficiency ratio were negative for chloride of about 20 percent. Six constituents or physical properties, dissolved phosphorous, chemical oxygen demand, dissolved zinc, total dissolved solids, dissolved chemical oxygen demand, and dissolved copper, were not included, because the difference between concentrations in samples from the inlet and outlet were not determined to be significant.
Total suspended solids
Filtration (mathematics)
Urban runoff
First flush
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Stormwater runoff from heavily travelled urban highways can adversely affect the quality of receiving waters. Nonpoint pollutants in highway runoff include heavy metals, suspended solids, micro-organics, oils and chlorides. These anthropogenic pollutants result from traffic activities, atmospheric deposition, engine exhaust, roadway degradation and highway maintenance. An effective control strategy for trapping runoff pollutants, especially heavy metals and suspended solids, is a partial exfiltration trench (PET). A PET is an engineered trench designed to exfiltrate some of the runoff captured during first-flush periods or long duration hydrographs. Narrow PETs installed outside the travelled pavement serve as multipurpose replacements for underdrains and can be located in restricted rights-of-way where space constraints preclude other pollutant control options. The hypothesis that heavy metal concentrations are significantly correlated to suspended solids in highway runoff is investigated in this paper. Runoff data from eight highway sites in the United States and Europe are analyzed to test this hypothesis. Results indicate a strong positive correlation between heavy metals and suspended solids for snow washoff events and a weaker positive correlation for rainfall events. Similar results are observed for correlations between heavy metals and suspended solid particle sizes. It is argued that a PET holds promise as an effective device for immobilizing heavy metals and trapping suspended solids generated during snow washoff, pavement first-flush and long duration rainfall events.
Total suspended solids
First flush
Deposition
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Purpose. Land use within a watershed affects surface water quality by creating a process by which diffuse pollutants such as suspended solids, trace metals, and nutrients enter rivers and streams. The purpose of this study is to assess pollution-load for Total Suspended Solids (TSS) and some trace metals in runoff samples collected during storm events in selected sub-catchment locations representing different land use areas in an urban watershed; and to determine the effects of land-use on the content of pollutants in stormwater using Event Mean Concentration (EMC).
Results. There were high EMC and Site Mean Concentrations (SMC) of TSS in stormwater in the six land-use zones examined, with values ranging from 154.0 mg L−1 to 1464.0 mg L−1; and 216.5 mg L−1 to 1153.4 mg L−1 for EMC and SMC respectively. The total content of suspended solids was significantly high, above the acceptable threshold of 100.0 mg L−1 stipulated by the WHO. The researchers also found a statistically significant variation in TSS loading of stormwater from the commercial land-use areas compared with the other land-use zones. A strong correlation was also observed between the volume of stormwater discharged and the TSS load. However, the concentrations of trace metals in stormwater were low across the land use zones. The commercial districts of the studied cities were found to be major sources of suspended solids in stormwater, and pollution of the urban watersheds leading to the deterioration of the rivers.
Scientific novelty. This study attempted to qauntify TSS load in stormwater and determine the contributions of the diffferent urban land-use areas to pollution yield.. It contributes to scientific efforts to directly quantify surface water pollution from nonpoint sources, since little attention has been paid to diffuse pollution, especially in sub-Saharan Africa; and provides baseline data for assessing urban stormwater in low-income countries.
Practical value. This study offers guidelines for city authorities to develop land use policies to control surface water pollution and urban waste. The findings may also serve as emperical basis for greater advocacy by civil society organizations for the proper management and control of urban rivers and streams for public health benefits.
Total suspended solids
First flush
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The rainwater and rainfall runoff of roofs in the central district of Beijing from June to September in 2019 were sampled and analyzed to study the characteristics of the water quality, the first flush effect, and the main influential factors and sources of pollutants. The results showed that the roof runoff was seriously polluted by total nitrogen, ammonia nitrogen, chemical oxygen demand, and total suspended solids whose event mean concentration (EMC) exceeded the fifth level of environmental quality standards for surface water (GB 3838-2002) (the EMC of suspended solids exceeded the second level of discharge standard of pollutants for municipal wastewater treatment plants (GB 18918-2002)). The rainwater was relatively less polluted than the rainfall runoff, but the EMC of ammonia nitrogen and total nitrogen of the rainwater also exceeded the standard in some rainfall events. The first flush intensity of the rainfall runoffs was between weak and medium. The sequence of strength of the first flush of different pollutants was ammonia nitrogen>total suspended solids>chemical oxygen demand>total nitrogen>mercury>zinc>total phosphorus>lead. The concentration of total suspended solids, chemical oxygen demand, and total phosphorus in roof runoff were significantly positively correlated with the length of rainfall and the dry period and negatively correlated with the rainfall intensity. According to the results of principal component analysis, the main pollutant in rainwater was nitrogen emitted by vehicles, and the main pollutants in roof runoffs were suspended solids, organic matters, and phosphorus pollutants released from the aging of roofing materials and the corrosion of metal down pipes.
Rainwater Harvesting
Total suspended solids
First flush
Biochemical oxygen demand
Total dissolved solids
Volatile suspended solids
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Among various drainage surfaces which allow rainwater to be utilised locally, roofs are frequently chosen solution. This is because they represent a big share of all sealed surfaces in cities and discharged liquids are considered potentially clean. Scientific reports confirm that pollutants accumulate on roofs and influence the quality of discharged water. Suspended solids are the biggest group of pollutants which occur in runoffs. The selection of rainwater pre-treatment installation and further use of the water depends on the concentration of suspended solids and their particle size. This article describes results of a research concerning suspended solids discharged from roofs made of traditional materials as well as green-roofs located in urban areas. The quantity and size of particles were assessed against rainfall characteristics: rainfall depth, length of antecedent dry weather periods and season. Results of the research show diversity of concentration levels and size of suspended solids within runoffs in reference to roofing materials, rainfall characteristics and season. The highest concentrations of suspended solids in runoff from traditional roofs were observed during rainfall depth less than 5 mm, after ancedent dry weather periods more than 50 h and in winter. These parameters did not have significantly influence on the low concentrations of suspended solids in runoff from green roofs. Suspended solids particles with the size of up to 200 μm constitute the biggest share of all roof runoffs.
Rainwater Harvesting
Total suspended solids
Total dissolved solids
First flush
Volatile suspended solids
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Anthropogenic constituents in highway runoff include metal elements and suspended solids which result from traffic activities, atmospheric deposition, roadway degradation and highway maintenance. A best management practice (BMP) for immobilizing heavy metals and suspended solids is a partial exfiltration trench (PET). A PET is designed to exfiltrate a percentage of infiltrated runoff to subsoil with the balance discharged through an underdrain. The PET functions through adsorptive-filtration, where dissolved metals are immobilized through sorption and metals associated with suspended solids are immobilized through filtration. An important PET design consideration is potential association of heavy metals with suspended solids. This paper investigates the correlation between heavy metals and suspended solids in highway runoff. Results indicate a strong positive correlation between heavy metal and suspended solid concentrations for snow washoff events and a poor correlation for rainfall-runoff events. Similar results are observed for correlations between metals and suspended particle sizes. From these findings, it is argued that a PET holds promise as a device for immobilizing metals associated with suspended solids transported during snow washoff and long duration rainfall events.
Total suspended solids
First flush
Filtration (mathematics)
Volatile suspended solids
Total dissolved solids
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