Clean lake

What happens if the flow into a compartment is not equal to the flow out of a compartment For example, when a pollutant just begins flowing into a clean lake, the lake is not yet at steady state. It takes some time for the flow out of the lake to increase to the new, higher (but constant) concentration of the pollutant. The time it takes to come up to this new concentration depends on the residence time of the pollutant in the lake. Long residence times imply that it takes a long time for the pollutant to come to the new concentration. 

First, let us consider a situation in which the concentration starts at zero and goes up to a steady-state value. An example is a clean lake in which someone starts dumping some pollutant at a constant rate (perhaps the green dye mentioned above). Because the dumping just started, the flow of the pollutant into the lake is greater than its flow out of the lake, and the flow into the lake is constant. We know that the concentration at time = 0 is... 

A soluble pollutant is dumped into a clean lake starting on day 0. The rate constant of the increase is 0.069 day-1, (a) Sketch a plot of the relative concentration from day 0 to day 60 be sure to label the axes with units and numbers, (b) What fraction of the steady-state concentration is reached after 35 days ... 

A pollutant is dumped into a clean lake at a constant rate starting on July 1, 1980. When the pollutant s concentration reaches 90% of its steady-state value, the flow of the pollutant is stopped. On what date will the concentration of the pollutant fall to 1% of its maximum concentration Assume that the rate constants of the increase and decrease are both 0.35 year-1. 

A lead recycling plant begins operation on the shores of a hitherto clean lake of volume 3.0 x 106 m3. It discharges into the lake 12 m3/h of waste containing 15 ppm of lead. The other inflow and outflow of the lake are rivers with flow rates of 8400 m3/h. (a) What is the steady-state concentration of lead in the lake Assume the... 

Chapter 8 will show how the by-product oxygen can be used to reducing or eliminating other sources of pollution not related to the use of fossil fuels. These sources will include pollution from the disposal of solid waste and treatment of sewage. In addition, it will show a possible method of cleaning lakes and rivers of the current pollution and regenerating and maintaining their natural purity. 

The effect of pH on the mobilization of zinc in a few highly acidic clean lakes has been studied (Sprenger et al. 1987 White and Driscoll 1987). In these lakes, in which the pH was <3.6, concentrations of zinc were elevated in the water column, and the concentration of zinc in the upper layer of sediment was substantially lower than values reported for other lakes at higher pH values. The relatively higher concentration of zinc in the water column compared to the sediment may be the result of lower adsorption of zinc on oxide surfaces due to low pH, solubilization of inorganic zinc from the sediment layer, and the dissociation of bound organic complexes of zinc present in the sediment and their subsequent release into the water phase. 

Since SO2 and NO2 are criteria pollutants, their emissions are regulated. In addition, for the purposes of abating acid deposition in the United States, the 1990 Clean Air Act Amendments require that nationwide SO2 and NO emissions be reduced by approximately 10 million and 2 million t/yr, respectively, by the year 2000. Reasons for these reductions are based on concerns which include acidification of lakes and streams, acidification of poorly buffered soils, and acid damage to materials. An additional major concern is that acid deposition is contributing to the die-back of forests at high elevations in the eastern United States and in Europe. 

The rainwater runoff from buildings depends on the geographical location and storm-return period specified. Rainwater runoff from a roof is relatively clean and can discharge directly to a watercourse, lake, etc. without passing through an interceptor. 

Thermal inversions make winter the most unfavorable season for clean air. Vast differences in air quality are found in the industrialized north, and the residential southwest regions. Particulate matter influences mainly the north, where industries, landfills, and the dried bed of Texcoco Lake are located. Sulfur oxides impinge primarily on the northeast and southwest. High carbon monoxide concentrations are found in heavy traffic areas such as the northwest. Ozone affects predominantly the southwest at any season. We have selected air quality records from data generated by stations registering the higher pollutant levels, as follows ... 

PEST. This code ( 3) was developed within the framework of Rensselaer Polytechnic Institute s CLEAN (Comprehensive Lake Ecosystem Analyzer) model. It includes highly elaborated algorithms for biological phenomena, as described in this volume (44). For example, biotransformation is represented via second-order equations in bacterial population density (Equation 5) in the other codes described in this section PEST adds to this effects of pH and dissolved oxygen on bacterial activity, plus equations for metabolism in higher organisms. PEST allows for up to 16 compartments (plants, animals, etc.), but does not include any spatially resolved computations or transport processes other than volatilization. 

Paasivirta, J., J. Sarkka, K. Surma-Aho, T. Humppi, T. Kuokkanen, and M. Marttinen. 1983. Food chain enrichment of organochlorine compounds and mercury in clean and polluted lakes of Finland. Chemosphere 12 239-252. 

In general, silver concentrations in surface waters of the United States decreased between 1970-74 and 1975-79, although concentrations increased in the north Atlantic, Southeast, and lower Mississippi basins (USPHS 1990). About 30 to 70% of the silver in surface waters may be ascribed to suspended particles (Smith and Carson 1977), depending on water hardness or salinity. For example, sediments added to solutions containing 2 pg Ag/L had 74.9 mg Ag/kg DW sediment after 24 h in freshwater, 14.2 mg/kg DW at 1.5% salinity and 6.9 mg/kg DW at 2.3% salinity (Sanders and Abbe 1987). Riverine transport of silver to the ocean is considerable suspended materials in the Susquehanna River, Pennsylvania — that contained as much as 25 mg silver/kg — resulted in an estimated transport of 4.5 metric tons of silver to the ocean each year (USEPA 1980). The most recent measurements of silver in rivers, lakes, and estuaries using clean techniques show levels of about 0.01 pg/L for pristine, nonpolluted areas and 0.01 to 0.1 pg/L in urban and industrialized areas (Ratte 1999). 

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