摘要:

Clear Lake, a 257 ha body of water located in south-central Minnesota, is a heavily utilized recreational lake which has become eutrophic because of the inflow of nutrient-rich runoff water from the adjacent City of Waseca. In 1981, 50 percent of the hydraulic load and 55 percent of the phosphorus load to the lake was diverted into a 21.4 ha marsh. The marsh system reduced the annual phosphorus load to Clear lake by 34 percent (768 kg). In 1986 construction was completed on a second marsh system which will filter urban and agricultural runoff carrying 20 percent of the phosphorus load into Clear Lake. The mean total phosphorus concentration in Clear lake has been reduced 31 percent, from 158 ug/L to 109 ug/L, since the diversion in 1981. The total nitrogen:total phosphorus ratio increased from 10:1 to 18:1 since the diversion began. Neither the Secchi disk depth nor the chlorophyllaconcentration was correlated with the reduced total phosphorus concentration in the lake. The control of internal loading will be necessary to eliminate nuisance algae conditions in Clear Lake.

ISSN:1040-2381    

DOI:10.1080/07438148709354785

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

This paper discusses the use of a soil filtration system constructed to provide additional treatment of urban stormwater following sedimentation. The system was constructed with a Clean Lakes Grant to remove solids and phosphorus from urban stormwater. The system showed severe operational problems following initial construction. During 1985, Minnesota Pollution Control Agency (MPCA) staff determined that proper system operation required corrective measures. A low cost renovation of the system was undertaken during the spring of 1986. Following filter renovation, a monitoring program studied filter efficiency in removing phosphorus and particulate matter. The renovated system operated well the first month, but following a week-long shutdown of the system, aerial hydraulic loading rate and filter efficiency decreased substantially. After three months of operation it was apparent that the renovation was only temporary because of an improper type of peat used in the system. Peat sand filters have been successfully employed for treatment of domestic wastewater and extending their use to treatment of stormwater seems feasible with proper construction. The Agency is considering using peat sand filters for treatment of stormwater in future lake restoration projects.

ISSN:1040-2381    

DOI:10.1080/07438148709354786

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

An empirical model previously developed for predicting phosphorus retention in reservoirs is tested against the urban lake/detention pond data set. Detention pond design criteria developed under the EPA's Nationwide Urban Runoff Program (NURP) are ovaluated using the model. For summer precipitation and runoff quality typical of St. Paul, Minnesota, a basin designed according to NURP criteria is estimated to have a long-term-average phosphorus removal efficiency of 47–68 percent. For a given loading regime, phosphorus removal is shown to be more sensitive to pond depth than to surface area. Specific design features for enhancing phosphorus removal (deepening, promoting infiltration, promoting plug flow, and chemical treatment) are discussed. The methodology can be used to evaluate wet detention pond design criteria in other regions, with substitution of appropriate precipitation and runoff quality characteristics.

ISSN:1040-2381    

DOI:10.1080/07438148709354787

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Patterns in alkalinity data for lakes and streams in Minnesota, Wisconsin, and Michigan were analyzed and mapped as a first step toward determining the potential sensitivity of surface waters to acidic deposition. The mapping was accomplished by: (1) assembling available alkalinity data on as many surface waters as possible, (2) plotting these data on relatively large-scale maps; and (3) analyzing the patterns of the 14,000 plotted values for spatial associations with other characteristics such as land use, geology, physiography, and hydrology to aid in extrapolation of the data. The level to which each factor influences alkalinity varied within the region. In northeast Minnesota and parts of upper Michigan, bedrock geology can influence surface water alkalinity. In other areas of the region, glacial drift is often very deep, and alkalinity concentrations are influenced by the composition of the drift, the lake hydrologic type, and the amount of groundwater contact. The lakes of lowest alkalinity are found in north-central Wisconsin and the upper peninsula of Michgan and tend to be small in size, comprise a small percent of total surface water area, and often occur in clusters. The mapping project helps meet the urgent need to understand the relative potential sensitivity of surface waters in the Upper Midwest, provides a tool for selecting geographic areas for more detailed studies, and allows more accurate regional assessments of effects of acidic deposition on aquatic resources.

ISSN:1040-2381    

DOI:10.1080/07438148709354788

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Developing lake management strategies that have utility across diverse geographic areas is difficult. For example, with over 12,000 lakes in Minnesota, determining carrying capacities, restoration goals, and lake protective standards cannot be practically made on a lake-by-lake basis. In light of this, the aquatic ecoregion approach was employed to assess regional patterns in watershed characteristics and inlake parameters such as phosphorus concentration, Secchi transparency, and lake mixing pattern. This approach defined seven distinct ecoregions, of which, the following four contain the majority of lakes in Minnesota: Northern Lakes and Forest (NLF), North Central Hardwood Forests (CHF), Western Corn Belt Plains (WCP) and the Northern Glaciated Plains (NGP). Analysis of total phosphorus data from approximately 1,100 lakes by ecoregion resulted in the following median epilimnetic concentrations: NLF – 23 μg P/L, CHF – 50 μg P/L, WCP – 121 μg P/L, and NGP – 176 μg P/L. Lake mixing patterns may be a further basis for organizing the data. These analyses indicate that the aquatic ecoregion approach is a valid method for grouping lake data and identifying spatial patterns of lake characteristics. Further, for Minnesota, this analysis indicates that no single total phosphorus concentration can be used as a basis for setting standards across Minnesota because of its tremendous diversity of lakes and attainable trophic states. Lake management schemes based on the ecoregion analysis presented.

ISSN:1040-2381    

DOI:10.1080/07438148709354789

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The ILWAS model was used as a framework to evaluate processes regulating the acid base chemistry of diverse lake types in the Adirondack Mountain region of New York State. The lakes selected for study represented both drainage and seepage basins distributed across regional edaphic and climatic gradients. Seventeen of the sites constitute a system of drainage lakes within the North Branch of the Moose River, located in the west-central Adirondacks. Variability in watershed characteristics of sub-basins in this drainage system and a wide range in surface water chemistry (pH 4.2–7.4) facilitated analysis of primary processes regulating surface water acidification. Additionally, the effects of these watershed acidity gradients on fish species distribution was assessed from recent and historical fish collections and by in situ bioassay to evaluate relative species sensitivity to acidity. Considerable variation in processes controlling acid-base chemistry of Adirondack lakes, both within drainage systems and regionally, were found as a result of variability in soil characteristics (primarily soil depth and mineralogy). hydrologic flowpaths, and reduction processes (both in-lake and watershed) controlling sulfate and nitrate concentrations. Soil characteristics and hydrologic flow paths largely determined base cation supply rates, whereas both hydrology and reduction processes effectively regulated acid anions supplied principally from atmospheric deposition. Inter-watershed acidity gradients related to these controlling processes and interspecific variation in physiological acid tolerance were found to be important determinants of fish species distribution patterns. Fish species with low acid tolerance (particularly cyprinids) had either disappeared from acidified lakes and streams or were found only in areas exhibiting low acidity. Currently, acid tolerant fish species (e.g., Yellow Perch,Percaflavescens) inadvertently introduced into Adirondack waters predominate in acidified drainage systems.

ISSN:1040-2381    

DOI:10.1080/07438148709354790

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

In the northern Great Lakes States, seepage lakes are considered more vulnerable to acidification than drainage lakes. The ILWAS model, which was developed for drainage lakes in the Adirondack Mountain Region of New York, has been revised for use in seepage lake systems. Contrasts were observed between the Wisconsin seepage lakes and the drainage lakes in the Adirondack Region of New York. (1) Atmospheric loading of hydrogen and sulfate ions was 77 and 62 percent respectively, lower in Wisconsin. (2) In contrast to the low alkalinity flow-through lakes in the Adirondacks, there are no observed spring pH depressions associated with snowmelt in Wisconsin seepage lakes. (3) Because of deep glacial deposits (32–190 m) at the Wisconsin sites, a longer contact time between groundwater and weatherable minerals provides a substantial buffering capacity via silicate hydrolysis. (4) Inlake alkalinity production by bacterial sulfate reduction in the sediments of Wisconsin seepage lakes plays a significant role in ameliorating the effects of acid deposition. After the ILWAS model was revised and calibrated for Round and East Eightmile lakes, scenarios were run on two other Wisconsin seepage lakes (Crystal and Vandercook) that have alkalinities of less than 30 μeq/L. These scenarios showed that a 25 percent reduction in sulfur loading would change the chemistry of these lakes slightly. The most important processes controlling the pH and alkalinity of these lakes are groundwater input and sediment sulfate reduction. Using these results, we propose new categories of sensitivities to acidification for seepage lakes in the northern Great Lakes States. Lakes with alkalinities greater than 40 μeq/L would not be considered sensitive to acid deposition. Lakes with alkalinities between 20 and 40 μeq/L would be moderately sensitive, and lakes with alkalinities less than 40 μeq/L would be considered sensitive.

ISSN:1040-2381    

DOI:10.1080/07438148709354791

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Many lakes in three areas in the Upper Midwest – northeastern Minnesota, northern Wisconsin, and the Upper Peninsula of Michigan – have low acid neutralizing capacity (ANC) and may be susceptible to change by acidic deposition. Northcentral Wisconsin and the Upper Peninsula of Michigan together contain about 150–300 acidic lakes (ANC ≤ 0), whereas none have been found in Minnesota. These acidic lakes are precipitation-dominated, Clearwater seepage lakes having small surface area, shallow depth, and low concentrations of dissolved organic carbon. The spatial distribution of these acidic lakes parallels a west to east gradient of increasing sulfate and hydrogen ion deposition. Several of these acidic lakes exhibit chemical characteristics and biological changes consistent with those observed elsewhere in waters reported to be acidified by acidic deposition. However, an hypothesis of recent lake acidification is not supported by analyses of either historical chemical data or diatom remains in lake sediments, and natural sources of acidity and alternative ecological processes have not been conclusively eliminated as causative factors. Streams in this three-state region have high ANC and appear to be insensitive to acidic deposition. The species richness and composition of lacustrine fish communities in the region are partly related to pH and associated chemical factors. Sport fishes considered acid-sensitive and of primary concern with regard to acidification include walleye, smallmouth bass, and black crappie. The fishery in at least one lake, Morgan Lake in Wisconsin (pH 4.6), may have declined because of acidification. Given the general lack of quantitative fishery data for acidic Wisconsin and Michigan lakes, however, more general conclusions concerning impacts or the absence of impacts of acidification on the region's fishery resources are not possible.

ISSN:1040-2381    

DOI:10.1080/07438148709354792

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The chemical composition of rainfall, agricultural runoff, groundwater, and pond water at several rural Oklahoma and north Texas locations was determined over a number of years (1972–1985). The inputs of acid, P, Cl, and cations in rainfall are not of major agronomic importance, although inputs of N (as NO3-N and NH4-N) and S (as SO4) in rainfall can contribute a significant proportion of the uptake of these elements by grasses or crops. The mean annual pH of rainfall was consistently greater than that of pure rainfall (5.6) averaging 6.5, while the average pH of two farm ponds (7.8) was even greater than that of rainfall. If a decrease in the pH of rainfall in the Southern Plains should occur in the future, the impact of the acidity on surface water will be reduced to a certain degree by the buffering capacity of the area soils. Appreciably more acid was added annually to the agricultural soils of the area via fertilizer P and N than in rainfall. Under present conditions it would take up to 1,500 years rainfall to add as much acid as added by fertilizer in one year. Even with a dramatic decrease in rainfall pH to 4.0, this period would be 10 years. Thus, rainfall acidity presents no immediate threat to agricultural soils, groundwater, or lakes in Oklahoma and north Texas under continuing management practices, although periodic monitoring is recommended due to an increasing number of coal-fired power stations located in this area.

ISSN:1040-2381    

DOI:10.1080/07438148709354793

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Midsummer zooplankton community structures of 50 Adirondack lakes were evaluated in relation to dominant vertebrate and invertebrate predators and selected limnological parameters. The most important factors structuring zooplankton grazer communities were extracted in a principal components analysis. The interaction of acidity status and vertebrate planktivore abundance explains the variation in lake scores for the first principal component. The second principal component was related to predation, while the third was related to lake trophic status and humic influence. The interaction of water quality and predator abundance structures grazer communities of Adirondack lakes.

ISSN:1040-2381    

DOI:10.1080/07438148709354794

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor