ISSN:0706-652X    

DOI:10.1139/f88-261

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The Turkey Lakes Watershed (TLW) in central Ontario was selected for intensive research into the effects of the long-range transport of air pollutants (primarily acidic deposition) at a site on the Canadian Shield having both vulnerable terrain and an undisturbed Great Lakes forest type. The terrestrial and aquatic resources within the basin are representative of the surrounding region of Algoma, although for Ontario, it does have high relief (290 m) and high annual precipitation (>1200 mm). The TLW contains a chain of four lakes (five distinct lake basins) that range from 5.8 to 52.0 ha in area and 2.2 to 12.2 m in mean depth. The lakes are dimictic and, except for the deepest lake, experience dissolved oxygen depletion in undisturbed bottom waters. There is a gradient in the major ion composition of lakes within the TLW, the most dilute waters occurring at high elevations. Calcium levels increase from 55 to 138 μmol∙L−1down the chain. Sulphate is the dominant lake water anion in the headwater lake, while alkalinity dominates in the lowest lake. Phosphorus is the limiting nutrient in these lakes; NO3-N levels are relatively high (7.9–16.4 μmol∙L−1) because the terrestrial basin exhibits low utilization of this nitrogen species. Seasonal and episodic variations in surface water composition can be large. The headwater lake contains no fish; however, fish communities in the lower three lakes (composed of 8-11 species) are typical of the Algoma region. The distribution of benthic organisms is primarily a function of lake depth and presence/absence of fish rather than variations in water chemistry. Zooplankton species composition is similar across all lakes, and cyanophytes are the dominant algae throughout. The forest is an uneven-aged, mature-to-overmature, old-growth tolerant hardwood stand. The principal tree species is sugar maple (90%) with lesser amounts of other hardwoods (9%, usually yellow birch) and various conifers (1%). Production is typical of forest at this northerly latitude (47°N). Foliar bioelement concentrations are generally similar to those observed at Hubbard Brook, New Hampsh

ISSN:0706-652X    

DOI:10.1139/f88-262

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Daily concentrations of sulphates and nitrates in air and precipitation were measured atthe Turkey Lakes Watershed from September 1980 until December 1984. The measurement data were used to estimate wet, dry, and total deposition of sulphates and nitrates to the watershed. Over the 4 yr, the annual values of total (wet plus dry) deposition ranged from 34 to 38 (± 15%) mmol∙m−2∙yr−1for SO42−and from 38 to 47 (± 30%) mmol∙m−2∙yr−1for NO3−. On a molar basis, the deposition of total NO3−exceeded the deposition of total SO42−by 19%. However, when converted to equivalents, total SO42−exceeded total NO3−by 68%. Dry deposition represented approximately 15 and 25% of the total deposition of SO42−and NO3−, respectively, to the watershed. Wet and dry deposition of sulphate and nitrate was found to be highly episodic, with the top 20% of daily events delivering 60–70% of the total sulphur and nitrogen deposition to the watershed. Statistically significant seasonal cycles were found in the concentration and deposition values of most of the sulphur and nitrogen species measured at the wa

ISSN:0706-652X    

DOI:10.1139/f88-263

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Four different types of atmospheric deposition measurements were made at the Turkey Lakes Watershed from 1981 to 1984. They included weekly and variable period bulk deposition measurements. The resulting annual and seasonal deposition estimates from the four methods were compared for numerical and statistical differences. Several results unexpected from the theory of the measurement methods appeared in the comparison: (1) one of the bulk deposition measurements produced lower deposition of acid-related ions than the two wet-only measurements and (2) the monthly wet-only measurements produced higher deposition of sulphate than the two bulk deposition data sets (by 6 and 19%). Several results were consistent with the theory of the measurements: (1) the daily wet-only measurements produced deposition values lower than the weekly bulk deposition measurements and (2) the wet-plus-dry deposition measurements produced higher estimates of sulphate and nitrate deposition than the two bulk data sets (15 – 35% higher). Laboratory biases appeared to be partially responsible for some of the differences found in the comparison.

ISSN:0706-652X    

DOI:10.1139/f88-264

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Bulk and wet-only deposition and the snowpack were monitored at the Turkey Lakes Watershed in northern Ontario over the winter and spring of 1986. Based on a comparison with snowpack and cumulative snowmelt, the bulk sampler overcollected major ions by factors ranging from 6 to 22%. Nitrate appeared to be preferentially collected by the bulk sampler relative to SO42−during snow events. Dry deposition was estimated to be 12 and 5% of total deposition forSO42−and NO3−, respectively. Ion budgets for cumulative bulk deposition and snowmelt supported the hypothesis that ion losses from the snowpack are insignificant during a winter having no melt episodes. Snowmelt was characterized by chemical fractionation of major ions; SO42−and H+in initial meltwaters were 10 times more concentrated than the premelt snowpack. Preferential elution of ions in the snowmelt followed the sequence: SO42−> NO3−> H+> Cl−. Snowmelt chemistry was used to predict changes in lake chemistry: H+, NO3−, and NH4+levels should increase in lake waters; Ca2+decreases through dilution by snowmelt; SO42−concentrations remain fairly constant.

ISSN:0706-652X    

DOI:10.1139/f88-265

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Ion mass budgets were determined for two water years (June – May 1981–83) for Batchawana L. South, Wishart L., Little Turkey L., and Turkey L. Water budgets balance within measurement error except for Little Turkey L. (output surplus for both water years) and Batchawana L. South (output surplus for 1982–83). Groundwater seepage is hypothesized to explain these water budget imbalances. The chemical budgets show that H+, NH4+, and NO3−are retained by the lakes to varying degrees. The major input pathway for H+and NH4+is via direct atmospheric deposition, while relatively weaker terrestrial retention of NO3−causes basin runoff to be the major input pathway for this parameter. All three species are playing an acidifying role on the Turkey Lakes Watershed. Chemical budgets for Mg2+, Na+, K+, SO42−, and Cl−are generally balanced for all lakes relative to the water budgets. In contrast, Ca2+and acid-neutralizing capacity (ANC) exhibit excess output over measured plus estimated inputs. Probable unmeasured inputs of these two parameters include groundwater seepage and Ca2+exchange with the sediments. In-lake generation of ANC by SO42−reduction is of minor importance.

ISSN:0706-652X    

DOI:10.1139/f88-266

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

To determine correctly the response of a basin to various acid loading events, the groundwater hydrology must be considered as a function of the basin stratigraphy and mineralogy. Groundwaters in the Turkey Lakes Watershed are well buffered and in general provide a reservoir of alkalinity for surface waters in the basin. The groundwater chemistry is dominated by the weathering of carbonates present in the tills. Groundwater can follow a variety of pathways through the subsurface. These pathways can have very different flow rates and groundwater chemistry. As a result of this the influence of groundwater on surface water is highly site specific.

ISSN:0706-652X    

DOI:10.1139/f88-267

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Two watersheds with seasonal pH depressions in the groundwater exhibit high aluminum concentrations associated with these acidification events. The watersheds receive similar atmospheric loadings of H+and SO42−but are covered by different surficial deposits. The aluminum is measured in four fractions by varying the pH and time conditions during analysis. The resulting classes calculated from these fractions are Class a, containing fast-reacting monomeric aluminum, predominantly inorganic Al3+and hydroxy compounds; Class b, containing fast-reacting complex aluminum species, mainly inorganic F−complexes and simple organic complexes; Class c, containing slow-reacting amorphous and some polymeric aluminum species; and a class containing a residue of unknown aluminum species adding to the total acid-extractable aluminum. There are significant differences in the distribution of the various aluminum species between the two watersheds, both with depth and in the predominant class identified. The generally higher values measured at one watershed are consistent with the lower carbonate content of the overburden. In both locations it appears that the controlling factor is the pH of the groundwater, with all but Class c species increasing with decreasing pH. The difference between the distributions of aluminum species in groundwater and surface water is under investigation to determine the influence of groundwater-bourne aluminum on the surface water into which it flows.

ISSN:0706-652X    

DOI:10.1139/f88-268

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Simulation results obtained from interfacing a hydrological model with a hydrogeochemical model are used to explain the increase of Ca2++ Mg2+, alkalinity, and pH in a progressively buffered stream system in the Turkey Lakes Watershed, Ontario. Results from the model, which were calibrated with observed data for 1981, were confirmed with those from 1982, 1983, and 1984. The results further supported the hypothesis that the increases of the groundwater input of Ca into the lower streams contributed to the increase of alkalinity and pH in the downstream lakes which appeared to have caused a corresponding increase in the biological primary productivity in these lakes.

ISSN:0706-652X    

DOI:10.1139/f88-269

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

A hydrological model applied to the Turkey Lakes Watershed at different locations produced results which agreed closely with observed stream flow, groundwater flow, snowpack, and snowpack chemistry. The model results are consistent with many of the episodic events that have occurred in the watershed. The snowpack sulphate concentration is simulated with a simple sulphate model linked to the hydrological model. The different calibrated hydrological coefficients were found to vary with the geology and geomorphology at several locations in he watershed. The general applicability of these coefficients was confirmed by comparing model results with a new set of data from subsequent years.

ISSN:0706-652X    

DOI:10.1139/f88-270

出版商:NRC Research Press    

年代:1988

数据来源: NRC