Mary Gail Perkins

Role of minerogenic particles in light scattering in lakes and a river in central New York

The role of minerogenic particles in light scattering in several lakes and a river (total of ten sites) in central New York, which represent a robust range of scattering conditions, was evaluated based on an individual particle analysis technique of scanning electron microscopy interfaced with automated x-ray microanalysis and image analysis (SAX), in situ bulk measurements of particle scattering and backscattering coefficients (bp and bbp), and laboratory analyses of common indicators of scattering. SAX provided characterizations of the elemental x-ray composition, number concentration, particle size distribution (PSD), shape, and projected area concentration of minerogenic particles (PAVm) of sizes>0.4 microm. Mie theory was applied to calculate the minerogenic components of bp (bm) and bbp (bb,m) with SAX data. Differences in PAVm, associated primarily with clay minerals and CaCO3, were responsible for most of the measured differences in both bp and bbp across the study sites. Contributions of the specified minerogenic particle classes to bm were found to correspond approximately to their contributions to PAVm. The estimates of bm represented substantial fractions of bp, whereas those of bb,m were the dominant component of bbp. The representativeness of the estimates of bm and bb,m was supported by their consistency with the bulk measurements. Greater uncertainty prevails for the bb,m estimates than those for bm, associated primarily with reported deviations in particle shapes from sphericity. The PSDs were well represented by the B component of the two-component model or a three parameter generalized gamma distribution [Deep-Sea Res. Part I 40, 1459 (1993)]. The widely applied Junge (hyperbolic) function performed poorly in representing the PSDs and the size dependency of light scattering in these systems, by overrepresenting the concentrations of submicrometer particles especially. Submicrometer particles were not important contributors to bm or bb,m.

The oxygen resources of the hypolimnion of ionically enriched onondaga lake, NY, U.S.A.

The depletion of hypolimnetic DO and the upper depth boundary of anoxia for four different years (1978, 1979, 1980 and 1981), and the accumulation of sulfide for a single year (1981), are documented for ionically enriched hypereutrophic Onondaga Lake, NY, USA. The depletion rate, represented as the areal hypolimnetic oxygen deficit (AHOD, g m−2 day−1), was extremely high (1.2–2.7 g m−2 day−1), The large differences in the rate within individual years and from year to year were largely a result of differences in attendant vertical mixing (parameterized as the hypolimnetic heating rate). The entire hypolimnion (depth interval from 11 to 20 m) was without O2 by late June of all 4 yr; anoxia was observed above the hypolimnion on some occasions when secondary stratification occurred. Sulfide accumulated progressively in the hypolimnion in 1981 following the onset of anoxia to a volume weighted concentration of I1 mg L−1. The ionic discharge from an adjoining alkali manufacturer exacerbated the problem of limited O2 resources of the hypolimnion by: (1) decreasing vertical mixing, (2) prolonging the duration of stratification, (3) causing abbreviated turnovers, and (4) encouraging increased rates of phytoplankton settling.

Failure of spring turnover in Onondaga Lake, NY, U.S.A.

Onondaga Lake, N.Y., failed to turnover in the spring of 1986 because of the strong chemical stratification under the ice that developed as a result of ionic discharges from an alkali plant. This stratification had a negative impact on the O2 resources of the lake, as the lower depleted layers of the lake were not replenished with O2. Anoxia and anaerobiesis in the bottom water expanded following ‘ice-out’. Comparison of characteristics observed for the winter through spring interval of 1986 with historic data indicates Onandaga Lake has failed to experience spring turnover in a number of years (approximately 7 of the last 18 yr) because of the ionic discharges from the alkali plant.

The Effect of Terrigenous Inputs on Spatial Patterns of Water Quality Indicators in South Lake, Lake Champlain

Spatial patterns of measures of trophic state, optical properties and particle composition are documented for Lake Champlain, with particular emphasis on the southernmost shallow section (< 10 m deep, ∼ 55 km in length) known as South Lake, to depict the impacts of terrigenous inputs. The analysis is supported by two surveys conducted in 1998 for South Lake (thirteen sites) following typical and unusually high runoff intervals, and for selected deep-water sites (thirteen) for the typical runoff interval. Terrigenous inputs, particularly as clays, cause light penetration to be lower, turbidity (Tn) and phosphorus (P) concentrations to be higher by a wide margin, and particle composition to differ greatly in South Lake relative to deeper portions of the lake. Generally progressive gradients are documented within South Lake for Secchi disc transparency (SD), the light attenuation coefficient, (Tn), particulate organic carbon, total P, and particulate P, that demonstrate diminishing impacts of the terrigenous inputs with the approach to the deeper portions of the lake. Increased loadings associated with high runoff impart greater, and a wider array of, impacts in South Lake, that appear to be relatively shortlived (less than 1 month). The high levels of inanimate particles (tripton) that prevail in South Lake systematically compromise total P concentration and SD as measures of trophic state. Despite lower levels, this terrigenous material also influences these measures in deep-water areas. Management strategies that focus on reductions in P loading will not result in substantive increases in SD in South Lake, as phytoplankton biomass is unimportant in regulating the prevailing clarity conditions. Erosion control may be a more promising alternative to pursue improved clarity in this portion of the lake.

Onondaga Lake and the dynamics of chloride in the Oswego River

The temporal distribution of chloride concentration in the Oswego River was determined at 6 hr intervals for a 3 mo period during the summer of 1982. The dynamics of relative flow and chloride contributions from the three major sources forming the Oswego River, and the dynamics of flow releases from one of the sources, chloride-polluted Onondaga Lake, were determined from the above measurements, available chloride concentrations, and flow data for the system, through application of a simple mass balance on chloride. The chloride concentration and load in the Oswego River were found to be highly variable with time, and largely due to the dynamics of flow release from Onondaga Lake. The chloride distribution in the Oswego River, with its unique dynamics and chemically conservative nature, make it a valuable hydraulic tracer for the system.