Thomas C. Young

Leachate characteristics and composition of cyanide-bearing wastes from manufactured gas plants.

Past activities associated with the manufacture of gas from hydrocarbon feedstocks resulted in the generation of substantial quantities of cyanide-bearing wastes produced as a result of product gas cleanup for the removal of hydrogen sulfide and hydrogen cyanide. Large quantities of these sites have been found at several manufactured gas plant sites. It was the purpose of this study to address questions relating to the availability of cyanide to the environment and to determine the chemical forms of cyanide in the waste. This information is necessary in order to assess the toxicity and possible methods of treatment and disposal of the material

Algal-Available Particulate Phosphorus in the Great Lakes Basin☆

For the purpose of comparing the relative availability of particulate phosphorus (P) from various sources to the Great Lakes, algal-available P was determined on suspended solids and bottom sediments from tributaries, wastewater suspended solids, lake bottom sediments, and eroding bluff solids from the region. Physicochemical and bioassay methods were used to estimate the rate and extent of available P release from particulates. Considering all types of particulates examined, ultimately available P ranged from nil to approximately 70 percent of total phosphorus (Total-P) content. During algal bioassays, changes in levels of base-extractable inorganic P (R-NaOH-P) in tributary suspended solids were nearly equivalent to the amounts of P used by algae during bioassays. For the tributary solids, ultimately available P averaged approximately 90 percent of R-NAOH-P. Consistent differences were found in amounts of available P among particles from different sources. Sources of particle-bound P ranked in order of decreasing availability were: wastewater solids, lake bottom sediments, tributary solids, and eroding bluff solids. Differences in available P release rates also existed among the different types of particles. Wastewater solids displayed the largest first-order release rates, eroding bluff samples and tributary-suspended solid samples that were high in apatite showed essentially no available P release, while other tributary suspended solids displayed intermediate release rates.

Colloid Aggregation: Numerical Solution and Measurements

Abstract A model has been developed that describes the kinetics of particle aggregation by a numerical solution of the von Smoluchowski equation. While the complete model incorporates surface chemical phenomena, this paper discusses only the physical aggregation process, and focuses on long-term aggregation where aggregates composed of many primary particles (up to 2000) are formed. Model simulations were compared with laboratory experiments that were conducted with hematite spheres aggregating with no applied shear stress. Comparison was achieved by minimizing the sum of squared differences between the model and experimental data using two fitting parameters: the collision efficiency and the fractal dimension of the aggregates. The model was sensitive to the two parameters, which had a small degree of dependence on one another as evidenced by the orientation of the joint confidence regions. Estimates of the fractal dimension varied inversely with collision efficiency and were between 1.25 and 1.5; lower than many estimates by others for diffusion-controlled processes but consistent with cluster–cluster aggregation of aggregates comprised of very dense particles. The collision efficiency was estimated to be 1×10−4 for slow aggregation conditions, and 2×10−4 under rapid aggregation; these values reflect inclusion of hydrodynamic interactions and their significance in a system dominated by differential settling.

Adsorption and Desorption of Zn, Cu, and Cr by Sediments from the Raisin River (Michigan)☆

Metal adsorption by Raisin River sediments in vitro depended linearly on soluble metal concentration to adsorption densities of 6,000–9,000 μg/g with 48 hr partition coefficients of approximately 50, 30, and 25 L/g for Cu, Cr, and Zn, respectively. Partition coefficients computed from field data spanned a comparatively wider range of values in a manner consistent with the often reported adsorbent concentration effect, but other factors likely contributed, too. Desorption of Zn was complete and rapid (24–48 hr) in contrast to Cr, which was incomplete and much slower; Cu desorption was intermediate to Zn and Cr. A reversible-resistant equilibrium model (DiToro et al. 1986) could not describe the observations as Cu and Cr had not reached metastable desorption equilibria after 24 days. Metal desorption, however, could be described kinetically by distributing sorbed cations between either of two classes: rapidly desorbing and slowly desorbing cations. Sequential and simultaneous desorption models gave similar predictions. Aqueous chemical considerations suggested precipitated as well as adsorbed species could give rise to the observations, but available data did not permit adequate tests of this hypothesis. The extent to which kinetic constraints rather than irreversible reactions account for the desorption-resistant binding signifies a potentially greater metal mobility or bioavailability than would otherwise be assumed.

Factors Affecting Metal Partitioning During Resuspension of Sediments from the Detroit River

Abstract The release of previously deposited substances from sediments may represent a significant source of contaminants to the overlying water. Of special concern is the partitioning between aqueous- and sediment-phase heavy metals in response to resuspension events induced by hydrodynamic forces. In this paper results from a set of field experiments are reported in which sediment cores from three stations in the Trenton Channel of the Detroit River were artificially resuspended. Statistical analysis of the data indicated that the concentrations of the dissolved metals Cd, Co, Cu, Ni, Pb, and Zn in the overlying water varied inversely with pH (p

Studies of heavy metal sorption by Trenton Channel (Detroit River) sediments

Sediment resuspension plays a dominant physical role in downstream transport of sediment-bound, or ‘in-place’ pollutants. During resuspension, however, numerous sorption reactions may alter contaminant phase distributions. Previous field resuspension studies on heavily contaminated sediments (Theis et al., 1988, J. Great Lakes Res. 14, 216) showed parallel trends in metal partitioning with pH and time for each of 7 metals (Cd, Co, Cr, Cu, Ni, Pb, Zn), when pH was < 7.5 during resuspension. To improve our ability to interpret follow-up laboratory partitioning experiments using sediments from the field sites, we conducted an evaluation of sediment sample storage as a potential factor leading to field-laboratory partitioning differences. Although metal sorption observed in the laboratory differed substantially from that observed in the field, sample storage effects, reported as holding time and changes in solid phase metal fractionation, gave minimal support for the hypothesis that sample storage caused the differences. It appears, rather, than our in vitro batch equilibrium systems incompletely replicated those attributes of a sediment-water system that are relevant to adsorption and desorption of heavy metals during a resuspension event. Accordingly, we conclude that a general improvement in the understanding of contaminant partitioning would result if future studies would assign greater importance to evaluating the effects of relevant physical phenomena on partitioning (e.g. particle interaction and shear stress), in addition to such widely studied chemical determinants as pH, time, and metal species.

The significance of shear stress in the agglomeration kinetics of fractal aggregates

Abstract The aggregation kinetics of fully destabilized colloidal hematite particles under conditions of varying laminar shear stress were investigated. Particle size distributions were measured over time, which allowed for a mechanistic evaluation of various aggregate–aggregate interaction rates. It was observed experimentally that large aggregates react rapidly with sub-micron size fractions under conditions of an applied shear stress; Brownian motion appears to dominate interactions only at early times when a monomodal size distribution exists. It was hypothesized that collisions between dissimilar sized aggregates are favored under laminar shear conditions. The experimental results also suggest that hydrodynamic influences are less important when porous, fractal aggregates are interacting than in interactions between impermeable spheres.

The Temporally Integrated Monitoring of Ecosystems (TIME) Project Design: 1. Classification of Northeast Lakes Using a Combination of Geographic, Hydrogeochemical, and Multivariate Techniques

This investigation is part of the Temporally Integrated Monitoring of Ecosystems ((TIME) project, an effort to meet the difficult challenge of monitoring surface water quality in the northeastern United States for signs of change in response to the Clean Air Act Amendments of 1990. The overall objective of the study was to develop a unified scheme for classifying lakes in the northeast into relatively homogeneous groups and improve the likelihood of detecting water quality trends in the region. The study approach involved combining the best elements of several procedures recently used for defining regional subpopulations of lakes; these were termed the hydrogeochemical model (HM), geographical model (GM), and multivariate statistical model (MSM). Lake and watershed data from the U.S. Environmental Protection Agency Eastern Lake Survey (ELS) were used to evaluate the classification methods and their modifications. After preliminary comparisons were made of the three classification schemes, it was concluded that the resulting subpopulations indicated that there was meaningful similarity among methods but that the significant dissimilarity reflected distinctive attributes of each classification method. These differences were deemed important; accordingly, integration of the methods entailed efforts to preserve parts of each. This was accomplished by assigning each lake of the ELS data set into a lake cluster that had been defined by jointly applying the HM and GM methods. Subsequently, the jointly classified clusters were aggregated by coupling an application of the MSM (cluster analysis) with subjective judgment regarding termination of the process of cluster formation. This integration of procedures gave rise to nine subpopulations that separated mainly on the basis of hydrogeochemical factors, though geographic influences also were evident in the results. The integrated classification procedure provided an explicit method involving the combination of several kinds of data to yield lake subpopulations. Although the process of integrating this information may stand alone as a useful exercise, the results obtained from the integrated classification model exhibited less dispersion than those formed by the parent procedures. This is an important consideration when subpopulation homogeneity is wanted as a means to improve trend detection. From the view of statistical efficiency, therefore, the integrated procedure may be considered to be more optimal than the parent schemes. When the complexity of the integrated approach is considered, however, we conclude that the next most precise classification scheme, the HM approach, may be preferred over the integrated classification for use in the design of an actual monitoring program.

Calibration of a Hydraulic Transport Model for Green Bay, Lake Michigan

Abstract The U.S. Environmental Protection Agency (USEPA) has developed and implemented a comprehensive plan for modeling the transport and fate of toxic chemicals in Green Bay, Lake Michigan. Characterization of the hydrodynamic behavior of Green Bay was a key step in the model calibration process. To accomplish this, the WASP4 finite-segment model framework was calibrated to describe chloride dynamics during an 18-month period (Jan 1989 to May 1990). Extensive use was made of field data (currents, water temperature, wind, and ice cover), and new interpretations of these data were developed. The direction of circulation in Green Bay typically reverses every three to five days during open water periods; these reversals are closely correlated to wind direction relative to the axis of the Bay. Inflows from Lake Michigan exceed the combined inflows of all tributaries by over twenty times; the circulation of these inflows through Green Bay are greatly enhanced each spring when the ice cover melts. During open water periods, bulk dispersion coefficients typically range from 20 to 120 m 2 /s in the longitudinal direction, and from 5 to 40 m 2 /s in the transverse direction. The calibrated advection and dispersion fields accurately describe the major hydrodynamic features of Green Bay, and were incorporated into input data sets for models of eutrophication, organic carbon sorbents, and toxic chemicals.

USE OF ACID LAKE REACIDIFICATION MODEL (ALaRM) TO ASSESS IMPACT OF BOTTOM SEDIMENTS ON CALCIUM CARBONATE TREATED LAKES

ABSTRACT A mathematical model (ALaRM) for predicting the reacidification profile of calcium carbonate treated lakes has been calibrated and confirmed using data from two Lake Acidification Mitigation Project (LAMP) lakes. This manuscript focused on the use of ALaRM to evaluate the relative impact of bottom sediment processes on the reacidification rate of the LAMP lakes. Prior to liming the lakes exhibited annual average sediment-to-water ANC fluxes of 194 and 240 meq/m2-yr for Woods Lake and Cranberry Pond, respectively. Following liming there was a period of net water-to-sediment ANC flux due to a reversal of the gradients of ANC-determining chemical species, indicating a buffering effect of bottom sediments on water column acid-base chemistry. A sensitivity analysis indicated that calcite treatment of sediments as well as the water column could mitigate the sediment reacidification-accelerating effect.