Thomas P. Markee

An assessment of the toxicity of phthalate esters to freshwater benthos. 2. Sediment exposures

Tests were performed with the freshwater invertebrates Hyalella azteca, Chironomus tentans, and Lumbriculus variegatus to determine the acute toxicity of six phthalate esters, including dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DBP), butylbenzyl phthalate (BBP), di-n-hexyl phthalate (DHP), and di-2-ethylhexyl phthalate (DEHP). It was possible to derive 10-d LC50 (lethal concentration for 50% of the population) values only for the four lower molecular weight esters (DMP, DEP, DBP, and BBP), for which toxicity increased with increasing octanol-water partition coefficient (Kow) and decreasing water solubility. The LC50 values for DMP, DEP, DBP, and BBP were 28.1, 4.21, 0.63, and 0.46 mg/L for H. azteca; 68.2, 31.0, 2.64, and > 1.76 mg/L for C. tentans; and 246, 102, 2.48, and 1.23 mg/L for L. variegatus, respectively. No significant survival reductions were observed when the three species were exposed to either DHP or DEHP at concentrations approximating their water solubilities.

Acute and chronic toxicities of arsenic(III) to fathead minnows, flagfish, daphnids, and an amphipod

Acute and chronic toxicities of arsenic (III) (As) to four species of freshwater organisms were determined. All tests were flow-through exposures except the daphnid (Daphnia magna) tests which were static concentration renewal exposures. Acute exposures of fathead minnows (Pimephales promelas), flagfish (Jordanella floridae), and an amphipod (Gammarus pseudolimnaeus) to As resulted in 96-hr LC50 or EC50 estimates of 14,100, 14,400, and 874 μg/L, respectively. Daphnids were exposed to As with and without food resulting in 96-hr EC50 estimates of 4,340 and 1,500 μg/L, respectively. Chronic exposures of 28 to 31 days duration were made for fathead minnows, flagfish, and daphnids. The chronic limit ranges (highest tested exposure concentration having no adverse effect and the lowest tested exposure concentration having an adverse effect) based upon the most sensitive measured parameters of body length and wet weight were 2,130 to 4,300 μg/L for fathead minnows and 2,130 to 4,120 μg/L for flagfish. Daphnids had chronic limits of 633 to 1,320 μg/L based upon survival and the measured parameters of reproduction and body length. Calculation of an acute test/chronic test ratio for fathead minnows, flagfish, and daphnids (fed and unfed) resulted in a range of values from 1.64 to 4.80.

Comparative toxicity and bioconcentration of nonylphenol in freshwater organisms

Degradation of alkylphenol ethoxylates to more persistent alkylphenols such as nonylphenol occurs in wastewater treatment plants where nonylphenol is released to aquatic systems. In this study, acute and chronic tests were conducted to determine the toxicity and bioconcentration of nonylphenol to freshwater organisms for use in deriving national water quality criteria. Acute median effect concentrations (EC50s) based on loss of equilibrium, immobility, and lethality for species representing several taxonomic groups ranged from 21 to 596 microg/L. The EC50s were up to a factor of 2 less than median lethal concentrations (LC50s) and decreased with time over the test periods of 24 to 96 h. In chronic tests, early life stages of rainbow trout were 14 times more sensitive to nonylphenol than in acute tests and approximately 20 times more sensitive than Daphnia magna exposed over their complete life cycle. Comparisons of chronic test endpoints showed that 20% effect concentrations (EC20s), determined by regression testing, and chronic values, determined by hypothesis testing, were similar for both the rainbow trout and Daphnia magna. The lowest mean tissue-effect concentrations of nonylphenol appeared to be greater for the fathead minnow than bluegill, and ranged from approximately 130 to 160 microg/g after 96-h exposure and from approximately 20 to 90 microg/g after 28-d exposure. Mean lipid normalized bioconcentration factors (BCFs) associated with no-effect concentrations were approximately 180 and 50 for the fathead minnow and bluegill, respectively. The present test results suggest that long-term exposures to nonylphenol at concentrations found in some surface waters could adversely impact sensitive components of freshwater communities.

A field investigation of the relationship between zinc and acid volatile sulfide concentrations in freshwater sediments

Understanding relationships between cationic metals such as cadmium, copper, nickel, lead and zinc, and amorphous iron sulfides, measured as acid volatile sulfide (AVS), is key to predicting metal bioavailability and toxicity insediments. The objective of the present study was to assess seasonal and spatial variations of AVS in freshwater sediments contaminated with zinc. Sediments were sampled from three streams with varying levels of zinc contamination at two different times, March and June of 1995, representing cold- and warm-weather situations. Interstitial (pore) water concentrations of zinc, and solid phase concentrations of AVS and zinc were measured in surficial and deep sediment horizons. Toxicity tests (10-d) with the amphipodHyalella azteca were conducted using intact cores. Sediment zinc concentrations from six sites within the primary test stream differed by about five-fold, and also varied seasonally. Acid volatile sulfide concentrations were generally lower than those of zinc, and pore water zinc concentrations typically were elevated. There was a positive correlation between solid-phase AVS and zinc concentrations, suggesting that the system was dominated by zinc, as opposed to iron sulfides. In contrast to expectations arising from some studies of seasonal variations of AVS in iron-dominated systems, AVS concentrations were smaller in June than in March. However, this was likely due to a major storm event and associated sediment scouring before the June sampling, rather than to seasonal processes related to variations in temperature and dissolved oxygen. Based upon an indirect analysis of depth variations in AVS, there was some indication that zinc sulfide might be less prone to oxidation than iron sulfide. There was a strong correlation between toxicity of the sediment samples toH. azteca and interstitial water concentrations of zinc; however, the possible contribution of other contaminants to sediment toxicity cannot be dismissed.

Chemical Loadings to Southwestern Lake Superior from Red Clay Erosion and Resuspension

Inputs of chemical parameters were calculated from estimated erosion and resuspension data and by using experimental measurements of chemical releases from both bluff samples and Lake Superior sediments in suspensions with Lake Superior water. The ability of suspended clay particles to remove manganese and copper ions from Lake Superior water was investigated. The loadings of easily leachable dissolved solids, phosphorus, nitrogen, chloride, silica, sodium, potassium, calcium, magnesium, aluminum and heavy metals from shoreline erosion and resuspended sediment were small compared to Lake Superior tributary inputs. Suspended sediment particles have a large capacity to remove copper and manganese ions from Lake Superior water. Each kilogram of suspended sediment particles of clay size can remove 175 mg of copper and 11 mg of manganese in Lake Superior water spiked to contain 10 μg/L of each metal.

Occurrence and Transport of Organic Microcontaminants in the Duluth-Superior Harbor

Abstract A large number of organic compounds were identified in sediments and suspended solids from St. Louis Bay in the Duluth harbor. Most of the organic compounds appeared to be naturally occurring plant decomposition products consisting of non-halogenated hydrocarbons, organic acids, aldehydes, ketones, amines, esters, alcohols, and phenols. However, the presence of polychlorinated biphenyls (PCBs) and polynuclear aromatic hydrocarbons (PAH) were confirmed by GC/MS methods. Particulate levels of PAH compounds such as fluorene, fluoranthene, and pyrene were found to lie in the 0.2 to 3 μg/g range. PCBs associated with suspended particles from St. Louis Bay and the Superior harbor were at concentrations of 0.2 to 0.9 μg/g and less than 0.1 μg/g, respectively. Measurements of PCBs in water from the St. Louis Bay showed an average value of 19 ng/L. Considering the concentration of PCBs in water and particulates in conjunction with average suspended solids levels, it was calculated that 81% of the PCBs were dissolved in water and 19% associated with suspended particles. It was estimated that suspended solid transport of PCBs and PAH to Lake Superior is less than 0.01% of airborne transport.

Kinetics of Red Clay Bluff Dissolution in Western Lake Superior

The dissolution of red clay bluff samples from the southwestern Lake Superior shoreline area in Lake Superior water or deionized water is studied by following the aqueous concentrations of reactive silica over a three month period. The dissolution process is initially rapid, followed by a first-order dissolution process (k = 9.4 × 10−7 sec−1) up to about thirty days. After about 30 days, the rate of dissolution of the bluff material follows linear kinetics (k = 5.4 × 10−8 mg SiO2/gram of bluff per second).