Major metal-binding phases in the aerobic layer of sediments are iron and manganese oxyhydroxides (FeOOH and MnOOH) and particulate organic carbon (POC). The acid-volatile sulfide (AVS) model propo...

Ecotoxicology of metals in aquatic sediments: binding and release, bioavailability, risk assessment, and remediation

Pollution-free stream water and sediments are crucial to support healthy stream flora and fauna, but urban surface runoff impairs water quality and leaves a legacy of pollution in the sediments. Pollution in sediments influences the development of macroinvertebrates, the lowest members of the food chain, leading to modification of the whole ecological structure. This review focuses on the sources and impacts of zinc, nickel, copper and oil derivative polycyclic aromatic hydrocarbon (PAH) contaminants on macroinvertebrates in urban streams. Land use, and the connectivity of the runoff and sediment are seen to have an effect on the ecological integrity of the watercourse but case examples are sparse. The literature indicates that while reduced species diversity has been identified at a number of sites the dynamics are neither well understood nor well modelled. The literature evidence is compared with field evidence from a study of 62 source areas in headwater catchments with residential, urban, industrial a...

Reviewing the impact of metals and PAHs on macroinvertebrates in urban watercourses

A 10-d growth test and an emergence test were performed with Chironomus riparius Meigen in four unpolluted lake sediments (organic carbon content 0.5–57%) using different feeding levels (Tetramin® at 0.03, 0.06, 0.12, or 0.33 mg/larva/d in the growth test and 0, 0.15, or 0.30 mg/larva/d in the emergence test) to study how sediment type and feeding level affect larval growth. To examine effects of larval density on growth, another growth test was performed using densities of one larva per 24, 12, 4.8, or 2.4 cm2 and a feeding level of Tetramin at 0.12 mg/larva/d. Regardless of sediment type, feeding was necessary in the experiments started with first-instar larvae. The effects of sediment physicochemical characteristics on larval growth and development could not be totally compensated for by food addition. When fed, larvae grew best in sandy sediment with low organic carbon content (0.5%). Acceptable survival was achieved with a very low food dose (0.03 mg/larva/d), but a somewhat higher dose (0.12 mg/larva/d) is recommended. Increment of feeding accelerated larval growth and development. Larval growth was correlated to the food dose per individual and to the density of food particles on the sediment surface.

Effect of sediment type, feeding level, and larval density on growth and development of a midge (Chironomus riparius)

The past, present and future status of the Sediment Quality Triad (SQT) concept is reviewed. The SQT has developed since its inception; some early data interpretation methods remain useful and have been improved (e.g. normalising to reference data), others have not proven to be as useful as originally anticipated (e.g. a single index coupled with triangular graphical plots). SQT studies have extended to Antarctica, and the SQT concept coupled with weight of evidence forms a major basis for sediment ecological risk assessment. Future trends in the usage and utility of the SQT are suggested.

The sediment quality triad: then, now and tomorrow

This study investigated the effectiveness of phosphorus (P) as an in situ remediation technique in site soils collected from the Tri-State mining area. The site soils were treated with two different types (KH2PO4 and Super Triple Phosphate fertilizer) and levels (600 and 5,000 mg/kg) of phosphorus. A toxicokinetic approach was used to determine whether phosphorus amendments reduced heavy metal bioavailability to the earthworm Eisenia fetida. Bioaccumulation factors were used as a measure of bioavailability. Depuration patterns of lead, zinc, and cadmium also were studied after removing earthworms from contaminated soils and then placing them in noncontaminated artificial soil. Results showed that the high phosphorus treatments significantly reduced lead, zinc, and cadmium bioavailability to the earthworms, probably due to formation of metal-phosphate complexes in the soils. Results also indicated that other soil characteristics in addition to amended phosphorus have an affect on bioavailability. Depuration experiments showed a biphasic elimination pattern for each metal. The current results indicate that phosphorus soil amendments may reduce ecological risk to soil-inhabiting invertebrates exposed to heavy metal-contaminated soils.

https://cfpub.epa.gov/ncer_abstracts/index.cfm/fuseaction/display.files/fileID/13133

Remediation of heavy metal-contaminated soils using phosphorus: evaluation of bioavailability using an earthworm bioassay.

This research investigated toxicity and bioaccumulation of a mixture of Cd, Cu, Pb, and Zn in Chironomus tentans in synthetic sediment, and compared predicted to measured steady-state bioaccumulation factors (BAFs). In a toxicity test, C. tentans were exposed to various dilutions of a base concentration (1.0 X) of a mixture of the four metals (5 {micro}g/g Cd. 10 {micro}g/g Cu. 70 {micro}g/g Pb, and 300 {micro}g/g Zn) in synthetic sediment. Mortality ranged from 17 to 100%. To measure bioaccumulation of the metals, C. tentans were exposed to 0.35 X the base concentration for a period of up to 14 d in two uptake tests. Bioaccumulation of all four metals increased over the 14-d uptake phases. Concentrations of metals in chironomids were significantly correlated with exposure time in the uptake phases. Only concentrations of copper approached background levels after 7 d depuration. Uptake rate coefficients and elimination rate constants were determined for each metal. Bioaccumulation factors were highest for Cd and lowest for Pb. With the exception of Pb, steady-state BAFs were within a factor of about two of those calculated using the first-order kinetic model. The high BAFs calculated may indicate greater bioavailability in synthetic sediment. Studies comparing toxicity andmore » bioaccumulation of natural and synthetic sediments are necessary before the use of synthetic sediments is widely adopted.« less

Elisabeth A. Harrahy

Papers

Toxicity and bioaccumulation of a mixture of heavy metals in Chironomus tentans (Diptera: Chironomidae) in synthetic sediment