Announcing the Perspectives column

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102147/1/etc2425.pd

Assessing sediment toxicity: Past, present, and future

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98149/1/etc2250-sm-0001-SuppTab-S1.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/98149/2/etc2250.pd

Clarifying and expanding the focus of Environmental Toxicology and Chemistry

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92138/1/1869_ftp.pd

Assessing contaminated sediments in the context of multiple stressors

Sediments have a major role in ecosystem functioning but can also act as physical or chemical stressors. Anthropogenic activities may change the chemical constituency of sediments and the rate, frequency, and extent of sediment transport, deposition, and resuspension. The importance of sediments as stressors will depend on site ecosystem attributes and the magnitude and preponderance of co-occurring stressors. Contaminants are usually of greater ecological consequence in human-modified, depositional environments, where other anthropogenic stressors often co-occur. Risk assessments and restoration strategies should better consider the role of chemical contamination in the context of multiple stressors. There have been numerous advances in the temporal and spatial characterization of stressor exposures and quantification of biological responses. Contaminated sediments causing biological impairment tend to be patchy, whereas more pervasive anthropogenic stressors, such as alterations to habitat and flow, physical disturbance, and nutrient addition, may drive large-scale ecosystem responses. A systematic assessment of relevant ecosystem attributes and reference conditions can assist in understanding the importance of sediments in the context of other stressors. Experimental manipulations then allow for the controlled study of dominant stressors and the establishment of causal links. This approach will result in more effective management of watersheds and waterways. Environ. Toxicol. Chem. 2010;29:2625–2643. © 2010 SETACPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78293/1/332_ftp.pd

Environmental Stressor Importance: Science versus Media

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152643/1/etc4606.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/152643/2/etc4606_am.pd

Editorial

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95638/1/2035_ftp.pd

Measurements of acid volatile sulfide and simultaneously extracted metals are irreproducible among laboratories

Partitioning with solid phases is a principal control on availability and associated toxicity of metals to aquatic biota. In anoxic sediments, environmentally active fractions of sulfide and associated metals are defined operationally as acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM). Ratios of these chemical parameters are often used in establishing equilibrium partitioning sediment benchmarks for toxicity and, therefore, require analytical accuracy to be useful. To investigate the reproducibility and accuracy of AVS and SEM measurements, we distributed subsamples of four physicochemically disparate stream sediments to seven independent laboratories, including our own, for analysis of both AVS and SEM (Cd, Cu, Pb, Ni, and Zn). Synthesis of these results shows that AVS varied from 70 to 3,500× and SEM ranged from 17 to 60× among laboratories for each of the four sediments. Inadequate detection limits for AVS precluded calculation of SEM:AVS ratios for two of the deposits, whereas the ratio varied more than 50-fold among laboratories for the other two sediments. This work highlights the need for improved quality control and standardization of methods for determination of AVS and SEM in sediments, and suggests that predictions of metal toxicity in sediments can be laboratory specific, which raises concerns on the use of the AVS:SEM model for risk assessments and regulatory decisions. Environ. Toxicol. Chem. 2010;29:1453–1456. © 2010 SETACPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77432/1/173_ftp.pd

Indirect effects of climate change on zinc cycling in sediments: The role of changing water levels

Increased variability in lake and river water levels associated with changing climate could impact the fate and effects of metals in redox‐sensitive sediments through the alteration of microbial communities and of acid–base and redox chemistry. The objective of the present study was to determine the influence of water level fluctuation on metal speciation in porewater and predict environmental risk to high‐carbonate systems. Using experimental microcosms with sediments collected from 4 metal‐contaminated coastal freshwater wetlands in Michigan, USA, we conducted water level fluctuation experiments. Porewater and sediment metals (Ca, Cu, Fe, Mg, Mn, Ni, Zn) and important metal binding phases (iron‐oxide speciation, acid‐volatile sulfide) were quantified. In a short‐term drying (seiche) experiment, there were decreases in all porewater metals after inundation of saturated sediments. During a drought experiment, re‐inundation of oxidized sediments increased porewater Cu, Zn, Mg, Ca for most sites. Porewater Zn increased after inundation to levels exceeding the US Environmental Protection Agency threshold for chronic toxicity. These data show that the dissolution of metal carbonates and metal sulfates contributes to metal release after re‐flooding and indicate that we might expect increased ecological risk to organisms present in drought‐sensitive regions where altered hydroperiods are likely to increase metal bioavailability. Environ Toxicol Chem 2017;36:2456–2464. © 2017 SETACPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138388/1/etc3783.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138388/2/etc3783_am.pd

Hyporheic Interactions Increase Zinc Exposure and Effects on Hyalella azteca in Sediments under Flow‐Through Conditions

Groundwater–surface water interactions in the hyporheic transition zone can influence contaminant exposure to benthic macroinvertebrates. In streams, hyporheic flows are subject to varying redox conditions, which influence biogeochemical cycling and metal speciation. Despite these relationships, little is known about how these interactions influence the ecological risk of contaminants. The present study investigated the effects of hyporheic flows and zinc (Zn)‐contaminated sediments on the amphipod Hyalella azteca. Hyporheic flows were manipulated in laboratory streams during 10‐d experiments. Zinc toxicity was evaluated in freshly spiked and aged sediments. Hyporheic flows altered sediment and porewater geochemistry, oxidizing the sediments and causing changes to redox‐sensitive endpoints. Amphipod survival was lowest in the Zn sediment exposures with hyporheic flows. In freshly spiked sediments, porewater Zn drove mortality, whereas in aged sediments simultaneously extracted metals (SEM) in excess of acid volatile sulfides (AVS) normalized by the fraction of organic carbon (fOC) [(SEM‐AVS)/fOC] influenced amphipod responses. The results highlight the important role of hyporheic flows in determining Zn bioavailability to benthic organisms, information that can be important in ecological risk assessments. Environ Toxicol Chem 2019;38:2447–2458. © 2019 SETACPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152028/1/etc4554.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/152028/2/etc4554_am.pd

A Large Mass of H2 in the Brightest Cluster Galaxy in Zwicky 3146

We present the Spitzer/IRS mid-infrared spectrum of the infrared-luminous (L_{IR}=4e11 L_sun) brightest cluster galaxy (BCG) in the X-ray-luminous cluster Z3146 (z=0.29). The spectrum shows strong aromatic emission features, indicating that the dominant source of the infrared luminosity is star formation. The most striking feature of the spectrum, however, is the exceptionally strong molecular hydrogen (H2) emission lines, which seem to be shock-excited. The line luminosities and inferred warm H2 gas mass (~1e10 M_sun) are 6 times larger than those of NGC 6240, the most H2-luminous galaxy at z <~ 0.1. Together with the large amount of cold H2 detected previously (~1e11 M_sun), this indicates that the Z3146 BCG contains disproportionately large amounts of both warm and cold H2 gas for its infrared luminosity, which may be related to the intracluster gas cooling process in the cluster core.Comment: 13 pages, 3 figures, 1 table; Accepted for publication in ApJ