Geology topics

Philip S. Rainbow

Publications and source records attributed to Philip S. Rainbow.

4 recordsLinked to original sources

USGS2014

In vivo retention of ingested Au NPs by Daphnia magna: No evidence for trans-epithelial alimentary uptake

In vivo studies with Daphnia magna remain inconclusive as to whether engineered nanoparticles (NPs) are internalized into tissues after ingestion. Here we used a three-pronged approach to study the in vivo retention and efflux kinetics of 20 nm citrate stabilized Au NPs ingested by this key aquatic species. Daphnids were exposed to suspended particles (600 μg L −1 ) for 5 h after which they were depurated for 24 h in clean water containing algae. Light microscopy was used to follow the passage of Au NPs through the gastrointestinal tract, Au body burdens were determined by ICP-MS (inductively coupled plasma mass spectrometry), and transmission electron microscopy (TEM) was used to examine the presence and distribution of Au NPs in tissues. Results revealed that the elimination of Au NPs was bi-phasic. The fast elimination phase lasted <1 h and the rate constant at which Au (of Au NPs) was eliminated was 1.12 ± 0.34 h −1 (±SE) which accounted for ∼75% of the ingested Au. The remaining ∼25% of the ingested Au NPs was eliminated at a 100-fold slower rate. TEM analysis revealed that Au NPs in the midgut were in close proximity to the peritrophic membrane after 1 and 24 h of depuration. There were no observations of Au NP uptake at the microvilli. Thus, although Au NPs were retained in the gut lumen, there was no observable internalization into the gut epithelial cells. Similar to carbon nanotubes and CuO NPs, our findings indicate that in daphnids the in vivo retention of Au NPs does not necessarily result in their internalization.

Chemosphere↗

USGS2014

Toxicity and accumulation of silver nanoparticles during development of the marine polychaete Platynereis dumerilii

Pollutants affecting species at the population level generate ecological instability in natural systems. The success of early life stages, such as those of aquatic invertebrates, is highly affected by adverse environmental conditions. Silver released into the environment from emerging nanotechnology represents such a threat. Sediments are sinks for numerous pollutants, which aggregate and/or associate with depositing suspended particles. Deposit feeder such as the annelid Platynereis dumerilii, which has a large associated literature on its development, is an excellent model organism for exposure studies in coastal environments. We exposed eggs, larvae, juveniles and adults of P. dumerilii to various concentrations of citrate (cit-Ag NPs) or humic acid (HA-Ag NPs) capped silver nanoparticles (Ag NPs) as well to dissolved Ag (added as AgNO3). We showed that mortality and abnormal development rate increased with younger life stages. While adults and juvenile were the most tolerant life stages, fertilized eggs were highly sensitive to AgNO3, cit-Ag NPs and HA-Ag NPs. Exposures to HA-Ag NPs triggered the highest cute toxicity responses in P. dumerilii and in most cases both Ag NPs were more toxic than AgNO3. Uptake rate of HA-Ag NPs in adult worms was also higher than from other Ag forms, consistent with toxicity to other life stages. The early stages of the life cycle of marine coastal organisms are more affected by Ag NPs than the juvenile or adult life stages, indicating that exposure experiments at the larval level contribute to realistic eco-toxicological studies in aquatic environments.

Science of the Total Environment↗

USGS2010

Calibrating biomonitors to ecological disturbance: a new technique for explaining metal effects in natural waters

Bioaccumulated toxic metals in tolerant biomonitors are indicators of metal bioavailability and can be calibrated against metal‐specific responses in sensitive species, thus creating a tool for defining dose–response for metals in a field setting. Dose–response curves that define metal toxicity in natural waters are rare. Demonstrating cause and effect under field conditions and integrated chemical measures of metal bioavailability from food and water is problematic. The total bioaccumulated metal concentration in any organism that is a net accumulator of the metal is informative about metal bioavailability summed across exposure routes. However, there is typically no one universal metal concentration that is indicative of toxicity, especially across species, largely because of interspecies differences in detoxification. Stressed organisms are also only present across a narrow range in the dose–response curve, limiting the use of singles species as both biomonitors and bioindicator of stress. Herein we show, in 3 field settings, that bioaccumulated Cu concentrations in a metal‐tolerant, riverine biomonitor (species of the caddisfly genus Hydropsyche spp.) can be calibrated against metal‐specific ecological responses across very wide ranges of contamination. Using the calibrated dose–response, we show that reduced abundance of species and individuals from particularly sensitive mayfly families (heptageniid mayflies) is more than 2‐fold more sensitive to bioavailable Cu than other traditional measures of stress like EPT or total number of benthic macroinvertebrate species. We propose that this field dose‐response curve be tested more widely for general application, and that calibrations against other stress responses be developed for biomonitors from lakes, estuaries, and coastal marine ecosystems.

Integrated Environmental Assessment and Management↗

USGS2005

Why is metal bioaccumulation so variable? Biodynamics as a unifying concept

Ecological risks from metal contaminants are difficult to document because responses differ among species, threats differ among metals, and environmental influences are complex. Unifying concepts are needed to better tie together such complexities. Here we suggest that a biologically based conceptualization, the biodynamic model, provides the necessary unification for a key aspect in risk: metal bioaccumulation (internal exposure). The model is mechanistically based, but empirically considers geochemical influences, biological differences, and differences among metals. Forecasts from the model agree closely with observations from nature, validating its basic assumptions. The biodynamic metal bioaccumulation model combines targeted, high-quality geochemical analyses from a site of interest with parametrization of key physiological constants for a species from that site. The physiological parameters include metal influx rates from water, influx rates from food, rate constants of loss, and growth rates (when high). We compiled results from 15 publications that forecast species-specific bioaccumulation, and compare the forecasts to bioaccumulation data from the field. These data consider concentrations that cover 7 orders of magnitude. They include 7 metals and 14 species of animals from 3 phyla and 11 marine, estuarine, and freshwater environments. The coefficient of determination ( R 2 ) between forecasts and independently observed bioaccumulation from the field was 0.98. Most forecasts agreed with observations within 2-fold. The agreement suggests that the basic assumptions of the biodynamic model are tenable. A unified explanation of metal bioaccumulation sets the stage for a realistic understanding of toxicity and ecological effects of metals in nature.

Environmental Science & Technology↗