Sediment Exposure Research Articles

Investigating physiological, cellular and molecular effects in juvenile blue crab, Callinectus sapidus, exposed to field-collected sediments contaminated by oil from the Deepwater Horizon Incident

Juvenile blue crabs, Callinectus sapidus, were exposed for 31days to six different sediments collected within the Pass a Loutre State Wildlife Management Area approximately 6months or 1.5years post-capping of the Macondo-252 well-head following the Deepwater Horizon (DWH) Incident. Based on forensic analysis to fingerprint for DWH oil, these sediments differed in their levels of DWH oil contamination, and included one reference sediment collected from a location with no detectable DWH oil present. The concentration of 50 individual parent and alkylation group polycyclic aromatic hydrocarbons (PAHs), saturated hydrocarbons (37 total), and total extractable hydrocarbons were determined in each sediment, as were biologically relevant metals, grain size distribution, percent total organic carbon, and percent total solids. Total concentrations of 50 PAHs (TPAH50) of initial treatment sediments ranged from 187μgkg−1 (reference site) to 2,086,458μgkg−1 (the highest DWH oil contaminated site). Multiple biological endpoints were measured including mortality, growth, and ecdysis. Additionally, early biomarkers of biological stress were examined in the hemolymph and hepatopancreas of crabs, including DNA damage (Comet assay) and expression of genes encoding Cu-metallothionein (CuMT), glutathione-S-transferase (GST), and manganese superoxide dismutase (MnSOD). Over the 31day exposure, there were no treatment related mortalities in juvenile blue crabs. The overall growth and molting of the crabs were not substantially different between the various sediment exposures over the exposure period. Additionally, none of the early biomarkers of biological stress were correlated with PAH concentrations. Overall, juvenile blue crabs did not appear to be negatively impacted during the 31day exposure by DWH oil contaminated sediments collected at least 6months post-capping of the Macondo-252 well-head.

Dinosaur footprints in the Upper Hauterivian deposits of the Palud Bay in Istria, Croatia

Sixteen dinosaur footprints are exposed along the upper-bedding plane of a single Upper Hauterivian limestone layer in the Palud bay (western Istria, Croatia). This distinct footprint-bearing horizon is part of the thick Mesozoic Adriatic-Dinaridic Carbonate Platform stratal succession. Strata at the Palud site are characterized by peritidal (shallow subtidal to intertidal) limestone with several shallowing-upward cycles composed of mudstone, peloidal wackestone/packstone, peloidal packstone/grainstone and fenestral mudstone/wackestone with common geopetal infill. The Late Hauterivian age of these deposits is determined from their microfossil assemblage, which is dominated by ostracods, benthic foraminifera and calcareous green algae Dasycladales. The Palud site dinosaur footprints are circular to elliptical in shape, with no clearly visible digit impressions (except for one questionable example), and are rather large with average length of 30 cm. Most footprints have a well-defined expulsion rim that represents displacement and compression of soft, waterlogged sediment substrate by the weight of the dinosaur. All of the footprints are of nearly same shape and size, which indicates that they were produced by the same kind of tracemaker – likely a sauropod dinosaur. These animals left their footprints on top of a shallowing-upward succession of an intertidal environment during a short subaerial exposure of fine-grained carbonate sediment.

Influence of copper oxide nanoparticle form and shape on toxicity and bioaccumulation in the deposit feeder, Capitella teleta

Few in vivo studies have been conducted to assess how nanoparticle (NP) characteristics such as particle form and shape affect their toxicity and bioaccumulation. In the present study, the deposit feeder, Capitella teleta, was used to investigate the influence of copper form (CuO NPs, micron-sized CuO particles, and aqueous Cu) and CuO NP shape (spheres, rods and platelets) on toxicity and bioaccumulation through sediment exposures of approximately 250 μg Cu/g dw sed. There were no effects of nanoparticle form or shape on mortality or growth rate during the exposure period. However, mortality increased to approximately 26.3% on average in all Cu treatments after the depuration period indicating a delayed effect of Cu exposure, despite more than 90% depuration of Cu during this period. A significant effect of nanoparticle shape was detected on body burden, the gross uptake rate constant and the depuration rate constant, suggesting preferential accumulation of rods by the worms. We recommend that additional sublethal endpoints and longer exposure durations should be examined to fully understand the environmental risks of CuO nanoparticles compared to other forms of Cu entering marine sediment systems.

Carbonate composition and its impact on fluvial geochemistry in the NE Tibetan Plateau region

Using co-variations of Sr/Ca and Mg/Ca, we examined the carbonate compositions of various bedrocks (silicate and carbonate rocks) and sediments (eolian and fluvial sediments, sand, and topsoil) found in the NE Tibetan Plateau (TP) region. A combined carbonate composition dataset based on our results and other reported data shows that bedrock carbonate composition on the NE TP displays a much broader range of Sr/Ca and Mg/Ca ratios than restricted source carbonate endmembers reported upon in previous studies. This has clear implications for modern weathering studies in addition to paleo-reconstructions in this tectonically active and climatically variable area during the Late Cenozoic. Bedrock carbonate compositions are characterized by disseminated carbonates with higher Sr/Ca and Mg/Ca ratios, and sedimentary carbonates (mostly marine) with lower Sr/Ca, but variable Mg/Ca, ratios. The mostly authigenic carbonates found in sediments show similar trends, with a gradient ~0.97–1.00 in a plot of log (Sr/Ca) versus log (Mg/Ca), suggesting that ‘calcite precipitation’ processes – i.e. the sources of the dissolved cations in the water – control their chemistry. Based on observations and modeling, we conclude that the mixing of authigenic and bedrock carbonate endmembers, plus the incongruent dissolution of bedrock carbonates, accounts for the bulk carbonate composition of sediments (e.g. loess, sand and topsoil). A comparison of bedrock and sedimentary carbonate composition with reported fluvial water data in the NE TP suggests that weathering of carbonates in terrigenous sediments, rather than in bedrock, is mostly responsible for the changes in fluvial Sr, Mg and Ca compositions. Our study suggests that interactions between carbonates and water occur widely during the exposure, transport and deposition of sediments, significantly modifying regional carbonate compositions and fluvial geochemistry.

Early Eocene volcanic ashes on Greifswalder Oie and their depositional environment, with an overview of coeval ash-bearing deposits in northern Germany and Denmark

Unconsolidated bentonites and carbonate-cemented volcanic ashes occur in northern Germany within the clay sequence of the Lamstedt and Schlieven Formations documented by several wells. Ash-bearing carbonate concretions (so-called cementstones) are also known from glacially transported rafts and erratic boulders on the Baltic Sea island Greifswalder Oie, representing the easternmost exposures of early Eocene sediments in the North Sea Basin. The ashes can be correlated with water-lain ashes of the Danish Fur and Olst Formations (mo-clay) generated during the opening of the North Atlantic Ocean about 55 Ma ago. Two types of cementstones can be distinguished on the basis of the mineralogical composition, sedimentary features and fossil content. Greifswalder Oie type I contains a black, up to 12-cm-thick ash deposit that follows above two distinct thin grey ash layers. The major ash unit has a rather homogeneous lower part; only a very weak normal grading and faint lamination are discernible. In the upper part, however, intercalations with light mudstone, in part intensively bioturbated, together with parallel and cross-lamination suggest reworking of the ash in a shallow marine environment. Major and trace element compositions are used to correlate type I ashes with those of the Danish-positive series which represent rather uniform ferrobasalts of the Danish stage 4, probably related to the emergence of proto-Iceland. In contrast, type II ash comprises a single, normally graded, about 5-cm-thick layer of water-lain air-fall tuff, which is embedded in fine-grained sandstone to muddy siltstone. Type II ash is characterised by very high TiO2 but low MgO contents. Exceptional REE patterns with a pronounced positive Eu anomaly suggest intense leaching of the glass that hampers exact correlation with pyroclastic deposits within the North Atlantic Igneous Province.

Application of endocrine disruptor screening program fish short-term reproduction assay: Reproduction and endocrine function in fathead minnow (Pimephales promelas) and killifish (Fundulus heteroclitus) exposed to Bermuda pond sediment.

A modified tier 1 Endocrine Disruptor Screening Program (EDSP) 21-d fish short-term reproduction assay (FSTRA) was used to evaluate the effects of sediment exposure from freshwater and brackish ponds in Bermuda on reproductive fecundity and endocrine function in fathead minnow (Pimephales promelas) and killifish (Fundulus heteroclitus). Reproductively active male and female fish were exposed to control sediment and sediment from 2 freshwater ponds (fathead minnow) and 2 marine ponds (killifish) contaminated with polyaromatic hydrocarbons and metals via flow-through exposure for 21 d. Reproductive fecundity was monitored daily. At termination, the status of the reproductive endocrine system was assessed by the gonadosomatic index, gonadal histology, plasma steroids (estrogen [E2], testosterone [T], and 11-ketotestosterone [11-KT]), steroidogenic enzymes (aromatase and combined 3β/17β -hydroxysteroid dehydrogenase [3β/17β-HSD]), and plasma vitellogenin (VTG). Decreased reproductive fecundity, lower male body weight, and altered endocrinological measures of reproductive status were observed in both species. Higher plasma T levels in female minnows and 11-KT levels in both male and female minnows and female killifish exposed to freshwater and brackish sediments, respectively. Decreased female E2 and VTG levels and gonadal cytochrome P19 (aromatase) activity were also found in sediment exposed females from both species. No effect on female 3β/17β-HSD activity was found in either species. The FSTRA provided a robust model capable of modification to evaluate reproductive effects of sediment exposure in fish.

OSL dating of fine-grained quartz from Holocene Yangtze delta sediments

Holocene flood events in the Yangtze River are associated with variations in East Asian Summer Monsoon (EASM) precipitation, and so Yangtze delta sediments may preserve information about the frequency and magnitude of EASM precipitation. These flood/drought cycles of the EASM directly affect the living standards of East Asian population. However, despite its importance, little chronological control is available for the Yangtze Delta sediments; because biogenic carbonate only occurs sporadically, it has proved the difficulty to discuss sedimentation mechanisms and rates in any detail.In 2013 two sediment cores (YD13-G3 and H1) were taken from the Yangtze subaqueous delta to investigate precipitation history. In this study, we investigate the potential of quartz OSL dating of the fine silt fraction (fine-grained quartz; 4–11 μm) from these cores to estimate the depositional age of the sediments. We test whether: (1) Yangtze subaqueous delta sediments contain quartz with suitable characteristics for dating, and (2) quartz grains are well-bleached during/before the transportation process, by examining a modern analogue of suspended particulate matter, and by cross-checking with the doses derived from infrared stimulated luminescence (IRSL) signals (both IR50 and pIRIR160) from feldspar in polymineral fine grains. We find that both the quartz and feldspar luminescence characteristics are satisfactory (quartz dose recovery ratio 1.067 ± 0.004; n = 250, pIRIR160 dose recovery ratio 1.01 ± 0.02; n = 151). Modern suspended particulate matter has measured quartz equivalent doses between 0.1 and 0.2 Gy, suggesting that this material was sufficiently bleached during/before transportation to allow dating of Holocene sediments (mean dose rates of ∼3 Gy ka−1). OSL ages of 44 samples from the 2 cores show apparently rapid accumulation at ∼6 ka between 9.65 and 5.50 m in core H1 and ∼2 ka throughout core G3 and between 5.0 and 0.0 m in core H1. The pIRIR160 signals suggest less light exposure of the core top sediments and of those from the transition layer between ∼6 ka to ∼2 ka, although there is no evidence for incomplete bleaching of quartz. The question remains as to whether significant deposition took place only at these two times, or whether the record has been disturbed by erosion/reworking.

Role of hydrological conditions on organic phosphorus forms and their availability in sediments from Poyang Lake, China.

Biogeochemical cycling of internal bioavailable organic phosphorus (OP) is an important source for algal bloom after exogenous P inputs are controlled. Biogeochemical cycling may be affected by hydrological processes and the water cycle and eventually result in water quality deterioration and accelerated lake eutrophication. Poyang Lake is the largest freshwater lake in China. The hydrological condition of the lake has significantly changed since 2003, thereby causing a continuous decline in water level. In this study, sediments were obtained from different elevations and different hydrological conditions in Poyang Lake. The sediments were subjected to sequential extraction and enzymatic hydrolysis to determine the transformation of OP into various chemical forms, their bioavailability, and the exchange between the sediments and overlying water. Results suggested that the descending water level caused by the changes in hydrological conditions was one of the major factors affecting OP dynamics. Long exposure of sediments resulted in high OP content and increased availability. The increased OP content in exposed sediments was primarily derived from H2O-Po and NaOH-EDTA-Po. Moreover, the increased OP availability in exposed sediments was mainly attributed to the increasing amount of orthophosphate caused by processes governing sediment exposure, promotion of OP release, and transformation of chemical forms from nonlabile to labile. Sediment exposure time and area have considerably expanded since 2003; hence, the amounts of OP and orthophosphate in the sediments have increased by as much as 600 and 120 tons in the lake every year, respectively. Although the increase in orthophosphate only accounted for 6% of the external total phosphorus, the local region may exhibit higher risk for OP release from the sediments, thereby accelerating quality deterioration. Therefore, maintaining reasonable hydrological conditions is important to protect Poyang Lake water.

Assessment of radium-226 bioavailability and bioaccumulation downstream of decommissioned uranium operations, using the caged oligochaete (Lumbriculus variegatus).

The present study investigated the integrated effects of several geochemical processes that control radium-226 ((226) Ra) mobility in the aquatic environment and bioaccumulation in in situ caged benthic invertebrates. Radium-226 bioaccumulation from sediment and water was evaluated using caged oligochaetes (Lumbriculus variegatus) deployed for 10 d in 6 areas downstream of decommissioned uranium operations in Ontario and Saskatchewan, Canada. Measured (226) Ra radioactivity levels in the retrieved oligochaetes did not relate directly to water and sediment exposure levels. Other environmental factors that may influence (226) Ra bioavailability in sediment and water were investigated. The strongest mitigating influence on (226) Ra bioaccumulation factors was sediment barium concentration, with elevated barium (Ba) levels being related to use of barium chloride in effluent treatment for removing (226) Ra through barite formation. Observations from the present study also indicated that (226) Ra bioavailability was influenced by dissolved organic carbon in water, and by gypsum, carbonate minerals, and iron oxyhydroxides in sediment, suggestive of sorption processes. Environmental factors that appeared to increase (226) Ra bioaccumulation were the presence of other group (II) ions in water (likely competing for binding sites on organic carbon molecules), and the presence of K-feldspars in sediment, which likely act as a dynamic repository for (226) Ra where weak ion exchange can occur. In addition to influencing bioavailability to sediment biota, secondary minerals such as gypsum, carbonate minerals, and iron oxyhydroxides likely help mitigate (226) Ra release into overlying water after the dissolution of sedimentary barite. Environ Toxicol Chem 2015;34:507-517. © 2014 SETAC.

Relative toxicity of bifenthrin to Hyalella azteca in 10 day versus 28 day exposures.

Many watersheds in the Central Valley region of California are listed as impaired due to pyrethroid-associated sediment toxicity. The Central Valley Regional Water Quality Control Board is developing numeric sediment quality criteria for pyrethroids, beginning with bifenthrin. Criteria are being developed using existing data, along with data from 10 d and 28 d toxicity tests with Hyalella azteca conducted as part of the current study. A single range-finder and 2 definitive tests were conducted for each test duration. Median lethal concentrations (LC50s), as well as LC20s and inhibition concentrations (IC20s) were calculated based on measured whole sediment bifenthrin concentrations and interstitial water concentrations. Sediment LC50s were also corrected for organic C content. Average LC50s were not significantly different in 10 d versus 28 d tests with H. azteca: 9.1 and 9.6 ng/g bifenthrin for 10 d and 28 d tests, respectively. Average LC20 values were also similar with concentrations at 7.1 and 7.0 for 10 d and 28 d tests, respectively. Bifenthrin inhibition concentrations (IC20s) based on amphipod growth were variable, particularly in the 28 d tests, where a clear dose-response relationship was observed in only 1 of the definitive experiments. Average amphipod growth IC20s were 3.9 and 9.0 ng/g for 10 d and 28 d tests, respectively. Amphipod growth calculated as biomass resulted in IC20s of 4.1 and 6.3 ng/g for the 10 d and 28 d tests, respectively. Lack of a clear growth effect in the longer term test may be related to the lack of food adjustment to account for amphipod mortality in whole sediment exposures. The average C-corrected LC50s were 1.03 and 1.09 μg/g OC for the 10 d and 28 d tests, respectively. Interstitial water LC50s were determined as the measured dissolved concentration of bifenthrin relative to interstitial water dissolved organic carbon. The average LC50s for dissolved interstitial water bifenthrin were 4.23 and 4.28 ng/L for the 10 d and 28 d tests, respectively. In addition, a set of 10 d and 28 d tests were conducted at 15 °C to assess the relative toxicity of bifenthrin at a lower temperature than the standard 23 °C test temperature. These results showed that bifenthrin was more toxic at the lower temperature, with LC50s of 5.1 and 3.4 ng/g bifenthrin in 10 d and 28 d tests, respectively. Amphipod growth at 15 °C after a 28 d exposure resulted in the lowest effect concentration of all experiments conducted (IC20 = 0.61 ng/g). This article discusses how bifenthrin dose-response data from 10 d and 28 d exposures inform development of sediment quality criteria for this pesticide for California Central Valley watersheds.

Heavy Metal Concentrations in Pores and Surface Waters during the Emptying of a Small Reservoir

The impact of reservoir emptying on the concentrations of dissolved heavy metals (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) in pore and surface waters was studied in the Aar Reservoir, a small reservoir in central Germany, during and after the emptying process. This study was conducted to observe binding changes within pore waters as well as the input of dissolved heavy metals in waters of the Aar Creek, what becomes possible when the reservoirs water table is removed and lake sediments become exposed. In pore waters, no clear shifting tendencies between dissolved and sorbed heavy metal fractions could be found after the completed sediment exposure. These relatively low dynamics in pore waters can be explained by the fine texture of the lake sediments, which are characterized by a high water holding capacity, what led to high remaining water contents and therefore slowed down the redox changes. A few days after the completed emptying, a general increase of dissolved heavy metal concentrations occurred in running waters of the Aar Creek as a result of pore water drainage. Here, element specific differences in mobilization and transportation abilities were found, what can be reconstructed by the ratio of dissolved heavy metals in pore and surface waters.

The relationship between concurrently measured SASS (South African Scoring System) and turbidity data archived in the South African River Health Programme’s Rivers Database

The need for monitoring the biological impacts of instream sediments has long been recognised, yet robust and scientifically defensible tools for doing so are still in the early stages of development because of the difficulties experienced by researchers in characterising the complicated mechanisms of biological effect elicited by sediment particles. Biological monitoring is one such tool, and this paper reports on the initial stages of a study to determine the most applicable approach for measuring the effects of instream sediments on aquatic macroinvertebrates in the South African context. In this first instance, the suitability of the rapid macroinvertebrate biomonitoring tool (the South African Scoring System) was investigated by determining the extent of the correlation between concurrently measured SASS metrics and turbidity data collected for the South African River Health Programme. All three SASS metrics – SASS score, number of taxa (NOT), and average score per taxon (ASPT) – were found to be significantly negatively correlated with turbidity, although variation in the data was high. Turbidity was found to be the major driver of change in ASPT. In contrast, electrical conductivity was the major driver of SASS scores and NOT, with turbidity a close second. When combined, electrical conductivity and turbidity accounted for 80% (SASS score) and 75% (NOT) of the variation in the regression model. Consequently, SASS metrics are a crude, but reliable, indicator of the negative biological implications of excessive instream sedimentation as measured by turbidity. A number of other potential biomonitoring approaches for detecting the impacts of fine sediment exposure are identified for further investigation: spatial analyses of macroinvertebrate assemblages; and the use of structural and functional metrics.Keywords: aquatic macroinvertebrates, suspended sediment, biomonitoring

Unraveling sea-level variations and tectonic uplift in wave-built marine terraces, Santa María Island, Chile

The architecture of coastal sequences in tectonically-active regions results mostly from a combination of sea-level and land-level changes. The objective of this study is to unravel these signals by combining sequence stratigraphy and sedimentology of near-shore sedimentary sequences in wave-built terraces. We focus on Santa María Island at the south-central Chile margin, which hosts excellent exposures of coastal sediments from Marine Isotope Stage 3. A novel method based on statistical analysis of grain-size distributions coupled with facies descriptions provided a detailed account of transgressive–regressive cycles. Radiocarbon ages from paleosols constrain the chronology between >53 and ~31calkaBP. Because the influence of glaciations can be neglected, we calculated relative sea-level curves by tying the onset of deposition on a bedrock abrasion platform to a global sea-level curve. The observed depositional cycles match those predicted for uplift rates between 1.2 and 1.8m/ka. The studied sedimentary units represent depositional cycles that resulted in reoccupation events of an existing marine terrace. Our study demonstrates wave-built marine terrace deposits along clastic shorelines in temperate regions can be used to distinguish between tectonic uplift and climate-induced sea-level changes.

Toxicity, bioaccumulation, and biotransformation of silver nanoparticles in marine organisms.

The toxicity, bioaccumulation, and biotransformation of citrate and polyvinylpyrrolidone (PVP) coated silver nanoparticles (NPs) (AgNP-citrate and AgNP-PVP) in marine organisms via marine sediment exposure was investigated. Results from 7-d sediment toxicity tests indicate that AgNP-citrate and AgNP-PVP did not exhibit toxicity to the amphipod (Ampelisca abdita) and mysid (Americamysis bahia) at ≤75 mg/kg dry wt. A 28-d bioaccumulation study showed that Ag was significantly accumulated in the marine polychaete Nereis virens (N. virens) in the AgNP-citrate, AgNP-PVP and a conventional salt (AgNO3) treatments. Synchrotron X-ray absorption spectroscopy (XAS) results showed the distribution of Ag species in marine sediments amended with AgNP-citrate, AgNP-PVP, and AgNO3 was AgCl (50–65%) > Ag2S (32–42%) > Ag metal (Ag0) (3–11%). In N virens, AgCl (25–59%) and Ag2S (10–31%) generally decreased and, Ag metal (32–44%) increased, relative to the sediments. The patterns of speciation in the worm were different depending upon the coating of the AgNP and both types of AgNPs were different than the AgNO3 salt. These results show that the AgNP surface capping agents influenced Ag uptake, biotransformation, and/or excretion. To our knowledge, this is the first demonstration of the bioaccumulation and speciation of AgNPs in a marine organism (N. virens).

A natural oil seep in the floodplain of the Amga River (Siberian Platform)

A natural oil seep has been revealed in the floodplain of the middle stream of the Amga River, in zone of the exposure of Middle Cambrian sediments. A distinctive feature of saturated hydrocarbons of this oil is the absence of 12- and 13-methylalkanes, biomarkers that are present in oils of the Vendian–Cambrian deposits of the Nepa–Botuobiyan petroliferous province. In this feature the studied seep oil is similar to the Middle Cambrian oil from hydrogeologic wells (1-P and 1-T) drilled earlier downstream of the Amga River.

Chronic TiO2 nanoparticle exposure to a benthic organism, Hyalella azteca: impact of solar UV radiation and material surface coatings on toxicity

There is limited information on the chronic effects of nanomaterials to benthic organisms, as well as environmental mitigating factors that might influence this toxicity. The present study aimed to fill these data gaps by examining various growth endpoints (weight gain, instantaneous growth rate, and total protein content) for up to a 21 d sediment exposure of TiO2 nanoparticles (nano-TiO2) to a representative benthic species, Hyalella azteca. An uncoated standard, P25, and an Al(OH)3 coated nano-TiO2 used in commercial products were added to sediment at 20mg/L or 100mg/L Under test conditions, UV exposure alone was shown to be a greater cause of toxicity than even these high levels of nano-TiO2 exposure, indicating that different hazards need to be addressed in toxicity testing scenarios. In addition, this study showed the effectiveness of a surface coating on the decreased photoactivity of the material, as the addition of an Al(OH)3 coating showed a dramatic decrease in reactive oxygen species (ROS) production. However, this reduced photoactivity was found to be partially restored when the coating had been degraded, leading to the need for future toxicity tests which examine the implications of weathering events on particle surface coatings.

The Geochemical Significance of Cambrian Organic Matter From Salt Range of Potwar Basin, Pakistan

Selected Cambrian sediments from Salt Range region of the Potwar Basin of Pakistan have been analyzed for saturated and aromatic hydrocarbons. Biomarker and nonbiomarker parameters are shown immature to marginally mature nature of marine organic matter deposited in suboxic depositional environment and carbonate settings. Interesting feature of straight chain hydrocarbons is the unusual abundance of even carbon numbered alkenes (C16–C28) that probably indicates the strong microbial activity/deposition or contamination by exposure of sediments to surface in younger times. Cambrian organic matter of Salt Range is not much affected and altered by subsurface temperature and pressure. Hence diagnostic molecular parameters are still showing distinction and valuable for interpretation of geochemical characteristics of Cambrian sedimentary organic matter.

The assumption of heterogeneous or homogeneous radioactive contamination in soil/sediment: does it matter in terms of the external exposure of fauna?

The classical approach to environmental radioprotection is based on the assumption of homogeneously contaminated media. However, in soils and sediments there may be a significant variation of radioactivity with depth. The effect of this heterogeneity was investigated by examining the external exposure of various sediment and soil organisms, and determining the resulting dose rates, assuming a realistic combination of locations and radionuclides. The results were dependent on the exposure situation, i.e., the organism, its location, and the quality and quantity of radionuclides. The dose rates ranged over three orders of magnitude. The assumption of homogeneous contamination was not consistently conservative (if associated with a level of radioactivity averaged over the full thickness of soil or sediment that was sampled). Dose assessment for screening purposes requires consideration of the highest activity concentration measured in a soil/sediment that is considered to be homogeneously contaminated. A more refined assessment (e.g., higher tier of a graded approach) should take into consideration a more realistic contamination profile, and apply different dosimetric approaches.

Impacts of catastrophic volcanic collapse on the erosion and morphology of a distal fluvial landscape: Hautapu River, Mount Ruapehu, New Zealand

Debris avalanches caused by the collapse of volcanic flanks pose a great risk to inhabited areas and may permanently change the surrounding landscape and its drainage systems. In this research, we explored the interplay between a debris avalanche and a tectonically uplifting surrounding landscape, providing insights into the long-term consequences of volcanic edifice failures. Exposures of coarse volcaniclastic sediments along the Hautapu River ∼50 km southeast of Mount Ruapehu, New Zealand, show evidence of the largest known collapse event of the stratovolcano, which was followed by a vigorous regrowth phase that produced numerous pyroclastic eruptions and pumice-rich lahars. Similar diamicton deposits are exposed within the river catchment adjacent to the west. Cover-bed stratigraphy and geochemical correlation of andesitic lava blocks within the debris-avalanche deposit with dated lavas exposed on the cone indicate that deposition occurred between 125 and 150 ka. The collapse took place during the shift from a glacial to an interglacial climate, when glaciers on the cone were in retreat, and high pore-water pressures combined with deep hydrothermal alteration weakened the cone. In addition, collapse may have been accompanied by magmatic unrest. The ∼2–3 km3 debris avalanche inundated an area of >260 km2 and entered the proto-Hautapu catchment, where it was channelized within the deeply entrenched valley. Mass-wasting events associated with postcollapse volcanism continued to be channeled into the proto–Hautapu River for another ∼10 k.y., producing long-runout lahars. Subsequently, the river catchment was isolated from the volcano by incision of the intervening Whangaehu River into the proximal volcaniclastic sediments, accompanied by regional faulting and graben deepening around Ruapehu. At present, the volcaniclastic deposits form a distinctive plateau on the highest topographic elevation within the Hautapu Valley, forming a reversed topography caused by preferred incision of the Hautapu River into softer Late Tertiary sediments concurrent with constant uplift.

Toxicity of two pyrethroid-based anti-sea lice pesticides, AlphaMax® and Excis®, to a marine amphipod in aqueous and sediment exposures

Abstract Pyrethroid pesticides used to control ectoparasitic sea lice in salmon aquaculture are released in effluent plumes from cage sites and have the potential to adversely affect non-target organisms. Pyrethroids have been shown to be highly toxic to crustaceans, but the toxicity of the pyrethroid-based anti-sea lice pesticides AlphaMax® (active ingredient (a.i.) deltamethrin) and Excis® (a.i. cypermethrin) has not been thoroughly studied for non-target, marine benthic crustaceans such as amphipods. The amphipod Echinogammarus finmarchicus, which is ubiquitous in near-shore environments in the northern Atlantic Ocean, was collected from the field for use in laboratory toxicity tests. Amphipods were exposed to the two pesticides in 1- and 24-h water-only, single-pulsed exposures and 10-day spiked sediment tests. In water-only tests, immobility occurred within 1- or 24-h of exposure to the highest test concentrations and delayed mortality and immobility were observed following exposure to lower concentrations as well. Effect thresholds ranged from 6.7–70 ng/L for deltamethrin and 20–220 ng/L for cypermethrin. Organisms exposed to sediment were affected within 2–4 days; resulting 10-d LC50s were 16 and 80 ng/g (dry weight) for deltamethrin and cypermethrin, respectively. Results suggest that amphipods in an effluent plume may be exposed to aqueous concentrations of pyrethroids sufficient to cause adverse effects, including delayed toxicity. In contrast, the 10-day sediment LC50s were much higher than (limited) reported environmental concentrations in sediment. Overall, these results suggest a low potential for risk from sediment exposures for a northern Atlantic species of amphipod that inhabits the near-shore environment where cage aquaculture sites are located.