Inhomogeneous distribution of polycyclic aromatic hydrocarbons in different size and density fractions of contaminated sediment from Auckland Harbour, New Zealand: an opportunity for mitigation

Polycyclic aromatic hydrocarbons (PAHs) in sediment from Auckland Harbour (New Zealand) are not distributed evenly throughout bulk sediment, but highly concentrated in coarser, low-density fractions. Concentrations of 24 PAHs, measured in sediment that was separated into six size fractions that were furthermore separated into two density sub-fractions by flotation in sodium-polytungstate solution (rho = 2.15 g cm(-3)), varied between 4-103 microg g(-1)dw among grain size fractions and 2-998 microg g(-1)dw for density sub-fractions. Highest PAH concentrations were measured in the low density, 125-250 microm fraction. All sediment fractions had a similar relative PAH composition, dominated by >3-ring PAHs, suggesting a common pyrogenic origin. Low density material had 10-200 times higher PAH concentrations and 10-100 times higher organic carbon (OC) content, yet differences in OC content only partially accounted for variations in PAH concentration. Low density particles contributed more than 75% of the Sigma PAH, while comprising only 3% of bulk sediment dry weight. This may have significant utility for contaminant mitigation efforts in Auckland Harbour.     

Influence of storm-related sediment storage on the sediment delivery from tributary catchments in the upper Waipaoa River,New Zealand

Although much is known about overall sediment delivery ratios for catchments as components of sediment production and sediment yield, little is known about the component of temporary sediment storage. Sediment delivery ratios focused on the influence of storm-related sediment storage are measured at Matakonekone and Oil Springs tributaries of the Waipaoa River basin, east coast of New Zealand. The terrace deposits of both tributaries show abundant evidence of storm-related sedimentation, especially sediment delivered from Cyclone Bola, a 50 year return rainfall event which occurred in 1988. The sediment delivery ratio is calculated by dividing the volume of sediment transported from a tributary to the main stream by the volume of sediment generated at erosion sites in the tributary catchment. Because the sediment delivery volume is unknown, it can be calculated as the difference between sediment generation volume and sediment storage volume in the channel reach of the tributary. The volume of sediment generated from erosion sites in each tributary catchment was calculated from measurements made on aerial photographs dating from 1960 (1:44 000) and 1988 (1:27 000). The volume of sediment stored in the tributary can be calculated from measurements of cross-sections located along the tributary channel, which are accompanied by terrace deposits dated by counting annual growth rings of trees on terrace surfaces. Sediment delivery ratios are 0·93 for both Matakonekone catchment and Oil Springs catchment. Results indicate that Oil Springs catchment has contributed more than twice the volume of sediment to the Waipaoa River than the Matakonekone catchment (2·75 × 10⁶ m³ vs 1·22 × 10⁶ m³). Although large volumes of sediment are initially deposited during floods, subsequent smaller flows scour away much of these deposits. The sediment scouring rate from storage is 1·25 × 10⁴ m³ a⁻¹ for Matakonekone stream and 0·83 × 10⁴ m³ a⁻¹ for Oil Springs stream. Matakonekone and Oil Springs channels respond to extreme storms by instantaneously aggrading, then gradually excavating the temporarily stored sediment. Results from Matakonekone and Oil Springs streams suggest a mechanism by which event recurrence interval can strongly influence the magnitude of a geomorphic change. Matakonekone stream with its higher stream power is expected to excavate sediment deposits more rapidly and allow more rapid re-establishment of storage capacity. Copyright © 1999 John Wiley & Sons, Ltd.     

青藏高原腹地现今地应力测量与应力状态研究

青藏高原腹地现今构造活动强烈,为了解强烈构造活动下的应力背景,我们在五道梁、风火山、雁石坪和安多不同构造部位的四个测点采用压磁应力解除法进行了现场应力实测工作,测量深度12～20m.测量结果表明, 最大主应力方向总体为北东向,与地质、地震以及大地测量等方面的研究成果基本吻合;最大主应力量值为3.6～6.8MPa（安多测点除外）,与其他地区测量结果相比,属于中等偏高;安多测点最大主应力方向为北西西向,最大主应力量值为8.1MPa,与其他测点有较大差别,反映了板块缝合带附近现今应力状态的复杂性.     

Soil CO2 flux baseline in an urban monogenetic volcanic field: the Auckland Volcanic Field, New Zealand

The Auckland Volcanic Field (AVF) is a dormant monogenetic basaltic field located in Auckland, New Zealand. Though soil gas CO₂ fluxes are routinely used to monitor volcanic regions, there have been no published studies of soil CO₂ flux or soil gas CO₂ concentrations in the AVF to date or many other monogenetic fields worldwide. We measured soil gas CO₂ fluxes and soil gas CO₂ concentrations in 2010 and 2012 in varying settings, seasons, and times of day to establish a baseline soil CO₂ flux and to determine the major sources of and controlling influences on Auckland's soil CO₂ flux. Soil CO₂ flux measurements varied from 0 to 203 g m^?2 day^?1, with an average of 27.1 g m^?2 day^?1. Higher fluxes were attributed to varying land use properties (e.g., landfill). Using a graphical statistical approach, two populations of CO₂ fluxes were identified. Isotope analyses of δ¹³CO₂ confirmed that the source of CO₂ in the AVF is biogenic with no volcanic component. These data may be used to assist with eruption forecasting in the event of precursory activity in the AVF, and highlight the importance of knowing land use history when assessing soil gas CO₂ fluxes in urban environments.     

Biomarkers of exposure and effect in flounder (Platichthys flesus) exposed to sediments of the Adriatic sea.

The modifications of several biomarkers were investigated in flounder (Platichthys flesus) when exposed in the laboratory to sediment samples collected from the Northern Adriatic Sea. Besides clean sand used as a control substrate, fish were exposed to sediments sampled offshore the delta of the Po River, the harbour of Trieste, and from the industrial harbour of Venice (Porto Marghera). After six days of exposure, the enzyme activities ethoxyresorufin-O-deethylase (EROD), UDP glucuronyltransferase (UDPGT), glutathione S-transferase (GST), glutathione reductase (GR) and glutathione peroxidase (GPx), were assayed in fish liver. In addition, the contents of reduced glutathione (GSH), nonprotein thiols (SH), total sugars and extractable lipids were also determined in hepatic tissue, as well as the number of micronucleated hepatocytes and biliary concentrations of fluorescent aromatic compounds (FAC). Despite some variability within treatment groups, differences among exposed organisms were evident and consistent with known contaminant levels of sampled areas. Microsomal activities (EROD, UD-PGT) and FAC levels were the most sensitive exposure indicators. Variations in the other biomarkers showed only tendencies which although not statistically significant were generally consistent with the contamination pattern.     

A stochastic estimation of sediment production in an urban catchment using the USLE model

The goals of this study were to map the spatial distribution of sediment production and to estimate the probability of this production at the waterline based on a high potential of silting. The RUSLE-GIS model and Monte Carlo simulation were used. A sensitivity analysis of stochastic factors was performed by calculating the simple correlation coefficient. This procedure was applied to the Estrada Nova catchment, located in the city of Belém, northern Brazil, which has been subject to channel improvements and the construction of a detention basin. The results indicate that, following the urbanization and drainage improvements, there was a reduction in the annual sediment production probability, which is consistent with the dynamics in land use. The erodibility was the most sensitive factor in the sedimentation estimates. The methodology was considered an alternative to estimate sediment production in an urban catchment.     

Burial, crawling and drifting behaviour of the bivalve Macomona liliana in response to common sediment contaminants

To investigate the effect of sediment contamination on the tellinid bivalve Macomona liliana, juvenile shellfish (about 1.3 mm long) were exposed to copper- and zinc-dosed sand, and sediments collected from several contaminated sites. The behavioural responses measured included burial rate, crawling and drifting. In copper-dosed sediment, a significant reduction in the number of shellfish burying after 10 min occurred at 25 mg Cu kg⁻¹ (dry wt). After a 96-h exposure, shellfish crawled away from sediment with 10 mg Cu kg⁻¹ (dry wt), and when a weak current was provided they left this 10 mg Cu kg⁻¹ (dry wt) sediment by drifting. Zinc-dosed sediment slowed burial at 80 mg Zn kg⁻¹ (dry wt), and stimulated crawling and drifting at 40 mg Zn kg⁻¹ (dry wt). Some of the field-collected contaminated sediments slowed burial and stimulated drifting, but none affected crawling. It appears that juvenile drifting induced by sediment contamination could play a role in determining M. liliana distributions.     

Assessment of recent sediment influence in an urban polluted subantarctic coastal ecosystem. Beagle Channel (Southern Argentina)

In this study, baseline information about the environmental status of Ushuaia (UB) and Golondrina (GB) bays is presented. Surface and bottom seawater and freshwater discharged from land were evaluated. Multivariate analysis identified different water quality zones within the bays, two of them located next to the north and northwest coastlines of UB, where the majority of human activities are developed. Porosity, total organic matter, biochemical components, ammonium, and phytopigments were determined in sediment samples from each quality zone. Benthic fluxes of nutrients and dissolved oxygen were assessed in situ using opaque chambers. In northwest zone of UB, carbon equivalents of proteins and carbohydrates in surficial sediments were the same order as in hypertrophic ecosystems, whereas ammonium and phosphate released from sediment greatly exceeded the allochthonous sources. Management of municipal wastewater is required to remediate this chronic pollution.     

Hydrodynamics and sediment-transport in the nearshore of Poverty Bay, New Zealand: Observations of nearshore sediment segregation and oceanic storms

Nearshore regions act as an interface between the terrestrial environment and deeper waters. As such, they play important roles in the dispersal of fluvial sediment and the transport of sand to and from the shoreline. This study focused on the nearshore of Poverty Bay, New Zealand, and the processes controlling the dispersal of sediment from the main source, the Waipaoa River. Hydrodynamics and sediment-transport in water shallower than 15 m were observed from April through mid-September 2006. This deployment afforded observations during 3-4 periods of elevated river discharge and 5 dry storms.Similar wind, river discharge, wave, current, and turbidity patterns were characterized during three of the wet storms. At the beginning of each event, winds blew shoreward, increasing wave heights to 2-3 m within Poverty Bay. As the cyclonic storms moved through the system the winds reversed direction and became seaward, reducing the local wave height and orbital velocity while river discharge remained elevated. At these times, high river discharge and relatively small waves enabled fluvially derived suspended sediment to deposit in shallow water. Altimetry measurements indicated that at least 7 cm was deposited at a 15 m deep site during a single discharge event. Turbidity and seabed observations showed this deposition to be removed, however, as large swell waves from the Southern Ocean triggered resuspension of the material within three weeks of deposition. Consequently, two periods of dispersal were associated with each discharge pulse, one coinciding with fluvial delivery, and a second driven by wave resuspension a few weeks later. These observations of nearfield sediment deposition contradict current hypotheses of very limited sediment deposition in shallow water offshore of small mountainous rivers when floods and high-energy, large wave and fast current, oceanic conditions coincide.Consistently shoreward near-bed currents, observed along the 10 m isobath of Poverty Bay, were attributed to a combination of estuarine circulation, Stokes drift, and wind driven upwelling. Velocities measured at the 15 m isobath, however, were directed more alongshore and diverged from those at the 10 m isobath. The divergence in the currents observed at the 10 and 15 m locations seemed to facilitate segregation of coarse and fine sediment, with sand transported near-bed toward the beach, while suspended silts and clays were exported to deeper water.     

A lithium isotopic study of sub-greenschist to greenschist facies metamorphism in an accretionary prism,New Zealand

To investigate the behavior of Li during low-grade metamorphism and fluid flux in an accretionary prism we measured the Li concentrations ([Li]) and isotopic compositions (δ⁷Li) of sub-greenschist and greenschist-facies Otago Schist composites, as well as cross-cutting quartz veins, which are interpreted to have precipitated from slab-derived fluids. The average [Li] of sub-greenschist facies composites (41 ± 13 μg/g, 2σ) is statistically distinct (97% confidence level, student t test) to that of greenschist facies composites (34 ± 9 μg/g, 2σ), which have experienced mass addition of silica in the form of quartz veins having [Li] between 0.4–2.3 μg/g. A linear regression of the correlation between [Li] and calculated mass additions suggests that the depletion of [Li] in greenschist facies composites is due to both dilution from the addition of the quartz veins, as well as metamorphic dehydration. The [Li] of both groups of composites correlates with their CIA (Chemical Index of Alteration) values (50–58), which are low, consistent with the inferred graywacke protolith of the Otago Schist. The δ⁷Li of sub-greenschist and greenschist facies composites are remarkably constant, with an average δ⁷Li of 0.2 ± 1.7 (2σ) and ?0.5 ± 1.9 (2σ), respectively, and comparable to that of the average upper continental crust. Thus, metamorphism has had no discernable effect on δ⁷Li in these samples. The Li isotopic signature of the schists is similar to that seen in pelitic sedimentary rocks and likely reflects the δ⁷Li of the protoliths. The surprisingly light δ⁷Li of the quartz veins (?2.8 to ?1.4) likely records kinetic fractionation associated with Li ingress into the veins from surrounding wallrock.An isotopic equilibrium fluid flow model indicates that: 1) if the [Li] of slab-derived fluids is less than a few μg/g, the δ⁷Li of the overlying lithologies (i.e., the schists) is not significantly influenced by the fluid flux, regardless of the δ⁷Li of the fluids, 2) the slab-derived fluids will have heavy δ⁷Li of > + 10 after reacting with the prism sediments during their ascent, and 3) the [Li] of the slab-derived fluids is likely in the range of 0 < [Li] ≤ 41(μg/g). Thus, isotopically heavy slab-derived fluids that traverse sediments in accretionary prisms may leave little trace in the rocks and their surface compositional characteristics will reflect the net result of their interaction with the sediments of the prism.     

Estimation of temporally averaged sediment delivery ratio using aggradational terraces in headwater catchments of the Waipaoa River,North Island,New Zealand

The sediment delivery ratio was estimated for two periods (28 years and eight years) following reforestation of seven tributary catchments (0·33 to 0·49 km²) in the headwaters of the Waipaoa River basin, North Island, New Zealand. In these catchments, gully erosion, which largely resulted from clearance of the natural forest between 1880 and 1920, is the main source of sediment to streams. Reforestation commenced in the early 1960s in an attempt to stabilize hillslopes and reduce sediment supply. Efforts have been partially successful and channels are now degrading, though gully erosion continues to supply sediment at accelerated rates in parts of the catchment. Data from the area indicate that the sediment delivery ratio (SDR) can be estimated as a function of two variables, ψ (the product of catchment area and channel slope) and A _g (the temporally averaged gully area for the period). Sediment input from gullies was determined from a well defined relationship between sediment yield and gully area. Sediment scoured from channels was estimated from dated terrace remnants and the current channel bed. Terrace remnants represent aggradation during major floods. This technique provides estimates of SDR averaged over periods between large magnitude terrace‐forming events and with the present channel bed. The technique averages out short‐term variability in sediment flux. Comparison of gully area and sediment transport between two periods (1960–1988 and 1988–1996) indicates that the annual rate of sediment yield from gullies for the later period has decreased by 77 per cent, sediment scouring in channels has increased by 124 per cent, and sediment delivered from catchments has decreased by 78 per cent. However, average SDR for the tributaries was found to be not significantly different between these periods. This may reflect the small number of catchments examined. It is also due to the fact that the volume of sediment scoured from channels was very small relative to that produced by gullies. According to the equation for SDR determined for the Waipaoa headwaters, SDR increases with increasing catchment area in the case where A _g and channel slope are fixed. This is because the amount of sediment produced from a channel by scouring increases with increasing catchment area. However, this relationship does not hold for the main stem of the study catchments, because sediment delivered from its tributaries still continues to accumulate in the channel. Higher order channels are, in effect, at a different stage in the aggradation/degradation cycle and it will take some time until a main channel reflects the effects of reforestation and its bed adjusts to net degradation. Results demonstrate significant differences among even low order catchments, and such differences will need to be taken into consideration when using SDR to estimate sediment yields. Copyright © 2001 John Wiley & Sons, Ltd.     

Invertebrate and microbial responses to inundation in an ephemeral river reach in New Zealand: effects of preceding dry periods

Inundation marks the shift from a terrestrial ecosystem to an aquatic ecosystem in ephemeral rivers. The forms and rates of responses by aquatic invertebrates and sediment microbes to inundation depend on desiccation resistance during preceding dry periods. We assessed invertebrate and microbial responses to inundation over a range of preceding dry periods in an ephemeral reach of the Selwyn River, New Zealand. Microbial response variables were dissolved oxygen consumption and non-specific esterase activity. Sampling sites along the reach had been continuously dry for 1–592 d prior to sample collection. The onset of flow simulated by an experimental inundation led to the appearance of aquatic invertebrates in all samples, but the assemblages varied with the length of the preceding dry period. Taxon richness decreased linearly with dry period length while density decreased exponentially. These patterns indicate that a large number of individuals from desiccation-sensitive taxa were eliminated soon after flow ceased, and a low-density assemblage composed of a small number of desiccation-resistant taxa persisted during prolonged dry periods. As with invertebrate density, sediment respiration and nonspecific esterase activity decreased with length of dry period, and were characterized by exponential decay functions. The results of the inundation experiments suggest that a temporal ecotone exists for about one week after the disappearance of flowing water, and before the terrestrial system stabilizes.     

Cenozoic volcanism, stress gradient and back-arc opening in the North Island, New Zealand: Origin of Taupo-Rotorua Depression

Abstract Extensive subduction-related and intraplate volcanism characterize Cenozoic magmatism in the North Is., New Zealand. Volcanics in the central North Is., predominantly intermediate to felsic, form above the dipping seismic zone and show tectonic/geochemical features common to magmatism in most subduction zones. Basaltic volcanism in Northland, the northern part of the North Is., has chemical characteristics typical of intraplate magmatism and may be caused by the upwelling of asthenospheric materials from deeper parts of the mantle. The rifting just behind the present volcanic front (the Taupo-Rotorua Depression), which follows the trench ward migration of the volcanic front and the gradual steepening of the subducted slab, is also a feature of the North Is. A possible mechanism for the back-arc rifting in the area is injection of asthenospheric materials into the mantle wedge; this asthenospheric flow results from the mantle upwelling beneath Northland and pushes both the rigid fore-arc mantle wedge and the subducted slab trenchwards. This mechanism is also consistent with the stress fields in the North Is.: dilatation in Northland, northwest-southeast tension in the Taupo-Rotorua Depression, and the northeast-southwest compression in the fore-arc region.     

Magma mingling in an andesite pyroclastic flow of the Pourahu Member, Ruapehu volcano, New Zealand

We describe a magma mingling episode from Ruapehu volcano between two andesite magmas, one very much minor in volume relative to the other. The event acted to trigger eruption of the andesitic Pourahu pyroclastic flow which is preserved in a thick sequence of tephras and laharic deposits in the southeastern ring plain of the volcano. The predominant andesite is pale brown coloured and porphyritic containing phenocrysts of plagioclase-clinopyroxene-orthopyroxene-Fe-Ti oxides. Rare clasts of a darker andesite are different texturally, less vesicular, and contain distinctive microphenocrysts of plagioclase and quench olivine. Equally rare clasts, of streaky pumice consisting of interbanded ‘dark’ and ‘light’ andesite attest to mingling between these two andesite components.Chemical analyses of discrete clasts demonstrate that the Pourahu pyroclastic flow andesites span much of the compositional spectrum of Ruapehu andesites. This observation demonstrates heterogeneity in the products of a relatively small eruption. The darker clast analyses and those from associated distal fall deposits lie within the fields defined by the dominant light coloured clasts. Phenocryst and microphenocryst geothermometry suggest slightly higher temperatures in the dark component. However, glasses from groundmass and phenocryst inclusions in the same specimen may differ considerably, leading us to conclude that many phenocrysts are in fact xenocrystic and were incorporated in the melts as they migrated towards the surface.We prefer a model in which a small volume of hot andesite magma injects a vent-feeding magma chamber, triggering vesiculation and eruption. We infer that the process of magma withdrawal extended downward into the magma body causing the dark component to intermingle with the lighter (dominant) component, ‘sucking’ more dark magma into the chamber. Our observations are entirely consistent with the existence of a plexus of small, possibly interlinked magma chambers beneath Ruapehu.     

Studies of a contaminated brackish marsh in the Hackensack Meadowlands of northeastern New Jersey: an assessment of natural recovery

Eight-Day Swamp is known to be contaminated with heavy metals, especially mercury. Sediment cores were collected to approximately 32 cm at 17 sites on four transects and analyzed at 1 or 2 cm intervals for seven metals and organic matter. Very high metal levels were found throughout the site. Long and Morgan's "effects range-median" (ER-M) was exceeded in more than 50% of slices for all elements except As. Hg had the highest concentration relative to ER-M; median Hg concentration was 72 times its ER-M. On the marsh plain, all metals showed enrichment at 14-20 cm depth of 10-40X over surficial sediments. 137Cs analysis showed sedimentation rates ranging from 0.33 to 0.50 cm yr(-1) over the last approximately 40 yr. These rates indicate that metal contamination peaks occurred in sediments deposited in the early 1960s. Thus, newer, less contaminated sediments are burying older, more contaminated layers and peak levels of contaminants are becoming less available to benthos.     

Modern sediment yield compared to geologic rates of sediment production in a semi‐arid basin,New Mexico: assessing the human impact

An Erratum has been published for this article in Earth Surface Processes and Landforms 29(13) 2004, 1707. In the semi‐arid Arroyo Chavez basin of New Mexico, a 2·28 km² sub‐basin of the Rio Puerco, we contrasted short‐term rates (3 years) of sediment yield measured with sediment traps and dams with long‐term, geologic rates (～10 000 years) of sediment production measured using ¹⁰Be. Examination of erosion rates at different time‐scales provides the opportunity to contrast the human impact on erosion with background or geologic rates of sediment production. Arroyo Chavez is grazed and we were interested in whether differences in erosion rates observed at the two time‐scales are due to grazing. The geologic rate of sediment production, 0·27 kg m^?2 a^?1 is similar to the modern sediment yields measured for geomorphic surfaces including colluvial slopes, gently sloping hillslopes, and the mesa top which ranged from 0·12 to 1·03 kg m^?2 a^?1. The differences between modern sediment yield and geologic rates of sediment production were most noticeable for the alluvial valley ?oor, which had modern sediment yields as high as 3·35 kg m^?2 a^?1. The hydraulic state of the arroyo determines whether the alluvial valley ?oor is aggrading or degrading. Arroyo Chavez is incised and the alluvial valley ?oor is gullied and piped and is a source of sediment. The alluvial valley ?oor is also the portion of the basin most modi?ed by human disturbance including grazing and gas pipeline activity, both of which serve to increase erosion rates. Copyright © 2004 John Wiley & Sons, Ltd.     

Deformation processes in the shallow levels of an accretionary prism: The Mesozoic Torlesse Terrane, South Island, New Zealand

Abstract The deformation style of the Torlesse Terrane along the southern Kaikoura coast, South Island, New Zealand, records shallow level deformation processes within an accretionary prism during the Early Cretaceous. The beds exhibit complicated structural features resulting from multistage deformations in a lithological unit, that were intimately related with the dewatering and lithification of terrigenous sediments. The earliest phase of deformation throughout the transect studied was the development of pinch-and-swell structures and boudinage fabrics due to layer-parallel extension while the beds were poorly consolidated. This was followed locally by mesoscopic tight to close recumbent folding. The beds are cut locally by two phases of mudstone intrusions. The earlier phase was initiated by 'in situ' fluidization of mudstone layers, whereas the later phase represented intrusion of siliceous claystone probably derived from an overpressured decollement. Minor faults at high-angles to bedding by layer-normal shortening then disrupted the beds throughout the transect. The deformation was followed by formation of meso- and macroscopic scale open to gentle folds by layer-parallel shortening. Kilometer-scale differential stratal rotations were produced during the final main tectonic phase that occurred in association with post-accretion Neogene regional disturbance.