Development of passive sampling devices for bioavailable contaminants of current and emerging concern: Waitemata Harbour case study     

M Stewart  M Cameron  M McMurtry  SG Sander  B Benedict  L Graham 《新西兰海洋与淡水研究杂志》2016,50(4):526-548

Bioavailable contaminant concentrations are an important component in assessing environmental effects as they directly affect ecosystem health. Shellfish contaminant monitoring programmes have traditionally filled this requirement but are being phased out in some jurisdictions. Passive sampling devices (PSDs) have the potential to replace shellfish monitoring; however, there are still knowledge gaps to address before this can occur. This study assessed the suitability of three different PSDs in providing the required information to replace shellfish monitoring. PSDs were deployed at three historic mussel monitoring sites with different levels of urban influence in the Waitemata Harbour, Auckland, New Zealand. Contaminants of interest were urban heavy metals, plus current and emerging organic contaminants. PSDs provided extremely low detection limits and, for some contaminants, very strong correlations to shellfish. PSDs can currently complement shellfish in monitoring, but it is premature to make conclusions as to the suitability of PSDs in replacing shellfish monitoring until more information is available.  相似文献   

The selectivity of slackly hung cod gillnets constructed from three different types of twine     

Stewart  Peter A. M. 《ICES Journal of Marine Science》1987,43(3):189-193

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A discus-hulled wave measuring buoy     

Robert H. Stewart 《Ocean Engineering》1977,4(2):101-107

Described herein is a self-contained, discus-hulled buoy 1.5 m dia., weighing 150 kg, which uses inertial instruments to measure wave height and tilt. Wave tank calibration and the theory of shallow draft buoys demonstrate such a hull accurately follows waves with length greater than twice the buoy diameter. The non-linear response of the buoy determines its sensitivity to low-frequency waves in a sea. And the ratio of wave signal to instrument “noise” is constant over the energetic part of the ocean-wave spectrum for measurements of wave acceleration and slope.  相似文献   

Effects of instream processes,discharge, and land cover on nitrogen export from southern Appalachian Mountain catchments     

Jackson R. Webster  Rebecca M. Stewart  Jennifer D. Knoepp  C. Rhett Jackson 《水文研究》2019,33(2):283-304

Catchments with minimal disturbance usually have low dissolved inorganic nitrogen (DIN) export, but disturbances and anthropogenic inputs result in elevated DIN concentration and export and eutrophication of downstream ecosystems. We studied streams in the southern Appalachian Mountains, USA, an area dominated by hardwood deciduous forest but with areas of valley agriculture and increasing residential development. We collected weekly grab samples and storm samples from nine small catchments and three river sites. Most discharge occurred at baseflow, with baseflow indices ranging from 69% to 95%. We identified three seasonal patterns of baseflow DIN concentration. Streams in mostly forested catchments had low DIN with bimodal peaks, and summer peaks were greater than winter peaks. Streams with more agriculture and development also had bimodal peaks; however, winter peaks were the highest. In streams draining catchments with more residential development, DIN concentration had a single peak, greatest in winter and lowest in summer. Three methods for estimating DIN export produced consistent results. Annual DIN export ranged from less than 200 g ha^?1 year^?1 for the less disturbed catchments to over 2,000 g ha^?1 year^?1 in the catchments with the least forest area. Land cover was a strong predictor of DIN concentration but less significant for predicting DIN export. The two forested reference catchments appeared supply limited, the most residential catchment appeared transport limited, and export for the other catchments was significantly related to discharge. In all streams, baseflow DIN export exceeded stormflow export. Morphological and climatological variation among watersheds created complexities unexplainable by land cover. Nevertheless, regression models developed using land cover data from the small catchments reasonably predicted concentration and export for receiving rivers. Our results illustrate the complexity of mechanisms involved in DIN export in a region with a mosaic of climate, geology, topography, soils, vegetation, and past and present land use.  相似文献   

The June 2013 Alberta Catastrophic Flooding Event: Part 1—Climatological aspects and hydrometeorological features          下载免费PDF全文

A. Q. Liu  C. Mooney  K. Szeto  J. M. Thériault  B. Kochtubajda  R. E. Stewart  S. Boodoo  R. Goodson  Y. Li  J. Pomeroy 《水文研究》2016,30(26):4899-4916

In June 2013, excessive rainfall associated with an intense weather system triggered severe flooding in southern Alberta, which became the costliest natural disaster in Canadian history. This article provides an overview of the climatological aspects and large‐scale hydrometeorological features associated with the flooding event based upon information from a variety of sources, including satellite data, upper air soundings, surface observations and operational model analyses. The results show that multiple factors combined to create this unusually severe event. The event was characterized by a slow‐moving upper level low pressure system west of Alberta, blocked by an upper level ridge, while an associated well‐organized surface low pressure system kept southern Alberta, especially the eastern slopes of the Rocky Mountains, in continuous precipitation for up to two days. Results from air parcel trajectory analysis show that a significant amount of the moisture originated from the central Great Plains, transported into Alberta by a southeasterly low level jet. The event was first dominated by significant thunderstorm activity, and then evolved into continuous precipitation supported by the synoptic‐scale low pressure system. Both the thunderstorm activity and upslope winds associated with the low pressure system produced large rainfall amounts. A comparison with previous similar events occurring in the same region suggests that the synoptic‐scale features associated with the 2013 rainfall event were not particularly intense; however, its storm environment was the most convectively unstable. The system also exhibited a relatively high freezing level, which resulted in rain, rather than snow, mainly falling over the still snow‐covered mountainous areas. Melting associated with this rain‐on‐snow scenario likely contributed to downstream flooding. Furthermore, above‐normal snowfall in the preceding spring helped to maintain snow in the high‐elevation areas, which facilitated the rain‐on‐snow event. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Facies in an Upper Permian volcanic succession,Emmaville Volcanics,Deepwater, northeastern New South Wales     

A. L. Stewart 《Australian Journal of Earth Sciences》2013,60(6):929-942

The Upper Permian Emmaville Volcanics at Deepwater, northeastern New South Wales, consist of a diverse succession of calc‐alkaline silicic‐intermediate ignimbrites, volcaniclastics and minor lavas. This 2.5 km‐thick sequence underlies and outcrops extensively along the northern margin of the Dundee Rhyodacite Outlier at Dundee. Detailed mapping and facies analysis have revealed eight locally mappable units namely; Magistrate Volcanic Member (rhyolitic ignimbrites), Wollundi Mudstone Member, Dellwood Ignimbrite Member, Marrawarra Rhyolite Member, Top‐Crossing Sandstone Member, Arranmor Ignimbrite Member, Yarramundi Andesite Member (lava, breccia) and Welcome Volcanic Member (rhyolitic ignimbrites). All volcanic units are contained in two fault‐bounded blocks of different lithology and structure. The volcanic succession ranges in composition from andesite to high‐silica rhyolite (58.6–78% SiO₂). Chemical characteristics include enrichment in K₂O (>3.5%), Al₂O₃ and large‐ion lithophile elements (LILE: Rb, K and light rare‐earth elements (LREE)), and depletion in high field strength elements (HFSE: Ti, Nb and Zr). These geochemical attributes reflect a continental subduction‐related signature. The facies architecture indicates that the principal volcanic features of the Late Permian palaeogeography in northeastern New South Wales was a topographically subdued depression flanked by low‐angle ignimbrite sheets with rhyolitic‐intermediate volcanic centres rising gently from the sloping terrain. The succession demonstrates that during the Late Permian andesitic volcanism was present, although localised. A modern analogue for the setting of the Emmaville Volcanics is the Quaternary Taupo Volcanic Zone (New Zealand).  相似文献   

Changing Times     

John P. Wilson  A. Stewart Fotheringham  David O'Sullivan 《Transactions in GIS》2012,16(1):1-2

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On the precipitation regions within two storms affecting Atlantic Canada     

N.R. Donaldson  R.E. Stewart 《大气与海洋》2013,51(1):108-129

Abstract

Two storms that produced heavy precipitation during the Canadian Atlantic Storms Program (CASP) field project are examined, with particular emphasis on their northern and western sectors. Precipitation was associated with upwards motion along the edges of an elevated warm core north of the surface low centre. Within the general pattern of precipitation, the highest rates occurred in narrow bands that were generally aligned with isotherms. The warm core contains regions of marginal symmetric instability and some of absolute instability.  相似文献   

Climate change and hydrology at the prairie margin: Historic and prospective future flows of Canada's Red Deer and other Rocky Mountain rivers          下载免费PDF全文

Laurens J. Philipsen  Karen M. Gill  Anita Shepherd  Stewart B. Rood 《水文研究》2018,32(17):2669-2684

The South Saskatchewan River Basin of southern Alberta drains the transboundary central Rocky Mountains region and provides the focus for irrigation agriculture in Canada. Following extensive development, two tributaries, the Oldman and Bow rivers, were closed for further water allocations, whereas the Red Deer River (RDR) remains open. The RDR basin is at the northern limit of the North American Great Plains and may be suitable for agricultural expansion with a warming climate. To consider irrigation development and ecological impacts, it is important to understand the regional hydrologic consequences of climate change. To analyse historic trends that could extend into the future, we developed century‐long discharge records for the RDR, by coordinating data across hydrometric gauges, estimating annual flows from seasonal records, and undertaking flow naturalization to compensate for river regulation. Analyses indicated some coordination with the Pacific decadal oscillation and slight decline in summer and annual flows from 1912 to 2016 (?0.13%/year, Sen's slope). Another forecasting approach involved regional downscaling from the global circulation models, CGCMI‐A, ECHAM4, HadCM3, and NCAR‐CCM3. These projected slight flow decreases from the mountain headwaters versus increases from the foothills and boreal regions, resulting in a slight increase in overall river flows (+0.1%/year). Prior projections from these and other global circulation models ranged from slight decrease to slight increase, and the average projection of ?0.05%/year approached the empirical trend. Assessments of other rivers draining the central and northern Rocky Mountains revealed a geographic transition in flow patterns over the past century. Flows from the rivers in Southern Alberta declined (around ?0.15%/year), in contrast to increasing flows in north‐eastern British Columbia and the Yukon. The RDR watershed approaches this transition, and this study thus revealed regional differentiation in the hydrological consequences from climate change.  相似文献   

An Assessment of Surface and Atmospheric Conditions Associated with the Extreme 2014 Wildfire Season in Canada’s Northwest Territories     

Bohdan Kochtubajda  Ronald E. Stewart  Mike D. Flannigan  Barrie R. Bonsal  Charles Cuell  Curtis J. Mooney 《大气与海洋》2019,57(1):73-90

Weather and climate are major factors influencing worldwide wildfire activity. This study assesses surface and atmospheric conditions associated with the 2014 extreme wildfires in the Northwest Territories (NWT) of Canada. Hot and dry conditions led to the NWT experiencing the most severe wildfire season in its recorded history. The season included a record number of cloud-to-ground lightning flashes and set a record for area burned. Lightning was the dominant ignition source and accounted for about 95% of the wildfires. Prolonged periods of smoke led to dramatic reductions in visibility, frequent road closures, and reduced air quality resulting in numerous health alerts. Temporal and spatial patterns of lightning characteristics in 2014, derived from Canadian Lightning Detection Network data, were different from those in other years with, for example, far more positive flashes from 0600 to 1200?utc (midnight to 6:00 am local time). The highest fraction of positive cloud-to-ground flashes (43.1%) occurred in the smoke-dominated North Slave region, which was more than in the Dehcho, South Slave, or Sahtu regions. Mid-tropospheric atmospheric circulation over a large region that included the NWT was classified into the six most common summer patterns. Results showed that ridging and ridge displacements occurred more frequently during 2014 although lightning was associated with all circulation patterns. This study has advanced the understanding of the roles of weather, lightning, and mid-tropospheric circulation patterns associated with extreme wildfires in northwestern Canada.  相似文献