Performance of an in situ passive sampling system for metals in stormwater

A passive sampler has been developed and is demonstrated in situ for urban runoff. The passive sampler is compared to conventional composite (time-dependent and flow-weighted) bottle sampling during and between storm events. The sampling was carried out at established stormwater stations; before and after a stormwater detention pond. In situ deployment of the passive sampler provides the metal concentrations, corresponding to the electrochemically available fraction of total metal, for time-dependent samples collected in parallel. The sampler provides improved accuracy compared to bottle sampling because contamination during sample transport and handling is minimised. Laboratory handling is reduced by direct analysis of the accumulated metals on the receiving membrane by laser ablation inductively coupled plasma mass spectrometry. Passive sampling also solves the problem of metal speciation change during transport to the laboratory, which is a potential problem for bottle samples. The low cost and convenience of the passive sampler and subsequent analysis should allow significantly more extensive spatial and temporal monitoring of metals in the aquatic environment than has previously been possible.     

Establishing the Canadian Community Monitoring Network

Community-based ecosystem monitoring activities in Canada are increasing in response to a number of factors including: (i) the needs of decision-makers for timely information on local environmental changes; (ii) limited use of government monitoring data and information by decision makers; (iii) government cuts to monitoring programs; (iv) the increasingly recognized need to include stakeholders in planning and management processes; and (v) the desire of citizens to contribute to environmental protection. To date there has been no network coordination of community based monitoring in Canada. This paper reports on the establishment of the Canadian Community Monitoring Network by Environment Canada's Ecological Monitoring and Assessment Network Coordinating Office and the Canadian Nature Federation. Information on research prepared in support of network establishment is presented along with a discussion of the potential of the network.     

Biological monitoring of a pulp and paper mill wastewater

The physico-chemical testing required under the E.P.A. licence enables one to gauge the chemical effects of the APM wastewater on the Latrobe River, but it tells us nothing about likely effects on the aquatic biota. The APM bio-monitoring programme was instigated to provide evidence of any effects of wastewater discharges on the rivers biota. To date the programme has shown no adverse impact downstream. The laboratory bioassays on fish and algae have recently given way to the river fauna surveys as the regular monitor of wastewater quality. It is intended to continue with regular river surveys using the river's residents as indicators of water quality and future surveys will investigate reasons for the presently obscure variation in macro-invertebrate populations.     

Post-remediation evaluation of a LNAPL site using electrical resistivity imaging

Present understanding of the earth's subsurface is most often derived from samples at discrete points (wells) and interpolations or models that interpret the space between these points. Electrical resistivity imaging techniques have produced an improved capability to map contaminants (especially NAPLs--NonAqueous Phase Liquids) away from traditional wells using actual field data. Electrical resistivity image data, confirmed by drilling, have demonstrated that LNAPL (Light NAPL--less dense than water, such as gasoline) contaminants exist outside of a delineated and remediated area in Golden, Oklahoma. The data also demonstrate that LNAPL exists between monitoring and remediation wells which indicate low contaminant levels when sampled. Additionally, the electrical images provided the drilling location with the highest concentration of hydrocarbon ever found on the site, even after two phases of remediation work had been performed, although the sampling protocols varied. The results indicate that current methods of post-remediation site characterization are inadequate for complete site characterization.     

The changing nature of the 206Pb/207Pb isotopic ratio of lead in rainwater, atmospheric particulates, pine needles and leaded petrol in Scotland, 1982-1998

The inductively coupled plasma-mass spectrometry (ICP-MS)-determined 206Pb/207Pb ratio of 145 samples of rainwater collected at 25 locations around Scotland during December 1997 and January 1998 and at three longterm monitoring stations in the northeast, central belt and southeast of the country from November 1997 to December 1998 averaged 1.144+/-0.017 (1 s). This represents a significant increase from the mean value of 1.120+/-0.016 recorded for the long-term sites in 1989 1991, only partly attributable to a concomitant increase in the 206Pb/207Pb ratio of leaded petrol from 1.075+/-0.013 to 1.088+/-0.007. The rainwater 206Pb/207Pb data for the late 1990s also contrast markedly with the lower 206Pb/207Pb ratios found for pine needle and atmospheric particulate samples from Scotland (e.g. Glasgow: 1.085+/-0.012 in 1985-1986, 1.099+/-0.007 in 1991-1992), England and Western Europe in this study for the period 1982-1992 when emissions of lead to the atmosphere from petrol-engined vehicles in the UK were approximately 2-9 times higher. The observed change in the lead isotopic signature of rainwater predominantly reflects the impact of measures, such as the introduction and growing uptake of unleaded petrol, to reduce car exhaust emissions of lead to the atmosphere in the UK. Based on the rainwater data, source apportionment calculations suggest a general decline in the contribution of leaded petrol to atmospheric lead in Scotland from 53-61% in 1989-1991 to 32-45% in 1997-1998, with a corresponding decline in the urban environment from 84-86% to 48-58%.     

Saturated and Unsaturated Water Flow in Inclined Porous Media

This paper considers the two-dimensional saturated and unsaturated flow of water through inclined porous media, namely a waste dump or hill slope. Since the partial differential equation governing this water flow transforms from being parabolic to elliptic as the water flow varies from unsaturated to saturated, an iterative, finite differencing scheme is used to develop a numerical solution. The model can be used to investigate the effects that hill slope angle, depth of soil cover and hilltop width have on water accumulation in the dump and the time required for saturation to occur at different areas in the dump domain. The accuracy and reliability of the computer based solution is tested for two different boundary conditions – (1) no flow on all boundaries (i.e., the internal redistribution of soil moisture to steady state) and (2) a constant rainfall flux on the dump surface. Numerical studies then show the effects of changing the hill slope angle, depth of layer, and dump geometry on the flow characteristics in the dump.     

A Comparison of Aerial and Ground Level Measurements of 137Cs in the Marshall Islands

The purpose of this paper is to present and compare two independent sets of environmental gamma spectrometry measurements of¹³⁷ Cs collected nearly 14 years apart. One set of data was collected in 1978 by a contractor of the U.S. Department of Energy during an aerial radiological survey of the northern atolls of the Marshall Islands. That program used helicopter mounted sodium-iodide scintillation detectors; measurements were made from an altitude of 38 m. The second measurement program was conducted from early 1990 through late 1994 by the Republic of the Marshall Islands Government in a survey of the entire nation. This latter program used ground level in situ gamma spectrometry with high-purity germanium detectors. In this comparison, we highlight differences between the findings of the two studies and probable reasons for those differences, though we also discuss the effectiveness of the two techniques for monitoring the ionizing radiation environment. In the comparison of exposure rates from ¹³⁷Cs, fair agreement was noted after accounting for radioactive decay during the intervening years. Though the distributions were statistically different over their entire range, they were nearly identical above 1 R h^-1. There was considerable difference in the estimates of¹³⁷ Cs inventory; the difference was greater at low activity levels with the NaI measurements consistently larger than the in situ measurements. Reasons for this difference is attributed to three factors which differed between the two studies: (1) the assumed penetration of the cesium into the soil column, (2) the assumption of soil density, and (3) differences in the ability of the two different detector systems to reject interfering spectral contributions. Precise measurement of the lowest levels has implications for determining those atolls that exceeded the deposition of ¹³⁷Cs from global fallout. This issue is discussed in addition to a comparison of the findings from the two measurement programs.     

Coral reef aerosol emissions in response to irradiance stress in the Great Barrier Reef,Australia

We investigate the correlation between stress-related compounds produced by corals of the Great Barrier Reef (GBR) and local atmospheric properties—an issue that goes to the core of the coral ecosystem’s ability to survive climate change. We relate the variability in a satellite decadal time series of fine-mode aerosol optical depth (AOD) to a coral stress metric, formulated as a function of irradiance, water clarity, and tide, at Heron Island in the southern GBR. We found that AOD was correlated with the coral stress metric, and the correlation increased at low wind speeds, when horizontal advection of air masses was low and the production of non-biogenic aerosols was minimal. We posit that coral reefs may be able to protect themselves from irradiance stress during calm weather by affecting the optical properties of the atmosphere and local incident solar radiation.     

The determinants of job seekers' reputation perceptions

Although job seekers' reputation perceptions may be based on different factors than other constituents (e.g., investors, consumers), we know little about the antecedents of job seekers' reputation perceptions. The present study utilizes verbal protocol analysis to explore the factors that job seekers consider when evaluating employers' reputations. Results from this qualitative investigation are complemented and cross‐validated with an experimental policy capturing study and a field study of recruiting organizations. Data from all three methodologies suggest that some factors affecting job seekers' reputation perceptions are quite different from factors that have been revealed in previous reputation research, which has focused primarily on executives. For example, results from the present study reveal that the type of industry in which a firm operates, the opportunities that a firm provides for employee development, and organizational culture affect job seekers' reputation perceptions. Copyright © 2000 John Wiley & Sons, Ltd.     

Solvent-Free Polymerization of l-Aspartic Acid in the Presence of d-Sorbitol to Obtain Water Soluble or Network Copolymers

l-Aspartic acid was thermally polymerized in the presence of d-sorbitol with the goal of synthesizing new, higher molecular weight water soluble and absorbent copolymers. No reaction occurred when aspartic acid alone was heated at 170 or 200 °C. In contrast, heating sorbitol and aspartic acid neat or with ammonium hydroxide gave a mixture of water soluble and insoluble copolymers of polysuccinimide and sorbitol. In the presence of phosphoric acid, sorbitol aspartate ester copolymers having both water soluble and highly swollen gel components were formed. These results indicate that polysaccharides such as sorbitol can readily react to form copolymer ester/amides with aspartic acid and such copolymers may have utility as biodegradable water soluble and swellable polyampholytes.