A ten channel fibre-optic device for distributed sensing of underground hydrocarbon leakage

With millions of fuel storage tanks and oil pipelines installed around the world, there is inevitably frequent leakage of potentially hazardous hydrocarbons. As many of these installations are below ground, it can often be many years before the extent of the leak is discovered. We have previously reported the development of a sensor for the detection of such subterranean leaks, using infrared reflectometry to interrogate a hydrocarbon sensitive membrane. However, a single sensor cannot provide any information about the flow rate or direction of the leak. This paper describes the extension of the technology to a multi-channel distributed sensing system, using optical fibres capable of distributing the sensors over large subterranean areas. Results are reported from the evaluation of the device, which consisted of monitoring the movement of different hydrocarbons (gasoline, diesel and insulating oil) through a vertical sand-filled vessel.     

Detecting and characterising sources of persistent organic pollutants (PAHs and PCBs) in surface sediments of an industrialized area (harbour of Trieste, northern Adriatic Sea)

A sediment sampling based on a two-dimensional mapping was performed in the harbour of Trieste (northern Adriatic Sea), considering 28 sites exposed to pollutant inputs from harbour and industrial activities. Polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were determined in surface sediments, because these very persistent pollutants seem to be responsible for the depletion of benthic populations observed in this area. The correlation matrix indicates that PAHs and PCBs are non-correlated, and probably have different sources. Both cluster analysis performed on the sampling sites and graphical drawing of the PAH sediment contents make it possible to locate along the shoreline a band of more polluted sediments, clustered around a site facing a steelmaking factory, to be considered as the main source point for PAHs. The evaluation of phenanthrene to anthracene (P/AN) and fluoranthene to pyrene (FL/PY) ratios permits the assessment of the pyrolytic, industrial origin of these PAHs, rejecting a second possible source of hydrocarbons (i.e., an oil-pipeline terminal, situated near the steelmaking factory). Graphical drawing of the total PCB iso-concentrations reveals a different source-point for this other category of very persistent pollutants.     

Accuracy and traceability in environmental monitoring--pitfalls in methylmercury determinations as a case study

The concepts of accuracy and traceability as applied to environmental analysis are still prone to misunderstandings. While accuracy refers to the closeness of analytical values to "true values" (trueness) and among various repetitions (precision), the term traceability implies a link of data obtained to established references through an unbroken chain of comparisons all with stated uncertainties. These misunderstandings, possibly occurring among the analytical community, may have consequences on environmental data interpretation. Recent discussions in the field of environmental speciation analysis illustrated that accuracy and traceability issues are still not firmly established within the environmental chemistry community. This paper discusses this issue, taking methylmercury as a case study.     

Organochlorine contaminants in seabird eggs from the Pacific coast of Canada, 1971–1986

Eggs were collected from seven seabird species at colonies on the British Columbia coast from 1983 to 1986 and analyzed for organochlorine contaminants. Total PCB levels (wet weight) were highest in double-crested cormorants (Phalacrocorax auritus) from the Fraser estuary (2.91 mg kg^-1) and the Strait of Georgia (3.79 mg kg^-1). Highest DDE levels were in fork-tailed storm-petrels (Oceanodroma furcata) from the Queen Charlotte Islands (1.68 mg kg^-1). Organochlorine levels were generally lower in eggs from the mid 1980s than in those collected in the early 1970s. Organochlorine levels in Pacific alcids and hydrobatids foraging in offshore locations were compared to those in the same or ecologically similar species from the Canadian Atlantic coast. DDT- and HCH-related compounds were higher in Pacific populations while levels of dieldrin, oxychlordane, and HCB were generally lower. With the exception of -HCH, levels of all measured organochlorines were lower in cormorants breeding in the Fraser River estuary than in cormorants from the St. Lawrence River estuary on the Atlantic coast.     

Organochlorine and mercury residues in Swainson's and ferruginous hawk eggs collected in North and South Dakota, 1974–79

Residues of organochlorine pesticides, polychlorinated biphenyls (PCBs), and mercury were measured in eggs of Swainson's hawks (Buteo swainsoni) and ferruginous hawks (B. regalis) collected in North and South Dakota during 1974–79. DDE was the most common compound detected in the eggs, but residues were below levels known to have adverse effects on reproduction. Other organochlorine compounds and mercury were found at low levels. Eggs of ferruginous hawks tended to contain more compounds with higher residues than eggs of Swainson's hawks.     

Second derivative spectroscopy for the determination of volatilized ammonia from urea-amended soil

A second derivative spectrometer custom fitted with a 1 m stainless steel White cell and maintained at 105°C is used to make real-time measurements of volatilized NH₃ from urea-amended soil. Comparison of the technique to impinger data shows a 5–16% discrepancy between the two techniques; however, other experiments presented suggests that this is not real. Sulfur dioxide and nitrous oxide interferences are discussed, though they were not found to be present in this study. Instrument response time is shown to be fast if 67% of the total response is achieved in less than 5 min. Fast response is achieved for ammonia if wall-adsorption effects are minimal and if ammonia mass flow is maintained at 0.2 μg min^-1.     

Water quality test based on dielectrophoretic measurements of fresh water algae Selenastrum capricornutum

A method is described whereby dielectrophoresis of algal cells is used to perform rapid water quality analysis, specifically detecting the presence of CuSO4. The dielectric collection spectrum of the fresh water alga Selenastrum capricornutum was determined for a range of concentrations of CuSO4 from 25 mg L(-1) to 0.25 mg L(-1) for exposure times of 15 min and 18 h. In all cases increasing the concentration of CuSO4 reduced cell collection, but a step reduction was observed in collection between 2 mg L(-1) and 5 mg L(-1). This method has potential for forming a rapid, low-cost test for water quality with broad specificity and significantly reduced analysis time compared to current methods.