Net-pen salmon aquaculture has well-known effects on coastal ecosystems: farm waste increases sediment organic content and the incidence of sediment anoxia, supports increased production of deposit-feeding invertebrates, and attracts higher densities of demersal fish and other mobile carnivores. These impacts are widely considered to be localized and transitory, and are commonly managed by imposing a period of fallowing between cycles of production. The implications of these ecosystemic effects for contaminant cycling, however, have not previously been considered. We found elevated levels of mercury in demersal rockfishes near salmon farms in coastal British Columbia, Canada, attributable to a combination of higher rockfish trophic position and higher mercury levels in prey near farms. Mercury concentrations in long-lived species such as rockfishes change over a longer time scale than cycles of production and fallowing, and thus at least some important effects of fish farms may not be considered transitory.
A methodology for monitoring low level of caffeine in aqueous samples via gas chromatography coupled with an ion-trap tandem mass spectrometry detection system (IT-MS/MS) was developed. Four IT-MS/MS operating parameters, including the collision-induced dissociation (CID) voltage, the excitation time (ET), the isolation time (IT) and the maximum ionization time (MIT) were optimized in order to maximize the sensitivity of the IT-MS/MS technique towards the analyte and its isotope-labeled standard. After optimization, a limit of detection of 500 fg microl(-1) with S/N = 3 was achieved. Taking into account blank values and the matrix background, a method detection limit of 1.0-2.0 ng l(-1) was derived and applied to all of the samples analyzed in the study. Various mass spectrometric conditions have been applied to caffeine and its trimethyl-(13)C-labeled standard to elucidate fragmentation pathways for new and commonly occurring product ions observed in the collision-induced dissociation (CID) spectra produced by the ion trap. Ion structures and fragmentation pathway mechanisms have been proposed and compared with previously published data. An isotope dilution method using (13)C-labeled caffeine as a surrogate internal standard was employed to determine and correct the recovery of native caffeine in water samples. The developed methodology has been applied for the determination of caffeine in surface marine and freshwater samples collected on the west coast of Vancouver Island in British Columbia, Canada. The results obtained for the marine water samples indicated a wide variation in the level of caffeine, ranging from 4.5 to 149 ng l(-1), depending on the location of the sampling site within the inlet. The concentrations of caffeine in samples from lakes associated with various residential densities ranged from ND to 6.5, 1.8 to 10.4 and 6.1 to 21.7 ng l(-1) for low, moderate and high residential densities, respectively.
Recently it has been shown that stable isotopes of nitrogen can be used to discriminate between organic and synthetic fertilizers, but the robustness of the approach is questionable. This work developed a comprehensive method that is far more robust in identifying an adulteration of organic nitrogen fertilizers. Organic fertilizers of various types (manures, composts, blood meal, bone meal, fish meal, products of poultry and plant productions, molasses and seaweed based, and others) available on the North American market were analyzed to reveal the most sensitive criteria as well as their quantitative ranges, which can be used in their authentication. Organic nitrogen fertilizers of known origins with a wide δ(15)N range between -0.55 and 28.85‰ (n = 1258) were characterized for C and N content, δ(13)C, δ(15)N, viscosity, pH, and nitrogen profile (urea, ammonia, organic N, water insoluble N, and NO3). A statistically significant data set of characterized unique organic nitrogen fertilizers (n = 335) of various known origins has been assembled. Deliberately adulterated samples of different types of organic fertilizers mixed with synthetic fertilizers at a wide range of proportions have been used to develop the quantitative critical characteristics of organic fertilizers as the key indicators of their adulteration. Statistical analysis based on the discriminant functions of the quantitative critical characteristics of organic nitrogen fertilizers from 14 different source materials revealed a very high average rate of correct classification. The developed methodology has been successfully used as a source identification tool for numerous commercial nitrogen fertilizers available on the North American market.
The use of nitrogen stable isotopes to discriminate between conventionally and organically grown crops has been further developed in this study. Soil and irrigation water from different regions, as well as nitrogen fertilizers used, have been examined in detail to determine their effects on nitrogen isotope composition of spinach, lettuce, broccoli and tomatoes. Over 1000 samples of various types of organically and conventionally grown produce of known origin, along with the samples of nitrogen fertilizers used for their growth, have been analysed in order to assemble the datasets of crop/fertilizer correlations. The results demonstrate that the developed approach can be used as a valuable component in the verification of agricultural practices for more than 25 different types of commercially grown green produce, either organic or conventional. Over a period of two years, various organic and non-organic greens, from different stores in Seattle (WA, USA) and Victoria (BC, Canada), were collected and analysed using this methodology with the objective of determining any pattern of misrepresentation.
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