Comparison of the Annular Denuder System and the Transition Flow Reactor for Measurements of Selected Dry Deposition Species

An intensive field study was conducted in Research Triangle Park, North Carolina in the fall of 1986. Ambient concentrations of the following constituents were obtained: nitric acid, nitrous acid, nitrogen dioxide, sulfur dioxide, ammonia, hydrogen ion, and particulate nitrate, sulfate, and ammonium. Results collected using the annular denuder system (ADS) and the transition flow reactor (TFR) are presented and compared.

Both types of samplers had operational detection limits on daily (22-hour) samples that were generally below 1 μg m_-3 suggesting that both samplers can provide sensitive measurements for most of the constituents of interest. Both the ADS and TFR show reasonable (>25 percent) within-sampler precision for most of the measured species concentrations, except TFR fine particulate nitrate measurements where results were frequently negative (The TFR fine particulate nitrate measurement is calculated using subtraction of positive numbers).

Comparison of ADS and TFR daily results showed good agreement for total particulate sulfate, the sum of total (coarse plus fine) particulate and gaseous nitrate, and ammonia. As a result of different inlet particle collection efficiencies, the ADS fine particulate sulfate exceeded the TFR (5 percent). In the absence of a filter to collect volatilized particulate ammonium in the ADS, the sum of total particulate and gaseous ammonium in the TFR exceeded that in the ADS. Of potentially more importance, ADS measurements of SO₂ and H⁺ exceeded those of the TFR, while TFR measurements of HNO₃ exceeded those of the ADS. Results of this study suggest that the TFR may provide biased measurements of SO₂, H⁺, HNO₃, and Fine NO₃ ^- that cannot be corrected without modifications to the fundamental design of the sampling system.     

Biological and chemical assessments of zinc ageing in field soils

As zinc (Zn) is both an essential trace element and potential toxicant, the effects of Zn fixation in soil are of practical significance. Soil samples from four field sites amended with ZnSO₄ were used to investigate ageing of soluble Zn under field conditions over a 2-year period. Lability of Zn measured using ⁶⁵Zn radioisotope dilution showed a significant decrease over time and hence evidence of Zn fixation in three of the four soils. However, 0.01 M CaCl₂ extractions and toxicity measurements using a genetically modified lux-marked bacterial biosensor did not indicate a decrease in soluble/bioavailable Zn over time. This was attributed to the strong regulatory effect of abiotic properties such as pH on these latter measurements. These results also showed that Zn ageing occurred immediately after Zn spiking, emphasising the need to incubate freshly spiked soils before ecotoxicity assessments.     

Contaminants in Muscle of Plaice and Halibut Collected From the St. Lawrence Estuary and Northwest Atlantic

Levels of aromatic hydrocarbons in muscle or plaice and halibut were determined by fluorescence, using the chrysene standard, as recommended by the International Oceanographic Commision, for the analysis of PAH in environmental extracts. Concentrations were highest in muscle of halibut collected at the most contaminated, nearshore site, in the Saguenay Fjord of the St. Lawrence Estuary, compared to other locations further from shore. Although concentrations of fluorescing compounds were not statistically different in plaice, the saturated hydrocarbons displayed unquestionably more biodegradation, with a decrease of n-alkanes and increase of branched aliphatics, at the less contaminated site. Synchronous fluorescence indicated the presence of benzenoid and biphenyl hydrocarbons in the extracted mixtures, while GC-MS-TIC analysis tentatively identified the presence of a series of benzenoid (alkyl benzenes), chlorinated (PCB and DDE), N (trialkylamines) and O (phenols) hydrocarbons. These anthropogenic compounds could derive from petroleum products, surfactants and common products used in industry and households. This study emphasizes the importance of a multispectroscopic approach when investigating complex environmental mixtures.     

Indicators of ecosystem health at the species level and the example of selenium effects on fish

Chemical monitoring of aquatic ecosystems describes the chemical exposures of aquatic biota and measures the success of pollution control. However, meeting water quality criteria cannot assure that aquatic biota are protected from the effects of unexpected chemicals, mixtures and interactions between toxicity and environmental stressors.Biological monitoring is an obvious solution since aquatic biota integrate spatial and temporal variations in exposure to many simultaneous stressors. Top predators, typical of specific ecosystems (e.g. lake trout in cold water oligotrophic lakes) indicate whether environmental criteria have been met. The presence of naturally reproducing, self-sustaining and productive stocks of edible fish demonstrates a high quality environment. If these conditions are not met, there is a clear sign of environmental degradation. Specific changes in population structure and performance may also diagnose which life stage is affected and the nature of the stressor.Unfortunately, environmental managers cannot rely solely on populations, communities or ecosystems to indicate chmical effects. The lag between identifying a problem and finding a cause may destroy the resource that we wish to protect, particularly where chemicals are persistent.A solution to this dilemma is the measurement of primary or secondary responses of individual organisms to chemical exposure. Since toxicity at any level of organization must start with a reaction between a chemical and a biological substrate, these responses are the most sensitive and earliest sign of chemical exposure and effect.Application of this idea requires research on molecular mechanisms of chemical toxicity in aquatic biota and adaptation of existing mammalian diagnostic tools. Since relevance of biochemical responses to populations and ecosystems is not obvious, there is a need to study the links between chemical exposure and responses of individuals, populations and ecosystems.The recognition of chemical problems and cause-effect relationships requires the integration of chemical and biological monitoring, using the principles of epidemiology to test the strength of relationships and to identify specific research needs. The contamination of a reservoir with selenium and impacts on fish populations provide an excellent example of this approach.     

Lignocellulose and lignin in the salt marsh grass Spartina alterniflora: initial concentrations and short-term,post-depositional changes in detrital matter

Individuals of Mytilus edulis of the same age (ca 2 months) were collected as spat from natural populations. Relative growth rates were determined among individuals differing in heterozygosity at five enzyme loci. Growth rate was positively correlated with individual heterozygosity and each of the five loci contributed about equally to the relatinship. More heterozygous individuals also achieved more uniform average growth rates. Although there was a deficiency of heterozygotes at each locus, relative to Hardy-Weinberg expectations, the magnitude of the deficiency, measured as F_IS, was less among faster growing mussels. Our results conform closely with those of Zouros et al. (1980) on the American oyster. We conclude that the relationship between multiple locus heterozygosity and growth rate is one that is general to a diversity of outbreeding plant and animal populations. Other studies indicate that this relationship is due to a greater average metabolic efficiency of more heterozygous individuals. This relationship does not emerge from experimental designs in which there has been limited genetic sampling of the natural genetic variation.     

Improved methodology for ATP determination in marine environments

A simple technique is described for de-salting and concentrating adenosine triphosphate (ATP) extracted from seawater or marine sediment samples prior to assays with the standard luciferin-luciferase procedure. The technique involves chromatography of H₂SO₄ extracts on columns of activated carbon. The efficiency of ATP recovery from marine sediments using this pre-treatment was superior to that attained with either boiling Tris extraction or with H₂SO₄ extraction without subsequent purification. All ions which interfere with the luciferase reaction or precipitate ATP upon neutralization of acid extracts are removed with this procedure, thus eliminating the 50- to 100-fold dilutions required with other acid-extraction procedures. In addition, the purified ATP extracts may be concentrated up to 100-fold, thus greatly improving the sensitivity of ATP measurement in samples containing very low biomass. This procedure has been applied to ATP determination in marine sediments in the upwelling area off northwest Africa. The average ATP concentrations in the upper 6 cm of sediment from 1000 and 200 m were 195 and 545 ng per ml wet sediment, respectively.     

Heavy metals--geochemical bogey men?

Heavy metals is a loose term usually used to indicate environmentally "bad" metals. It is poorly defined with a multitude of often contradictory definitions based on density, atomic weight, atomic number or other properties of the elements or their compounds. Alternative, scientifically rigorous definitions exist for subgroups of metals and should be used instead.     

The influence of time on lead toxicity and bioaccumulation determined by the OECD earthworm toxicity test

Internationally agreed standard protocols for assessing chemical toxicity of contaminants in soil to worms assume that the test soil does not need to equilibrate with the chemical to be tested prior to the addition of the test organisms and that the chemical will exert any toxic effect upon the test organism within 28 days. Three experiments were carried out to investigate these assumptions. The first experiment was a standard toxicity test where lead nitrate was added to a soil in solution to give a range of concentrations. The mortality of the worms and the concentration of lead in the survivors were determined. The LC50s for 14 and 28 days were 5311 and 5395 microgPb g(-1)soil respectively. The second experiment was a timed lead accumulation study with worms cultivated in soil containing either 3000 or 5000 microgPb g(-1)soil. The concentration of lead in the worms was determined at various sampling times. Uptake at both concentrations was linear with time. Worms in the 5000 microg g(-1) soil accumulated lead at a faster rate (3.16 microg Pb g(-1)tissue day(-1)) than those in the 3000 microg g(-1) soil (2.21 microg Pb g(-1)tissue day(-1)). The third experiment was a timed experiment with worms cultivated in soil containing 7000 microgPb g(-1)soil. Soil and lead nitrate solution were mixed and stored at 20 degrees C. Worms were added at various times over a 35-day period. The time to death increased from 23 h, when worms were added directly after the lead was added to the soil, to 67 h when worms were added after the soil had equilibrated with the lead for 35 days. In artificially Pb-amended soils the worms accumulate Pb over the duration of their exposure to the Pb. Thus time limited toxicity tests may be terminated before worm body load has reached a toxic level. This could result in under-estimates of the toxicity of Pb to worms. As the equilibration time of artificially amended Pb-bearing soils increases the bioavailability of Pb decreases. Thus addition of worms shortly after addition of Pb to soils may result in the over-estimate of Pb toxicity to worms. The current OECD acute worm toxicity test fails to take these two phenomena into account thereby reducing the environmental relevance of the contaminant toxicities it is used to calculate.     

Effects of metals on life cycle parameters of the earthworm Eisenia fetida exposed to field-contaminated, metal-polluted soils

Two control and eight field-contaminated, metal-polluted soils were inoculated with Eisenia fetida (Savigny, 1826). Three, 7, 14, 21, 28 and 42 days after inoculation, earthworm survival, body weight, cocoon production and hatching rate were measured. Seventeen metals were analysed in E. fetida tissue, bulk soil and soil solution. Soil organic carbon content, texture, pH and cation exchange capacity were also measured. Cocoon production and hatching rate were more sensitive to adverse conditions than survival or weight change. Soil properties other than metal concentration impacted toxicity. The most toxic soils were organic-poor (1-10 g C kg(-1)), sandy soils (c. 74% sand), with intermediate metal concentrations (e.g. 7150-13,100 mg Pb kg(-1), 2970-53,400 mg Zn kg(-1)). Significant relationships between soil properties and the life cycle parameters were determined. The best coefficients of correlation were generally found for texture, pH, Ag, Cd, Mg, Pb, Tl, and Zn both singularly and in multivariate regressions. Studies that use metal-amended artificial soils are not useful to predict toxicity of field multi-contaminated soils.     

The estimation of the photodegradation of organic compounds by hydroxyl radical reaction rate constants obtained from nuclear magnetic resonance spectroscopy chemical shift data

The use of nuclear magnetic resonance chemical shift data for predicting the rate of photodegradation of organic chemicals in air, due to reaction with hydroxyl radicals, has been critically examined. Relationships between the average ¹³C or ¹H chemical shift and the hydroxyl radical rate constant have been studied for a wide range of compounds. Recommendations regarding the utility of the procedure are made.