VOC Emission Controls for Can End Sealing Compounds

Regulations require that emissions of VOC from the application of can end sealing compounds be limited to 440 grams per liter. One can manufacturer has investigated the cost and feasibility of a VOC capture/control system and the availability and efficacy of water-based and high solids end sealing compounds. After characterizing and optimizing VOC evaporation rates, a prototype VOC containment system was tested on one can end sealing compound line. An 83 percent VOC capture efficiency was obtained at approximately 950 acfm. A cost analysis for a full facility capture and control system gave cost-effectiveness values of $1.21 to $2.36 per pound of VOC controlled. An evaluation oflow-VOC end sealing compounds, including long term pack tests, produced a water-based compound that could be implemented on pet food can ends by early 1986. Continuation of pack tests could allow full facility conversion to zero VOC water-based compounds by mid- to late-1987. Using an innovative averaging technique, the can manufacturer has achieved equivalent compliance with the 440 grams per liter standard.     

Evaluating factors influencing groundwater vulnerability to nitrate pollution: developing the potential of GIS

The 1991 EU Nitrate Directive was designed to reduce water pollution from agriculturally derived nitrates. England and Wales implemented this Directive by controlling agricultural activities within their most vulnerable areas termed Nitrate Vulnerable Zones. These were designated by identifying drinking water catchments (surface and groundwater), at risk from nitrate pollution. However, this method contravened the Nitrate Directive because it only protected drinking water and not all waters. In this paper, a GIS was used to identify all areas of groundwater vulnerable to nitrate pollution. This was achieved by constructing a model containing data on four characteristics: the quality of the water leaving the root zone of a piece of land; soil information; presence of low permeability superficial (drift) material; and aquifer properties. These were combined in a GIS and the various combinations converted into a measure of vulnerability using expert knowledge. Several model variants were produced using different estimates of the quality of the water leaving the root zone and contrasting methods of weighting the input data. When the final models were assessed all produced similar spatial patterns and, when verified by comparison with trend data derived from monitored nitrate concentrations, all the models were statistically significant predictors of groundwater nitrate concentrations. The best predictive model contained a model of nitrate leaching but no land use information, implying that changes in land use will not affect designations based upon this model. The relationship between nitrate levels and borehole intake depths was investigated since there was concern that the observed contrasts in nitrate levels between vulnerability categories might be reflecting differences in borehole intake depths and not actual vulnerability. However, this was not found to be statistically important. Our preferred model provides the basis for developing a new set of groundwater Nitrate Vulnerable Zones that should help England and Wales to comply with the EU Nitrate Directive.     

湖泊沉积物对磷酸盐的负吸附研究

分别在高、低两种磷酸盐质量浓度下，研究了6个湖泊沉积物对磷酸盐的负吸附。结果表明，(1)污染严重的湖泊沉积物不仅在上覆水体水质好转时，可能向上覆水体释放磷，即使上覆水体水质没有好转，在一定条件也可能释放；而较为清洁的湖泊沉积物，在上覆水体水质下降时，可能从上覆水体中吸附磷。在水质好转情况下，也可能向上覆水体中释放磷。(2)湖泊沉积物吸附磷酸盐过程中存在负吸附，吸附研究中使用较高质量浓度磷溶液是负吸附现象被掩盖的原因；在吸附研究中不仅要重视负吸附，而且初始磷酸盐质量浓度不能太高。(3)沉积物对磷酸盐的吸附／解吸平衡质量浓度与其有机质、CEC、总氮、总磷以及各形态磷含量均有显著的正相关关系，相比而言。与总磷以及各形态磷含量的相关性最高。污染较为严重的沉积物对磷酸盐的吸附／解吸平衡质量浓度也较高。     

Uptake and depuration of organic contaminants by blue mussels (Mytilus edulis) exposed to environmentally contaminated sediment

Experiments were designed to expose blue mussels (Mytilus edulis) to contaminated sediment collected from Narragansett Bay, Rhode Island, USA in 1982. Measurements were taken to allow comparisons of the uptake and depuration of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). In addition, concentration factors in the mussels were calculated separately against the dissolved and particulate phase concentrations and the results from the exposure and control systems were compared. Both PAHs and PCBs were rapidly accumulated by the mussels exposed to the contaminated sediment. After the mussels were transferred to control seawater, individual PAHs were depurated with half-lives ranging from 12 to 30 d. Individual PCBs showed depuration half-lives which ranged from 16 to 46 d. Concentration factors in the mussels calculated against the particulate phase concentrations were very different in the exposure and control systems. Concentration factors calculated using only the dissolved phase concentrations (bioconcentration factors) showed excellent agreement in the two systems, possibly an indication that the dissolved phase was the direct source of the contaminants accumulated by the mussels. The bioconcentration factors for PCBs were higher than those of PAHs when compounds with similar n-octanol/water partition coefficients were compared.     

Deconstructing an assemblage of “turtle” barnacles: species assignments and fickle fidelity in Chelonibia

Barnacles in the genus Chelonibia are commensal with a variety of motile marine animals including sea turtles, crustaceans, and sirenians. We conducted a worldwide molecular phylogenetic survey of Chelonibia collected from nearly all known hosts to assess species relationships, host-fidelity, and phylogeographic structure. Using DNA sequences from a protein-coding mitochondrial gene (COI), a mitochondrial rRNA gene (12S), and one nuclear rRNA gene (28S), we found that of four species, three (C. testudinaria, C. patula, and C. manati) are genetically indistinguishable. In addition, we show each utilizes a rare androdioecious mode of reproduction involving complemental males. In contrast, the fourth species (C. caretta), which is hermaphroditic and specializes on turtles, is genetically distinct—leading to the conclusion that the three former taxa are morphotypes of the same species and should be synonymized under C. testudinaria. Phylogenetic analysis resulted in three geographic clades (Atlantic, Indian Ocean/western Pacific, and eastern Pacific) with haplotype parsimony networks revealing no shared haplotypes among geographic regions. Analysis of molecular variance detected significant differences among sequences by region (p < 0.005); conversely, there were no significant differences among sequences when grouped by host or taxonomic designation. Average pairwise genetic distances were lower between the eastern Pacific and Atlantic clades (0.053 ± 0.006) than between the eastern Pacific and Indian Ocean/western Pacific clades (0.073 ± 0.008), suggesting Atlantic and eastern Pacific populations were connected more recently, perhaps until the rise of the Isthmus of Panama. Host use by Chelonibia morphotypes is discussed along with speculation on possible ancestral hosts and support for a “turtle-first” hypothesis.     

Forecasting New Zealand Mudsnail invasion range: model comparisons using native and invaded ranges.

Evaluations of the potential distribution of invasive species can increase the efficiency of their management by focusing prevention measures. Generally, ecological models are built using occurrence data from a species' native range to predict the distribution in areas that the species may invade. However, historical and geographical constraints can limit a species' native distribution. Genetic Algorithm for Rule-set Production (GARP), an ecological niche modeling program, was used to predict the potential distribution of the invasive, freshwater New Zealand mudsnail, Potamopyrgus antipodarum, in Australia and North America. We compared the strength of the predictions made by models built with data from the snail's native range in New Zealand to models built with data from the locations invaded by the species. A time-series analysis of the Australian models demonstrated that range-of-invasion data can make better predictions about the potential distribution of invasive species than models built with native range data. Large differences among the model forecasts indicate that uncritical choice of the data set used in training the GARP models can result in misleading predictions. The models predict a large expansion in the range of P. antipodarum in both Australia and North America unless prevention measures are implemented rapidly.     

Fetal tissue involvement in the late infantile type of neuronal ceroid lipofuscinosis

Prenatal diagnosis in a pregnancy at risk for late infantile neuronal ceroid lipofuscinosis (Batten's disease) was undertaken at 17 weeks' gestation by ultrastructural examination of amniotic fluid cells. The presence of curvilinear profiles indicated an affected fetus and the diagnosis was confirmed, after the pregnancy was terminated, by the finding of many typical curvilinear profiles in multiple tissues which included skin, amnion, umbilical vessels, blood, liver, and brain. Comparison between the involved cells in the amniotic fluid and fetal tissues suggests that these cells are probably derived from the periderm, and possibly also from the amnion. The prominent presence of cytosomes in the periderm and intermediate cells of the fetal epidermis and occasionally also in the endothelial cells of the dermis suggests that fetal skin may be a useful alternative site for assessing fetal involvement. Control specimens of the amniotic fluid, fetal skin, amnion, and liver showed no similar cytosomes. However, some control amniotic fluid samples did contain cells with large collections of irregular trilaminar membranes, and these could be open to misinterpretation. It is important that only typical curvilinear profiles are considered as an indication of an affected pregnancy.