Water Resources: The Delaware Basin

Philadelphia is in competition with New York City and Baltimore in staking a claim for the water resources it will need in the next half century and beyond. A new governmental organization having a delegation of both state and federal powers for continuous planning and for unified management and control of the water resources of the entire Delaware River Basin has been proposed; and a federal-state compact for its establishment is being negotiated.     

Polychlorinated naphthalenes in air and snow in the Norwegian Arctic: a local source or an Eastern Arctic phenomenon?

PCNs were measured in air and snow during separate field campaigns at Ny-Alesund (April 2001) and Troms? (February/March 2003) in the Norwegian Arctic. Air concentrations ranged from 27 to 48 and 9 to 47 pg sigmaPCN m(-3) for Ny-Alesund (n=6) and Troms? (n=10), respectively. These concentrations (including the tri-chlorinated naphthalenes) greatly exceeded concentrations previously measured in the Canadian Arctic, but did fall within the upper range of concentrations observed over the eastern Arctic Ocean and regional seas. Local sources appear to be affecting concentrations observed at both sites, with the presence of several hexa-chlorinated naphthalenes at Troms? probably attributed to local/regional sources. Use of air mass back trajectories at Troms? revealed that background air concentrations in the Norwegian Arctic are likely to range between <9 and 20 pg sigmaPCN m(-3) and that contemporary concentrations derived close to potential sources (i.e. arctic towns) may equal or exceed those of PCBs. The mean concentration in surface snow was 350 and 240 pg sigmaPCN L(-1) (meltwater) (or 0.014 and 0.01 pg g(-1) (snow)) at Ny-Alesund and Troms?, respectively. The wide variation in concentrations observed between fresh snowfalls could be explained by different snow densities (as a surrogate of snow surface area), rather than attributed to varying air concentrations. A statistically significant inverse relationship was found between snow density and concentrations of tri- to penta-chlorinated homologues and compliments similar findings for the polychlorinated biphenyls (PCBs). This suggests that the vapour-sorbed quantity changes rapidly with snow ageing/compaction; with implications for the fate of these chemicals in the Arctic.     

Continuous-flow metal biosorption in a regenerable Sargassum column

Metal biosorption behavior of raw seaweed S. filipendula in ten consecutive sorption-desorption cycles has been investigated in a packed-bed flow-through column during a continuous removal of copper from a 35mg/L aqueous solution at pH 5. The elutant used was a 1% (w/v) CaCl2/HCl-solution at pH 3. The sorption and desorption was carried out for an average of 85 and 15h, respectively, representing more than 41 days of continuous use of the biosorbent. The weight loss of biomass after this time was 21.6%. The Cu-biosorption capacity of the biomass, based on the initial dry weight, remained relatively constant at approximately 38 mg Cu/g. Loss of sorption performance was indicated by a shortening breakthrough time and a broadening mass-transfer zone. The column service time, considered up to 1 mg Cu/L in the effluent, decreased continuously from 25.4 h for the first to 12.7 h for the last cycle. The critical bed length, representing the mass-transfer zone, increased almost linearly from 28 to 34cm. "Life-factors" for S. filipendula were found to be 0.0008h(-1) for the breakthrough time and 0.008cm/h for the critical bed length, using an exponential decay and linear fitting functions, respectively. Regeneration with CaCl2/HCl at pH 3 provided elution efficiencies up to 100%. Maximum concentration factors were determined to be in the range 16-44, a decreasing tendency was observed with an increasing exposure time.     

Modelling air pollution for epidemiologic research--part II: predicting temporal variation through land use regression

Over recent years land use regression (LUR) has become a frequently used method in air pollution exposure studies, as it can model intra-urban variation in pollutant concentrations at a fine spatial scale. However, very few studies have used the LUR methodology to also model the temporal variation in air pollution exposure. The aim of this study is to estimate annual mean NO₂ and PM₁₀ concentrations from 1996 to 2008 for Greater Manchester using land use regression models. The results from these models will be used in the Manchester Asthma and Allergy Study (MAAS) birth cohort to determine health effects of air pollution exposure.The Greater Manchester LUR model for 2005 was recalibrated using interpolated and adjusted NO₂ and PM₁₀ concentrations as dependent variables for 1996-2008. In addition, temporally resolved variables were available for traffic intensity and PM₁₀ emissions. To validate the resulting LUR models, they were applied to the locations of automatic monitoring stations and the estimated concentrations were compared against measured concentrations.The 2005 LUR models were successfully recalibrated, providing individual models for each year from 1996 to 2008. When applied to the monitoring stations the mean prediction error (MPE) for NO₂ concentrations for all stations and years was -0.8 μg/m³ and the root mean squared error (RMSE) was 6.7 μg/m³. For PM₁₀ concentrations the MPE was 0.8 μg/m³ and the RMSE was 3.4 μg/m³.These results indicate that it is possible to model temporal variation in air pollution through LUR with relatively small prediction errors. It is likely that most previous LUR studies did not include temporal variation, because they were based on short term monitoring campaigns and did not have historic pollution data. The advantage of this study is that it uses data from an air dispersion model, which provided concentrations for 2005 and 2010, and therefore allowed extrapolation over a longer time period.     

Earthquake-induced net section fracture in brace connections — experiments and simulations

Results from six tests, finite element simulations and a synthesis of previous test programs on slotted end bracing connections are presented. The main objective of the research is to examine the deformation capacity of these connections, with the ultimate objective of minimizing the requirement for net section reinforcement that is often inconvenient from the perspective of fabrication. The experiments and simulations feature commonly used pipe specimens and end details. The main parameters investigated include the gusset plate thickness, the slot length and introduction of a wrap-around weld that eliminates the reduced section at the edge of the gusset plate. The results indicate that even without reinforcement, the connections offer adequate to excellent deformation capacity if they are provided with the wrap-around weld or if the net section strength is larger than the gross yield strength. This may be achieved in situations where shear lag in the connection is minimal, and where the area reduction due to the slot is small relative to the gross area. Design considerations are presented along with limitations of the study.     

Human response to blast-induced vibration and air-overpressure: an Indian scenario

Ground vibration (V_max) and air-overpressure/noise (p) are some of the negative effects of blasting. The associated human annoyance and complaints are expected to show an increasing trend in the future as there is no economically viable alternative to blasting in mines in India.A study of the human response to blasting in four mining localities across India has shown that the response is not simply political, as frequently assumed. It has been found that irrespective of those questioned, a basic concern for the safety of property was the main response. There was a greater response from the middle-aged and middle-educated while fewer women than men responded. Assuming that a 100% negative response from the inhabitants will translate into complaints, a methodology is suggested to take account of the human response criteria when considering blasting within 400 m of habitations.     

CROSS - a Program for Determination of Coefficients of Subgrade Reaction

Soil Mechanics and Foundation Engineering -     

Spatial patterns of cadmium and lead deposition on and adjacent to National Park Service lands in the vicinity of Red Dog Mine, Alaska

Heavy metal escapement associated with ore trucks is known to occur along the DeLong Mountain Regional Transportation System (DMTS) haul road corridor in Cape Krusenstern National Monument, northwest Alaska. Heavy metal concentrations in Hylocomium splendens moss (n = 226) were used in geostatistical models to predict the extent and pattern of atmospheric deposition of Cd and Pb on Monument lands. A stratified grid-based sample design was used with more intensive sampling near mine-related activity areas. Spatial predictions were used to produce maps of concentration patterns, and to estimate the total area in 10 moss concentration categories. Heavy metal levels in moss were highest immediately adjacent to the DMTS haul road (Cd > 24 mg/kg dw; Pb > 900 mg/kg dw). Spatial regression analyses indicated that heavy metal deposition decreased with the log of distance from the DMTS haul road and the DMTS port site. Analysis of subsurface soil suggested that observed patterns of heavy metal deposition reflected in moss were not attributable to subsurface lithology at the sample points. Further, moss Pb concentrations throughout the northern half of the study area were high relative to concentrations previously reported from other Arctic Alaska sites. Collectively, these findings indicate the presence of mine-related heavy metal deposition throughout the northern portion of Cape Krusenstern National Monument. Geospatial analyses suggest that the Pb depositional area extends 25 km north of the haul road to the Kisimilot/Iyikrok hills, and possibly beyond. More study is needed to determine whether higher moss heavy metal concentrations in the northernmost portion of the study area reflect deposition from mining-related activities, weathering from mineralized Pb/Zn outcrops in the broader region, or a combination of the two. South of the DMTS haul road, airborne deposition appears to be constrained by the Tahinichok Mountains. Heavy metal levels continue to diminish south of the mountains, reaching a minimum in the southernmost portion of the study area near the Igichuk Hills (45 km from the haul road). The influence of the mine site was not studied.     

Characteristics and stabilities of residues from the Wheal Jane constructed wetlands

The characteristics and solubilities of residues formed during effluent treatment at the Wheal Jane constructed wetland facility in Cornwall, UK are described. The constructed wetland treats an acidic (pH 3 to 4) mine discharge enriched in iron (<100 mg/l), zinc (<80 mg/l), manganese (<20 mg/l) and arsenic (<2 mg/l). The processing strategy adopted at the site is to remove elements selectively from the mine water in distinct unit process operations and concentrate the iron and base metals into residues within the circuits. Solubility tests conducted on the materials from the aerobic and anaerobic cells attempt to simulate future possible leaching processes within landfill sites used for ultimate disposal. The tests used in the evaluation included TCLP, MARG, washing and column leaching. The aerobic solids overall have very low solubilities which are well below the TCLP thresholds for As, Cd and Pb. The TCLP results for these toxic elements are supported by the washing and column test work. The anaerobic substrates are carbonaceous in nature, composed of straw, wood pulp and manure. They contain minimal amounts of toxic compounds and are considered to be less of a disposal problem. Ochre precipitated at a pH of 3-4 in the aerobic cells contains significant concentrations of arsenic (>0.1%). This element is carcinogenic, and such residues are classified as hazardous waste under current UK landfill regulations. This classification does not take into consideration the solubility of the material but is based solely on the bulk chemical composition.     

Evaluation of the fern Azolla for growth, nitrogen and phosphorus removal from wastewater

Water fern (Azolla filiculoides Lam.) has been assessed for nitrogen and phosphorus removal in outdoor experiments comparing sewage water (S) from an experimental aquaculture plant, well water (W) and mineral growth medium Hoagland (H). The experiments were undertaken during the spring and the summer. The yield of fern biomass and nitrogenase activity was higher in H than in W and S waters. The enzyme activity had a decreasing trend with significant differences (p < 0.05) in the three waters. Peroxidase (POD) activity in April decreased with significative differences in W and S waters (p < 0.05). The electrical conductivity and the concentrations of NO3- in the three waters decreased significantly (p < 0.05). The highest removal of nitrate from the media was obtained in July. In S water, NO2- concentration decreased, while it increased in W water. PO(4)3- concentration was very low in W and S waters and decreased in H medium. The results obtained confirm the ability of the fern to grow in sewage water.