Progress toward remediation of the Sydney Tar Ponds: A major Canadian PCB/PAH “superfund” site

The Muggah Creek estuary in Sydney, Nova Scotia, received liquid and solid wastes from a steel mill and its associated coke ovens for approximately 100 years. This resulted in pollution of soils and sediments with polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), heavy metals, and other pollutants, including those in untreated domestic wastewaters. The Canadian federal and Nova Scotia provincial governments organized the Sydney Tar Ponds Agency (STPA) to develop a remediation approach for the Coke Ovens site soils and Sydney Tar Ponds sediments. The STPA developed a remediation approach for the Sydney Tar Ponds sediments, involving solidification/stabilization (S/S) through mixing cement and other materials into the sediments, and then capping them as a waste pile. High‐density polyethylene (HDPE) plastic sheeting vertical barriers are proposed to be used to divert groundwater and surface water from entering into the S/S‐treated sediments and to collect any water and associated pollutants released from the S/S‐treated sediments. The Coke Ovens site soils are proposed to be landfarmed to reduce some of the PAHs and other pollutants and then capped with a layer of soil. This remediation program is estimated to cost on the order of $400 million (CAN). This article presents a review of the significant potential problems with the STPA proposed remediation strategy of the Sydney Tar Ponds sediments and Coke Ovens site soils. © 2006 Wiley Periodicals, Inc.     

Modelling nitrogen fluxes at the landscape scale

The distribution and impacts of different nitrogen pollutants are inextricably linked. To understand the problem fully, the interactions between the different pollutants need to be taken into account. This is particularly important when it comes to abatement techniques, since measures to reduce emissions of one nitrogen pollutant can often lead to an increase in another. This project represents a step towards greater understanding of these issues by linking together new and existing nitrogen flux models into a larger framework. The modelling framework has been constructed and some of the nitrogen flows between fields, farms and the atmosphere have been modelled for a UK study area for typical farm management scenarios.     

Rapid amino acid cycling in arctic and antarctic soils

Amino acids constitute one of the largest inputs of organic nitrogen (N) to most polar soils and have been hypothesized to be important in regulating vegetational succession and productivity in Arctic ecosystems. Our understanding of amino acid cycling in these soils, however, is poor. The aim of this study was to investigate the size and rate of turnover of the amino acid pool in a range of Arctic and Antarctic soils. Our results indicate that in polar soils with either high or low ornithogenic inputs the amino acid pool is small in comparison to the inorganic N pool (NO^–₃ and NH⁺₄). The free amino acid pool constituted only a small proportion of the total dissolved organic nitrogen (DON) pool in these soils. Here we show that these low concentrations may be due to rapid use by the soil microbial community in both Arctic and Antarctic soils. The turnover of the amino acid pool in soil was extremely rapid, with a half-life ranging from 2 to 24 h, indicating that this N pool can be turned over many hundred times each summer when polar soils are frequently unfrozen. The implications of amino acids in N cycling and plant and microbial nutrition are discussed.     

Radiogenic Lead Isotopes and Time Stratigraphy in the Hudson River, New York

Radionuclide, radiogenic lead isotope and trace metal analyses on fine-grained sediment cores collected along 160 km of the upper and tidal Hudson River were used to examine temporal trends of contaminant loadings and to develop radiogenic lead isotopes both as a stratigraphic tool and as tracers for resolving decadal particle transport fluxes. Very large inputs of Cd, Sb, Pb, and Cr are evident in the sediment record, potentially from a single manufacturing facility. The total range in radiogenic lead isotope ratios observed in well-dated cores collected about 24 km downstream of the plant is large (e.g., maximum difference in ²⁰⁶Pb/²⁰⁷Pb is 10%), characterized by four major shifts occurring in the 1950s, 1960s, 1970s and 1980s. The upper Hudson signals in Cd and radiogenic lead isotopes were still evident in sediments collected 160 km downstream in the tidal Hudson. The large magnitude and abrupt shifts in radiogenic lead isotope ratios as a function of depth provide sensitive temporal constraints that complement information derived from radionuclide analyses to significantly improve the precision of dating assignments. Application of a simple dilution model to data from paired cores suggests much larger sediment inputs in one section of the river than previously reported, suggesting particle influxes to the Hudson have been underestimated.     

Measurements of PCB Fluxes into the Atmosphere from a Site Receiving Stabilized Dredged Material

A 50 ha known contaminated site in Bayonne, New Jersey, U.S.A. is permitted to receive up to 3 × 10⁶ m³ of sediment dredged from navigation channels in the New York/New Jersey Harbor. Much of the sediment is expected to contain low to moderate concentrations of industrial and agricultural chemicals, including Polychlorinated Biphenyls (PCBs). The dredged material brought to the site is stabilized with cement and then placed as a capping and grading layer. The flux of PCBs from drying stabilized dredged material has been estimated from measurements of PCB air concentrations at two heights above the ground along with micrometeorological observations. A statistically significant gradient in PCB concentrations has been consistently measured in the first 3 m above the ground. Observed PCB fluxes were highest over freshly placed stabilized dredged sediment and decreased as it cured. The highest flux observed in this study was 7214 ng/m²/h, but during subsequent sampling intervals at the same site, the flux estimates decreased by an order of magnitude over a 5-day interval.     

The Chemical Recycling of PET in the Framework of Sustainable Development

In this investigation, all the techniques used in the chemical recycling of polyethylene terephthalate (PET) are critically reviewed according to the overall benefits together with the environmental surcharge that they cause. Those, which are consistent with the principles of sustainable development, are indicated. Experimental data are presented for the acid hydrolysis of PET and compared with previous results on the alkaline hydrolysis of PET with, or without, the use of a phase transfer catalyst. Overall material balances are carried out for the hydrolysis of PET. Finally, it can be postulated that recycling according to the scheme: is the only one within the framework of sustainable development. Therefore, the recycling of PET does not only serve as a partial solution to the solid waste problem but also contributes to the conservation of raw petrochemical products and energy.     

Assessing the Collection of Urban Solid Wastes: A Step Towards Municipality Benchmarking

The assessment of collection systems for municipal wastes is becoming an issue of increasing importance among local authorities. This paper contributes to this task by addressing and discussing a set of parameters that are characterizing certain aspects of the efficiency and effectiveness of the waste collection process. Case-study area for testing this set is the Thessaloniki Urban Area in Northern Greece. Specifically, a set of four evaluation indicators is initially discussed and quantified for each of the 14 considered municipalities, while the multiple-criteria decision support method of Analytical Hierarchy Process is finally applied to globally rank the municipalities. As a result, a classification of all examined municipalities is derived and various conclusions are drawn on certain efficiency and effectiveness aspects of waste collection systems.     

Superfund site remediation by landfilling—overview of landfill design,operation, closure,and postclosure issues

This article discusses the appropriateness of using landfills as part of remediating hazardous chemical and Superfund sites, with particular emphasis on providing for true long‐term public health and environmental protection from the wastes and contaminated soils that are placed in the landfills. On‐site landfilling or capping of existing wastes is typically the least expensive approach for gaining some remediation of existing hazardous chemical/Superfund sites. The issues of the deficiencies in US EPA and state landfilling approaches discussed herein are also applicable to the landfilling of municipal and industrial solid “nonhazardous” wastes. These deficiencies were presented in part as “Problems with Landfills for Superfund Site Remediation” at the US EPA National Superfund Technical Assistance Grant Workshop held in Albuquerque, New Mexico, in February 2003. They are based on the author's experience in investigating the properties of landfill liners and the characteristics of today's landfills, relative to their ability to prevent groundwater pollution and to cause other environmental impacts. Discussed are issues related to both solid and hazardous waste landfills and approaches for improving the ability of landfills to contain wastes and monitor for leachate escape from the landfill for as long as the wastes in the landfill will be a threat. © 2004 Wiley Periodicals, Inc.