John S. Poland

Extraction and speciation of arsenic in plants grown on arsenic contaminated soils

A sequential arsenic extraction method was developed that yielded extraction efficiencies (EE) that were approximately double those using current methods for terrestrial plants. The method was applied to plants from two arsenic contaminated sites and showed potential for risk assessment studies. In the method, plants were extracted first by 1:1 water-methanol followed by 0.1M hydrochloric (HCl) acid. Total arsenic in plant and soil samples collected from contaminated sites was mineralized by acid digestion and detected by inductively coupled plasma-atomic emission spectrometry (ICP-AES) and hydride generation-atomic absorption spectrometry (HG-AAS). Arsenic speciation was done by high performance liquid chromatography coupled with HG-AAS (HPLC-HGAAS) and by HPLC coupled with ICP-mass spectrometry (HPLC-ICP-MS). Spike recovery experiments with arsenite (As(III)), arsenate (As(V)), methylarsonic acid (MA) and dimethylarsinic acid (DMA) showed stability of the species in the extraction processes. Speciation analysis by X-ray absorption near edge spectroscopy (XANES) demonstrated that no transformation of As(III) and As(V) occurred due to sample handling. Dilute HCl was efficient in extracting arsenic from plants; however, extraction and determination of organic species were difficult in this medium. Sequential extraction with 1:1 water-methanol followed by 0.1M-HCl was most useful in extracting and speciating both organic and inorganic arsenic from plants. Trace amounts of MA and DMA in plants could be detected by HPLC-HGAAS aided by the process of separation and preconcentration of the sequential extraction method. Both organic and inorganic arsenic compounds could be detected simultaneously in synthetic gastric fluid extracts (GFE) but EEs by this method were lower than those of the sequential method. The developed sequential method was shown to be reliable and applicable to various terrestrial plants for arsenic extraction and speciation.

Remediation of former military bases in the Canadian Arctic

Abstract This paper describes novel aspects of the remediation of three former military bases in the Canadian Arctic. At Iqaluit, the site has been totally cleaned up. All buildings were demolished, and soils contaminated with metals and polychlorinated biphenyls (PCBs) removed. Soils were excavated and most containerized and shipped south for disposal; soils containing 1–5 ppm PCBs were buried on site along with nonhazardous debris. PCB-contaminated concrete foundations were also investigated and removed. While most contamination was in the surface of the active layer, some migration of PCBs along the surface of the underlying bedrock at greater depth was found. At Sarcpa Lake, a dump leaching PCBs was excavated. Methodology was developed for this investigation and the difficulties of excavation in permafrost are described. The PCBs in the dump were from electrical equipment and/or PCB-containing paint used at this former Distant Early Warning (DEW) Line site. Investigation of the painted material at the site showed PCB levels as high as 7.4% in the paint. Wall swab results show that the repainting of the walls had effectively rendered the PCBs unavailable to solvent washing. At Resolution Island, the extent of contamination is much larger than the other two sites. Interceptor barriers were designed and installed in the leachate pathways carrying PCBs between the site and the ocean. At this site, the presence of petroleum products along the drainage pathway has led to increased transport of PCBs due to their higher solubility in these solvents as compared to water. Current progress at this unique remote site and the options for dealing with the contaminated soil are discussed.

The determination of the chloride content of concrete

Abstract The free chloride in concrete is a factor in the corrosion of embedded steel while bound chloride is not. Various procedures for the recovery and determination of free chloride in concrete have been examined. The methods involved hot and cold water extractions with results dependent upon the subdivision of the sample and the nature, temperature and duration of the extraction step. Some methods were found to extract chloride from the aggregrate material although this is not thought to contribute to the corrosion process. A continuous, 24 hour, Soxhlet extraction of a 30 g sample broken into 1 2 inch pieces was found effective in distinguishing free chloride in the concrete from aggregrate chloride.

Metal contamination in sediments and biota of the Bay of Quinte, Lake Ontario, Canada

The Bay of Quinte receives drainage from several large river systems, including the Moira River which carried sediment from mines into the Bay from the 1880s to the 1960s. We are investigating possible metal contamination of submerged weed beds and marsh biota which may contribute to the low diversity and biomass of macrophyte beds and Typha marshes in the Bay. In 1987, sediment, macrophytes and snails were sampled in wetlands close to the Moira River and at Hay Bay (part of the Bay of Quinte presumably unaffected by mine effluents) located 20 km from the Moira. Some element concentrations in sediment and biota were determined by neutron activation analysis (NAA) including Al, As, Br, Ca, Co, Cl, Cr, Cs, Fe, Hf, K, La, Na, Mg, Sb, Sc, Rb, Ta, Th, Ti, U, V and Zn. Other elements were analysed by acid dissolution and atomic absorption spectrophotometry (AAS) including Ag, As, Cu, Hg, Ni, Pb, and Zn. Levels of As in sediments and plants were higher close to the Moira River, whereas Cu and Ni showed the opposite pattern in sediments. The usefulness of species as bioassays differed: Stagnicola elodes Say accumulated significantly higher levels of Cu (35 vs 18 ppm) and V (l. l vs 0.5 ppm) than Planorbella trivolvis Say collected from the same sites. The macrophyte, Myriophyllum spicatum L. acted as an accumulator of Pb (up to 9.6 ppm), whereas Pb in Vallisneria americana Michx. at the same sites was undetectable.

CATHODIC PROTECTION AND HYDROGEN GENERATION

The potential at which hydrogen evolution occurs on the surface of steel embedded in concrete must be determined accurately if cathodic protection is to be safely applied to prestressed concrete structures. Concrete specimens containing embedded steel were polarized using both a rectified unfiltered alternating current (A.C.) and a true direct electrical current (D.C.) from a potentiostat. Commercial cathodic protection rectifiers possess characteristics between these two extremes. The specimens were enclosed in bell jars, and samples of the air above the specimens were periodically collected. The presence and quantity of hydrogen was determined using gas chromatography. Details of the study are described. It was found that applied D.C. potentials of 1.3 and 1.4 volts, 32 and 79%, respectively, of the applied engergy was being used to generate hydrogen.

Conducting environmental analyses at remote sites in cold climates

Clean-up sites in cold climates present unique challenges for the analytical chemist, primarily because of transportation constraints and limited infrastructure. Excavation of chemically contaminated soils and dumps requires a quick turnaround for analytical results. This is mainly due to the cost factors involved in having expensive heavy equipment idle and the short working seasons, but also because of melting of exposed permafrost during excavation. Three options are available for conducting analyses at remote polar sites. These are off-site determinations, the use of on-site test kits (or simple procedures), and the deployment of a mobile laboratory. This paper discusses these options and provides details of available on-site techniques as well as specific examples of their application in remote northern sites. The design and operation of a mobile laboratory at Resolution Island, Nunavut, is described, and available test kits are compiled and reviewed.