H. Schreier

Effects of natural acids on surface properties of asbestos minerals and kaolinite

Serpentine, and other asbestos minerals, are considered potential hazards to human respiratory health. It has been postulated that the surface characteristics of these substances, such as surface charge and adsorbed metals, notably Fe and other transition metals, may be the major agents responsible for their toxicity. There is a general consensus that the amphibole group of minerals possesses a greater health risk than serpentines dominated by chrysotile. There have been suggestions that natural processes can alter the surfaces of these minerals and reduce their potency. This study examined the effects of carbonic acid, oxalic acid and hydrochloric acid on the surface characteristics of two trioctahedral minerals, actinolite (amphibole) and chrysotile (serpentine), and compared the results to a non-asbestiform, dioctahedral mineral, kaolinite. Results confirm that the treatments alter the mineral surfaces by changing the zeta potential of the asbestiform minerals from positive to negative and by removing considerable amounts on non-crystalline Fe and other metals. X-ray analyses indicated that mineral structure was little affected by the treatments, and TOF-SIMS revealed that treatments did remove surface adsorbed metals and cations in octahedral coordination within the samples.

Phosphorus dynamics and soil P-fertility constraints in Nepal

There are significant differences between the red and non-red soils in the Middle Mountains of Nepal, and inherent differences in the parent materials and soil management seem to have the greatest influence on fertility and P dynamics. The red soils with Munsell Hue color of 2.5 YR and 5 YR, were found to have higher P sorption capacity than the non-red soils (Hue 7.5-10 YR), and the Al (AAO) content was found to be the best predictive variable for P sorption. Using a 2×2×2×3 factorial design and GIS overlay techniques, a P-sorption map for a case study watershed was produced. The results may be used for determining where agricultural intensification with chemical fertilizer applications is most effective. The amorphous Fe and Al content is critical in determining P dynamics, and without high organic matter input, the red soils are highly deficient in available P. Management influences the P-sorption capacity in that the Al (AAO) content decreased in irrigated red soils whereas the Fe (AAO) content increased significantly. Irrigation reduces the amorphous Al content and this results in a 10 to 30% reduction in P sorption. Since most red soils are acidic and are deficient in carbon, the reduction of amorphous Al via irrigation has a positive effect on management by significantly reducing P sorption. The reducing conditions created by flood irrigation during the monsoon season and the addition of exchangeable bases from sediments and irrigation water increase pH values by up to 0.5 units and alter the amorphous Al and Fe content in these soils and, hence, P availability.

Developing Indicators for Regional Water Quality Assessment: An Example from British Columbia Community Watersheds

An increased understanding of regional surface water quality and the key factors which differentiate regional from local differences is necessary for monitoring impacts such as mountain pine beetle infestation and related land management practices. This study develops a framework to identify water quality indicators which differentiate parameters influenced by rock type, by relatively short term anthropogenic activities, and those resulting from longer term climatic variability. Rock type was an overriding factor related to stream water chemistry in this British Columbia case study; with differences between watersheds differentiated by Ca, EC, Al and Fe. Grouping watersheds by their dominant rock type permitted the investigation of water quality with other watershed characteristics. The % forest cover, % pine cover, and dominant runoff processes demonstrated significant relationships with soluble cations, metals, turbidity and total organic carbon. Turbidity levels showed low variability, and relationships with mountain pine beetle were not strong; suggesting the need for more detailed data sets, selective monitoring of storm events, and longer term monitoring to improve predictive capacity.

Arsenic in Groundwater Wells in Quaternary Deposits in the Lower Fraser Valley of British Columbia

Elevated arsenic (As) concentrations levels have been found in private groundwater wells in the Lower Fraser Valley of British Columbia (BC) in a regional survey. Forty-three percent of the 98 tested wells showed total As concentrations above the 0.010 mg/L Maximum Acceptable Concentration (MAC) and another 40% were above 0.0003mg/L, a level of concern because of possible long-term lifetime exposure that could result in increased risk of negative health effects. There is clear evidence that As in this region is of natural origin and likely associated with marine and glaciomarine deposits. Arsenic was predominantly found in deep wells, and was positively correlated with variables reflective of marine environments such as B, Na, K, Mo, Cl, PO4, pH and specific conductance. Sixty-seven percent of the samples located in the marine and glaciomarine deposits of the Salish and Capilano formation had As concentrations above the MAC. In contrast, only 28% of all samples in the Fort Langley Formation and 16% of the samples on glaciofluvial sediments of the Vashon and Sumas Drift Formation had As concentrations above the MAC. Arsenic was predominantly found in aquifers that are classified as confined and of low vulnerability, while wells in unconfined glaciofluvial deposits showed little evidence of As.