J. M. Arocena

Prescribed fire-induced changes in properties of sub-boreal forest soils

Pile and windrow burning of logging slash are important silvicultural practices in sub-boreal forests, yet, little is known about their effects on soil properties. We investigated the physical, chemical, and mineralogical properties of soils collected 2 years after prescribed pile and windrow burning treatments of clearcut forest site in the central interior of British Columbia. We also used scanning electron microscopy to investigate the effects of fire on soil morphology, particularly, soil aggregate and sand fraction. We observed higher soil pH, exchangeable Ca, Mg, K and Na and base saturation in burnt plots compared to unburnt plots. The concentrations of total and available N were similar in all treatments. In general, pile burning had more significant effects on soil properties than windrow burning. Pile and windrow burning reduced the amount of 2:1 expanding clays (vermiculite) but not kaolinite in the clay fractions of Ae and Bm horizons indicating that the temperature <500 °C. Prescribed burns may also have caused the cracks in sand-sized amphibole, perhaps reducing their sizes into silt fraction and finer. The prescribed burns may also be responsible for the cracking patterns observed in soil aggregates and sand fraction potentially contributing to increased weathering rates.

Uptake, Distribution, and Speciation of Chromium in Brassica Juncea

Brassica juncea (Indian mustard) has been widely used in phytoremediation because of its capacity to accumulate high levels of chromium (Cr) and other metals. The present study was conducted to investigate mechanism(s) involved in Cr binding and sequestration by B. juncea. The plants were grown under greenhouse conditions in field-moist or air-dried soils, amended with 100 mg kg−1 of Cr (III or VI). The plant concentrated Cr mainly in the roots. B. juncea removed an average of 48 and 58 μg Cr per plant from Cr (III) and Cr (VI)-treated soils, respectively. The uptake of Cr was not affected by the moisture status of the soils. X-ray absorption near-edge spectroscopy measurements showed only Cr (III) bound predominantly to formate and acetate ligands, in the bulk and rhizosphere soils, respectively. In the plant tissues, Cr (III) was detected, primarily as acetate in the roots and oxalate in the leaves. X-ray microprobe showed the sites of Cr localization, and probably sequestration, in epidermal and cortical cells in the roots and epidermal and spongy mesophyll cells in the leaves. These findings demonstrate the ability of B. juncea to detoxify more toxic Cr (VI), thereby making this plant a potential candidate for phytostabilization.

Evaluation of iron-phosphate as a source of internal lake phosphorus loadings

Biological, physical and chemical characteristics of the water column of a shallow (Zmax = 9.2 m), small (surface area 3.8 km2) residential and recreational lake near Prince George, British Columbia, indicated that the system was being loaded internally with phosphorus (P) from the sediments. The abundance of P released from the fine glaciolacustrine, and organic rich sediments was resulting in excess algal and weed growth. It was postulated that iron-phosphate reduction at redox potentials below approximately 200 mV and/or bacterially mediated orthophosphate (PO4-P) releases could be occurring. The development of an appropriate nutrient management strategy required that the process associated with the sediment P release be determined. The MINTEQA2 geochemical model was used to predict the release of orthophosphate (PO4-P) into the interstitial water with the assumption that P is present alternately as strengite, variscite and hydroxyapatite. The predicted release of PO4-P from these P containing minerals was compared to the concentration of PO4-P and total phosphorus (TP) in the overlying hypolimnion. In order to improve the accuracy of the model prediction, the proportion of the sediment present as iron-bound phosphate was estimated. A significant correlation between the observed hypolimnetic TP and interstitial PO4-P concentrations as predicted from iron-bound P dissolution (r2 = 0.59) was found. Total phosphorus release rates to the hypolimnion were also found to be strongly correlated to the iron-bound P component of the sediment (r2 = 0.88). Multivariate regression analyses showed significant relationships between hypolimnetic PO4-P and sediment iron-bound P, Eh, and interstitial Fe (r2 = 0.76). These results provided sufficient evidence to conclude that PO4-P in the system is predominantly bound to Fe-containing minerals and therefore could be managed using treatment techniques that address iron-bound phosphates.

Extraction of Potassium and/or Magnesium from Selected Soil Minerals by Piloderma

Piloderma is a broad host range ectomycorrhizal fungal genus that may benefit conifer growth through increased soil nutrient availability via enhanced soil mineral weathering. In an in vitro study, we investigated the ability of Piloderma to extract K and/or Mg from three soil minerals commonly found in soils of central British Columbia: biotite, microcline, and chlorite. The growth, hyphal morphology, and chemical composition were compared among Piloderma grown for 110 days in media optimized for fungal growth as well as in media where K and/or Mg were supplied from biotite, microcline, and chlorite. Piloderma grown in treatments with low K showed fibrillar growths, hyphal swellings, and hyphae devoid of ornamentation, possibly indicating nutrient deficiency. Differences were found in growth rates, morphologies, and Mg content in hyphae grown in chlorite and biotite treatments, suggesting that Mg was limiting to the normal growth of Piloderma . Energy dispersive X-ray analysis indicated that Piloderma extracted significantly more K from biotite than from microcline. The high Ca and O content of hyphal ornamentation were mainly composed of Ca-oxalate crystals. The study indicated that K and Mg are essential for vigorous Piloderma growth and that Piloderma may provide more available K to host plant through accelerated weathering of biotite, compared to microcline and chlorite sources. The differences were attributed to the ability of Piloderma to efficiently extract K from the interlayer of biotite. However, the exact mechanism by which Piloderma supplies plant roots with K extracted from biotite is still largely unknown.

Organic acid-induced release of lead from pyromorphite and its relevance to reclamation of Pb-contaminated soils.

The long-term stability of pyromorphite [Pb(5)(PO(4))(3)Cl] (PY) in root-soil interface (or rhizosphere) where production of organic acids from biological activities takes place is not fully understood. We conducted a 1-year long laboratory batch dissolution experiment to elucidate the release of Pb (and P) from PY by four commonly occurring low molecular weight organic acids (LMWOA) in rhizosphere: acetic, citric, malic and oxalic acid. Mean maximum amount of Pb in milliQ (mQ) water (1.8microM) was lower than in solutions from LMWOA alone or in combination with each other (i.e., mixed acid). However, there was no significant difference in the amount of Pb (and P) in solution in all treatments including mQ water after 6months. Among the 100microM LMWOA, mean of five highest soluble Pb (muM Pb in solution) followed the order: oxalic acid (17.6)>citric (6.2)>malic (5.6)>acetic acid (3.0microM Pb). Mixed acid solution had a maximum amount of 14.0microM Pb. We calculated a range of solubility product constant (K(sp)) of PY in this study from 8.6x10(-54) (mQ) to 7.0x10(-45)(oxalic acid); these values are within the range of PY K(sp) reported elsewhere. Despite the low K(sp) values, LMWOA-induced released Pb from PY are in concentrations higher than both Canadian and international drinking water and agricultural water use quality standards. This suggests that soil organic acids such as in rhizosphere can potentially liberate Pb from PY in contaminated soils.

Mineralogy and genesis of selected soils and their implications for forest management in central and northeastern British Columbia

Soil properties in central and northeastern British Columbia are strongly influenced by parent materials because of geologically young till, glaciolacustrine, and glaciofluvial deposits. We examined pedogenesis on various parent materials to support studies of long-term forest productivity. We sampled nine pedons developed on till (Bobtail, Lucille Mountain, Skulow Lake, Log Lake, Topley, and Kiskatinaw), glaciofluvial (Bowron), and glaciolacustrine (Aleza Lake 1, 2) deposits. The Skulow Lake pedon is distinctive in the occurrence of talc, while the Lucille Mountain pedon has the only clay fraction in which kaolinite is absent. Other pedons on till contain mica, kaolinite, chlorite, smectite, and vermiculite. The Bowron pedon has mica, kaolinite, and chlorite, while the Aleza Lake pedons have mica, kaolinite, chlorite, and 2:1 expanding minerals. In pedons with low amount of 2:1 expanding clays in the C horizon, mica and chlorite appear to degrade into 2:1 expanding clays, while in pedons with C horizons ...

Chemical and mineral composition of ectomycorrhizosphere soils of subalpine fir (Abieslasiocarpa (Hook.) Nutt.) in the Ae horizon of a Luvisol

Differences in the properties of bulk forest and rhizosphere soils are often attributed to ectomycorrhizal association, or the symbiosis characterized by a fungal sheath surrounding the root (mantle) and intercellular root colonization (Hartig net). We compared the soil pH, total C, N, cation exchange capacity, and the contents of mica, chlorite, kaolinite, 2:1 expandable clays, feldspars and amorphous materials between two ectomycorrhizosphere soils (or soil environment in the vicinity of ectomycorrhizae (ECM)) and non-ectomycorrhizosphere soils to study the influence of ectomycorrhizae on chemical and mineralogical properties of soils. The two ectomycorrhizosphere soils were characterized by ectomycorrhizal colonization dominated by (1) Piloderma spp., and (2) Mycelium radicis atrovirensand cottony yellow-brown (MRA-CYB) types or where Piloderma spp. colonization was <2%. Our results showed that total C and N were higher in ectomycorrhizosphere than non-ectomycorrhizosphere soils, and the ectomycorrhizo...

Heterogeneous distribution of trace elements and fluorine in phosphogypsum by-product

Phosphogypsum (PG), a by-product from phosphate fertilizer production, is composed mainly of gypsum (CaSO 4 .2H 2 O) but also contains minor quantities of trace elements (TE), rare earth elements (REE) and F. Some elements may be elevated in quantities to be of environmental concern. This study determined the distribution of TE, REE and F among three size fractions ( 53 μm) in PGs derived from three different phosphate rock sources. Fine fraction PG (<20 μm) composed of <10% of total PG mass but was highly enriched in TE, REE and F compared to unfractionated PG. For PG derived from Idaho rock, Se in the fine fraction was enriched 830 times over soil and 415 times over shale while Cd was enriched in the fine fraction 70-fold over shale and soil. Fluorine was elevated 37 times in the fine fraction compared to shale. The same trends were observed for PG derived from Togo and Florida rocks. Elevated elemental concentrations in fine particles and particle sorting during PG deposition may contribute to chemical heterogeneity of PG repositories, and make elements more susceptible to mobilization processes, such as leaching and erosion. Removal of fines will improve the utilization of PG in other industries, such as for use as an amendment to agricultural soils

Adsorption of Orange II dye in aqueous solution onto surfactant-coated zeolite: Characterization, kinetic and thermodynamic studies

Adsorption of anionic dye - Orange II - in aqueous solution onto hexadecyltrimethylammonium bromide (HDTMA)-coated zeolite (HCZ) reached 38.96mg/g compared with 8.13mg/g onto natural zeolite. Fourier Transform Infrared (FTIR), scanning electronic microscopy (SEM) and X-ray powder diffraction (XRD) data showed that HDTMA-coated zeolite developed surficial positive charges. The adsorption reaction fits the Freundlich isotherm (R(2)=0.93) and the value of 1/n was less than unity (=0.81) and suggest a multi-layer physi-sorption process. The kinetics of the adsorption is a pseudo-second-order model. The activation energy (Ea) of the reaction is +35.70kJ/mol to further support a physi-sorption process while the ΔH(o) (+82.79kJ/mol) is characteristic for an endothermic reaction. The ΔG(o) values of -2.33, -0.98 and -0.37kJ/mol at 25°C, 30°C and 35°C, respectively implied that the adsorption reaction was feasible and thermodynamically spontaneous. We proposed that both electrostatic interactions and partitioning process are involved in the adsorption mechanisms of Orange II dye onto HCZ.

Heterogeneous distribution of radionuclides, barium and strontium in phosphogypsum by-product

Phosphogypsum (PG) is a high volume by-product of the phosphate fertilizer industry which is composed mainly of CaSO4·2H2O. Impurities in PG include F, trace elements and naturally-occurring radionuclides. Radium-226 content is sufficiently high in some PGs that it has limited PG usage in building materials and as an amendment to agricultural soils. Radium likely exists in PG as a sulfate solid solution with Ba, and possibly Sr. This study determined the distribution of 226Ra, Ba, Sr, U, Th and 210Pb among three size fractions (fine: 53 μm) in PGs derived from three different phosphate rock sources. All chemical species, except for Sr in PG derived from Idaho rock, were enriched in the <20-μm fraction relative to the other size fractions and relative to unfractionated PG. On average, fine fraction 226Ra and 210Pb contents were enriched approximately sixfold over unfractionated PG. 226Ra was enriched in the fine fraction to a greater degree than were Ba or Sr, indicating that Ra behavior in PG is distinct from these other elements. The combination of (i) particle sorting during PG deposition, and (ii) non-uniform distribution of radionuclides in PG, may contribute to radionuclide heterogeneity at PG repositories.