Background. More than ten million small-scale miners (SSM) worldwide use mercury to extract gold, releasing large amounts of the toxic element into the environment. Alternatives to mercury have been suggested over the years to little avail. A group of miners in the Philippines has demonstrated that borax, when used as a flux for smelting gold out of heavy mineral concentrates, is an effective and safer substitute for mercury. Objectives. To present a basic comparison of the mercury amalgamation and borax methods of gold extraction for SSM. Methods. Borax was added to milled ore to reduce the melting point of gold to a level accessible to SSM. The amount of gold captured, and the amount of mercury released into the environment, was compared to two common amalgamation methods: whole ore and heavy metal. Discussion. The borax method appears to capture more gold, as well as eliminate the use of mercury. It is also less expensive. It is important to stop the use of mercury amongst SSM. However, health and environmental arguments alone are not enough to convince miners to switch. The argument of improving gold-capture rates while reducing costs is more compelling, and may help propagate the technique among small-scale miners. Conclusions. Scientific research should continue in order to further establish the uses and limitations of the borax method. Competing Interests. Leoncio Na-Oy provides training in the borax method of gold extraction.

Alberta’s oil sands are located in the boreal forest where surface mining requires reconstruction of these landscapes using waste saline and sodic overburden (SSOB) piles. The impact of these SSOB materials, however, on root development of planted boreal species is unknown. The objective of this study was to examine the effect of SSOB material on the root distributions of planted boreal species. Root distributions for planted mixedwood stands were measured using soil cores and compared with soil physical and chemical properties on three reclaimed sites. Soil pH ranged from 6.1 to 7.5 across all three reclaimed sites. Sodium adsorption ratio ranged from <30 in the SSOB at the youngest site to <4 at the oldest site while soil electrical conductivity ranged from <12 and <4 dS m−1 in the SSOB at the youngest and oldest site, respectively. Root length distributions were concentrated in the upper 30 cm of the soil profile and ranged from 0.96 to 7.99 cm cm−3. The roots were observed in the SSOB and accounted for 1.3% to 2.2% of the total root length in the profile. The root length density was also negatively correlated with Na and EC at all sites. The root distributions on these young reclaimed sites were similar to those from undisturbed boreal forest stands overlying saline soils, suggesting that root distributions on these reclaimed sites appear to be unaffected by the SSOB; however, further monitoring will be required as the stand matures to determine future impacts of the SSOB on forest productivity.

Explosive compounds, including known toxicants 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), are loaded to soils during military training. Their fate in soils is ultimately controlled by soil mineralogical and biogeochemical processes. We detonated pure mineral phases with Composition B, a mixture of TNT and RDX, and investigated the fate of detonation residues in aqueous slurries constructed from the detonated minerals. The pure minerals included Ottawa sand (quartz and calcite), microcline feldspar, phlogopite mica, muscovite mica, vermiculite clay, beidellite (a representative of the smectite clay group), and nontronite clay. Energy-dispersive X-ray spectrometry, X-ray diffraction, and gas adsorption surface area measurements were made of the pristine and detonated minerals. Batch slurries of detonated minerals and deionized water were sampled for 141 days and TNT, RDX, and TNT transformation products were measured from the aqueous samples and from the mineral substrates at day 141. Detonated samples generally exhibited lower gas adsorption surface areas than pristine ones, likely from residue coating, shock-induced compaction, sintering, and/or partial fusion. TNT and RDX exhibited analyte loss in almost all batch solutions over time but loss was greater in vermiculite, beidellite, and phlogopite than in muscovite and quartz. This suggests common phyllosilicate mineral substrates could be used on military training ranges to minimize off-site migration of explosive residues. We present a conceptual model to represent the physical and chemical processes that occurred in our aqueous batches over time.

Lake water calcium (Ca) decline has recently been recognized as a stressor impacting softwater lake districts that have experienced long-term patterns of acid deposition and/or timber harvesting. Declining aqueous Ca levels may impact the survival of aquatic biota, particularly Ca-rich cladoceran taxa such as daphniids. Daphnia pulex are sensitive to laboratory Ca levels below 1.5 mg l−1; however, responses of cladoceran communities to Ca decline in natural environments require further study. Dickie Lake (Ontario, Canada) is the site of an inadvertent natural experiment, providing insight into the effects of changing aqueous Ca availability upon cladoceran communities, as the lake has a history of acidification, followed by recent (1990s) Ca additions to the watershed via applications of calcium-rich road dust suppressants. Paleolimnological analyses were used to examine changes in cladoceran community structure (with a focus upon Ca-rich daphniids) from pre-industrial times to present day. Three distinct temporal stages were apparent in Dickie Lake’s daphniid community: 1870–1950, 1950–1990, and 1990–present. The daphniid community of the pre-industrial assemblages was dominated by members of the Daphnia longispina species complex, but shifted in the late 1950s to more acid- and Ca-insensitive members of the D. pulex species complex. During the most recent stage, coincident with dust suppressant applications, both daphniid complexes are well represented. Observed transitions between daphniid species complexes provide further evidence of the influence of Ca availability upon cladoceran community structure, indicating the potential importance of the controlled addition of Ca to freshwater systems (i.e., liming) as a mitigation/recovery strategy as Ca declines continue.

Constructed wetlands are recognized as a reliable technology for rural wastewater treatment. However, conventional constructed wetlands face problems with low pollutant removal efficiency and limited oxygen transfer capability. Therefore, a novel vertical flow constructed wetland (VFCW) system with drop aeration was developed in this study. Two pilot-scale vertical flow constructed wetlands of 0.75 m2 each were constructed with the same dimensions and configuration but different media, one of which (named as CW1) was filled with a 1:1 mixture (by weight) of zeolite and dolomite and the other (named as CW2) with the same zeolite only. The oxygen transfer capability of a multilevel two-layer drop aeration device, organics and nitrogen removal of CW1 and CW2, and pollutant distribution along the depths of CW1 and CW2 in different operational phases were studied. The results demonstrated that compared with the direct drop aeration process, the multilevel, two-layer drop aeration device supplied 2–6 mg/L higher dissolved oxygen per meter of drop height, and after installation of the six-level, two-layer drop aeration devices, the 5-day biochemical oxygen demand removal load was improved from 8.1 to 14.2 g m−2 day−1 for CW1. With regard to the different filter media, nitrogen removal was improved by the adsorption of zeolite in the first year, with 5–36% higher NH 4 + –N removal efficiency of CW2 compared with that in CW1. Since it did not have a significant positive effect on phosphate removal, dolomite can be replaced by zeolite. The chemical oxygen demand removal mainly took place in the upper 15-cm filter layer in different operational phases, while nitrogen distribution along the depths of the VFCWs was different in different operational phases. In addition, as no operational problems occurred, the vertical flow constructed wetland system with drop aeration is an appropriate alternative for rural wastewater treatment, with numerous advantages of low capital and operation costs, no energy consumption, easy maintenance, high hydraulic loading rate, high pollutant removal efficiency, and no clogging.

A novel system for organic waste stabilization and reuse, combined with production of nitrate-rich liquid fertilizer was developed by manure digestion followed by volatilization of ammonia-rich gas (originating in manure extract) and its nitrification and recovery. This approach has several advantages, including biowaste stabilization and high recovery (over 60%) of manure N mainly as nitrate which is a better N form for many plants as compared to ammonium as the sole fertilizer N. Moreover, the potential utilization of different wastes as N sources in organic horticulture is possible as well as removal of suspended particles and microorganisms (including pathogens) that might otherwise clog the irrigation system and pose health risks, respectively. In a pilot-scale study, the system yielded several hundred liters of nitrate-rich (ca. 11 g N L−1) liquid fertilizer using guano as substrate. In a fertilization experiment, lettuce fertigated with the nitrate-rich extract exhibited better growth and quality compared to the common organic practice of fertigation with guano extract. The resulting stabilized biowaste was estimated as “low-risk” according to current guidelines and may be used for liming or land application.

The speciation and distribution of trace and major elements (Al, As, Cd, Cr, Cu, Fe, Mn, Ni, P, Pb and Zn) in the sediments of Emigrant Creek Dam (ECD), New South Wales Australia were investigated using sequential extraction, postextraction normalisation and spatial mapping to indicate source and dispersion patterns. Subsurface coring provided an estimate of elemental enrichment and showed that As 1.9 > P 1.7 > N 1.5 ≈ Cd 1.5 > Mn 1.3 were enriched. Moreover, a high proportion of the enriched elements (mean 57, 34, 47 and 87 % for As, P, Cd and Mn, respectively) were assessed as being bioavailable. Comparisons with ISQGs found that sediments from sites in proximity to Emigrant Creek inflows had the highest accumulations of metals and the greatest potential for causing biological harm. Spatially, contaminants accumulate in ECD sediments adjacent to anthropogenic sources including a cattle dip site, dredged sediment and macrophyte dump areas, and agricultural/residential runoff. Moreover, the integrated technique and postextraction normalisation allow assessment of texturally diverse and difficult sediments.

Polybrominated diphenyl ethers (PBDEs) and perfluorinated compounds (PFCs) are both classes of persistent organic pollutants with potential major health and environmental concerns. Many PBDE- and PFC-containing products are ultimately discarded in landfills. In samples from 28 landfills and dumpsites across Canada, PBDEs and PFCs were detected in almost all landfill leachate samples, with concentrations up to 1,020 and 21,300 ng/L, respectively. Mean concentrations were 166 ng/L for PBDEs and 2,950 ng/L for PFCs. Landfill leachates from southern Canada generally had greater concentrations of PBDEs and PFCs than those from northern Canada. The dominant compounds were decabromodiphenyl ether (BDE-209) (mean contribution 52 %) for the PBDEs and perfluorohexanoic acid (mean contribution 25 %) for the PFCs. There were strong correlations for some compounds within each contaminant class, such as the major congeners in the penta-BDE commercial mix (BDE-47, BDE-99, and BDE-100). Estimated average ∑PBDE and ∑PFC loadings from an urban landfill to the environment were calculated to be 3.5 and 62 tonnes/year, respectively.

Constanta harbor has been contaminated for decades with petroleum and petroleum products, which contain different toxic organic solvents. A novel solvent-tolerant bacterium, Vibrio alginolyticus IBBCₜ₂ was isolated from a seawater sample (Constanta harbor). Alkanes (i.e., n-hexane, n-decane, cyclohexane) with logarithm of partition coefficient in n-octanol and water (log P OW ) > 3.35, were less toxic for V. alginolyticus strain IBBCₜ₂, compared with aromatics (i.e., toluene, m-xylene, ethylbenzene) with log P OW < 3.17. The high organic solvent resistance of V. alginolyticus IBBCₜ₂ could be due to the presence of some catabolic (alkB, alkB/alkB1, todC1, xylM, C23DO) and transporter (HAE1, acrAB) genes. The adaptation mechanisms, underlying cyclohexane, n-hexane, n-decane, toluene, m-xylene, and ethylbenzene resistance in V. alginolyticus IBBCₜ₂ showed a complex response of cells 60 min after solvent shock (i.e., modifications of the cell viability, changes in the membrane’s lipid and protein profile, modifications of the genomic fingerprinting). Exposure of V. alginolyticus IBBCₜ₂ cells to salt stress decreases the organic solvents tolerance of this bacterium.

The present work investigated the ability of inactive brown seaweed, Turbinaria conoides, to biosorb aluminum(III) and cadmium(II) ions in both single and binary systems. Initial experiments were undertaken to determine the influence of pH and biosorption isotherms of each metallic ion. Owing to the presence of carboxylic groups, T. conoides exhibited high uptake capacity towards Al(III) and Cd(II) through ion-exchange mechanism. In the case of Al(III), T. conoides exhibited maximum biosorption at pH 4 with a capacity of 2.37 mmol/g, whereas the highest Cd(II) biosorption occurred at pH 5 with a capacity of 0.96 mmol/g. For both metal ions, T. conoides exhibited fast kinetics. Several models were used to describe isotherm (Langmuir, Freundlich, Redlich-Peterson, and Toth) and kinetic (pseudo-first and pseudo-second order) data. Desorption and reuse of T. conoides biomass in three repeated cycles was successful with 0.1 M HCl as elutant. In binary systems, the presence of Cd(II) severely affected Al(III) uptake by T. conoides. Compared to single-solute systems, Al(III) uptake was reduced to 56% compared to only 27% for Cd(II). Based on the model parameters regressed from the respective monometal systems, multicomponent Langmuir and Freundlich models were used to predict binary (Al + Cd) system of which the multicomponent Freundlich model was able to describe with good accuracy.