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Sulfur oxidizing bacteria (SOB) play a key role in sulfur cycling in mine tailings impoundment (TI) waters, where sulfur concentrations are typically high. However, our understanding of SOB sulfur cycling via potential S oxidation pathways (sox, rdsr, and S4I) in these globally ubiquitous contexts, remains limited. Here, we identified TI water column SOB community composition, metagenomics derived metabolic repertoires, physicochemistry, and aqueous sulfur concentration and speciation in four Canadian base metal mine, circumneutral-alkaline TIs over four years (2016 - 2019). Identification and examination of genomes from nine SOB genera occurring in these TI waters revealed two pH partitioned, metabolically distinct groups, which differentially influenced acid generation and sulfur speciation. Complete sox (csox) dominant SOB (e.g., Halothiobacillus spp., Thiomonas spp.) drove acidity generation and S2O32- consumption via the csox pathway at lower pH (pH ~5 to ~6.5). At circumneutral pH conditions (pH ~6.5 to ~8.5), the presence of non-csox dominant SOB (hosting the incomplete sox, rdsr, and/or other S oxidation reactions; e.g. Thiobacillus spp., Sulfuriferula spp.) were associated with higher [S2O32-] and limited acidity generation. The S4I pathway part 1 (tsdA; S2O32- to S4O62-), was not constrained by pH, while S4I pathway part 2 (S4O62- disproportionation via tetH) was limited to Thiobacillus spp. and thus circumneutral pH values. Comparative analysis of low, natural (e.g., hydrothermal vents and sulfur hot springs) and high (e.g., Zn, Cu, Pb/Zn, and Ni tailings) sulfur systems literature data with these TI results, reveals a distinct TI SOB mining microbiome, characterized by elevated abundances of csox dominant SOB, likely sustained by continuous replenishment of sulfur species through tailings or mining impacted water additions. Our results indicate that under the primarily oxic conditions in these systems, S2O32- availability plays a key role in determining the dominant sulfur oxidation pathways and associated geochemical and physicochemical outcomes, highlighting the potential for biological management of mining impacted waters via pH and [S2O32-] manipulation. [ABSTRACT FROM AUTHOR]

Environmental context: High-quality ecotoxicology data are required to derive reliable water quality guideline values that ensure long-term protection of marine biota from arsenate. Tropical and temperate marine biota have sensitivity to arsenate covering three to four orders of magnitude due to the range of arsenate detoxification mechanisms used to reduce toxicity. The water quality guideline values derived in this study will contribute to robust risk assessments of arsenate in marine environments. Rationale: There are very few high-quality chronic inorganic arsenate (AsV) toxicity data to assess the risks to marine ecosystems. We aimed to determine the range in chronic toxicity of AsV to marine biota and derive reliable water quality guideline values (GVs) for the long-term protection of marine ecosystems. Methodology: We generated chronic toxicity data based on measured dissolved (<0.45 µm filtered) AsV concentrations for 13 marine species representing seven taxonomic groups from temperate and tropical environments. Effect concentrations at the 10% level (EC10) were used in a species sensitivity distribution (SSD) to derive water quality GVs. Results: The range of concentrations causing chronic 10, 20 and 50% adverse effects were 13–26 000, 18–34 000 and 32–330 000 µg AsV L–1, respectively. Increased phosphate and nitrate concentrations were found to reduce the toxicity of AsV to certain microalgal, sea urchin and bivalve species. The range in effect concentrations for tropical versus temperate species overlapped at all effect levels. The GVs for the long-term protection of 80, 90, 95 and 99% of marine biota were: 48, 22, 12 and 4.8 µg AsV L–1, respectively. Discussion: Recommendations on performing toxicity tests with arsenic to prevent artefacts associated with arsenic speciation were made to improve future research on arsenic toxicity. The new data will improve the reliability status of the Australian and New Zealand AsV GVs for marine water quality and fill a data gap for global risk assessments of AsV for marine biota. Environmental context. High-quality ecotoxicology data are required to derive reliable water quality guideline values that ensure long-term protection of marine biota from arsenate. Tropical and temperate marine biota have sensitivity to arsenate covering three to four orders of magnitude due to the range of arsenate detoxification mechanisms used to reduce toxicity. The water quality guideline values derived in this study will contribute to robust risk assessments of arsenate in marine environments. [ABSTRACT FROM AUTHOR]

Micronutrients play key roles in numerous metabolic processes in cyanobacteria. However, our understanding of whether the micronutrient cobalt influences the productivity of freshwater systems or the occurrence of cyanobacterial blooms is limited. This study aimed to quantify the concentration of Co necessary for optimal cyanobacterial growth by exposing Microcystis aeruginosa to a range of Co concentrations under culture conditions. Extended exposure to concentrations below ˜0.06 μg · L−1 resulted in notable inhibition of M. aeruginosa growth. A clear negative relationship was observed between Co concentration in solution and intracellular Fe quota of M. aeruginosa, possibly due to decreased transport of Fe at higher Co concentrations. Cyanocobalamin and any Co within the structure of cyanocobalamin appears to be non‐bioavailable to M. aeruginosa, instead they likely rely on the synthesis of a structural variant – pseudocobalamin, which may have implications for the wider algal community as the variants of cobalamin are not necessarily functionally exchangeable. To evaluate the likelihood of Co limitation of cyanobacterial growth under field conditions, a survey of 10 freshwater reservoirs in South‐Eastern Australia was conducted. Four of the ten sites had dissolved Co concentrations below the 0.06 μg · L−1 threshold value. All four of these sites rarely undergo cyanobacterial blooms, strengthening evidence of the potential for Co to limit growth, perhaps either alone or in combination with phosphorus. [ABSTRACT FROM AUTHOR]

This study examines metal sulfides stability to oxidation in seawater. The acid volatile sulfide/simultaneously extracted metals (AVS/SEM) theory is used to evaluate sediment quality to predict the absence of toxicity of Ca, Cu, Ni, Pb, and Zn.

Sample preservation and storage procedures (acidification with HN[O.sub.3] and storage in plastic bottles) normally employed prior to the determination of dissolved Cu in sulfidic waters were compared with sample preservation involving the initial oxidation of sulfide with [H.sub.2][O.sub.2] or [S.sub.2][[O.sub.5].sup.2-] followed by acidification. Acidification alone was demonstrated to be inadequate and resulted in a significant underestimation of dissolved Cu (losses ranging from 50% to >90%). Similar losses were observed in both polyethylene and Teflon storage bottles. Experiments suggest that losses of copper occur following sample acidification owing to the formation of stable copper sulfide phases which adsorb onto container surfaces. It is therefore recommended that an oxidative pretreatment step is carried out prior to the acidification of porewaters collected for metal analysis. The results of this study suggest that much of the previous data reporting dissolved Cu concentrations in sulfidic waters and porewaters may be in error.

Aerated water allowed FeS abd MnS model phases, which were found to be particularly labile, to oxidize rapidly. Meanwhile, it took CdS, CuS, PbS and ZnS model phases several stabilize kinetically. Results reveal that FeS and MnS phases may reduce the effects bioirrigation during bioturbation. Moreover, trace metal sulfide phases may stay unoxidized for a certain period of time.

Steam distillation was evaluated as a technique for the separation of methylmercury from natural water samples prior to quantification by GC-atomic fluorescence spectrometry. Recoveries of methylmercury chloride spikes ranged from [approximately]100% in a wide variety of natural freshwater and estuarine samples to 80% in seawater. The addition of ammonium pyrrolidine dithiocarbamate (APDC) was found to improve the recovery of methylmercury chloride spikes in MilliQ water from 73 to 89% and in seawater from 80 to 85%. Codistillation of inorganic mercury was eliminated by addition of APDC to the samples. Precision in MilliQ water was 2.0% RSD at 0.2 ng[multiplied by][L.sup.-1] C[H.sub.3]HgCl (n = 10) and 1.6% RSD at 2.0 ng[multiplied by][L.sup.-1] C[H.sub.3]HgCl (n = 10). The limit of detection for the method was 0.024 ng[multiplied by][L.sup.-1] (3 [Sigma]) for a 50 mL sample. The steam distillation procedure was tested for and found free of measurable artifactual formation of methylmercury. The method was compared to nitrogen-assisted distillation and found to give comparable results with the added advantage of handling sample sizes up to 100 mL. Compared to previously employed separation procedures, steam distillation offers the advantages of robustness and a considerably increased sample throughput (at least four samples per hour) without any compromise in analytical performance.

Analysis of plant and algal interference in rapid enzyme-based assays reveals the significant interference of plant and algae in the detection of coliform bacteria and Escherichia coli on the basis of thin production of beta-D-galactosidase and beta-D-glucronidase, respectively. The enzyme level, its dilution and the number of algal cells determine the level of plant and algal interference in tests such as Colilert. Application of masking agents helps reduce these interferences in the enzyme-based assays.