What do elevated background contaminant concentrations mean for AMD risk assessment and management in Western Australia?

Water quality contaminants include a range of naturally occurring chemicals that can cause degradation of aquatic ecosystem water values when concentration ranges exceed biological tolerances. Both acid and metalliferous drainage (AMD) and acid sulfate soil (ASS) can increase contaminant concentrations through reduced pH and increased solute concentrations especially of toxic metals and metalloids. Water quality guideline criteria are typically used to maintain existing end use value objectives when managing AMD/ASS-affected waters. However, surface and ground waters of catchments comprising mining resources often show elevated solute concentrations in baseline conditions due to their unique geologies. From an AMD and ASS risk assessment perspective, regional water quality may therefore be unique and locally-relevant such that site-specific water quality guidelines may therefore be required to most reasonably manage water quality objectives. We provide case study examples from iron ore and coal mining from the Western Australian regions of the Pilbara, and the South-west to show that defining water quality criteria for closure is more than just using generic national guidelines, but an explicit consideration of the baseline regional bio-physico-chemical context

Ecological Restoration of Novel Lake Districts: New Approaches for New Landscapes

Mine void pit lakes often contain water of poor quality with potential for environmental harm that may dwarf other mine closure environmental issues in terms of severity, scope, and longevity. This is particularly so when many pit lakes occur close together and thus form a new ‘‘lake district’’ landscape. Pit lakes that can be developed into healthy lake or wetland ecosystems as a beneficial end use provide opportunities for the mining industry to fulfil commitments to sustainability. Clearly articulated restoration goals and a strategic closure plan are necessary to ensure pit lake restoration toward a new, yet regionally-relevant, aquatic ecosystem, which can achieve sustainability as an out-of-kind environmental offset. Such an approach must also consider obstacles to development of a self-sustaining aquatic ecosystem, such as water quality and ecological requirements. We recommend integration of pit lakes into their catchments as a landscape restoration planning exercise with clearly-identified roles and objectives for each new lake habitat and its surrounds

Regulation of artisanal small scale gold mining (ASGM) in Ghana and Indonesia as currently implemented fails to adequately protect aquatic ecosystems

Artisanal small scale gold mining (ASGM) operations are largely unregulated, informal and transient. Rudimentary mining and processing techniques used in ASGM often result in degraded environmental, safety, health and social conditions. ASGM requires permanent sources of water, placing most operations close to natural water bodies. Until recently, the impact on these environments has been largely overlooked, with most studies focussing primarily on mercury contamination and health concerns. Based on Ghanaian and Indonesian experiences, regulation of ASGM is a good step toward improvement, but here we argue that regulation alone is insufficient to improve environmental performance, particularly when the impacts of ASGM on aquatic ecosystems are largely unknown

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Upper and lower concentration thresholds for bioremediation of Acid Mine Drainage using bulk organic substrates

Acidic pit lakes can form in open cut mine voids that extend below the groundwater table. The aim of this research was to determine what bulk organic material concentrations best stimulated sulphate-reducing bacteria (SRB) for acid mine drainage (AMD) treatment within a pit lake. An experiment was carried out to assess the effect of different substrate concentrations of sewage sludge on AMD bioremediation efficiency. Experimental microcosms were made of 300 mm long and 100 mm wide acrylic cores, with a total volume of 1.8 L. Four different concentrations of sewage sludge (ranging from 30 to 120 g/L) were tested. As the sewage sludge concentration increased, the bioremediation efficiency also increased, reflecting the higher organic carbon concentrations. Sewage sludge contributed alkaline materials that directly neutralised the AMD in proportion to the quantity added and therefore played a primary role in stimulating SRB bioremediation. The lowest concentration of sewage sludge (30 g/L) tested proved to be inadequate for effective SRB bioremediation. However, there were no measurable beneficial effects on SRB bioremediation efficiency when sewage sludge was added at concentrations ˃60 g/L. We compared our results with existing literature data to develop a conceptual model for remediation of AMD in pit lakes through organic material amendments. The model indicated that labile organic carbon availability was more important to the bioremediation rate than AMD strength, so long as iron and sulphate concentrations were not limiting. The conceptual model also indicates that bioremediation may still occur when only low concentrations of organic carbon are present in the pit lakes, albeit at a very slow rate. The model also demonstrates the presence of an organic material amendment threshold where excess organic carbon does not measurably influence the final outcome. The conceptual model defined is well supported by the results of the microcosm experiment

How does storage affect the quality and quantity of organic carbon in sewage for use in the bioremediation of acidic mine waters?

Pit lakes (abandoned flooded mine pits) represent a potentially valuable water resource. However, acid mine drainage (AMD) generation due to mining activities often results in pit lake waters with low pH, high sulphate and dissolved metal concentrations. Sulphate reduction-based bioremediation offers tremendous scope for removal of acidity and metals from pit lake water. In this study, the effect of storing sewage on its carbon quality for bioremediation of acidic pit lake water was studied. In addition, the effectiveness of labile organic carbon (lactic acid and ethanol) on SRB activity was tested. Bioremediation experiments were performed in controlled and replicated microcosms with acidic (pH 2.2) water from a pit lake by addition of stored (3 years at 4 °C) sewage for stimulation of sulphate reducing bacteria (SRB) activity. This sewage had been previously used successfully in remediating to pH 7 water from this pit lake. The initial aim was to test the sewage at lower doses (18 and 28 g/L) and in a pulsed addition (over 5 weeks). Bioremediation efficacy was evaluated by measuring pit lake water pH increase, redox potential decrease, and acidity and sulphate removal. Though the stored sewage had retained a very similar high total organic carbon (TOC) equivalent to prior to storage, it failed to increase dissolved organic carbon (DOC) levels in pit lake water. Microcosms amended with doubled doses of sewage and an extended remediation time still failed to demonstrate any substantial improvement in water quality, other than a small amount of sulphate reduction and direct neutralisation by the sewage. In order to determine if low DOC concentrations in sewage were the cause of the bioremediation failure, labile organic carbon (LOC), consisting of 50:50 (w/w) lactic acid and ethanol, was added to all microcosm treatments at concentrations of 3000, 6000 and 9000 mg/L. After LOC addition, water quality improved with effective removal of acidity, sulphate and metals in the lowest carbon concentration (3000 mg/L). However, 6000 and 9000 mg/L LOC concentrations showed a delay in response due to the increased acidity associated with the lactic acid addition. The experiments showed that pulsed dosing of carbon simply slowed the commencement of remediation but it was ultimately able to reach the same effectiveness as the equivalent quantity added all at once. Prolonged storage of sewage leads to loss of LOC. In situ pit lake remediations which aim to make use of sewage as the main carbon source will need to factor in the storage time required to obtain sufficient sewage for the treatment into the design. Pulsing may help reduce issues with storage or supplementation with LOC may need to be considered. Results highlight that LOC is a more useful indicator of material effectiveness compared to a simple measures of TOC