Sustainable remediation of abandoned lead mine tailings

The extraction of lead (Pb) has occurred throughout Europe for over 3,000 years, bringing substantial benefits to economies, technological advances and the development of infrastructure. The relative ease of extraction and refinement of Pb, coupled with its usefulness in a range of applications resulted in extensive, and often unmanaged, exploitation of this element. The environmental legacy of historic Pb mining activities are evident throughout Europe, with hundreds of abandoned mine tailings documented throughout the EU and in the UK. These mining sites often present a risk of point and diffuse source pollution, with the main issues occurring from the introduction of potentially toxic elements (PTE) into the surrounding environment. Abandoned (Pb) mines are often inherited by new landowners who are consequently liable for their management, generating a burden of responsibility that may involve restorative action. Unfortunately, the cost of conventional remedial strategies is frequently prohibitive for small landowners to undertake, leading to the possible continued dereliction of these sites. Identifying economically feasible and effective solutions to this issue is therefore of importance. Critically, reducing the risk of PTE impacts to the environment is pertinent, as are endeavours to convert these derelict mines into more productive landscapes. Therefore, the overarching aim of this thesis was to further knowledge on ecologically driven remedial approaches to metalliferous mine tailings to lessen the economic issues faced in environmental protection. In particular, the thesis aimed to ascertain if it was feasible to use native plant species and locally available waste materials to promote the revegetation of abandoned Pb mines, and consequently provide a sustainable vegetative barrier that could limit PTE release into the surrounding environment. The investigation was centred on two abandoned Pb mines, located on the West coast of Scotland (Tyndrum) and the South of France (Le Bleymard). Geo-statistical investigations identified elevated concentrations of total Cd, Pb and Zn at both sites combined with a lack of organic matter, plant nutrients and poor physical structure conditions for vegetation. Contrasting findings were identified, with the Tyndrum tailings exhibiting a higher potential mobility of PTE than Le Bleymard and a particular risk of hydrological movement of PTE enriched material from the mine to the wider environment. In opposition, the calcareous nature of the Le Bleymard tailings minimised PTE mobility via surface absorption and precipitation mechanisms, with the greatest risk to the surrounding environment likely caused by the aeolian transportation of fine particulates and inhalation of PTE enriched material. The use of inverse distance weighting and empirical Bayesian kriging highlighted the heterogeneous distribution of PTE enriched material at Tyndrum and the movement of small (<100 μm), Pb enriched particulates at Le Bleymard. A combination of laboratory and field studies highlighted the use of common bent (Agrostis capillaris) as a useful phytostabilisation species, which was observed to be tolerant of up to 10,000 mg kg-1 Pb, 12,000 mg kg-1 Zn, and 180 mg kg-1 Cd in plant tissues. Furthermore, this species was generally effective in reducing the transference of PTE from the roots to aerial compartments of the plant, therefore minimising possible PTE transference to the food web. It was found that laboratory studies involving the spiking of PTE into synthetic growth media substantially underestimated plant uptake of Pb, Zn and Cd in the field and so should be used with caution when informing field trials. The addition of organic amendments into the tailings produced contrary results depending on the source of the organic amendment and the underlying tailing characteristics. Broadly, the introduction of organic amendments into the slightly acidic tailings at Tyndrum can elicit the mobility of Pb by complexation with soluble Fe compounds and organic ligands, whilst concurrently promoting the immobilisation of Cd and Zn. Over a longer period, the separate incorporation of spent coffee grounds (SCG) and green waste compost (GWC) reduced the concentration of weakly associated Pb by complexation with stable organic matter and Fe/Mn oxy-hydroxides by 36.9 and 28.9 % respectively. Furthermore, improvements in plant available nitrogen (N), phosphorous (P), microbial activity and organic matter were observed in both field and laboratory settings, with the inclusion of SCG observed to have the largest effect across all properties. Contrasting results were found in the calcareous tailings of Le Bleymard, where the potential mobilisation effects generated by organic amendments to PTE were mitigated by the elevated pH and occurrence of adsorption and precipitation events, leading to initial net gains of increased tailing fertility and minimal PTE mobilisation. However, a loss of plant available and total N coupled with the immobilisation of soluble P was observed, which was partially attributable for the stunted growth of A.capillaris during field trials when comparing the study sites. The use of A.capillaris and the incorporation of organic amendments in the potential remediation of two contrasting abandoned Pb tailings were found to be substantially influenced by the underlying geo-chemical characteristics of the mine tailings. In conclusion it was suggested that the re-vegetation of the Tyndrum tailings could be achieved using SCG or a similar material which would provide a source of plant and microbial support combined with a high capacity for stable complexation of PTEs with C compounds. For Le Bleymard, suggesting a suitable material is more difficult due to conflicting needs to balance the risk of PTE release via the acidification of the tailings and enhancing the availability of plant nutrients. Overall, it was found that the use of A.capillaris combined with SCG or a comparable organic material could be highly effective in revegetation efforts at the Tyndrum site. However, wider investigations are suggested to be undertaken to identify a suitable material in the promotion of vegetation at the Le Bleymard tailings. It can be concluded that this work has furthered our understanding of ecologically driven rehabilitation of abandoned mine tailings and has highlighted the need for more work to be completed on calcareous mine tailings

Evidence of continued injecting drug use after attaining sustained treatment-induced clearance of the hepatitis C virus: implications for reinfection

Background: People who inject drugs (PWID) are at the greatest risk of hepatitis C virus (HCV) infection, yet are often denied immediate treatment due to fears of on-going risk behaviour. Our principal objective was to examine evidence of continued injecting drug use among PWID following successful treatment for HCV and attainment of a sustained viral response (SVR). Methods: PWID who attained SVR between 1992 and June 2012 were selected from the National Scottish Hepatitis C Clinical Database. Hospitalisation and mortality records were sourced for these patients using record linkage techniques. Our primary outcome variable was any hospitalisation or death, which was indicative of injecting drugs post-SVR. Results: The cohort comprised 1170 PWID (mean age at SVR 39.6y; 76% male). The Kaplan Meier estimate of incurring the primary outcome after three years of SVR was 10.59% (95% CI, 8.75–12.79) After adjusting for confounding, the risk of an injection related hospital episode or death post-SVR was significantly increased with advancing year of SVR: AHR:1.07 per year (95% CI, 1.01–1.14), having a pre-SVR acute alcohol intoxication-related hospital episode: AHR:1.83 (95% CI, 1.29–2.60), and having a pre-SVR opiate or injection-related hospital episode: AHR:2.59 (95% CI, 1.84–3.64). Conclusion: Despite attaining the optimal treatment outcome, these data indicate that an increasing significant minority of PWID continue to inject post-SVR at an intensity which leads to either hospitalisation or death and increased risk of reinfection

Competing risk bias in prognostic models predicting hepatocellular carcinoma occurrence: impact on clinical decision making

Existing models predicting hepatocellular carcinoma (HCC) occurrence do not account for competing risk events and, thus, may overestimate the probability of HCC. Our goal was to quantify this bias for patients with cirrhosis and cured hepatitis C. We analyzed a nationwide cohort of patients with cirrhosis and cured hepatitis C infection from Scotland. Two HCC prognostic models were developed: (1) a Cox regression model ignoring competing risk events and (2) a Fine-Gray regression model accounting for non-HCC mortality as a competing risk. Both models included the same set of prognostic factors used by previously developed HCC prognostic models. Two predictions were calculated for each patient: first, the 3-year probability of HCC predicted by model 1 and second, the 3-year probability of HCC predicted by model 2. The study population comprised 1629 patients with cirrhosis and cured HCV, followed for 3.8 years on average. A total of 82 incident HCC events and 159 competing risk events (ie, non-HCC deaths) were observed. The mean predicted 3-year probability of HCC was 3.37% for model 1 (Cox) and 3.24% for model 2 (Fine-Gray). For most patients (76%), the difference in the 3-year probability of HCC predicted by model 1 and model 2 was minimal (ie, within 0 to ±0.3%). A total of 2.6% of patients had a large discrepancy exceeding 2%; however, these were all patients with a 3-year probability exceeding >5% in both models. Prognostic models that ignore competing risks do overestimate the future probability of developing HCC. However, the degree of overestimation—and the way it is patterned—means that the impact on HCC screening decisions is likely to be modest

Long-distance optical-conveyor-belt transport of ultracold 133 Cs and 87 Rb atoms

We report on the transport of a thermal cloud of ultracold cesium and rubidium atoms over about 37 cm in under 25 ms using an optical conveyor belt formed by two counterpropagating beams with a controllable frequency difference that generate a movable optical lattice. By carefully selecting the waists and focus positions, we are able to use two static Gaussian beams for the transport, avoiding the need for a Bessel beam or variable-focus lenses. We characterize the transport efficiency for both species, including a comparison of different transport trajectories, gaining insight into the loss mechanisms and finding the minimum jerk trajectory to be optimum. Using the optimized parameters, we are able to transport up to 7×106 cesium or rubidium atoms with an efficiency up to 75%. To demonstrate the viability of our transport scheme for experiments employing quantum gas microscopy, we produce Bose-Einstein condensates of either species after transport and present measurements of the simultaneous transport of both species

The risk of hepatocellular carcinoma in cirrhotic patients with hepatitis C and sustained viral response:role of the treatment regimen

Background &amp; Aims: Previous studies have reported a high frequency of hepatocellular carcinoma (HCC) occurrence in patients with advanced liver disease, after receipt of interferon (IFN)-free therapy for hepatitis C virus (HCV) infection. Our objective was to verify and account for this phenomenon using data from the Scottish HCV clinical database. Methods: We identified HCC-naïve individuals with liver cirrhosis receiving a course of antiviral therapy in Scotland from 1997–2016 resulting in a sustained virologic response. Patients were followed-up from their treatment start date to the earliest of: date of death, date of HCC occurrence, or 31 January 2017. We used Cox regression to compare the risk of HCC occurrence according to treatment regimen after adjusting for relevant co-factors (including: demographic factors; baseline liver disease stage; comorbidities/health behaviours, virology, and previous treatment experience). HCC occurrence was ascertained through both the HCV clinical database and medical chart review. For our main analysis, treatment regimen was defined as IFN-free vs. IFN-containing. Results: A total of 857 patients met the study criteria, of whom 31.7% received an IFN-free regimen. Individuals receiving IFN-free therapy were more likely to be: older; of white ethnicity, Child-Turcotte-Pugh B/C vs. Child-Turcotte-Pugh A; thrombocytopenic; non-genotype 3; and treatment experienced. HCC occurrence was observed in 46 individuals during follow-up. In univariate analysis, IFN-free therapy was associated with a significantly increased risk of HCC (HR: 2.48; p = 0.021). However, after multivariate adjustment for baseline factors, no significant risk attributable to IFN-free therapy persisted (aHR: 1.15, p = 0.744). Conclusion: These findings suggest that the higher incidence of HCC following sustained virologic response with IFN-free therapy relates to baseline risk factors/patient selection, and not the use of IFN-free therapy per se. Lay summary: We examined the risk of liver cancer in 857 patients with cirrhosis in Scotland who received hepatitis C antiviral therapy and achieved a cure. We compared the risk of first-time liver cancer in patients treated with the newest interferon-free regimens, to patients treated with interferon. After accounting for the different characteristics of these two treatment groups, we found no evidence that interferon-free therapy is associated with a higher risk of liver cancer

Effect of Theophylline as Adjunct to Inhaled Corticosteroids on Exacerbations in Patients With COPD: A Randomized Clinical Trial

Importance: Chronic obstructive pulmonary disease (COPD) is a major global health issue and theophylline is used extensively. Preclinical investigations have demonstrated that low plasma concentrations (1-5 mg/L) of theophylline enhance antiinflammatory effects of corticosteroids in COPD.  Objective: To investigate the effectiveness of adding low-dose theophylline to inhaled corticosteroids in COPD.  Design, Setting, and Participants: The TWICS (theophylline with inhaled corticosteroids) trial was a pragmatic, double-blind, placebo-controlled, randomized clinical trial that enrolled patients with COPD between February 6, 2014, and August 31, 2016. Final follow-up ended on August 31, 2017. Participants had a ratio of forced expiratory volume in the first second to forced vital capacity (FEV1/FVC) of less than 0.7 with at least 2 exacerbations (treated with antibiotics, oral corticosteroids, or both) in the previous year and were using an inhaled corticosteroid. This study included 1578 participants in 121 UK primary and secondary care sites.  Interventions: Participants were randomized to receive low-dose theophylline (200 mg once or twice per day) to provide plasma concentrations of 1 to 5 mg/L (determined by ideal body weight and smoking status) (n = 791) or placebo (n = 787).  Main Outcomes and Measures: The number of participant-reported moderate or severe exacerbations treated with antibiotics, oral corticosteroids, or both over the 1-year treatment period.  Results: Of the 1567 participants analyzed, mean (SD) age was 68.4 (8.4) years and 54% (843) were men. Data for evaluation of the primary outcome were available for 1536 participants (98%) (772 in the theophylline group; 764 in the placebo group). In total, there were 3430 exacerbations: 1727 in the theophylline group (mean, 2.24 [95% CI, 2.10-2.38] exacerbations per year) vs 1703 in the placebo group (mean, 2.23 [95% CI, 2.09-2.37] exacerbations per year); unadjusted mean difference, 0.01 (95% CI, −0.19 to 0.21) and adjusted incidence rate ratio, 0.99 (95% CI, 0.91-1.08). Serious adverse events in the theophylline and placebo groups included cardiac, 2.4% vs 3.4%; gastrointestinal, 2.7% vs 1.3%; and adverse reactions such as nausea (10.9% vs 7.9%) and headaches (9.0% vs 7.9%).  Conclusions and Relevance: Among adults with COPD at high risk of exacerbation treated with inhaled corticosteroids, the addition of low-dose theophylline, compared with placebo, did not reduce the number COPD exacerbations over a 1-year period. The findings do not support the use of low-dose theophylline as adjunctive therapy to inhaled corticosteroids for the prevention of COPD exacerbations