Zinc transport and partitioning of a mine-impacted watershed: An evaluation of water and sediment quality

Watershed systems influenced by mining waste products can persist for many years after operations are ceased, leading to negative impacts on the health of the surrounding environment. While geochemical behaviors of these trace metals have been studied extensively at the benchtop-scale, much fewer studies have looked at controls on their distributions at the watershed-level. In this study, trace metals (As, Cd, Cr, Cu, Ni, and Zn) were reported from water and stream bed sediments at eight sites between the years 2014-2018 along a watershed undergoing active remediation efforts. Zn was determined to be the only trace metal analyzed with concentrations above EPA and Kansas Department of Health guidelines for both water and sediment in the watershed, and thus was the primary focus for determining the health of the watershed system. Controls on trace metal pollution distribution over the watershed were investigated to determine where remediation efforts should be focused. Surface cover seemed to have the highest effectivity with pasture lands having a strong positive correlation to Zn concentrations. Initial remediation efforts were assessed by calculating the geoaccumulation index (I_geo) and the contamination factor (C_f-sediment) from sediments and contamination factor from water (C_f-water) after decades of chat pile removal efforts. Most of the sites showed significant reduction in metal concentration values compared to previous studies in the watershed for water and sediment, with four sites still reporting concentrations that reveal potential health risks. Results from this study will inform management and policy makers for areas to focus their remediation efforts on the Spring River Watershed as well as providing a framework for assessing pollution at a watershed scale.

Assessing the efficiency and mechanism of zinc adsorption onto biochars from poultry litter and softwood feedstocks

The efficiency and adsorption mechanism of zinc removal was assessed in aqueous solution using four biochars from multiple biomass residues (poultry litter and three tree species). The effect of pH, kinetic effects, and isotherm fittings were investigated, as well as zinc-laden biochar using x-ray diffraction and absorption near edge structure. Sorbent load results showed softwood biochar exhibited the greatest zinc removal from both deionized (15 mg_Zn/L) and mining influenced river water (10 mg_Zn/L). The Langmuir isotherm was the best fit for the majority of the biochars. Exchangeable cations contributed most for the adsorption mechanism from the softwood biochars, while precipitation was greatest contribution for the poultry litter biochar. Overall, our results suggest that biochars from Douglas Fir trees are more efficient at removing zinc from aqueous solutions (up to 19.80 mg_Zn/g) compared to previously studied biochars (0.61 to 11.0 mg_Zn/g) and should be used for future remediation efforts.

Isotope ratio mass spectrometry and spectroscopic techniques for microplastics characterization

Micro- and nano-scale plastic particles in the environment result from their direct release and degradation of larger plastic debris. Relative to macro-sized plastics, these small particles are of special concern due to their potential impact on marine, freshwater, and terrestrial systems. While microplastic (MP) pollution has been widely studied in geographic regions globally, many questions remain about its origins. It is assumed that urban environments are the main contributors but systematic studies are lacking. The absence of standard methods to characterize and quantify MPs and smaller particles in environmental and biological matrices has hindered progress in understanding their geographic origins and sources, distribution, and impact. Hence, the development and standardization of methods is needed to establish the potential environmental and human health risks. In this study, we investigated stable carbon isotope ratio mass spectrometry (IRMS), attenuated total reflectance - Fourier transform infrared (ATR-FTIR) spectroscopy, and micro-Raman spectroscopy (μ-Raman) as complementary techniques for characterization of common plastics. Plastic items selected for comparative analysis included food packaging, containers, straws, and polymer pellets. The ability of IRMS to distinguish weathered samples was also investigated using the simulated weathering conditions of ultraviolet (UV) light and heat. Our IRMS results show a difference between the δ13C values for plant-derived and petroleum-based polymers. We also found differences between plastic items composed of the same polymer but from different countries, and between some recycled and nonrecycled plastics. Furthermore, increasing δ13C values were observed after exposure to UV light. The results of the three techniques, and their advantages and limitations, are discussed.

Sources, transport, measurement and impact of nano and microplastics in urban watersheds

The growing and pervasive presence of plastic pollution has attracted considerable interest in recent years, especially small (< 5 mm) plastic particles known as 'microplastics' (MPs). Their widespread presence may pose a threat to marine organisms globally. Most of the nano and microplastic (N&MP) pollution in marine environments is assumed to originate from land-based sources, but their sources, transport routes, and transformations are uncertain. Information on freshwater and terrestrial systems is lacking, and data on nanoplastic pollution are particularly sparse. The shortage of systematic studies of freshwater and terrestrial systems is a critical research gap because estimates of plastic release into these systems are much higher than those for oceans. As most plastic pollution originates in urban environments, studies of urban watersheds, particularly those with high population densities and industrial activities, are especially relevant with respect to source apportionment. Released plastic debris is transported in water, soil, and air. It can be exchanged between environmental compartments, adsorb toxic compounds, and ultimately be carried long distances, with potential to cause both physical and chemical harm to a multitude of species. Measurement challenges and a lack of standardized methods has slowed progress in determining the environmental prevalence and impacts of N&MPs. An overall aim of this review is to report the sources and abundances of N&MPs in urban watersheds. We focus on urban watersheds, and summarize monitoring methods and their limitations, knowing that identifying N&MPs and their urban/industrial sources is necessary to reduce their presence in all environments.

Recent advances in flue gas desulfurization gypsum processes and applications - A review

Flue gas desulfurization gypsum (FGDG) is an industrial by-product generated during the flue gas desulfurization process in coal-fired power plants. Due to its abundance, chemical and physical properties, FGDG has been used in several beneficial applications. However, during the past decade, the rate of beneficially used FGDG has gradually decreased, while its production has drastically increased. The presence of hazardous elements such as arsenic, mercury, cadmium, lead, and selenium in FGDG has reduced its beneficial value. Nevertheless, due to the recent developments in flue gas desulfurization processes, the "modern" FGDG contains lesser amounts of these elements, thus increasing its beneficial value and appeal to be included in other products. Hence, there are novel and traditional FGDG applications in different reuse scenarios investigated recently that have been deemed to pose minimal environmental concern - these need to be better understood. This review summarizes beneficial FGDG applications that have been deemed to pose minimal environmental concern, emphasizing their principles, research gaps, and potential developments, with the aim of increasing the reuse rate of FGDG.

Comparison of the efficiency of chitinous and ligneous substrates in metal and sulfate removal from mining-influenced water

Mining-influenced water (MIW) remediation is challenging, not only due to its acidity and high metal content, but also due to its presence in remotely located mine sites with difficult surrounding environments. An alternative to common remediation technologies, is the use of sulfate-reducing bacteria (SRB) to achieve simultaneous sulfate reduction and metal removal in on-site anaerobic passive systems. In these systems, the organic carbon source (substrate) selection is critical to obtaining the desired effluent water quality and a reasonable treated volume. In this study, we evaluated the use of two different substrates: a chitinous product obtained from crushed crab shells, and a more traditional ligneous substrate. We put the substrates, both with and without water pretreatment consisting of aeration and pH adjustment, in anaerobic experimental columns. The treatment with the chitinous substrate was more effective in removing metals (Al, Cu, Fe, Cd, Mn, Zn) and sulfate for a longer period (458 days) than the ligneous substrate (78 days) before suffering Zn breakthrough. The reactors fed with pretreated water had longer operational periods and lower metals and sulfate concentrations in the effluent than those with untreated influent water. Zn was consistently removed to levels <0.3 mg/L for 513 days in the chitinous substrate columns, while levels <0.3 mg/L were maintained for only 140 days in the ligneous substrate pretreated column. The highest sulfate removal rates achieved in this study were in the range of 5-6 mol/m³/d for the chitinous substrate and 1-2 mol/m³/d for the ligneous substrate. Overall, the chitinous substrate proved to be more efficient in the removal of all the aforementioned metals and for sulfate when compared to the ligneous substrate. This could be the determinant when selecting a substrate for passive systems treating acidic MIW, particularly when Zn and Mn removal is necessary.

Assessing the Impact of Removing Select Materials from Coal Mine Overburden, Central Appalachia Region, USA

The exposure of readily soluble components of overburden materials from surface coal mining to air and water results in mineral oxidation and carbonate mineral dissolution, thus increasing coal mine water conductivity. A conductivity benchmark of 300 μS/cm for mine water discharges in the Appalachian region has been suggested to protect aquatic life and the environment. A USGS screening-level leach test was applied to individual strata from three cores collected from a surface mine site in the Central Appalachian region to generate preliminary conductivity rankings, which were used to classify strata for two disposal scenarios: (i) Unmodified Scenario, which included all extracted strata and (ii) Modified Scenario, which excluded 15% (by mass) of the overburden materials with the highest conductivities. We evaluated overburden leaching conductivity using EPA Method 1627 in 18 dry-wet cycles, generating conductivities of 1,020-1,150 μS/cm for the Unmodified Scenario and 624-979 μS/cm for the Modified Scenario. Hence, overburden segregation was successful in reducing the leachate conductivity, but did not reach the proposed benchmark. The leachate was dominated by sulfate in the first four cycles and by bicarbonates in cycles 5-18 in columns with higher sulfur content, while bicarbonates were dominant throughout experiments with lower sulfur content in overburden. The use of conductivity rankings, isolation of potentially problematic overburden strata, and appropriate materials management could reduce conductivity in Central Appalachian streams and other surface mining areas.

Mechanisms and effectivity of sulfate reducing bioreactors using a chitinous substrate in treating mining influenced water

Mining-influenced water (MIW) is one of the main environmental challenges associated with the mining industry. Passive MIW remediation can be achieved through microbial activity in sulfate-reducing bioreactors (SRBRs), but their actual removal rates depend on different factors, one of which is the substrate composition. Chitinous materials have demonstrated high metal removal rates, particularly for the two recalcitrant MIW contaminants Zn and Mn, but their removal mechanisms need further study. We studied Cd, Fe, Zn, and Mn removal in bioactive and abiotic SRBRs to elucidate the metal removal mechanisms and the differences in metal and sulfate removal rates using a chitinous material as substrate. We found that sulfate-reducing bacteria are effective in increasing metal and sulfate removal rates and the duration of operation in SRBRs, and that the main mechanism involved was metal precipitation as sulfides. The solid residues provided evidence of the presence of sulfides in the bioactive column, more specifically ZnS, according to XPS analysis. The feasibility of passive treatments with a chitinous substrate could be an important option for MIW remediation.

Assessing metal mobilization from industrial lead-contaminated soils in an urban site

A series of leaching and partitioning tests (Toxicity Characteristic Leaching Procedure (TCLP), Synthetic Precipitation Leaching Procedure (SPLP), Controlled Acidity Leaching Protocol (CALP), Acid Neutralization Capacity (ANC), and sequential extraction) were applied to three different soils to study the potential mobility of metals into groundwater. Two of these soils were lead (Pb)-contaminated soils (Hotspot 1 and Hotspot 2) collected from an urban site associated with lead smelting and other industrial operations. The third sample (Stockpile) was soil affected by previous contamination in the area, removed from residential properties, stockpiled, and selected to be used as fill material in the studied site. The TCLP and CALP showed that Pb could be released from both hotspots, but were not released in the acidic rainfall extraction fluid of the SPLP. The sequential extraction showed that Pb in the hotspot soils was associated with the carbonate fraction, while As was associated with the Fe and Mn oxides. The stockpile released traces of Pb or As in the TCLP and CALP, but the ANC only released Pb under acidic conditions and the SPLP did not release Pb or As. Overall, the projected repository with Stockpile would not pose imminent danger to groundwater because, under the expected environmental conditions, Pb and As tend to remain in the solid phase.

Assessment of primary stability of the implant placed in prepared infected extraction sockets

Background

Dental conditions like periodontal, periapical pathologies and failed endodontically treated teeth are one of the commonest reasons for tooth removal. These conditions also contraindicate replacement of such teeth with immediate implant procedures.

Aim

This study aimed to evaluate the clinical and radiological fate of immediately placed dental implants in debrided infected dentoalveolar sockets.

Materials and methods

A total of 24 implants were immediately placed into prepared infected sockets. The pathology at the receptacle sockets included subacute periodontal infection, perio-endo infection, chronic periapical infection, periodontal cyst and traumatic infected teeth. The treatment protocol emphasized on meticulous debridement of the infected sockets under pre- and post-surgical antibiotic therapy. Follow up of at least 24 months was done to evaluate the survival of implants.

Results

At the end of follow up time period of 24 months, all 24 implants were stable with no signs of clinical mobility and infection. However, on radiological examination, crestal bone loss was observed during the osseointegration periods which settled at the level of first thread.

Conclusion

Survival of immediately placed implants in infected sockets is predictable and depends on the meticulous debridement of dentoalveolar sockets along with adequate pre- and post-operative antibiotic coverage.

Evaluation of metal partitioning and mobility in a sulfidic mine tailing pile under oxic and anoxic conditions

Mining-influenced water emanating from mine tailings and potentially contaminating surface water and groundwater is one of the most important environmental issues linked to the mining industry. In this study, two subsets of Callahan Mine tailings (mainly comprised of silicates, sulfides, and carbonates) were collected using sealed containers, which allowed keeping the samples under anoxic conditions during transportation and storage. Among the potential contaminants, in spite of high concentrations of Cu, Mn, Pb, and Zn present in the solid mine tailings, only small amounts of Mn and Zn were found in the overlying pore water. The samples were subjected to leaching tests at different reduction-oxidation (redox) conditions to compare metal and S mobilization under oxic and anoxic conditions. It was observed that Cd, Cu, Mn, Pb, S, and Zn were mobilized at higher rates under oxic conditions, while Fe was mobilized at a higher rate under anoxic conditions in comparable constant pH experiments. These results suggest that metal mobilization is significantly impacted by redox conditions. When anoxic metal mobilization assessment is required, it is recommended to always maintain anoxic conditions because oxygen exposure may affect metal mobilization. A sequential extraction performed under oxic conditions revealed that most of the metals in the samples were associated with the sulfidic fraction and that the labile fraction was associated with Mn and moderate amounts of Pb and Zn.

Restructuring an undergraduate dental curriculum to global standards--a case study in an Indian dental school

Globalisation has affected all aspects of life and dentistry is no exception. In the context of today's dentist being a global citizen, undergraduate training in dentistry is set to ensure converging standards so that international recognition of dental qualifications can move forward. The decision of the Dental Council of India to expand the undergraduate dental program to five years provides an opportunity to be part of the endeavor of the Global Dental Congress to achieve converging standards which was initially for the European Union, and now spreading out globally. Economic emergence in Indian subcontinent has resulted in growing oral health care needs both in quality and quantity. To address this issue, the graduating dentist needs to be trained following a competency based curricular model. Access to Internet facilitated the goal of achieving converging standards of dental schools to be feasible because of the instant communication and capacity to share information about training strategies via technology across the globe. Upgrading the undergraduate training to global standards by dental schools in India could be a wise and strategic move both for attracting students to study in India, as well as retaining the graduates after their training. The following is a case study of an Indian dental school set to restructure the undergraduate curriculum to global standards using the 8 steps of Kotter's transformational change. Change in curriculum and the subsequent accreditation of the school in global platform not only attracts prospective students but also results in producing competent dentists. Dental education provided by the institution can result in quality assurance, benchmarking the assessment system to achieve international recognition. This paper highlights the need and importance of facilitation of international convergence with long term aspirations for mutual recognition of international degrees.

Environmental impact of the use of contaminated sediments as partial replacement of the aggregate used in road construction

The Indiana Harbor Canal (IHC) is a waterway extensively polluted with heavy metals and petroleum. Since there are limited disposal options for the petroleum-contaminated sediments (PCSs) of the canal, the environmental impact of IHC dewatered sediment when used as partial replacement of the aggregate used in hot mix asphalt (HMA) for road construction was investigated. In order to assess the long term migration of the target contaminants into the environment, the TCLP, SPLP, and a Constant pH leaching test were applied to a HMA mixture containing 10% of dewatered PCS, a conventional HMA, and the dewatered PCS. None of the heavy metals significantly leached from any of the tested materials in any of the conducted tests. Despite the presence of PAHs in the PCS, these were not found in any of the leachate samples. Finally, among the measured VOCs, only acetone and 2-butanone were found to leach from the asphalt mixtures and the sediment in the Constant pH experiment. It was concluded that it may be environmentally safe to replace the aggregates of the HMA used in road construction in the studied proportions with dewatered PCS based upon leaching levels as compared to TCLP regulated levels. This could be a viable, beneficial use option for the PCS, and therefore, for the canal remediation.

Treatment of groundwater contaminated with PAHs, gasoline hydrocarbons, and methyl tert-butyl ether in a laboratory biomass-retaining bioreactor

In this study, we investigated the treatability of co-mingled groundwater contaminated with polycyclic aromatic hydrocarbons (PAHs), gasoline hydrocarbons, and methyl tert-butyl ether (MtBE) using an ex-situ aerobic biotreatment system. The PAHs of interest were naphthalene, methyl-naphthalene, acenaphthene, acenaphthylene, and carbazole. The gasoline hydrocarbons included benzene, toluene, ethyl benzene, and p-xylene (BTEX). Two porous pot reactors were operated for a period of 10 months under the same influent contaminant concentrations. The contaminated groundwater was introduced into the reactors at a flow rate of 4 and 9 l/day, resulting in a hydraulic retention time (HRT) of 32 and 15 h, respectively. In both reactors, high removal efficiencies were achieved for the PAHs (>99%), BTEX and MtBE (>99.7%). All the PAHs of interest and the four BTEX compounds were detected at concentrations less than 1 mug/l throughout the study duration. Effluent MtBE from both reactors was observed at higher levels; nevertheless, its concentration was lower than the 5 mug/l Drinking Water Advisory for MtBE implemented in California.

Immediate postexpansion changes following the use of the transpalatal distractor

PURPOSE

This study analyzed the immediate postexpansion positional changes of the maxillary halves resulting from the use of the transpalatal distractor (Surgi-Tec NV, Bruges, Belgium).

PATIENTS AND METHODS

Corticotomies were performed in the same way as surgically assisted rapid palatal expansion, all from a buccal sulcus approach. Titanium abutment plates with box extension were placed horizontally in the vertical wall of the palatal vault overlying the second premolar root through a mucoperiosteal incision and fixed with titanium screws 5 mm in length. An appropriate telescopic distraction module was fitted in the slots of the boxes. Expansion started 1 week after surgery, at a rate of 0.33 mm/d. Digital measurements on digital photographs of the models were obtained from 20 postadolescent patients before and immediately after transpalatal distraction. The distractor was placed at the level of the second premolar. Pterygomaxillary separation was not performed. Changes in the intercanine, interpremolar and intermolar width, in the dental arch perimeter, and in the premolar and molar angulations in the frontal plane were analyzed and correlated.

RESULTS

Width expansions of 35.7%, 31.7%, and 22.7% were noted in the canine, premolar, and molar regions, respectively. There was a mean increase of the arch perimeter of 10.5%, which correlated well (P <.001) with the expansion at the canine and premolar level. The mean angulation changes in the frontal plane of the premolar and molar segments were minimal, -8.3 degrees +/- 9.6 degrees and 0.9 degrees +/- 9.9 degrees, respectively. The change in angulation at the molar level correlated (P <.005) with the amount of expansion in that region. Premolar angulation did not correlate with the expansion, and segment angulation did not correlate with age.

CONCLUSIONS

The expansion at the canine level was 1.5 times greater than at the molar level (corrected value relative to the original intermolar width). The change in arch perimeter can be predicted from the expansion at the canine and premolar level. Expansion in the frontal plane occurs with little tipping of the segments.

Proteus syndrome. A case report of a hamartomatous syndrome with severe mandibular hemihypertrophy

Proteus syndrome is a rare congenital hamartomatous malformation that is characterized by a wide range of deformities, including craniofacial deformities. Skin and skeletal developmental malformations are common and may assume tremendous proportions. The syndrome is often mistaken for other, more commonly recognized conditions, including neurofibromatosis. The soft-tissue masses in Proteus syndrome are not nerve tumors but are usually hamartomatous proliferations. The case report describes its varied manifestations, which include significant craniofacial dysmorphism, and discusses the differential diagnosis and management.

Regional metastasis in polymorphous low grade adenocarcinoma. Report of a case

A case of cervical lymph node metastases of polymorphous low grade adenocarcinoma is reported, originating from a minor salivary gland in the soft palate in a 76-year-old man, 19 years after initial presentation. The clinical course, histopathology, and literature review on the metastatic aspect of the tumour are presented. This has emphasized the need for increased awareness of this recently described tumour and the need for lifelong follow up.