Crop uptake of heavy metals in response to the environment and agronomic practices on land near mine tailings in the Zambian Copperbelt Province.

A field experiment was undertaken on farmers' fields adjacent to a large mine tailings dam in the Zambian mining town of Kitwe. Experimental plots were located close to the tailings (≤ 200 m) or further away (300-400 m) within the demarcated land farmed by the same community. This study evaluated the uptake of Cd, Cu, Ni, Pb and Zn by pumpkin leaves and maize grown in soil amended with lime and manure applied at agronomic rates, and the subsequent risk of dietary exposure to the local community, typical of many similar situations across the Zambian Copperbelt. Treatments, combinations of lime and manure (present or absent), were applied to subplots selected independently and randomly within each main plot, which represented variable geochemistry across this study site as a result of windblown/rain-driven dust from the tailings. Total elemental concentrations in crops were determined by ICP-MS following microwave-assisted acid digestion. Concentrations of Cu and Pb in pumpkin leaves were above the prescribed FAO/WHO safe limits by 60-205% and by 33-133%, respectively, while all five metals were below the limit for maize grain. Concentration of metals in maize grain was not affected by the amendments. However, lime at typical agronomic application rates significantly reduced concentrations of Cd, Cu, Pb and Zn in the pumpkin leaves by 40%, 33%, 19% and 10%, respectively, and for manure Cd reduced by 16%, while Zn increased by 35%. The uptake of metals by crops in locations further from the tailings was greater than closer to the tailings because of greater retention of metals in the soil at higher soil pH closer to the tailings. Crops in season 2 had greater concentrations of Cu, Ni, Pb and Zn than in season 1 due to diminished lime applied only in season 1, in line with common applications on a biannual basis. Maize as the staple crop is safe to grow in this area while pumpkin leaves as a readily available commonly consumed leafy vegetable may present a hazard due to accumulation of Cu and Pb above recommended safe limits.

Review: mine tailings in an African tropical environment-mechanisms for the bioavailability of heavy metals in soils.

Heavy metals are of environmental significance due to their effect on human health and the ecosystem. One of the major exposure pathways of Heavy metals for humans is through food crops. It is postulated in the literature that when crops are grown in soils which have excessive concentrations of heavy metals, they may absorb elevated levels of these elements thereby endangering consumers. However, due to land scarcity, especially in urban areas of Africa, potentially contaminated land around industrial dumps such as tailings is cultivated with food crops. The lack of regulation for land-usage on or near to mine tailings has not helped this situation. Moreover, most countries in tropical Africa have not defined guideline values for heavy metals in soils for various land uses, and even where such limits exist, they are based on total soil concentrations. However, the risk of uptake of heavy metals by crops or any soil organisms is determined by the bioavailable portion and not the total soil concentration. Therefore, defining bioavailable levels of heavy metals becomes very important in HM risk assessment, but methods used must be specific for particular soil types depending on the dominant sorption phases. Geochemical speciation modelling has proved to be a valuable tool in risk assessment of heavy metal-contaminated soils. Among the notable ones is WHAM (Windermere Humic Aqueous Model). But just like most other geochemical models, it was developed and adapted on temperate soils, and because major controlling variables in soils such as SOM, temperature, redox potential and mineralogy differ between temperate and tropical soils, its predictions on tropical soils may be poor. Validation and adaptation of such models for tropical soils are thus imperative before such they can be used. The latest versions (VI and VII) of WHAM are among the few that consider binding to all major binding phases. WHAM VI and VII are assemblages of three sub-models which describe binding to organic matter, (hydr)oxides of Fe, Al and Mn and clays. They predict free ion concentration, total dissolved ion concentration and organic and inorganic metal ion complexes, in soils, which are all important components for bioavailability and leaching to groundwater ways. Both WHAM VI and VII have been applied in a good number of soils studies with reported promising results. However, all these studies have been on temperate soils and have not been tried on any typical tropical soils. Nonetheless, since WHAM VII considers binding to all major binding phases, including those which are dominant in tropical soils, it would be a valuable tool in risk assessment of heavy metals in tropical soils. A discussion of the contamination of soils with heavy metals, their subsequent bioavailability to crops that are grown in these soils and the methods used to determine various bioavailable phases of heavy metals are presented in this review, with an emphasis on prospective modelling techniques for tropical soils.

Percutaneous intervention for infrageniculate arterial disease in women may be associated with better outcomes when compared to men.

OBJECTIVE: The purpose of this study was to identify any gender-associated differences in the percutaneous treatment of infrageniculate lesions in individuals with chronic critical limb ischemia. METHODS: A retrospective chart review was performed on 112 index tibial lesions in 81 consecutive patients operated on from January 2005 to February 2011. All patients were treated for critical limb ischemia-defined as rest pain or tissue loss. Patient demographics, comorbidities, clinical presentation, vascular studies, lesion characteristics, procedures, and postoperative complications were entered into a database for review. Patients were evaluated for primary patency, secondary patency, limb salvage, and mortality rates. RESULTS: Sixty-three index tibial lesions were treated percutaneously in 43 women, compared to 49 lesions in 38 men. There was a trend toward increased cardiac disease (65.8% men vs 44.2% women; P = .052) and smoking (52.6% men vs 32.6% women; P = .070) in men. Men were more likely than women to have TransAtlantic Inter-Society Consensus (TASC) C and D lesions (83.7% vs 65.1%; P = .023) and to be treated for total occlusion (44.9% vs 25.4%; P = .031). There were no significant gender-related differences in length of stay or postoperative complications. Women had statistically better primary patency rates than men at 12 and 24 months (77.5% ± 6.9% and 72.9% ± 7.8% in women vs 58.7% ± 9.3% and 45.2% ± 9.9% in men; P = .032). Women also had statistically better secondary patency rates than men at 12 and 24 months (90.4% ± 4.8% and 85.1% ± 6.8% in women vs 76.0% ± 8.1% and 58.5% ± 10.8% in men; P = .028). Female gender remained an independent predictor of superior patency even after controlling for gender-related differences in TASC grade. There were no significant differences in limb salvage rates at 12 and 24 months (92.1% ± 4.4% and 85.0% ± 7.9% in women vs 88.3% ± 6.4% and 83.4% ± 7.7% in men; P = .985). Overall survival rates were similar (59.8% ± 7.6% for women and 68.0% ± 8.1% for men at 24 months; P = .351). CONCLUSIONS: Percutaneous intervention may be an equally effective or better treatment option for women with chronic limb ischemia and tibial disease when compared to men. In this study, male gender was an independent predictor of poorer primary and secondary patency rates after infrageniculate intervention. There were no differences in postoperative wound complications between genders. Endovascular procedures may lessen the gap in gender-related treatment outcomes and postoperative complications seen after open arterial reconstructions.

MULTILAYERED OPTIC DISK HEMORRHAGE IN ADULTS WITHOUT A POSTERIOR VITREOUS DETACHMENT.

PURPOSE: To describe 2 cases of multilevel optic disk hemorrhages in adults without a posterior vitreous detachment. METHODS: The findings on clinical examination, color fundus photography, fluorescein angiography, spectral domain optical coherence tomography at presentation and follow-up are presented. RESULTS: Two patients ages 61 and 49 years presented with unilateral floaters secondary to microscopic vitreous hemorrhage. Their best-corrected visual acuities were 20/30 and 20/20, respectively. Fundus examination showed similar nasal crescent of peripapillary subretinal hemorrhage and superior flame hemorrhage. Fluorescein angiography for both patients showed blockage from hemorrhages without leakage. Spectral domain optical coherence tomography showed that the posterior hyaloid was attached at the macula and optic nerve for both patients. Both patients experienced spontaneous resolution of symptoms and signs. CONCLUSION: Previous reports of multilevel optic disk hemorrhages in adults variably suggested the necessity of a posterior vitreous detachment. This report illustrates that a posterior vitreous detachment confirmed on spectral domain optical coherence tomography is not a necessary prerequisite for this entity.

Do soil amendments used to improve agricultural productivity have consequences for soils contaminated with heavy metals?

This study presents an analysis of the effects of manure and lime commonly used to improve agricultural productivity and evaluates the potential for such soil amendments to mobilise/immobilise metal fractions in soils contaminated from nearby mine tailings in the Zambian Copperbelt. Lime and manure were applied at the onset of the study, and their effects were studied over two planting seasons, i.e. 2016-17 and 2017-18. Operationally defined plant-available Cd, Cu, Ni, Pb and Zn in the soil, were determined by extraction with DTPA-TEA (diethylenetriaminepentaacetic acid-triethanolamine) and 0.01 M Ca(NO3)2, before, and after, applying the amendments. In unamended soils, Cd was the most available and Ni the least. Lime application decreased extractable Cd, Cu, Ni, Pb and Zn. The response to lime was greater in soils with an initially acidic pH than in those with approximately neutral pH values. Manure increased DTPA extractable Zn, but decreased DTPA and Ca(NO3)2 extractable Cd, Cu and Pb. Combined lime and manure amendment exhibited a greater reduction in DTPA extractable Cd, Ni, Pb, Zn, as well as for Ca(NO3)2 extractable Cd compared to separate applications of lime and manure. The amendments had a significant residual effect on most of the soil fractions between season 1 and 2. The results obtained in this study showed that soil amendment with minimal lime and manure whilst benefiting agricultural productivity, may significantly reduce the mobility or plant availability of metals from contaminated agricultural soils. This is important in contaminated, typical tropical soils used for crop production by resource poor communities affected by mining or other industrial activities.

Aflibercept-Related Sterile Intraocular Inflammation Outcomes.

PURPOSE: A recent increase in sterile intraocular inflammation after aflibercept (EYLEA; Regeneron Pharmaceuticals, Inc, Tarrytown, NY) injection was reported to the American Society of Retina Specialists' Research and Safety in Therapeutics Committee. This study describes their clinical characteristics and outcomes. DESIGN: Case series. PARTICIPANTS: Sixty-eight eyes of 66 patients (97% reported from May 2017 through February 2018). METHODS: Exclusion criteria were intravitreal antibiotic injection and follow-up of less than 7 days. Diagnosis was at each physician's discretion. MAIN OUTCOME MEASURES: Presenting signs and symptoms, injection characteristics, management details, and visual outcomes. RESULTS: Mean time to presentation was 2.6 days (median, 2.0 days; range, 0-15 days). Symptoms included blurry vision (93%), floaters (60%), pain (44%), severe pain (6%), and photophobia (19%). Mean visual acuities before and after injection were 20/50 and 20/178, respectively. All patients showed intraocular inflammation: 24% with only vitritis, 16% with only anterior chamber reaction, and 60% with both. Less common findings included keratic precipitates (22%), corneal edema (13%), conjunctival injection (10%), chemosis (4%), hypopyon (4%), and fibrin (3%). Two patients were affected bilaterally. Treatment included topical steroids (93%), with 1% supplemented by oral steroids. Inflammation resolved in 79% at study completion (mean, 34 days; range, 7-105 days; 51% resolved by 1 month). This group's mean final visual acuity (VA) was 20/55, and 15% lost 2 lines or more. This vision loss was associated with shorter time to presentation (P < 0.0001), magnitude of decrease in presenting VA (P = 0.0004), presence of fibrin (P = 0.02), and trended toward receiving only observation (P = 0.10). There were no other presenting factors that significantly affected visual outcome. In patients with unresolved inflammation at the final visit, mean follow-up was 29 days, and mean final VA was 20/118. Overall, 26 aflibercept lots were involved. CONCLUSIONS: This is the largest study of aflibercept-related sterile intraocular inflammation, and is the only large report to exclude eyes injected with intraocular antibiotics. Most patients presented early with decreased VA and intraocular inflammation, but without injection, hypopyon, fibrin, or severe pain. Final VA remained decreased in a significant minority of patients.

Distribution and speciation of phosphorus in foreshore sediments of the Thames estuary, UK.

Estuarine sediments can be a source of Phosphorus (P) to coastal waters, contributing to nutrient budgets and geochemical cycles. In this work, the concentration and speciation of P in 47 cores were examined from the inter-tidal mud flats of the tidal river Thames (~120km). Results of P concentration and speciation were combined with published data relating to known sediment dynamics and water chemistry (salinity) within the estuary to produce a conceptual model of sediment-P behaviour. Results demonstrated significant P desorption occurring after sediment passed through the Estuarine Turbidity Maximum and when the salinity of the river water exceeded ~6ppt. It was found that organic P was desorbed to a greater extent than inorganic P in the lower estuary. Models were used to identify those geochemical parameters that contributed to the Total P (R2=0.80), oxalate extractable P (R2=0.80) and inorganic P (R2=0.76) concentrations within the Thames estuary.

Soil natural capital in europe; a framework for state and change assessment.

Soils underpin our existence through food production and represent the largest terrestrial carbon store. Understanding soil state-and-change in response to climate and land use change is a major challenge. Our aim is to bridge the science-policy interface by developing a natural capital accounting structure for soil, for example, attempting a mass balance between soil erosion and production, which indicates that barren land, and woody crop areas are most vulnerable to potential soil loss. We test out our approach using earth observation, modelling and ground based sample data from the European Union's Land Use/Cover Area frame statistical Survey (LUCAS) soil monitoring program. Using land cover change data for 2000-2012 we are able to identify land covers susceptible to change, and the soil resources most at risk. Tree covered soils are associated with the highest carbon stocks, and are on the increase, while areas of arable crops are declining, but artificial surfaces are increasing. The framework developed offers a substantial step forward, demonstrating the development of biophysical soil accounts that can be used in wider socio-economic and policy assessment; initiating the development of an integrated soil monitoring approach called for by the United Nations Intergovernmental Technical Panel on Soils.

Assessing potential risk of heavy metal exposure from consumption of home-produced vegetables by urban populations.

We performed a risk assessment of metal exposure to population subgroups living on, and growing food on, urban sites. We modeled uptake of cadmium, copper, nickel, lead, and zinc for a selection of commonly grown allotment and garden vegetables. Generalized linear cross-validation showed that final predictions of Cd, Cu, Ni, and Zn content of food crops were satisfactory, whereas the Pb uptake models were less robust. We used predicted concentrations of metals in the vegetables to assess the risk of exposure to human populations from homegrown food sources. Risks from other exposure pathways (consumption of commercially produced foodstuffs, dust inhalation, and soil ingestion) were also estimated. These models were applied to a geochemical database of an urban conurbation in the West Midlands, United Kingdom. Risk, defined as a "hazard index," was mapped for three population subgroups: average person, highly exposed person, and the highly exposed infant (assumed to be a 2-year-old child). The results showed that food grown on 92% of the urban area presented minimal risk to the average person subgroup. However, more vulnerable population subgroups (highly exposed person and the highly exposed infant) were subject to hazard index values greater than unity. This study highlights the importance of site-specific risk assessment and the "suitable for use" approach to urban redevelopment.

Lability, solubility and speciation of Cd, Pb and Zn in alluvial soils of the River Trent catchment UK.

Alluvial soils can store a wide range of metal contaminants originating from point and diffuse sources. The biological health of these soils is important as they act as an interface between terrestrial and aquatic environments, therefore playing an important role in maintaining the quality of surface waters. The aim of this work was to examine the lability, solubility and bioavailability of Pb, Zn and Cd in the top (0-15 cm) and sub soil (35-50 cm) of metal contaminated alluvial soils from the Trent catchment, U.K. Samples (n = 46) were collected from within 10 m of the river bank. Sources of contamination include historical mining, industry, sewage treatment works and energy production. Enrichment factors based on total metal concentrations showed that contamination in soils declined with distance from the mining areas before rising again as a result of general urbanisation and identified point sources (e.g. river dredging activities). Pore waters were extracted and isotopic dilution and single extraction assays were undertaken on the soils to assess the lability and solubility of the metals. Multi-element isotopic dilution assays were used to determine the labile pool or E-value of these metals in the soil. E-value concentrations were found to range between 0.5 and 14 mg kg(-1), 11-350 mg kg(-1) and 25-594 mg kg(-1) for Cd, Pb and Zn, respectively. Comparison of the E-value assay with the EU standard extraction assay for trace element availability (0.05 M EDTA) showed that EDTA extractions generally over-estimated the E-value for Zn and Pb, with the difference being greater as contamination levels increased. Bioavailability of the metals was assessed by speciating the pore waters [MSol] using WHAM 7 to obtain estimates of free ion activities (M(2+)). Values of (M(2+)) were compared to published 'median critical limits' for soils that estimate levels of protection for 95% of biological species. For each of the three metals, (M(2+)) was found to exceed these critical limits at some sites. Solubility of the metals are reported using Kd values expressed using both the total and E-value as the solid phase. Finally we examine the use of different metal pools (total, E-value, EDTA-extractable) and different measures of Fe oxide pools (total, free total, free amorphous), in predicting [MSol] concentrations and (M(2+)) using WHAM 7 in assemblage modelling mode. Overall best simultaneous model predictions for the three metals were obtained using the E-values. Larger over-estimates of [MSol] and (M(2+)) were produced using the EDTA and total metal pools whereas a better fitting in the prediction was obtained when models used either the total or the free total FeOx pools.

Measurement and dynamic modeling of trace metal mobilization in soils using DGT and DIFS.

The technique of diffusive gradients in thin-films (DGT) accumulates metals on a Chelex resin after their diffusive transport through a hydrogel. It lowers metal concentrations in soil solution adjacent to the device and induces resupply of metal associated with the solid phase. DGT devices were deployed in an alluvial gley soil for 21 different time periods between 4 h and 19.5 d. The accumulated masses of Cu, Cd, Ni, and Zn were used to calculate the distribution coefficient for labile metal, Kdl, and adsorption and desorption rate constants. Calculations were performed using a dynamic numerical model of DGT-induced fluxes in soils (DIFS). It assumes first-order exchange between solid phase and solution and diffusional transport in both the soil solution and the hydrogel. The DIFS model fitted changes in accumulated mass with time very well. Values of Kdl calculated from DIFS of 100 (Cd), 250 (Cu), 150 (Ni), and 150 (Zn) were larger than values of distribution coefficients estimated by exchange with Ca(NO3)2 but similar to those estimated by isotopic exchange (Cd and Zn only). These results suggest that the solid-phase pool of metal affected by the removal of labile metal by DGT, which operates on a time scale of minutes, is similar to the solid-phase pool of metal that can isotopically exchange with solution on a time scale of 2 d. Response times of minutes were consistent with interaction rates with surfaces, and desorption rate constants agreed with other reported values. An appraisal of the DIFS model demonstrated the importance of the labile pool size in the solid phase for controlling supply to a sink, such as DGT or a plant. As values of Kdl and kinetic parameters are obtained using DGT with minimal soil disturbance and by a similar mechanism to that involved in plant uptake, they may be pertinent to bioavailability studies.