Impact resistance of guards on grinding machines

Guards on machine tools are meant to protect persons from injuries caused by parts ejected with high kinetic energy from the machine's working zone. With respect to stationary grinding machines, Standard No. EN 13218:2002, therefore, specifies minimum wall thicknesses for guards. These values are mainly based on estimations and experience instead of systematic experimental investigations. This paper shows to what extent simple impact tests with standardizable projectiles can be used as basis for the evaluation of the impact resistance of guards, provided that not only the kinetic energy of the projectiles used but also, among others, their geometry corresponds to the abrasive product fragments to be expected.     

The WWDU (Work With Display Units) Conference as a Platform for Occupational Health and Safety in the Past—And as a WWCS (Work With Computer Systems) Conference in the Future

The real burden of occupational diseases, specifically work-related musculoskeletal disorders (MSDs), and its impact on workers’ productivity is not known. The situation is critical in developing countries where only cases that cause workers’ disability are recorded. In this study, the incidence of MSDs in Colombia was estimated by using the age and gender specific double incidence rate of repetitive strain injuries diseases in Finland for 2002. The results showed that the estimated number of MSDs recorded in Colombia during 2005 was 23,477 cases at the rate of 11.6 cases per 10,000 workers. The estimated total cost of these MSD cases relative to workers’ productivity was US $171.7 million, representing around 0.2% of Colombia’s Gross Domestic Product for 2005. The systematic appraisal of the incidence of MSDs and their associated cost on workers’ productivity are necessary in developing countries to reduce the costly impact on productivity and to increase workers’ well-being.     

Two Pilot Plant Reactors Designed for the In Situ Bioremediation of Chlorobenzene-contaminated Ground Water: Hydrogeological and Chemical Characteristics and Bacterial Consortia

The SAFIRA in situ pilot plant in Bitterfeld, Saxonia-Anhalt, Germany, currently serves as the test site for eight different in situ approaches to remediate anoxic chlorobenzene (CB)-contaminated ground water. Two reactors, both filled with originallignite-containing aquifer material, are designed for themicrobiological in situ remediation of the ground water bythe indigenous microbial consortia. In this study, thehydrogeological, chemical and microbiological conditions of theinflowing ground water and reactor filling material are presented,in order to establish the scientific basis for the start of thebioremediation process itself. The reactors were put intooperation in June 1999. In the following, inflow CB concentrationsin the ground water varied between 22 and 33 mg L^-1; achemical steady state for CB in both reactors was reachedafter 210 till 260 days operation time. The sediments werecolonized by high numbers of aerobic, iron-reducing anddenitrifying bacteria, as determined after 244 and 285 days ofoperation time. Furthermore, aerobic CB-degrading bacteria weredetected in all reactor zones. Comparative sequence analysis of16S rDNA gene clone libraries suggest the dominance of Proteobacteria (Comamonadaceae, Alcaligenaceae, Gallionella group, Acidithiobacillus) and members of theclass of low G+C gram-positive bacteria in the reactorsediments. In the inflowing ground water, sequences withphylogenetic affiliation to sulfate-reducing bacteria andsequences not affiliated with the known phyla of Bacteria, were found.     

Rotifers colonising sediments with shallow gas hydrates

Rotifers, one of the smallest metazoans, are only seldom found in marine environments. Surprisingly, we discovered high abundances of at least two new species of rotifers settling in anoxic and highly sulphidic sediments associated with shallow gas hydrates (GH) at the southern crest of Hydrate Ridge off Oregon, NE Pacific, in a water depth of about 780 m. At basins adjacent to Hydrate Ridge, 1,285–2,304 m deep, we found rotifers co-occurring with the sulphide-oxidising bacteria Thioploca sp.     

Exposure of aboriginal people to methylmercury due to gold mining in the Amazon, Brazil

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Methane emissions and related physicochemical soil and water parameters in rice–fish systems in Bangladesh

Lowland rice fields constitute a semi aquatic environment, which is potentially suitable for fish production. Little is known about the effect of fish on greenhouse gas emissions from integrated rice–fish systems. An experiment was carried out at the Bangladesh Agricultural University to assess the effect of the stocking of fish on methane emissions from rice fields. Common carp, Cyprinus carpio L., and Nile Tilapia, Oreochromis niloticus (L.) were stocked in a mixed culture and subjected to three different input regimes: (1) urea fertilization according to the recommendation of the Bangladesh Rice Research Institute (BRRI), (2) supplementary feeding at 2 × maintenance level and (3) an elevated feeding schedule where 4 × maintenance level was fed initially and 2 × maintenance level towards the end of the growth period. Rice only with urea fertilization according to BRRI-recommendation was included as the control. The presence of fish increased methane emissions in all three rice–fish treatments. Average emission over the cropping season was 34, 37, and 32 mg m⁻² h⁻¹ in the rice–fish treatments, respectively, and 20 mg m⁻² h⁻¹ in rice only. Apart from an increase in methane emission, a significant drop (p < 0.05) in floodwater pH and dissolved oxygen concentration was observed in the rice–fish plots. Both parameters were the lowest in the treatment where a higher feeding rate was provided. Due to the fish activity, floodwater in the rice–fish treatments was more turbid, as reflected in higher particulate inorganic matter (PIOM). An elevated level of dissolved methane was observed in the floodwater of the feed supplemented rice–fish plots. Methane emissions showed negative correlation with morning and afternoon pH of the floodwater (r = −0.46; r = −0.56, p < 0.001) and morning and afternoon dissolved oxygen level (r = −0.53; r = −0.46, p < 0.001). Positive correlations were recorded between morning and afternoon floodwater temperature (r = 0.49; r = 0.44, p < 0.001) and with air temperature (r = 0.54, p < 0.001). The results suggest that the stocking of fish has an increasing effect on methane emissions from rice fields.     

Decrease of Pb bioavailability in solis by addition of phosphate ions

Bioavailability of Pb in contaminated soils can be highly decreased by conversion of labile Pb species into pyromorphite Pb₅(PO₄)₃Cl, induced by amendment with a phosphate source. However, PO₄ ³⁻ can be specifically adsorbed on goethite α-Fe(OH)₃ present in soils. We demonstrate that despite the stability of phosphate ions adsorbed on goethite surface, the reaction between goethite-adsorbed phosphates and aqueous lead in the presence of Cl⁻ results in crystallization of pyromorphite. Two morphological forms of pyromorphite formed on goethite were observed: 1) incrustations, indicating direct reaction of Pb and Cl ions with PO₄ ³⁻ adsorbed on goethite surface, and 2) aggregates of pyromorphite crystals indicating that the reaction with PO₄ ³⁻ ions took place in the volume of the solution. This suggests that precipitation of pyromorphite is faster than desorption of phosphates and that aqueous Pb may serve as a sink for phosphate ions by shifting the equilibrium and inducing PO₄ ³⁻ desorption.     

Polybrominated diphenyl ethers (PBDEs) in sediment by salinity and land-use type from Australia

Brominated flame retardants, including polybrominated diphenyl ethers (PBDEs) have been incorporated in numerous products to reduce flammability. Depending on their bromination, PBDEs are relatively persistent in the environment and have the potential to bioaccumulate through the food web. The present study was initiated to provide a better understanding on the levels and possible origin of PBDEs in the aquatic environment of Australia. PBDEs were detected at 35 out of 46 sites and concentrations were relatively low in the majority of samples analysed. Mean+/-standard deviation and median SigmaPBDE concentrations across all sites were 4707+/-12,580 and 305 pg g(-1) dw, respectively, excluding the limit of detection. At 83% of sites, concentrations were below 1000 pg g(-1) dw, whereas elevated levels were found at sites downstream of STP outfalls and in areas dominated by industrial and urban land-use types. Concentrations of PBDEs differed significantly (p=0.007) among sites according to predominant type of land-use. Significantly (p=0.02) higher SigmaPBDE concentrations were also present in estuarine compared to freshwater environments, while PBDEs were below the limit of detection at the marine site. At most sites, BDE-209 contributed the highest proportion to the SigmaPBDE concentrations. The exception was one site with an elevated concentration of BDE-183. Sampling and analytical variability were investigated as part of this study. Results showed generally satisfactory results for repeat analysis at a different laboratory and low variability among samples collected within 1000 m at low contaminated sites. However, at sites with elevated PBDE levels, sampling variability was high, with several fold to magnitudes of higher concentrations present among replicate sites. Corresponding to findings from elsewhere, these results demonstrate that urban and industrial activities provide the key input sources of PBDEs to the aquatic environment and provide a baseline for further investigation into the specific origin of contamination, as well as information on the background status of aquatic sediment contamination with PBDEs.     

Regional patterns of heavy metal exposure and contamination in the fish fauna of the Kharaa River basin (Mongolia)

Regional Environmental Change - Past and present gold mining operations scattered throughout the Kharaa River basin, Mongolia, have been identified as a major source of heavy metal and metalloid...     

Use of Predictive Weather Uncertainties in an Irrigation Scheduling Tool Part I: A Review of Metrics and Adjoint Methods

Irrigation management consists of many components. In this work we review and recommend rainfall forecast performance metrics and adjoint methodologies for the use of predictive weather data within the Colorado State University Water Irrigation Scheduler for Efficient Application (WISE). WISE estimates crop water uses to optimize irrigation scheduling. WISE and its components, input requirements, and related software design issues are discussed. The use of predictive weather allows WISE to consider economic opportunity‐costs of decisions to defer water application if rainfall is forecast. These capabilities require an assessment of the system uncertainties and use of weather prediction performance probabilities. Rainfall forecasts and verification performance metrics are reviewed. In addition, model data assimilation methods and adjoint sensitivity concepts are introduced. These assimilation methods make use of observational uncertainties and can link performance metrics to space and time considerations. We conclude with implementation guidance, summaries of available data sources, and recommend a novel adjoint method to address the complex physical linkages and model sensitivities between space and time within the irrigation scheduling physics as a function of soil depth. Such tool improvements can then be used to improve water management decision performance to better conserve and utilize limited water resources for productive use. Editor’s note : This paper is part of the featured series on Optimizing Ogallala Aquifer Water Use to Sustain Food Systems. See the February 2019 issue for the introduction and background to the series.