Efficient water treatment achieved in recirculating aquaculture system using woodchip denitrification and slow sand filtration

Environmental Science and Pollution Research - For a recirculating aquaculture system (RAS), a passive water treatment system was designed for efficient discharge nutrient removal and water reuse...     

Safety Management in Multiemployer Worksites in the Manufacturing Industry: Opinions on Co-Operation and Problems Encountered

Co-operation between different parties and effective safety management play an important role in ensuring safety in multiemployer worksites. This article reviews safety co-operation and factors complicating safety management in Finnish multiemployer manufacturing worksites. The paper focuses on the service providers’ opinions; however, a comparison of the customers’ views is also presented. The results show that safety-related co-operation between providers and customers is generally considered as successful but strongly dependent on the partner. Safety co-operation is provided through, e.g., training, orientation and risk analysis. Problems encountered include ensuring adequate communication, identifying hazards, co-ordinating work tasks and determining responsibilities. The providers and the customers encounter similar safety management problems. The results presented in this article can help companies to focus their efforts on the most problematic points of safety management and to avoid common pitfalls.     

Shear layer over floodplain vegetation with a view on bending and streamlining effects

Environmental Fluid Mechanics - Shrubby and woody vegetation growing on floodplains profoundly influences hydrodynamic and transport processes in riverine systems. Existing hydrodynamic research is...     

Methane oxidation at a surface-sealed boreal landfill

Methane oxidation was studied at a closed boreal landfill (area 3.9 ha, amount of deposited waste 200,000 tonnes) equipped with a passive gas collection and distribution system and a methane oxidative top soil cover integrated in a European Union landfill directive-compliant, multilayer final cover. Gas wells and distribution pipes with valves were installed to direct landfill gas through the water impermeable layer into the top soil cover. Mean methane emissions at the 25 measuring points at four measurement times (October 2005–June 2006) were 0.86–6.2 m³ ha^?1 h^?1. Conservative estimates indicated that at least 25% of the methane flux entering the soil cover at the measuring points was oxidized in October and February, and at least 46% in June. At each measurement time, 1–3 points showed significantly higher methane fluxes into the soil cover (20–135 m³ ha^?1 h^?1) and methane emissions (6–135 m³ ha^?1 h^?1) compared to the other points (<20 m³ ha^?1 h^?1 and <10 m³ ha^?1 h^?1, respectively). These points of methane overload had a high impact on the mean methane oxidation at the measuring points, resulting in zero mean oxidation at one measurement time (November). However, it was found that by adjusting the valves in the gas distribution pipes the occurrence of methane overload can be to some extent moderated which may increase methane oxidation. Overall, the investigated landfill gas treatment concept may be a feasible option for reducing methane emissions at landfills where a water impermeable cover system is used.     

X-ray diffraction study of calcification processes in embryos and larvae of the brooding oyster Ostrea edulis

X-ray powder diffraction was used to study shell calcifications of the oyster Ostrea edulis, sampled in the Limski Kanal, Istria (Adriatic Sea), in May 1992. All the developmental stages were followed, from the embryonic stage through the transition between the trochophore and veliger larva (prodissoconch I and II) and later, after swarming, the pelagic free-swimming larval stages, up to their settlement and attachment (from the D-shaped to the fully formed pediveliger larva), and finally during metamorphosis and juvenile stages (dissoconch). In the first gastrula stage, only an amorphous tissue is present (a periostracum and organic matrix). The beginning of shell formation (at the end of gastrulation) in early trochophores is manifested by the appearance of calcite (up to 1–7% of total volume) and then aragonite (about 1%). In the later stage of the veliger larva the fraction of calcite decreases as well as the amorphous fraction, while the fraction of aragonite rapidly increases. In the prodissoconch II stage and during the whole pelagic period aragonite is dominant, accompanied by a very small amorphous fraction and traces of calcite. The shell mineral composition does not change until metamorphosis, whereupon the fraction of calcite rapidly increases and the fraction of aragonite decreases. The postmetamorphic valves of the juvenile and adult oyster consist mainly of calcite, except the resilium and myostracum which remain aragonitic, possibly as a continuation of the inner layer of the larval shell. Received: 28 May 1997 / Accepted: 1 July 1997     

A Review of Global and Regional Sulfur Emission Scenarios

The paper reviews base year emission inventories, driving forces, and long-term scenarios of sulfur emissions as background material for developing a new set of IPCC emissions scenarios. The paper concludes that future sulfur emission trends will be spatially heterogeneous (decline in OECD countries, rapid increase particularly in Asia) and therefore cannot be modeled at a global scale only. In view of ecosystems and food production impacts future sulfur emissions will need to be increasingly controlled also outside OECD countries. As a result, future sulfur emissions are likely to remain significantly below the values projected in the previous IPCC IS92 high emissions scenarios.     

Heavy metal removal from industrial effluents by sorption on cross-linked starch: chemical study and impact on water toxicity

Batch sorption experiments using a starch-based sorbent were carried out for the removal of heavy metals present in industrial water discharges. The influence of contact time, mass of sorbent and pollutant load was investigated. Pollutant removal was dependent on the mass of sorbent and contact time, but independent of the contaminant load. The process was uniform, rapid and efficient. Sorption reached equilibrium in 60 min irrespective of the metal considered (e.g. Zn, Pb, Cu, Ni, Fe and Cd), reducing concentrations below those permitted by law. The material also removed residual turbidity and led to a significant decrease in the residual chemical oxygen demand (COD) present in the industrial water discharge. The germination success of lettuce (Lactuca sativa) was used as a laboratory indicator of phytotoxicity. The results show that the sorption using a starch-based sorbent as non-conventional material, is a viable alternative for treating industrial wastewaters.     

A strong test of a maximum entropy model of trait-based community assembly

We evaluate the predictive power and generality of Shipley's maximum entropy (maxent) model of community assembly in the context of 96 quadrats over a 120-km2 area having a large (79) species pool and strong gradients. Quadrats were sampled in the herbaceous understory of ponderosa pine forests in the Coconino National Forest, Arizona, U.S.A. The maxent model accurately predicted species relative abundances when observed community-weighted mean trait values were used as model constraints. Although only 53% of the variation in observed relative abundances was associated with a combination of 12 environmental variables, the maxent model based only on the environmental variables provided highly significant predictive ability, accounting for 72% of the variation that was possible given these environmental variables. This predictive ability largely surpassed that of nonmetric multidimensional scaling (NMDS) or detrended correspondence analysis (DCA) ordinations. Using cross-validation with 1000 independent runs, the median correlation between observed and predicted relative abundances was 0.560 (the 2.5% and 97.5% quantiles were 0.045 and 0.825). The qualitative predictions of the model were also noteworthy: dominant species were correctly identified in 53% of the quadrats, 83% of rare species were correctly predicted to have a relative abundance of < 0.05, and the median predicted relative abundance of species actually absent from a quadrat was 5 x 10(-5).