Experimental analysis of open check dams and protection bars against debris flows and driftwood

Environmental Fluid Mechanics - The paper addresses the influence of intense sediment transport (bed load and debris flow) on the efficiency of the structures aimed at the interception of wood...     

Scale-up of electrochemical oxidation system for treatment of produced water generated by Brazilian petrochemical industry

Scale-up of anodic oxidation system is critical to the practical application of electrochemical treatment in bio-refractory organic wastewater treatment. In this study, the scale-up of electrochemical flow system was investigated by treating petrochemical wastewater using platinized titanium (Ti/Pt) and boron-doped diamond (BDD) anodes. It was demonstrated that flow cell was successfully scaled-up because when it was compared with batch mode (Rocha et al. 2012b), higher performances on organic matter removal were achieved. Under the suitable operating conditions and better anode material, the chemical oxygen demand (COD) of petrochemical wastewater was reduced from 2,746 to 200 mg L^?1 within 5 h with an energy consumption of only 56.2 kWh m^?3 in the scaled-up BDD anode system. These results demonstrate that anode flow system is very promising in practical bio-refractory organic wastewater treatment.     

Detection of human-induced environmental disturbances in a show cave

Purpose  

We investigated the effects of human-induced disruption in a subterranean stable environment containing valuable Palaeolithic paintings and engravings (Ardales Cave, Southern Spain) using a double analytical approach.     

Evaluation of particulate matter abatement strategies for almond harvest

Almond harvest accounts for substantial PM10 (particulate matter [PM] < or =10 microm in nominal aerodynamic diameter) emissions in California each harvest season. This paper evaluates the effects of using reduced-pass sweepers and lower harvester separation fan speeds (930 rpm) on lowering PM emissions from almond harvesting operations. In-canopy measurements of PM concentrations were collected along with PM concentration measurements at the orchard boundary; these were used in conjunction with on-site meteorological data and inverse dispersion modeling to back-calculate emission rates from the measured concentrations. The harvester discharge plume was measured as a function of visible plume opacity during conditioning operations. Reduced-pass sweeping showed the potential for reducing PM emissions, but results were confounded because of differences in orchard maturity and irrigation methods. Fuel consumption and sweeping time per unit area were reduced when comparing a reduced-pass sweeper to a conventional sweeper. Reducing the separation fan speed from 1080 to 930 rpm led to reductions in PM emissions. In general, foreign matter levels within harvested product were nominally affected by separation fan speed in the south (less mature) orchard; however, in samples conditioned using the lower fan speed from the north (more mature) orchard, these levels were unacceptable.     

A decision framework for possible remediation of contaminated sediments in the River Kymijoki, Finland

Background, aim, and scope  The paper describes the spatial contamination of the River Kymijoki, South-Eastern Finland, and the coastal region of the Gulf of Finland with PCDD/Fs and mercury. The findings of ecotoxicologial and human health studies are also reported, including environmental and human risk assessments. Sediments from the River Kymijoki, draining into the Gulf of Finland, have been heavily polluted by the pulp and paper industry and by chemical industries. A wood preservative, known as Ky-5, was manufactured in the upper reaches of the river between 1940 and 1984 causing severe pollution of river sediments with polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF). Moreover, the sediments have been polluted with mercury (Hg) from chlor-alkali production and the use of Hg as a slimicide in pulp and paper manufacturing. Materials and methods  An extensive sediment survey was conducted as well as sediment transport modeling, toxicity screening of sediment invertebrates, and a survey of contaminant bioaccumulation in invertebrates and fish. Studies on human exposure to PCDD/Fs and the possible effects on hypermineralization of teeth as well as an epidemiological study to reveal increased cancer risk were also conducted. An assessment of the ecological and human health risks with a null hypothesis (no remediation) was undertaken. Results  The sediment survey revealed severe contamination of river and coastal sediments with PCDD/Fs and Hg. The total volume of contaminated sediments was estimated to reach 5 × 10⁶ m³ and hot spots with extremely high concentrations (max 292,000 ng g⁻¹ or 1,060 ng I-TEQ g⁻¹ d.w.) were located immediately downstream from the pollution source (approximately 90,000 m³). Sediment contamination was accompanied by changes in benthic assemblages, but direct effects were masked by many factors. The fish showed only slightly elevated PCDD/F levels in muscle, but orders of magnitude higher in the liver compared with reference freshwater sites and the Baltic Sea. The concentrations in human fat did not reveal high human exposure in the Kymijoki area in general and was lower than in sea fishermen. The relative risk for total cancer among farmers was marginally higher (RR = 1.13) among those living close to the river, compared with farmers living further away, and the possibility of increased cancer risk cannot be ruled out. A conservative risk assessment revealed that the present probability of exceeding the WHO upper exposure limit of 4 pg WHO-TEQ kg⁻¹ d⁻¹ for PCDD/Fs and DL-PCBs was 6%. The probability of exceeding the WHO limit value of 0.23 μg kg⁻¹ d⁻¹ for methyl mercury was estimated to be notably higher at 62%. Based on these studies and the estimated risks connected with different remediation techniques a general remediation plan with cost benefit analysis was generated for several sub-regions in the river. Dredging, on-site treatment, and a close disposal of the most contaminated sediments (90,000 m³) was suggested as the first phase of the remediation. The decision regarding the start of remediation will be made during autumn 2008. Conclusions  The sediments in the River Kymijoki are heavily polluted with PCDD/Fs and mercury from earlier chlorophenol, chlor-alkali, and pulp and paper manufacturing. A continuous transport of contaminants is taking place to the Gulf of Finland in the Baltic Sea. The highly increased PCDD/F and Hg levels in river sediments pose an ecotoxicological risk to benthic fauna, to fish-eating predators and probably to human health. The risks posed by mercury exceed those from PCDD/Fs and need to be evaluated for (former) chlor-alkali sites and other mercury releasing industries as one basis for remediation decision making. Recommendations and perspectives  The studies form the basis of a risk management strategy and a plan for possible remediation of contaminated sediments currently under consideration in the Southeast Finland Regional Environment Centre. It is recommended that a detailed restoration plan for the most seriously contaminated areas should be undertaken. Based on current knowledge, the restoration of the whole river is not feasible, considering the current risk caused by the contaminated sediment in the river and the costs of an extensive restoration project. The experiences gained in the present case should be utilized in the evaluation of PCDD/F- and mercury-contaminated sites in other countries. The case demonstrates that the historic reservoirs are of contemporary relevance and should be addressed, e.g., in the national implementation plans of the Stockholm Convention. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Anticipatory capacity in response to global change across an extreme elevation gradient in the Ica Basin,Peru

Regional Environmental Change - Mountainous areas with extreme elevation gradients and corresponding ranges of biophysical and socioeconomic conditions are highly vulnerable to global change. We...     

Critical review of the building downwash algorithms in AERMOD

The only documentation on the building downwash algorithm in AERMOD (American Meteorological Society/U.S. Environmental Protection Agency Regulatory Model), referred to as PRIME (Plume Rise Model Enhancements), is found in the 2000 A&WMA journal article by Schulman, Strimaitis and Scire. Recent field and wind tunnel studies have shown that AERMOD can overpredict concentrations by factors of 2 to 8 for certain building configurations. While a wind tunnel equivalent building dimension study (EBD) can be conducted to approximately correct the overprediction bias, past field and wind tunnel studies indicate that there are notable flaws in the PRIME building downwash theory. A detailed review of the theory supported by CFD (Computational Fluid Dynamics) and wind tunnel simulations of flow over simple rectangular buildings revealed the following serious theoretical flaws: enhanced turbulence in the building wake starting at the wrong longitudinal location; constant enhanced turbulence extending up to the wake height; constant initial enhanced turbulence in the building wake (does not vary with roughness or stability); discontinuities in the streamline calculations; and no method to account for streamlined or porous structures.

Implications: This paper documents theoretical and other problems in PRIME along with CFD simulations and wind tunnel observations that support these findings. Although AERMOD/PRIME may provide accurate and unbiased estimates (within a factor of 2) for some building configurations, a major review and update is needed so that accurate estimates can be obtained for other building configurations where significant overpredictions or underpredictions are common due to downwash effects. This will ensure that regulatory evaluations subject to dispersion modeling requirements can be based on an accurate model. Thus, it is imperative that the downwash theory in PRIME is corrected to improve model performance and ensure that the model better represents reality.     

Radical precursors and related species from traffic as observed and modeled at an urban highway junction

Nitrous acid (HONO) and formaldehyde (HCHO) are important precursors for radicals and are believed to favor ozone formation significantly. Traffic emission data for both compounds are scarce and mostly outdated. A better knowledge of today's HCHO and HONO emissions related to traffic is needed to refine air quality models. Here the authors report results from continuous ambient air measurements taken at a highway junction in Houston, Texas, from July 15 to October 15, 2009. The observational data were compared with emission estimates from currently available mobile emission models (MOBILE6; MOVES [MOtor Vehicle Emission Simulator]). Observations indicated a molar carbon monoxide (CO) versus nitrogen oxides (NO_x) ratio of 6.01 ± 0.15 (r ² = 0.91), which is in agreement with other field studies. Both MOBILE6 and MOVES overestimate this emission ratio by 92% and 24%, respectively. For HCHO/CO, an overall slope of 3.14 ± 0.14 g HCHO/kg CO was observed. Whereas MOBILE6 largely underestimates this ratio by 77%, MOVES calculates somewhat higher HCHO/CO ratios (1.87) than MOBILE6, but is still significantly lower than the observed ratio. MOVES shows high HCHO/CO ratios during the early morning hours due to heavy-duty diesel off-network emissions. The differences of the modeled CO/NO_x and HCHO/CO ratios are largely due to higher NO_x and HCHO emissions in MOVES (30% and 57%, respectively, increased from MOBILE6 for 2009), as CO emissions were about the same in both models. The observed HONO/NO_x emission ratio is around 0.017 ± 0.0009 kg HONO/kg NO_x which is twice as high as in MOVES. The observed NO₂/NO_x emission ratio is around 0.16 ± 0.01 kg NO₂/kg NO_x, which is a bit more than 50% higher than in MOVES. MOVES overestimates the CO/CO₂ emission ratio by a factor of 3 compared with the observations, which is 0.0033 ± 0.0002 kg CO/kg CO₂. This as well as CO/NO_x overestimation is coming from light-duty gasoline vehicles.

Implications: Nitrous acid (HONO) and formaldehyde (HCHO) are important precursors for radicals that ultimately contribute to ozone formation. There still exist uncertainties in emission sources of HONO and HCHO and thus regional air quality modeling still tend to underestimate concentrations of free radicals in the atmosphere. This paper demonstrates that the latest U.S. Environmental Protection Agency (EPA) traffic emission model MOVES still shows significant deviations from observed emission ratios, in particular underestimation of HCHO/CO and HONO/NO_x ratios. Improving the performance of MOVES may improve regional air quality modeling.     

Bioindication of volatile elements emission by the Puyehue-Cordón Caulle (North Patagonia) volcanic event in 2011

The emission of volatile pollutants from the volcanic eruption of the Puyehue-Cordón Caulle complex (North Patagonia Andean Range) that started in June 4th, 2011, was investigated by bioindication means with the epyphytic fruticose lichen Usnea sp. The elemental composition of pooled samples made up with 10 lichen thalli were analysed by Instrumental Neutron Activation Analysis. Eleven sampling sites were selected within the impacted region at different distance from the volcanic source. Five sites were selected as they were already sampled in a previous study prior to the eruption. Two other new sampling sites were selected from outside the impacted zone to provide non-impacted baseline sites.The elements associated with the lichen incorporation of particulate matter (PM) of geological origin were identified by linear correlation with a geochemical tracer (Sm concentrations). The elements associated with PM uptake were Ce, Eu, Fe, Hf, La, Lu, Na, Nd, Sb, Sc, Se, Ta, Tb, Th, U, and Yb. Arsenic and Cs concentrations showed contributions exceeding the PM fraction in sites near the volcanic centre, also higher than the baseline concentrations, which could be associated with permanent emissions from the geothermal system of the Puyehue-Cordón Caulle complex. The lichen concentrations of Ba, Ca, Co, Hg, K, Rb, Sr, and Zn were not associated with the PM, not showing higher concentrations in the sites nearby the volcanic source or respect to the baseline values either. Therefore, there is no indication of the emission of volatile forms of these elements in the lichen records. The lichen records only identified Br volatile emissions associated with the Puyehue-Cordón Caulle complex eruption in 2011.