Determination of Frequency for Remeasuring Ground and Vegetation Cover Factor Needed for Soil Erosion Modeling

Determining a remeasurement frequency of variables over time is required in monitoring environmental systems. This article demonstrates methods based on regression modeling and spatio-temporal variability to determine the time interval to remeasure the ground and vegetation cover factor on permanent plots for monitoring a soil erosion system. The spatio-temporal variability methods include use of historical data to predict semivariograms, modeling average temporal variability, and temporal interpolation by two-step kriging. The results show that for the cover factor, the relative errors of the prediction increase with an increased length of time interval between remeasurements when using the regression and semivariogram models. Given precision or accuracy requirements, appropriate time intervals can be determined. However, the remeasurement frequency also varies depending on the prediction interval time. As an alternative method, the range parameter of a semivariogram model can be used to quantify average temporal variability that approximates the maximum time interval between remeasurements. This method is simpler than regression and semivariogram modeling, but it requires a long-term dataset based on permanent plots. In addition, the temporal interpolation by two-step kriging is also used to determine the time interval. This method is applicable when remeasurements in time are not sufficient. If spatial and temporal remeasurements are sufficient, it can be expanded and applied to design spatial and temporal sampling simultaneously.     

Stratification effects on hydrodynamics and mixing at a river confluence with discordant bed

Environmental Fluid Mechanics - Stratification effects induced by density differences between the incoming flows are investigated at a medium-size stream confluence with a highly discordant bed....     

Field effectiveness evaluation of advanced driver assistance systems

Abstract

Objective: Advanced driver assistance systems (ADAS) are a class of vehicle technologies designed to increase safety by providing drivers with timely warnings and autonomously intervening to avoid hazardous situations. Though laboratory testing suggests that ADAS technologies will greatly impact crash involvement rates, real-world evidence that characterizes their effectiveness is still limited. This study evaluates and quantifies the association of ADAS technologies with the likelihood of a moderate or severe crash for new-model BMWs in the United States.

Methods: Vehicle ADAS option information for the cohort of model year 2014 and later BMW passenger vehicles sold after January 1, 2014 (n?=?1,063,503), was coded using VIN-identified options data. ADAS technologies of interest include frontal collision warning with autonomous emergency braking, lane departure warning, and blind spot detection. BMW Automated Crash Notification system data (from January 2014 to November 2017) were merged with vehicle data by VIN to identify crashed vehicles (n?=?15,507), including date, crash severity (delta V), and area of impact. Using Cox proportional hazards regression modeling, the study calculates the adjusted hazard ratio for crashing among BMW passenger vehicles with versus without ADAS technologies. The adjusted percentage reduction in moderate and severe crashes associated with ADAS is interpreted as one minus the hazard ratio.

Results: Vehicles equipped with both autonomous emergency braking and lane departure warning were 23% less likely to crash than those not equipped (hazard ratio [HR]?=?0.77; 95% confidence interval [CI], 0.73–0.81), controlling for model year, vehicle size and body type. Autonomous emergency braking and lane departure warning generally occur together, making it difficult to tease apart their individual effects. Blind spot detection was associated with a 14% reduction in crashes after controlling for the presence of autonomous emergency braking and lane departure warning (HR =0.86; 95% CI, 0.744–0.99). Differences were observed by vehicle type and crash type. The combined effect of autonomous emergency braking and lane departure warning was greater in newer model vehicles: Equipped vehicles were 13% less likely to crash (HR =0.87; 95% CI, 0.79–0.95) among 2014 model year vehicles versus 34% less likely to crash (HR =0.66; 95% CI, 0.57–0.77) among 2017 model year vehicles.

Conclusion: This robust cohort study contributes to the growing evidence on the effectiveness of ADAS technologies.     

Treatment technologies for PAH-contaminated sites: a critical review

To reduce environmental and human health risks of contaminated sites, having a comprehensive knowledge about the polycyclic aromatic hydrocarbon (PAH) removal processes is crucial. PAHs are contaminants which are highly recognized to pose threats to humans, animals, and plants. PAHs are hydrophobic and own two or more benzene rings, and hence are resistant to structural degradation. There are various techniques which have been developed to treat PAH-contaminated soil. Four distinct processes to remove PAHs in the contaminated soil, thought to be more effective techniques, are presented in this review: soil washing, chemical oxidation, electrokinetic, phytoremediation. In a surfactant-aided washing process, a removal rate of 90% was reported. Compost-amended phytoremediation treatment presented 58–99% removal of pyrene from the soil in 90 days. Chemical oxidation method was able to reach complete conversion for some PAHs. In electrokinetic treatment, researchers have achieved reliable results in removal of some specific PAHs. Researchers’ innovations in novel studies and advantages/disadvantages of the techniques are also investigated throughout the paper. Finally, it should be noted that an exclusive method or a combination of methods by themselves are not the key to be employed for remediation of every contaminated site but the field characteristics are also essential in selection of the most appropriate decontamination technique(s). The remedy for selection criteria is based on PAH concentrations, site characteristics, costs, shortcomings, and advantages.     

Chemical composition and mass closure of ambient PM10 at urban sites

The chemical composition of PM10 was studied during summer and winter sampling campaigns conducted at two different urban sites in the city of Thessaloniki, Greece (urban-traffic, UT and urban-industrial, UI). PM10 samples were chemically analysed for minerals (Si, Al, Ca, Mg, Fe, Ti, K), trace elements (Cd, Cr, Cu, Mn, Pb, V, Zn, Te, Co, Ni, Se, Sr, As, and Sb), water-soluble ions (Cl^?, NO₃^?, SO₄^2?, Na⁺, K⁺, NH₄⁺, Ca²⁺, Mg²⁺) and carbonaceous compounds (OC, EC). Spatial variations of atmospheric concentrations showed significantly higher levels of minerals, some trace metals and TC at the UI site, while at the UT site significantly higher levels of elements like Cd, Ba, Sn, Sb and Te were observed. Crustal elements, excepting Ca at the UI site, did not exhibit significant seasonal variations at any site pointing to constant emissions throughout the year. In order to reconstruct the particle mass, the determined components were classified into six classes as follows: mineral matter (MIN), trace elements (TE), organic matter (OM), elemental carbon (EC), sea salt (SS) and secondary inorganic aerosol (SIA). Good correlations with slopes close to 1 were found between chemically determined and gravimetrically measured PM10 masses for both sites. According to the chemical mass closure obtained, the major components of PM10 at both sites were MIN (soil-derived compounds), followed by OM and SIA. The fraction unaccounted for by chemical analysis comprised on average 8% during winter and 15% during summer at the urban-industrial site, while at the urban-traffic site the percentages were 21.5% in winter and 4.8% in summer.     

Kinetics of the tropospheric formaldehyde loss onto mineral dust and urban surfaces

The kinetics of the heterogeneous reaction between gaseous HCHO and TiO₂/SiO₂ mineral coatings were investigated using a coated-wall flow tube to mimic HCHO loss on mineral aerosol and TiO₂ coated depolluting urban surfaces. The measured uptake kinetics were strongly enhanced when the flow tube was irradiated with 340–420 nm UV light with an irradiance of 1.45 mW cm^?2. The associated BET uptake coefficients ranged from (3.00 ± 0.45) × 10^?9 to (2.26 ± 0.34) × 10^?6 and were strongly dependent on HCHO initial concentration, relative humidity, temperature, and TiO₂ content in the mineral coating, which ranged from 3.5 to 32.5 ppbv, 6–70%, 278–303 K, and 1–100 %wt, respectively. The measured kinetics were well described using a Langmuir–Hinshelwood type formalism. The estimated uptake coefficients were used to discuss the importance of heterogeneous HCHO surface loss, in terms of deposition lifetimes, as compared to major homogeneous gas-phase losses such as OH reaction and photolysis. It is found that deposition may compete with gas-phase removal of HCHO in a dense urban environment if more than 10% of the urban surface is covered with TiO₂ treated material.     

Use of CALPUFF for exposure assessment in a near-field,complex terrain setting

CALPUFF is an atmospheric source-receptor model recommended by the U.S. Environmental Protection Agency for use on a case-by-case basis in complex terrain and wind conditions. The ability of the model to provide useful information for exposure assessments in areas with those topographical and meteorological conditions has received little attention. This is an important knowledge gap for use of CALPUFF outside of regulatory applications, such as exposure analyses conducted in support of risk assessments and health studies. We compared deposition of cadmium (Cd), lead (Pb), and zinc (Zn) calculated with CALPUFF as a result of emissions from a zinc smelter with corresponding concentrations of the metals measured in attic dust and soil samples obtained from the surrounding area. On a point-by-point analysis, predictions from CALPUFF explained 11% (lead) to 53% (zinc) of the variability in concentrations measured in attic dust. Levels of heavy metals in soil interpolated to 100 residential addresses from the distribution of concentrations measured in soil samples also agreed well with deposition predicted with CALPUFF: R² of 0.46, 0.76, and 079 for Pb, Cd, and Zn, respectively. Community-average concentrations of Cd, Pb, and Zn measured in soil were significantly (p < 0.0001) and strongly correlated (R² ranged from 0.77 to 0.98) with predicted deposition rates. These findings demonstrate that CALPUFF can provide reasonably accurate predictions of the patterns of long-term air pollutant deposition in the near-field associated with emissions from a discrete source in complex terrain. Because deposition estimates are calculated as a linear function of air concentrations, CALPUFF is expected to be reliable model for prediction of long-term average, near-field ambient air concentrations in complex terrain as well.     

SWOT Analysis and Challenges of Nile Basin Initiative：An Integrated Water Resource Management Perspective

River Nile is one of the longest transboundery rivers and it is shared and used by Burundi,Democratic Republic of Congo,Egypt,Ethiopia,Eritrea,Kenya,Rwanda,Sudan,Tanzania and Uganda.As of today,the Nile is a crucial resource for the economic development of the Nile Basin countries and a vital source of livelihood for 160 million inhabitants as well as 300 million people living in the 10 riparian countries.The Nile Basin Initiative(NBI) is one of the international cooperative river basin management program and regional partnership where all the Nile Basin countries except Eritrea unite to pursue long-term sustainable development,improved land use practices and management.This review therefore focused on the challenges not faced on NBI in terms of integrated use of the river and conducted analysis of strengths,weaknesses,opportunities and threats(SWOT) based on secondary data.The result of the review revealed that for decades,the Nile Basin people have been facing many complex environmental,social,economic and political challenges that have made it difficult for the proper management and sustainability of Nile water.The initiative provides training to develop skills in government ministries,non-governmental organizations and local communities in each country.It is also working to raise awareness of critical environmental issues by strengthening networks of environmental education practitioners;developing curriculum in the education sector.The challenges of NBI include the involvement and funding of World Bank,lack of sufficient staff,procedural and policies conflicts,lack of coordination and linkage with other regional institutions and lack of recognition as river basin organization.Considering the complex nature of the project,it is recommended that the NBI should come up with a strong multi-disciplinary monitoring and evaluation team to follow up all implemented projects.The NBI should carry out participatory land use planning in communities along the river basin.Moreover,livelihood analysis should be carried out especially in communities along the Nile to come up with poverty eradication projects which are socially acceptable,applicable,economically viable and affordable.     

Optimum conditions for microbial carbonate precipitation

The type of bacteria, bacterial cell concentration, initial urea concentration, reaction temperature, the initial Ca(2+) concentration, ionic strength, and the pH of the media are some factors that control the activity of the urease enzyme, and may have a significant impact on microbial carbonate precipitation (MCP). Factorial experiments were designed based on these factors to determine the optimum conditions that take into consideration economic advantage while at the same time giving quality results. Sporosarcina pasteurii strain ATCC 11859 was used at constant temperature (25°C) and ionic strength with varying amounts of urea, Ca(2+), and bacterial cell concentration. The results indicate that the rate of ureolysis (k(urea)) increases with bacterial cell concentration, and the bacterial cell concentration had a greater influence on k(urea) than initial urea concentration. At 25 mM Ca(2+) concentration, increasing bacterial cell concentration from 10(6) to 10(8)cells mL?1 increased the CaCO(3) precipitated and CO(2) sequestrated by over 30%. However, when the Ca(2+) concentration was increased 10-fold to 250 mM Ca(2+), the amount of CaCO(3) precipitated and CO(2) sequestrated increased by over 100% irrespective of initial urea concentration. Consequently, the optimum conditions for MCP under our experimental conditions were 666 mM urea and 250 mM Ca(2+) at 2.3×10? cells mL?1 bacterial cell concentration. However, a greater CaCO(3) deposition is achievable with higher concentrations of urea, Ca(2+), and bacterial cells so long as the respective quantities are within their economic advantage. X-ray Diffraction, Scanning Electron Microscopy and Energy Dispersive X-ray analyzes confirmed that the precipitate formed was CaCO(3) and composed of predominantly calcite crystals with little vaterite crystals.