Ecological Engineering Practices for the Reduction of Excess Nitrogen in Human-Influenced Landscapes: A Guide for Watershed Managers

Excess nitrogen (N) in freshwater systems, estuaries, and coastal areas has well-documented deleterious effects on ecosystems. Ecological engineering practices (EEPs) may be effective at decreasing nonpoint source N leaching to surface and groundwater. However, few studies have synthesized current knowledge about the functioning principles, performance, and cost of common EEPs used to mitigate N pollution at the watershed scale. Our review describes seven EEPs known to decrease N to help watershed managers select the most effective techniques from among the following approaches: advanced-treatment septic systems, low-impact development (LID) structures, permeable reactive barriers, treatment wetlands, riparian buffers, artificial lakes and reservoirs, and stream restoration. Our results show a broad range of N-removal effectiveness but suggest that all techniques could be optimized for N removal by promoting and sustaining conditions conducive to biological transformations (e.g., denitrification). Generally, N-removal efficiency is particularly affected by hydraulic residence time, organic carbon availability, and establishment of anaerobic conditions. There remains a critical need for systematic empirical studies documenting N-removal efficiency among EEPs and potential environmental and economic tradeoffs associated with the widespread use of these techniques. Under current trajectories of N inputs, land use, and climate change, ecological engineering alone may be insufficient to manage N in many watersheds, suggesting that N-pollution source prevention remains a critical need. Improved understanding of N-removal effectiveness and modeling efforts will be critical in building decision support tools to help guide the selection and application of best EEPs for N management.     

Geochemistry and toxicity of sediment porewater in a salt-impacted urban stormwater detention pond

A comprehensive study was carried out to investigate the impacts of road salts on the benthic compartment of a small urban detention facility, Rouge River Pond. Although the pond is an engineered water body, it is representative of many small urban lakes, ponds and wetlands, which receive road runoff and are probable high impact areas. Specific objectives of the study were to document the porewater chemistry of an aquatic system affected by elevated salt concentrations and to carry out a toxicological assessment of sediment porewater to determine what factors may cause porewater toxicity. The results indicate that the sediment porewater may itself attain high salt concentrations. The computations show that increased chloride levels have important implications on the Cd complexation, augmenting its concentration in porewater. The toxicity tests suggest that the toxicity in porewater is caused by metals or other toxic chemicals, rather than high levels of chloride.     

Simulated marine respirometry of biodegradable polymers

Eleven microorganisms were isolated from several temperate marine locations in the northeast Altantic coast of the United States and one tropical location in the Pacific Ocean (Hawaii) for the purpose of developing a rapid and accurate method of screening biodegradable materials for their susceptibility to mineralization. The materials evaluated in this study included chemically modified starch, amylose and pullulan, poly(3-hydroxybutyrate-co-valerate), (PHB/V), cellulose acetate, and a modified lignin/styrene. Some of the soluble, unmodified, biologically produced substrates such as starch, pullulan, and amylose mineralized rapidly. In general, the synthetic, insoluble polymers and the chemically modified polymers, such as acetylated and chlorinated amylose and pullulan, mineralized more slowly, although the ultimate mineralization of some of the substituted polysaccharides equaled or exceeded that of the unmodified substrate. The insoluble bacterial polyester, PHB/V, degraded rapidly after a short induction period. Initial respiration rate data, in general, could not be used as a predictor of ultimate mineralization. It was found that the cumulative level of carbon dioxide evolved signifies the minimum extent of biodegradation of the substrate, and the oxygen consumed is a good indicator of the maximum extent of substrate degradation.Paper presented at the Biodegradable Materials and Packaging Conference, September 22–23, 1993, Natick, Massachusetts.     

Intake of phthalates and di(2-ethylhexyl)adipate: results of the Integrated Exposure Assessment Survey based on duplicate diet samples and biomonitoring data

Phthalates are ubiquitous environmental chemicals with potential detrimental health effects. The purpose of our study was to quantify dietary intake of phthalates and of DEHA (Di-ethylhexyl adipate) using duplicate diet samples and to compare these data with the calculated data based on urinary levels of primary and secondary phthalate metabolites. 27 female and 23 male healthy subjects aged 14-60 years collected daily duplicate diet samples over 7 consecutive days. Overall, 11 phthalates were measured in the duplicates by GC/MS and LC/MS methods. Urinary levels of primary and secondary phthalate metabolites are also available. The median (95th percentile) daily intake via food was 2.4 (4.0) microg/kg b.w. (Di-2-ethylhexyl phthalate, DEHP), 0.3 (1.4) microg/kg b.w. (Di-n-butyl phthalate, DnBP), 0.6 (2.1) microg/kg b.w. (Di-isobutyl phthalate, DiBP) and 0.7 (2.2) microg/kg b.w. for DEHA. MEPH (Mono-2-ethylhexyl phthalate) was detectable only in minor concentrations in the samples, thus conversion of DEHP to MEHP and dietary intake of MEHP were negligible. When comparing back-calculated intake data of the DEHP metabolites with dietary DEHP intake from the day before significant correlations were observed for most of the metabolites. No correlation was found for DnBP and only a weak but significant correlation for DiBP. The median and 95th percentile daily dietary intake of all target analytes did not exceed the recommended tolerable daily intake. Our data indicated that food was the predominant intake source of DEHP, whilst other sources considerably contributed to the daily intake of DnBP and DiBP in an adult population.     

Photochemical oxidation of p-chlorophenol by UV/H2O2 and photo-Fenton process. A comparative study

In this study, photochemical advanced oxidation processes (AOPs) utilizing the combinations of UV/H2O2 and the photo-Fenton reaction (UV + classical Fenton reaction) were investigated in lab-scale experiments for the degradation of p-chlorophenol. The study showed that the photo-Fenton process, (a mixture of hydrogen peroxide and ferrous or ferric ion), was the most effective treatment process under acidic conditions and produced a higher rate of degradation of p-chlorophenol at a very short radiation time. It accelerated the oxidation rate by 5-9 times the rate for the UV/H2O2 process. The reaction was found to follow the first order, the reaction was influenced by the pH, the input concentration of H2O2 and the amount of the iron catalyst and the type of iron salt. The experimental results showed that the optimum conditions were obtained at a pH value of 3, with 0.03 mol/l H2O2, and 1 mmol/l Fe(II) for the UV/H2O2/Fe(II) system and 0.01 mol/l H2O2 and, 0.4 mmol/l Fe(III) for the UV/H2O2/Fe(III) system. The reactions were accompanied by the generation of Cl- which reached its maximum value at a short reaction time when using the photo-Fenton process. Finally a rough comparison of the specific energy consumption shows that photo-Fenton process reduced the energy consumption by at least 73 to 83% compared with the UV/H2O2 process.     

The effects of surfactant formulation on nonequilibrium NAPL solubilization

Surfactant-enhanced aquifer remediation (SEAR) involves the injection of surfactant solutions into aquifers contaminated with nonaqueous phase liquids (NAPL). Batch and column experiments were used to assess the effect of surfactant formulation on the rate of NAPL solubilization. The experimental variables were surfactant type, surfactant concentration, electrolyte concentration, and cosolvent concentration. Model equations were proposed and solved to describe solubilization under the conditions of each type of experiment. Using these models, a solubilization rate constant, kappa(b), and an overall mass transfer rate coefficient, kappa, were estimated from the batch and column experiments, respectively. The solubilization rate constant was consistently sensitive to surfactant type, surfactant concentration, and electrolyte concentration. The estimated solubilization rate constants varied over two orders of magnitude. The results of the column experiments also were sensitive to the surfactant formulation. Variations in the fitted mass transfer rate coefficient parameter, beta(0), were related to variations in the surfactant formulations. A comparison between the results of the batch and column experiments yields an apparent relationship between beta(0) and kappa(b). This relationship suggests that the mass transfer rate coefficient is directly related to the formulation of the surfactant solution.     

Fatal motorcycle crashes in wide urban area of Zagreb,Croatia—A 10-year review

Objective: The objective of our study was to determine the prevalence of alcohol and drug intoxication among fatally injured motorcyclists in a wide urban area of Zagreb, Croatia.

Methods: We conducted a single-center observational retrospective study over a 10-year period (2007–2016) in 3 counties covering an area including 1.2 million residents. We reviewed the records on fatally injured motorcyclists, collecting information relating to sex, age, cause of death, time of death in relation to the time of the crash, and the circumstances of the crash (time of day, day of the week, season). Blood alcohol concentration (BAC) and toxicology analysis results were collected and analyzed.

Results: We identified 163 deaths (95.7% males, 4.3% females). Overall, 64.2% of the victims were 20 to 39 years old. The majority (50.9%) of those fatally injured were responsible for causing the traffic crash; the rest were determined not to be responsible or the responsibility could not be determined. The most frequent causes of death were multiple injuries (55.8%) and isolated head trauma (23.3%). The rider’s BAC was above the legal limit for driving (>0.50?g/kg) in 53.8% of cases, with a mean BAC of 1.91?g/kg. There was no difference in riding a motorcycle with a BAC above the legal limit between groups defined as younger (≤39 years of age) and older (≥40 years of age). The number of people with an illegal BAC was significantly higher during weekends than during the work week. The BAC of riders who were responsible for the crash was significantly higher than that of those who were not responsible or whose responsibility could not be determined. Use of illegal drugs or nontherapeutic use of legal drugs was not common and was detected in 10.4% of fatally injured riders.

Conclusions: Alcohol intoxication has a major role in motorcycle crash–related mortality. A significant difference in BAC between fatally injured riders responsible for the accident and those who were not responsible implies that measures directed toward prevention of drinking and driving behavior could lower the number of fatal motorcycle crashes. Weekend measures, especially during spring and summer, could have particularly significant effects.     

Dispersal and social organization in the Neotropical Grey sac-winged bat Balantiopteryx plicata

Recent evidence suggests that tropical bats may frequently depart from the predominant mammalian male-biased dispersal pattern. So far, two emballonurid bat species that are closely related to our study species (Grey sac-winged bat, Balantiopteryx plicata) have been found to exhibit exceptional female-biased dispersal that is in accordance with father–daughter inbreeding avoidance. In contrast, using a combination of long-term behavioral observations of banded bats and DNA sequencing of the mitochondrial d-loop, our results suggest that B. plicata is the first Neotropical emballonurid with female philopatry and frequent male dispersal. However, just like in the other emballonurids, the age of females at first conception fell below the tenure of males. Thus, philopatric B. plicata females might face a father–daughter inbreeding risk if mating with males from their roosts. Such risk could be circumvented if mating occurs outside the nursing roost, e.g., in male mating aggregations. In contrast to other Neotropical emballonurid bats, the Grey sac-winged bat forms colonies with a greatly male-biased sex ratio (only 5 and 21 % females). Males of such colonies showed high roost fidelity and the sex ratio did not change throughout the year and for up to many years, suggesting an important role in mating. We conclude that studying the diverse mating and dispersal patterns of Neotropical emballonurids shows great potential to enlarge our understanding on how the proposed ultimate causes (i.e., avoidance of inbreeding and local competition between kin) affect the evolution of sex-biased dispersal.     

Beat frequency of cilia in the branchial basket of the ascidian Ciona intestinalis in relation to temperature and algal cell concentration

To elucidate the effects of temperature and algal cell concentration on pumping of water in the ascidian Ciona intestinalis a number of different experiments were performed. Beat frequency of the lateral cilia in the openings of the branchial sac was measured in intact specimens using a microprojection objective and a monochrome CCD video camera. At constant low algal cell concentration, beat frequencies increased linearly with temperature from 4.0 Hz (±0.5) at 7.4 °C to 13.6 Hz (±1.6) at 20.1 °C. At a constant temperature of 15 °C, beat frequency decreased with increasing algal cell concentration from approximately 3000 to >10 000 Rhodomonas sp. cells ml⁻¹. The decrease was observed both in experiments where the ascidians had been acclimated to a fixed algal cell concentration and in experiments with changing concentrations. Effect of algal cell concentration on squirting/siphon closure and flow velocity in the exhalent siphon was measured using a thermistor. At low algal cell concentrations, flow velocity in the exhalent siphon was stable, apart from a few short squirts. At very high algal cell concentrations, the flow velocity was reduced and much less stable, with prolonged squirting. The effect of gut content on filtration was studied in experiments with specimens acclimated to high algal cell concentrations. Results showed a close relation between gut clearance and filtration rate. From the experimental results and a qualitative analysis of the Ciona-pump it was concluded that the ciliary beat frequency is proportional to the water flow through the sea squirt and that changes in pumping caused by temperature or algal cell concentration are under nervous control or governed by enzyme kinetics, rather than being a result of physico-mechanical properties, i.e. pump efficiency versus flow resistance, of the ascidian pump. Received: 6 October 1997 / Accepted: 8 October 1998