Partitioning and granulometric distribution of metal leachate from urban traffic dry deposition particulate matter subject to acidic rainfall and runoff retention

Vehicular transportation coupled with urban hydrology is a significant source as well as vector of particulate matter (PM) and particulate-bound metal inventories in urban systems. This study examines the granulometric distribution of metals from dry deposition PM generated from 17 dryfall periods and equilibrium metal partitioning with runoff PM distribution from eight rainfall-runoff events at an urban inter-state watershed in Baton Rouge, LA. Dry deposition PM is a coarse non-uniform gradation with a d(50m)=304mum and a peak surface area at 106mum. Results indicate acid rain is not a significant metal contributor to runoff but is capable of leaching metals from PM to runoff. Retained runoff partitioning resulted in particulate-bound predominance for As, Cd, Cr, Cu, Pb, and Zn while Ca and Mg remained predominately dissolved. The finer PM fraction (<75mum) generates the highest metal concentrations and the highest metal mass is associated with the coarser fraction (>75mum). This coarse fraction is also the most labile when exposed to acidic rainfall; generating up to 90% of the total metal mass leached from the entire PM gradation. Comparing dry deposition and runoff PM of equal mass and size gradation, retained runoff PM is enriched with metals (except Pb). Results indicate the labile coarse fraction of dry deposition PM can be a significant source of metal leaching while runoff PM (mobilized dry deposition PM) stored in a BMP can be metal-enriched with the potential for re-leaching or scour.     

Some potential errors in the measurement of mercury gas exchange at the soil surface using a dynamic flux chamber

A series of controlled environment experiments were conducted to examine the use of a dynamic flux chamber to measure soil emission and absorption of total gaseous mercury (TGM). Uncertainty about the appropriate airflow rates through the chamber and chamber exposure to ambient wind are shown to be major sources of potential error. Soil surface mercury flux measurements over a range of chamber airflow rates showed a positive linear relationship between flux rates and airflow rate through the chamber. Mercury flux measurements using the chamber in an environmental wind tunnel showed that exposure of the system to ambient winds decreased the measured flux rates by 40% at a wind speed of 1.0 m s(-1) and 90% at a wind speed of 2 m s(-1). Wind tunnel measurements also showed that the chamber footprint was limited to the area of soil inside the chamber and there is little uncertainty of the footprint size in dry soil.     

Atmospheric NH3 and NO2 concentration and nitrogen deposition in an agricultural catchment of Eastern China

To assess the atmospheric environmental impacts of anthropogenic reactive nitrogen in the fast-developing Eastern China region, we measured atmospheric concentrations of nitrogen dioxide (NO₂) and ammonia (NH₃) as well as the wet deposition of inorganic nitrogen (NO₃⁻ and NH₄⁺) and dissolved organic nitrogen (DON) levels in a typical agricultural catchment in Jiangsu Province, China, from October 2007 to September 2008_. The annual average gaseous concentrations of NO₂ and NH₃ were 42.2 μg m⁻³ and 4.5 μg m⁻³ (0 °C, 760 mm Hg), respectively, whereas those of NO₃⁻, NH₄⁺, and DON in the rainwater within the study catchment were 1.3, 1.3, and 0.5 mg N L⁻¹, respectively. No clear difference in gaseous NO₂ concentrations and nitrogen concentrations in collected rainwater was found between the crop field and residential sites, but the average NH₃ concentration of 5.4 μg m⁻³ in residential sites was significantly higher than that in field sites (4.1 μg m⁻³). Total depositions were 40 kg N ha⁻¹ yr⁻¹ for crop field sites and 30 kg N ha⁻¹ yr⁻¹ for residential sites, in which dry depositions (NO₂ and NH₃) were 7.6 kg N ha⁻¹ yr⁻¹ for crop field sites and 1.9 kg N ha⁻¹ yr⁻¹ for residential sites. The DON in the rainwater accounted for 16% of the total wet nitrogen deposition. Oxidized N (NO₃⁻ in the precipitation and gaseous NO₂) was the dominant form of nitrogen deposition in the studied region, indicating that reactive forms of nitrogen created from urban areas contribute greatly to N deposition in the rural area evaluated in this study.     

An evaluation of mercury levels in Louisiana fish: Trends and public health issues

To characterize statewide fish tissue mercury levels in edible finfish the first comprehensive analysis of Louisiana's fish tissue mercury database was conducted. Analyses were based on fifteen years of fish tissue mercury data collected from 368 waterbodies between 1994 and 2008 (n = 14,344). The overall objectives of this study were to establish baseline fish tissue mercury levels; and evaluate species-specific temporal and spatial trends in fish tissue mercury levels. Fish tissue mercury levels ranged from 0.001 ppm (the detection limit) to 5.904 ppm for king mackerel; with an overall geometric mean of 0.218 ppm. Ninety-five percent of samples had mercury levels below the FDA's action level of 1.0 ppm for methylmercury in commercial food. Forty-four percent of all samples had mercury levels above the U.S. EPA's methylmercury fish tissue criterion of 0.3 ppm for sportfish. Species of potential concern include cobia, king mackerel, blackfin tuna, greater amberjack, spotted bass, bowfin, largemouth bass and freshwater drum. There was a significant but small decline in statewide length-adjusted largemouth bass mercury levels between 1994-1999 to 2003-2008 (p < 0.05). The highest fish mercury levels were observed in Pearl, Calcasieu, Mermentau, Ouachita, Pontchartrain and Sabine basins. Length-adjusted largemouth bass mercury levels were significantly higher in wetlands and rivers/streams vs. lakes; and in wetlands vs. estuaries (p < 0.05). Data were analyzed from a public health perspective to make recommendations for optimizing monitoring and outreach.     

Hair mercury concentrations of children and mothers in Korea: implication for exposure and evaluation

BACKGROUND: Mercury is a global pollutant that affects neurodevelopment of children. OBJECTIVE: The objectives were to measure and evaluate mercury concentration of children and mothers, and its association with exposure. METHODS: A cross-sectional assessment was done using questionnaires and hair mercury were analysed by Cold Vapor Atomic Absorption Spectrometry in the National Institute for Minamata Disease in Japan. RESULTS: A total of 112 children and 111 mothers were included; mean age was 34 months and 32 years, respectively. 17.9% of children and 34.2% of mothers had concentrations greater than 1 parts per million (ppm) as reference level. Body weight at birth, feeding methods, maternal age, and maternal education level were significantly different in each group (p<.05). Mean maternal hair mercury level (0.91 ppm) was higher than children (0.74 ppm), and has a positive correlation between them (p<.05). 68.1% of children, 75% of pregnant period, 63.4% of lactating period, and 78.6% of last six months have been consuming fish. With multiple regression analysis, hair mercury levels in children aged less than 6 months had a linear relationship with body weight at birth, gestational weeks, feeding methods (breast- or bottle- feeding) and maternal educational level. While children aged over 6 months significantly differed with gender, frequency of fish servings per week, and frequency of maternal fish consumption in lactation period. And hair mercury levels had inverse linear relationship with maternal monthly income in this age group. Maternal mercury levels had linear relationship with maternal age. CONCLUSION: Mercury levels in children may be affected by their mothers due to similar dietary patterns. Further long-term large-scale and follow-up studies are needed.     

Application of state-of-the-art in measurement and data analysis techniques for vibration evaluation of a tall building

Recent advancements in sensing and data acquisition technology have made monitoring of structures and infrastructure more affordable and, at the same time, more comprehensive. Examples of such advancements are application of wireless technology for communication, the utilisation of fully automated systems for long-term monitoring and the remote control of the sensing system over Internet. Although each of these technologies has been used in different structural health monitoring projects in the recent years, inclusion of an all-in-one sensing system represents the state-of-the-art in measurement techniques. This paper presents the integration of all of the above-mentioned advanced monitoring approaches in one sensing system for forensic quantification of an in-service tall building. The inclusive measurement and monitoring system along with advanced data analysis techniques enabled extraction of detailed information about dynamic characteristics of the building structure and development of reliable conclusions regarding its performance. It is shown that the performance of the investigated structural components is satisfactory in terms of strength demand. However, the level of vibration in some portions of the structure does not meet the limits of human comfort. In addition, wind-speed spectrum, acceleration response spectrum and the modes of lateral vibration are extracted to assist with evaluation of the structure's performance.     

An evaluation of teeth of ringed seals (Phoca hispida) from Greenland as a matrix to monitor spatial and temporal trends of mercury and stable isotopes

Total mercury (Hg) concentrations were measured in teeth of ringed seals from Qeqertarsuaq, central West Greenland (1982 to 2006) and Ittoqqortoormiit, central East Greenland (1986 to 2006). Stable isotopic ratios of carbon (¹³C/¹²C) and nitrogen (¹⁵N/¹⁴N) were determined as well to provide insights into diet variations between regions or through time. Mercury concentrations decreased the first years of life of the animals suggesting that Hg had been transferred from the mother to the foetus and newborn. The Hg concentrations in teeth were significantly lesser in ringed seals from central West Greenland compared to those from central East Greenland. Carbon and nitrogen stable isotopic values measured in the animals differed also significantly between the two regions. Increasing temporal trends of dental Hg concentrations between 1994 and 2006 were observed in ringed seals from both central West Greenland and central East Greenland. These increases were attributed to global changes in environmental Hg levels since no temporal trends in δ¹⁵N values were found to support the hypothesis of a diet shift over time. Furthermore, a decreasing temporal trend in δ¹³C values was observed in the teeth of seals from central East Greenland, and explained by a likely change over time towards more pelagic feeding habits; alternatively, the so-known Seuss effect was thought to be responsible for this decrease. Finally, it was concluded that the tooth of ringed seal was a good monitoring tissue to assess Hg trends.