STREAM PHOSPHORUS EXPORTS FROM WATERSHEDS WITH CONTRASTING LAND USES IN SOUTHERN ONTARIO1

: The export of dissolved molybdate reactive phosphorus (DMRP) from 22 watersheds in the Duffin Creek drainage basin near Toronto Ontario was measured over a 25-month period. The annual average loss varied from 0.027 to 2.11 kg P/ha. Phosphorus levels in a number of watersheds were strongly influenced by effluent from a sewage treatment plant which contributed about 68 percent of the annual DMRP input to Duffin Creek. An analysis of 12 watersheds which did not contain major point pollution sources revealed that DMRP concentration and losses had a significant positive correlation with crop area and a strong negative association with forest, abandoned farm land, and area of sand + sandy loam soils. The causal relationships underlying these simple correlations are difficult to evaluate because of considerable multicollinearity between land use, soil, and topographic variables. Analysis of a mass balance for the downstream reaches of Duffin Creek indicated that there was considerable retention of phosphorus in the river channel particularly during summer low flows.     

A COMPARISON OF MODELS PREDICTING GROUND WATER LEVELS ON HILLSIDE SLOPES1

ABSTRACT: A comparative study of ground water level predictions on hillside slopes using two models is presented. The models are a simplified mass balance model that has components for evapotran-spiration, recharge, and drainage; and a two-dimensional finite difference model that employs kriging to estimate soil parameters and accounts for non-uniform thickness of the soil layer. These models are representative of a wide range of modeling capabilities and are used to illustrate the sensitivity of ground water level predictions to the sophistication of the modeling techniques. The drainage and recharge components of the two models are evaluated and the importance of unsaturated flow in recharge computations is underscored. Piezometric observations in a small drainage depression on the slope of Kennel Creek Valley in Tongass National Forest, Alaska, were used to evaluate the two models. The results show that, although the predictions differ from the field observations, the simple physically-based mass balance model predicts the ground water levels as well as the two-dimensional model. It is suggested that caution should be exercised in using complex models to validate simpler models.     

Variation of particle number and mass concentration in various size ranges of ambient aerosols in Eastern Germany

There is an ongoing debate on the question which size fraction of particles in ambient air may be responsible for short-term responses of the respiratory system as observed in several epidemiological studies. However, the available data on ambient particle concentrations in various size ranges are not sufficient to answer this question.Therefore, on 180 days during the winter 1991/92 daily mean size distributions of ambient particles were determined in. Erfurt, a city in Eastern Germany. In the range 0.01–0.3 μm particles were classified by an electrical mobility analyzer and in the range 0.1–2.5 μm by an optical particle counter. From the derived size distributions, number and mass concentrations were calculated.The mean number concentration over this period of time was governed by particles smaller than 0.1 μm (72%), whereas the mean mass concentration was governed by particles in the size range 0.1–0.5 pm (83%). The contribution of particles larger than 0.5 μm to the overall number concentration was negligible and so was the contribution of particles smaller than 0.1 μm to the overall mass concentration. Furthermore, total number and mass concentrations in the range 0.01–2.5 μm were poorly correlated.The results suggest that particles larger than 2.5 μm (or even larger than 0.5 μm) are rare in the European urban environment so that the inhalation of these particles is probably not relevant for human health. Since particle number and mass concentrations can be considered poorly correlated variables, more insight into health-related aspects of particulate air pollution will be obtained by correlating respiratory responses with mass and number concentrations of ambient particles below 0.5 μm.     

Using dispersion and mesoscale meteorological models to forecast pollen concentrations

This work describes the results of research into a source-oriented pollen concentration forecasting technique. Tests were conducted using the National Center for Atmospheric Research/ Penn State Fifth Generation Mesoscale Model (MM5), the National Oceanographic and Atmospheric Administration (NOAA) Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT_4) Model combined with the locations of oak trees and their aerial coverage from biogenic emissions land cover database version 3.1 (BELD3). Daily forecasts of pollen concentrations via MM5 and HYSPLIT_4 were made with 30-min increments and tested against 30-min oak pollen data collected by the St. Louis County Department of Health in Clayton, Missouri, for the month of April 2000.Results from these tests show that the combination of MM5 and HYSPLIT_4 with accurate source locations can provide short-term forecasts as indicated by the levels of forecast pollen and actual oak pollen levels, which follow similar profiles for the day. From the 30 individual pollen concentration forecasts, two example forecasts are presented. Additional studies need to be conducted to further validate these results, using an array of pollen collectors. A better understanding of the biology of pollen release is critical to improving these pollen concentration forecasts.     

A study into the parameters affecting selected reaction monitoring of 2,3,7,8-TCDD

The use of high resolution (10,000 resolving power) coupled gas chromatography - mass spectrometry is a well established technique in the analysis of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) but in the case of heavily contaminated stack samples interferences can still occur. A complementary technique that offers high specificity is selected reaction monitoring (SRM).A study has been made into the effects that affect the metastable dissociation of 2,3,7,8-TCDD in the first field free region (FFR1) of a magnetic sector mass spectrometer, and monitored using SRM.Monatomic, diatomic and polyatomic gases have been investigated in the collision chamber of the mass spectrometer, as have the effects of electron energy, source temperature and trap current on the dissociation, and optima conditions determined for them.     

A statistical comparison of naphthenic acids characterized by gas chromatography-mass spectrometry

Naphthenic acids are complex mixtures of alkyl-substituted acyclic and cycloaliphatic carboxylic acids, with the general chemical formula C_nH_2n+zO₂, where n is the carbon number and Z specifies a homologous family. These acids have a variety of commercial uses, including being used as wood preservatives. They are found in conventional and heavy oils, and in the oil sands of northeastern Alberta, Canada. Naphthenic acids are major contributors to the toxicity of tailings waters that result from the oil sands extraction process. Eight naphthenic acids preparations (four from commercial sources and four from the oil sands operations) were derivatized and analyzed by gas chromatography–mass spectrometry. The composition of each mixture was summarized as a three-dimensional plot of the abundance of specific ions (corresponding to naphthenic acids) versus carbon number (ranging from 5 to 33) and Z family (ranging from 0 to −12). The data in these plots were divided into three groups according to carbon number (group 1 contained carbon numbers 5–14, group 2 contained carbon numbers 15–21, and group 3 contained carbon numbers 22–33). A t-test, using arcsine-transformed data, was applied to compare corresponding groups in samples from various sources. Results of the statistical analyses showed differences between various commercial naphthenic acids preparations, and between naphthenic acids from different oil sands ores and tailings ponds. This statistical approach can be applied to data collected by other mass spectrometry methods.     

Source characterization and identification by real-time single particle mass spectrometry

A Real-Time Single Particle Mass Spectrometer, RSMS-3, was deployed to Wilmington, Delaware to study regional and local contributions to fine and ultra-fine urban particulate matter (PM). Approximately two-thirds of PM₁ consisted of internally mixed secondary aerosol. The remaining one-third was externally mixed including biomass burning (13%), fossil fuel combustion (7%) and various industrial sources (13%). In this last group, particle classes containing specific combinations of transition and/or heavy metals gave wind-rose plots consistent with specific point sources. For example, particles containing V and Ni were detected from different wind directions than those containing V and Fe. Samples from two industrial emission stacks, a steel manufacturing facility 10 km away and a coal-fired electrical power generation facility 5 km away, were analyzed and compared to the ambient data set. In each case, a direct correlation was found: a Pb–Zn–K–Na class for the steel manufacturing facility and an Fe–La/Ce class for the power generation facility. The ambient particle classes showed additional small signals from secondary components indicating atmospheric processing. Ambient particle classes containing only a subset of these elements, such as Zn only, Fe only and Pb–K only, were nonspecific, that is, the wind-rose plots were more diffuse and the particles could not be mapped to individual sources. The merits of stack sampling as an aid to interpreting single particle data sets are discussed.     

化学质量平衡受体模型新技术的应用──TEDA大气颗粒物来源解析实例

本文结合实例介绍了大气颗粒物来源解析最常用的模型－化学质量平衡（ＣＭＢ）的原理、有效方差最小二乘解法及诊断检验技术，并用ＭＰＩＮ矩阵检验了拟合元素对拟合源的灵敏度，奇异值分解法（ＳＶＤ）鉴别了共线源，得出天津市经济技术开发区（ＴＥＤＡ）的ＴＳＰ主要来源为风沙、扬尘，其次为燃煤飞灰和木灰。     

Experimental Study of Gas-Liquid Interfacial Properties in a Stepped Cascade Flow

Gas-liquid interface measurements were conducted in a strongly turbulent free-surface flow (i.e., stepped cascade). Local void fractions, bubble count rates, bubble size distributions and gas-liquid interface areas were measured simultaneously in the air-water flow region using resistivity probes. The results highlight the air-water mass transfer potential of a stepped cascade with measured specific interface area over 650 m^–1 and depth-average specific area up to 310 m^–1. A comparison between single-tip and double-tip resistivity probes suggests that simple robust single-tip probes may provide accurate, although conservative, gas-liquid interfacial properties. The latter device may be used in the field and in prototype plants. Notation a = specific interface area (m^–1); a _mean = depth-average specific interface area (m^–1): a _mean=frac1Y ₉₀limits sup> Y ₉₀ sup ₀(1–C)dy; C = local void fraction; C _gas = dissolved gas concentration (kg m^–3); C _mean = depth-average mean air concentration defined as: C _mean=1–d/Y ₉₀; C _s = saturation concentration (kg m^–3); D = dimensionless air bubble diffusivity (defined by [1]); d = equivalent clear-water flow depth (m): d=limits sup> Y ₉₀ sup ₀(1–C) dy; d_ab = air bubble diameter (m); d_c = critical flow depth (m); for a rectangular channel: d _c=sqrt[3]q _w ²/g; F = air bubble count rate (Hz); F _max = maximum bubble count rate (Hz), often observed for C=50%; g = gravity acceleration (m s^–2); h = step height (m); K _L = liquid film coefficient (m s^–1); K = integration constant defined as: K=tanh ^–1 sqrt0.1)+(2D)^–1 [1]; L = chute length (m); N = velocity distribution exponent; ———– ^*Corresponding author, E-mail: h.chanson@mailbox.uq.edu.au Q _w = water discharge (m³ s^–1); q _w = water discharge per unit width m² s^–1); t = time (s); V = local velocity (m s^–1); V _c = critical flow velocity (m s^–1); for a rectangular channel: V _c=sqrt[3]q _w g V _max = maximum air-water velocity (m s^–1); V ₉₀ = characteristic air-water velocity (m s^–1) where C = 90%; W = channel width (m); x = longitudinal distance (m) measured along the flow direction (i.e., parallel to the pseudo-bottom formed by the step edges); y = distance (m) normal to the pseudo-bottom formed by the step edges; Y₉₀ = characteristic distance (m) where C=0.90; Y ₉₈ = characteristic distance (m) where C=0.98; = slope of pseudo-bottom by the step edges; = diameter (m).