Ambient Background Concentrations Research Articles

Practical estimation and use of natural background concentrations in surface waters for nickel in Europe.

Estimates of ambient background concentrations in surface waters, referred to as natural background concentrations (NBCs) in European guidance documents, may be an important factor in determining whether a monitoring site meets the legally binding Environmental Quality Standard (EQS) when assessing naturally occurring substances. Here, we focus on utilizing routine regulatory surface water monitoring data to provide risk assessors and environmental practitioners with a transparent, implementable, repeatable, and resource-effective approach to estimate NBCs. The methodology does not use additional environmental sampling beyond that which is routine or require advanced statistical methods, or the incorporation of highly specialist, and not always readily accessible, local knowledge. It determines both whether a site is suitable for NBC assessment as well as the identification of suitable surrogate sites and local NBCs using 11 criteria: six for identifying if a site is suitable for NBC correction, and five for identifying suitable surrogate sites for local NBC values. The criteria consider both the extent of any EQS exceedance, after accounting for bioavailability in line with the European guidance and potential anthropogenic impacts at the site, and can be applied in a simple sequential procedure. The method has been applied to derive NBCs for nickel on three case-study countries-Cyprus, France, and Spain-to determine its useability and impact on compliance. The methodology presented addresses a gap in the current guidance regarding the practical and consistent implementation of NBCs and could be applied to other naturally occurring substances in an EQS or Water Quality Guideline compliance assessment process. Integr Environ Assess Manag 2024;00:1-14. © 2024 WCA Environment Ltd and NiPERA Inc. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

US and international per- and polyfluoroalkyl substances surface water quality criteria: A review of the status, challenges, and implications for use in chemical management and risk assessment.

Regulation of per- and polyfluorinated substances (PFAS) in surface water is a work-in-progress with relatively few criteria promulgated in the United States and internationally. Surface water quality criteria (SWQC) or screening values derived for perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) by Australia, Canada, the European Union (EU), and four US states (Florida, Michigan, Minnesota, and Wisconsin), and the San Francisco Bay Regional Water Quality Control Board (SFB RWQCB; California) were compared. Across these eight jurisdictions, promulgated numeric criteria for the same compound and receptor span over five orders of magnitude as a result of different approaches and data interpretations. Human health criteria for PFOS range from 0.0047 to 600 ng/L depending on route of exposure (e.g., fish consumption or drinking water) and are lower than most ecological criteria for protection of aquatic and wildlife receptors. Data gaps and uncertainty in chronic toxicity and bioaccumulation of PFOS and PFOA, as well as the use of conservative assumptions regarding intake and exposure, have resulted in some criteria falling at or below ambient background concentrations and current analytical detection limits (around 1 ng/L for commercial laboratories). Some jurisdictions (e.g., Australia, Canada) have deemed uncertainty in quantifying water-fish bioaccumulation too great and set fish tissue action levels in lieu of water criteria. Current dynamics associated with the emerging and evolving science of PFAS toxicity, exposure, and environmental fate (i.e., data gaps and uncertainty), as well as the continuous release of scientific updates, pose a challenge to setting regulatory limits. Integr Environ Assess Manag 2024;20:36-58. © 2023 AECOM Technical Services, Inc and The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Ambient background and quality reference values for trace metals in soils from Algeria

The establishment of the reference ambient background concentrations (ABCs) and quality reference values (QRVs) for trace metal (TM) concentrations in soils are required for the environmental assessment and any implementation of a protective action. This information is lacking for soils of the eastern Mitidja plain, which is an important agricultural production area in Algeria. Data for the aqua regia extractable Cd, Cr, Cu, Fe, Ni, Pb and Zn concentrations from 180 composite topsoil samples taken across the Mitidja plain in a stratified random pattern were statistically analysed. Descriptive statistical methods and linear regression equations were applied to determine the upper limit of the ABCs for the TMs. After removal of outliers, the derived QRVs were: Cd 0.24, Cr 62.1, Cu 99.3, Fe 45 590, Ni 47.7, Pb 33 and Zn 115 mg/kg. Iron is a macro element in the soils, but is included as its concentration can be used to normalise the concentrations of the other elements. The derived QRVs are similar or less than those reported for other regions of the world, apart from Cu, where a wide range (36 to 206 mg/kg) is reported. These reference values can be used to identify areas that may require follow-up surveys or to identify priority sites for decision making.

Laboratory and field evaluation of a low-cost methane sensor and key environmental factors for sensor calibration.

Low-cost sensors enable finer-scale spatiotemporal measurements within the existing methane (CH4) monitoring infrastructure and could help cities mitigate CH4 emissions to meet their climate goals. While initial studies of low-cost CH4 sensors have shown potential for effective CH4 measurement at ambient concentrations, sensor deployment remains limited due to questions about interferences and calibration across environments and seasons. This study evaluates sensor performance across seasons with specific attention paid to the sensor's understudied carbon monoxide (CO) interferences and environmental dependencies through long-term ambient co-location in an urban environment. The sensor was first evaluated in a laboratory using chamber calibration and co-location experiments, and then in the field through two 8 week co-locations with a reference CH4 instrument. In the laboratory, the sensor was sensitive to CH4 concentrations below ambient background concentrations. Different sensor units responded similarly to changing CH4, CO, temperature, and humidity conditions but required individual calibrations to account for differences in sensor response factors. When deployed in-field, co-located with a reference instrument near Baltimore, MD, the sensor captured diurnal trends in hourly CH4 concentration after corrections for temperature, absolute humidity, CO concentration, and hour of day. Variable performance was observed across seasons with the sensor performing well (R 2 = 0.65; percent bias 3.12%; RMSE 0.10 ppm) in the winter validation period and less accurately (R 2 = 0.12; percent bias 3.01%; RMSE 0.08 ppm) in the summer validation period where there was less dynamic range in CH4 concentrations. The results highlight the utility of sensor deployment in more variable ambient CH4 conditions and demonstrate the importance of accounting for temperature and humidity dependencies as well as co-located CO concentrations with low-cost CH4 measurements. We show this can be addressed via Multiple Linear Regression (MLR) models accounting for key covariates to enable urban measurements in areas with CH4 enhancement. Together with individualized calibration prior to deployment, the sensor shows promise for use in low-cost sensor networks and represents a valuable supplement to existing monitoring strategies to identify CH4 hotspots.

Presence of Priority Polycyclic Aromatic Hydrocarbons, Chromium, Copper and Lead in Two selected Brownfield Sites in United Kingdom

In recent years, concerns about adverse effects of increasing land contamination paralleled with the increasing demand for land has emphasized need for sustainable remediation strategies. Soil samples were collected from two brownfield sites, in Saltley, Birmingham and Swansea, South Wales, United Kingdom and analysed to establish the extent of contamination by priority polycyclic aromatic hydrocarbon (PAH) compounds. Saltley site had a total PAH concentration of 41.0 mg kg-1 with high concentrations of phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene and benzo[a]pyrene, total benzo[a]pyrene equivalent value of 6.0 mg kg-1 and total carcinogenic PAH of 19.0 mg kg-1. At the Swansea site, total PAH concentration ranged from 5.0 – 85.0 mg kg-1 with pyrene, fluoranthene, benzo[a]anthracene, chrysene, benzo[a]pyrene as the predominant PAHs, total benzo[a]pyrene equivalent value of 0.9 – 2.0 mg kg-1 and total carcinogenic PAH concentration of 2.6 – 11.0 mg kg-1. Heavy metal concentrations were above the ambient background concentrations for urban/industrial area. Both brownfield sites had a mixture of PAH and heavy metal contamination in varying concentrations with implication for the selection of efficient remedial strategies to enable their redevelopment.

Development and validation of freshwater sediment quality assessment guidelines for trace elements in Korea

Sediment quality assessment guidelines(SQAGs) for seven trace elements were suggested to build an assessment system of freshwater sediment quality for a regulatory program in Korea. In this study, current one-step SQAGs were divided into three levels based on the probability of toxicity occurrence, namely, the threshold-effect-level(TEL), the probable-effect-level(PEL), and the apparent-effect-threshold(AET). A sediment toxicity database consisting of field-collected sediments and toxicity results from three different species were used to derive TEL, PEL, and AET. The ambient background concentrations of trace elements in freshwater sediments were used instead of the TEL values because TEL values were lower than the ambient background levels. To validate the reliability of the new SQAGs, a separate sediment toxicity database based on G. sobaegensis was used. When the mean quotient value for the PEL was 0.34, the reliability reached a maximum of 87% with a positive predictive value of 94% and a negative predictive value of 85%. These results showed the newly derived SQAGs were very useful for assessing and predicting the toxicity of field sediments in Korea. Finally, ambient background concentrations, a mean quotient of PEL of 0.34, and AETs were used to classify the quality of the field-collected sediments into four categories.

Quantifying factors related to urban metal contamination in vegetable garden soils of the west and north of Melbourne, Australia

Vegetable gardens in cities provide communities with fresh vegetables but also may contribute towards public exposure to metals present in soil from historical pollution. Contamination of some Melbourne garden soils with Pb (range 12.9–773 mg kg−1 in soil) was found with some soils exceeding the Australian human health screening criteria for residential land use of 300 mg kg−1. Cadmium concentrations (0.12–1.04 mg kg−1) were above the ambient background soil concentrations of <1 mg kg−1. Nickel concentrations (7.6–40.5 mg kg−1) and Cr (11.6–49.4 mg kg−1) were within the range of expected ambient background concentrations. Distance from the nearest arterial road, house age and the likely use of lead-based paints were the main factors explaining approximately 75% of soil Pb variability in garden soils. Metal concentrations in garden soils of wooden houses were found to be significantly higher than the garden soil of brick and concrete houses (Pb (p < 0.0001)) and Cd (p < 0.001)). Significant correlations were found between backyard garden soil metal concentration and house age for Pb (R2 = 0.83, p < 0.0001) and Cd (R2 = 0.40, p < 0.0002) and the distance from arterial roads for Pb (R2 = 0.38, p < 0.002), while Cr and Ni are related to soil characteristics cation exchange capacity, organic matter, and pH. Vegetable garden with elevated Pb and Cd had recognizable risk factors such as older, painted structures on adjacent houses and closer proximity to arterial roads with higher frequency traffic.

Exposure to benzene, toluene, ethylbenzene, xylene, formaldehyde, and acetaldehyde in and around gas stations in Japan

We investigated the personal exposure of gas station employees to benzene, toluene, ethylbenzene, xylene, formaldehyde, and acetaldehyde at three full-service gas stations in Okayama, Japan. We also assessed both the indoor (offices) and ambient background concentrations. The personal exposure, indoor, and ambient concentrations of benzene were 57.3, 6.11, and 1.31 μg/m3, respectively, in spring and 17.0, 2.04, and 0.603 μg/m3, respectively, in winter. Those for toluene were 196, 25.8, and 2.66 μg/m3, respectively, in spring and 30.6, 5.31, and 1.23 μg/m3, respectively, in winter. The personal exposure concentrations of benzene, toluene, ethylbenzene, and xylene for a gas station employee were significantly higher than those for indoors and the ambient air. However, the personal exposure, indoor, and ambient concentrations of formaldehyde were 5.08, 10.1, and 4.29 μg/m3, respectively, in spring and 11.6, 24.1, and 6.04 μg/m3, respectively, in winter. The indoor concentrations of formaldehyde were significantly higher than both the personal exposure concentrations for gas station employees and the ambient concentrations. The excess lifetime cancer risk from benzene exposure was estimated to be 2.22 × 10−5, 2.43 × 10−6, and 2.56 × 10−7 for full-service gas station employees, self-service gas station employees, and self-service gas station users who are assumed to use the station once a week, respectively. Assuming the occupational exposure to toluene, ethylbenzene, and xylene at the gas station were comparable to the maximum 2-h average exposure levels in the present study, the total hazard quotient for non-carcinogenic risk was calculated to be much lower than 1 (2.72–5.56 × 10−3) based on the TLV-TWA (8-h).

Ambient geochemical baselines for trace elements in Chernozems\u2014approximation of geochemical soil transformation in an agricultural area

The legal regulatory/action levels of trace elements in soils are established at high concentrations, at which the crucial functions of soil are at risk or are eliminated. However, concentrations below these action levels, but above presumed natural levels, may also limit particular ecosystem services, including organic food production. Thus, defining the (ambient) background concentrations is an essential part of environmental or health risk assessment, e.g., on Chernozems, which are considered to be the most productive soils and ones that should be protected against all forms of contamination. Based on 28 profiles of chernozemic soils developed from loess in an agricultural region of SW Poland presumed to be free of industrial contamination, ambient geochemical baselines have been derived for Fe and six trace metals for four standardized soil layers, including the topsoil (plow layer) and parent material layers. The median values for the plow layer (1.89% for Fe, and 537, 49, 17, 14, and 26 mg kg−1 for Mn, Zn, Pb, Cu, and Ni, respectively) are lower than the values reported for other Chernozems in SE Poland/Europe/the world, and thus may serve as a general geochemical baseline for chernozemic soils developed from loess. The concentration of Cd, although lower than in other Chernozems around the world, is higher than in Ukrainian Chernozems and thus may serve as a local (or Central European) baseline only. The median concentrations of Fe, Cu, Mn, and Zn are very close to their concentrations in the Chernozem buried under the Neolithic kurgan. However, Pb and Cd concentrations are two times higher than in the buried soil, indicating the scale of general contamination of the topsoil horizons of arable soils. Concentrations of the elements under study, excluding Fe, in both the buried and surface soils are significantly higher in the topsoil layer compared to parent material (loess), and this justifies the separate baseline values for topsoil horizons, instead of background values derived universally for parent rock types. This is essential, in particular in soils texturally differentiated within profiles, where the subsoil material has a different origin and cannot be considered the parent material for topsoil horizons. Underlying or locally outcropped bedrock (e.g., serpentinite rocks) may naturally enhance the total concentration of trace elements in the entire soil profile by the addition of metal-rich regolith particles during the formation of surface covers, e.g., by eolian processes under periglacial conditions (Late Pleistocene). Such soils are naturally enriched with metals (with nickel in the case of serpentinite bedrock), cannot be considered contaminated, and thus require a separate legal treatment, including separate (or individually suited) background baselines for health risk assessments.

How do chronic nutrient loading and the duration of nutrient pulses affect nutrient uptake in headwater streams?

Our study aimed to analyze the effects of chronic nutrient loading on the capacity of headwater streams to retain phosphorus and ammonium pulses of different duration. For this purpose, we selected nine headwater streams located across a gradient of increasing agricultural land use and eutrophication. In each stream, we performed sequential plateau additions with increasing nutrient concentrations in summer 2015 and instantaneous slug additions in summer 2016 under similar hydrological conditions. We modelled kinetic uptake curves from the slug additions via the Tracer Additions for Spiraling Curve Characterization method and calculated ambient uptake parameters. Ambient uptake rates generally increased (1.4–20.8 µg m−2 s−1 for NH4–N and 0.3–10.3 µg m−2 s−1 for SRP, respectively), while ambient uptake velocities decreased from oligotrophic to polytrophic streams (1.8–14.0 mm min−1 for NH4–N and 1.6–9.9 mm min−1 for SRP, respectively). However, correlations between ambient uptake parameters and background concentrations were weak. Concentration-dependent uptake rates followed either a linear or a Michaelis–Menten saturation model, regardless of the degree of nutrient loading. Uptake rate curves showed counter-clockwise hysteresis in oligotrophic streams and clockwise hysteresis in streams of higher trophic states, indicating a reduced significance of hyporheic uptake with increasing nutrient loading. Comparisons of slug and plateau additions revealed that oligotrophic streams were most efficient in uptake during short nutrient pulses, while eutrophic streams profited from longer pulse duration. The results indicate that nutrient uptake is increasingly transport-controlled in polluted streams where increased biofilm thickness and clogging of sediments restrict nutrient transport to reactive sites.

Dam reservoirs as an efficient trap for historical pollution: the passage of Hg and Pb through the Ohře River, Czech Republic

The concentration of Hg and Pb pollutants was examined in sediments of a central European lowland river, the Ohře River. The pollution originated from several sources that were active mainly between the thirteenth and twentieth centuries. Its passage through the river system has been altered by two dam reservoirs built in the 1960s. The pre-dam pollution levels were evaluated from historical floodplain and dam reservoir sediments. We evaluated influence of damming on pollution status of sediments using the concept of ambient background concentrations based on the examination of polymodality in the distribution of concentrations and identification of breaks between the concentration modes. The Skalka Dam Reservoir has suppressed the transport of Hg pollution from a chemical factory in Marktredwitz, Germany (nineteenth and twentieth centuries): the dam has decreased the Hg concentrations in the downstream channel sediments by an order of magnitude compared to pre-dam conditions. The concentration of Hg in suspended particulate matter in the outflow from the Skalka Reservoir varies between 10 and 60% of the inflow concentrations depending on the discharge. The Nechranice Dam Reservoir has suppressed the passage of Pb pollution originating from historical metal mining, which has led Pb concentrations in sediments downstream to decrease to the levels of average topsoil pollution in the sub-catchments without ore mining. Both reservoirs act as sediment traps and thus play a beneficial role for the quality of the Ohře River downstream environment.

Environmental and anthropogenic influences on ambient background concentrations of fluoride in soil

Excess exposure to fluoride causes substantive health burden in humans and livestock globally. However, few studies have assessed the distribution and controls of variability of ambient background concentrations of fluoride in soil. Ambient background concentrations of fluoride in soil were collated for Greater Melbourne, Greater Geelong, Ballarat and Mitchell in Victoria, Australia (n = 1005). Correlation analysis and machine learning techniques were used to identify environmental and anthropogenic influences of fluoride variability in soil. Sub-soils (>0.3 m deep), in some areas overlying siltstone and sandstone, and to a lesser extent, overlying basalt, were naturally enriched with fluoride at concentrations above ecological thresholds for grazing animals. Soil fluoride enrichment was predominantly influenced by parent material (mineralogy), precipitation (illuviation), leaching during palaeoclimates and marine inputs. Industrial air pollution did not significantly influence ambient background concentrations of fluoride at a regional scale. However, agricultural practices (potentially the use of phosphate fertilisers) were indicated to have resulted in added fluoride to surface soils overlying sediments. Geospatial variables alone were not sufficient to accurately model ambient background soil fluoride concentrations. A multiple regression model based on soil chemistry and parent material was shown to accurately predict ambient background fluoride concentrations in soils and support assessment of fluoride enrichment in the environment.

Geochemical indices and regression tree models for estimation of ambient background concentrations of copper, chromium, nickel and zinc in soil

Geochemical ratios between elements of environmental concern and Fe have been recommended for estimation of “background” concentrations of Cr, Cu, Ni and Zn in soil. However, little research has occurred to assess the consistency of geochemical ratios across soils developed in different environments. Broad application of generic geochemical ratios could result in under or over estimation of anthropogenic impacts to soil and subsequent inaccurate assessment of risk to the environment. A soil survey was undertaken in Victoria, Australia, including collection of samples (n = 622) from surface (0–0.1 m below ground level) and sub-surface (0.3–0.6 m below ground level) soils, overlying Tertiary-Quaternary basalt, Tertiary sediments and Silurian siltstones and sandstones. Samples were analyzed for metals and soil physical and chemical properties (particle size, cation exchange capacity, organic matter and pH). Geochemical correlations between elements in soils from different parent materials and environments were compared against geochemical relationships reported in Australia and internationally. Ratios of Cr and Fe were relatively consistent across parent materials, and comparable to published models for estimation of background Cr. Conversely, ratios between Cu, Ni, and Zn with Fe, were variable between soils developed in different weathering environments and/or soil depths. Alternative regression equations and rule based regression tree models were developed as an improved means for prediction of ambient background Cu, Ni and Zn concentrations in soil. Ambient background concentrations of Ni and Cr were predictable across parent materials and depths, allowing these models to be extended to soils across Australia and potentially internationally.

Gaseous air pollution background estimation in urban, suburban, and rural environments

There is a great demand for estimating the ambient air pollutant background concentrations in order to assess the effectiveness of different emission control strategies. In this paper, the background concentrations of four pollutants, namely sulfur dioxide (SO2), nitrogen oxides (NOx), carbon monoxide (CO), and ozone (O3) pollutants in urban, suburban, and rural environments were investigated using Kolmogorov–Zurbenko (KZ) filter technique. Air quality data from monitoring stations over a period of 4 years (2007–2010) was analyzed for three locations in Kuwait, namely urban, suburban, and rural. The spatial and temporal (daily, weekly, and monthly) variations of the four pollutants were analyzed. The results show that the levels of ambient air pollutant background concentrations were high in the urban site compared to suburban and rural area. The diurnal variation of SO2 concentration showed an early morning peak, while the diurnal variation of NOx concentration constituted has two peaks, one was in the early morning hours (5 to 8 a.m.) and the second was in nighttime hours (8 to 11 p.m.). These two peaks were observed at all three locations. The monthly background NOx concentration reached a maximum in winter and minimum in summer. Diurnal variation of CO concentration showed a similar trend to SO2 concentrations in all three locations. Because of the photochemical reactions that occur in the atmosphere, the background concentration of O3 showed an inverse relation with respect to background concentration of NOx.

Evaluation of environmental and anthropogenic influences on ambient background metal and metalloid concentrations in soil

There has been a global shift in environmental risk assessment towards quantifying ambient background concentrations of metals/metalloids in soil. Whilst bedrock has been shown to be a key driver of metal/metalloid variability in soil, few researchers have assessed controls of ambient background concentrations in soils of similar bedrock. A soil survey was undertaken ofGreater Melbourne, Greater Geelong, Ballarat and Mitchell in Victoria, Australia for elements of potential environmental concern: As, Cd, Cr, Cu, Ni, Hg, Pb and Zn. Samples (n=622) were collected from surface (0 to 0.1m) and sub-surface (0.3 to 0.6m) soils, overlying Tertiary-Quaternary basalt, Tertiary sediments and Silurian siltstone and sandstone. In addition, background soil data from open-source environmental assessment reports (n=5512) were collated to support the understanding of natural enrichment, particularly at depths >0.6m. Factor analysis, supported by correlation analysis and auxiliary geo-spatial data, provided an improved understanding of where and how background metal/metalloid enrichment occurs in the environment. Weathering during paleoclimates was the predominant influence of background metal/metalloid variability in soils overlying similar bedrock. Other key influences of metal/metalloid variability in soil included hydraulic leaching of alkali elements, biological cycling, topography and alluvial transfer of silt and sand from mineralised regions. In addition, urbanisation positively correlated with Pb and Zn concentrations in surface soils suggesting that anthropogenic activities may have resulted in diffuse Pb and Zn contamination of urban soil.

Are Lead Exposures a Risk in European Fresh Waters? A Regulatory Assessment Accounting for Bioavailability.

An indicative compliance assessment of the Europe-wide bioavailable lead Environmental Quality Standard of 1.2µgL-1 (EQS) was undertaken against regulatory freshwater monitoring data from six European member states and FOREGS database. Bio-met, a user-friendly tool based upon Biotic Ligand Models (BLMs) was used to account for bioavailability, along with the current European Water Framework Directive lead dissolved organic carbon correction approach. The outputs from both approaches were compared to the BLM. Of the 9054 freshwater samples assessed only 0.6% exceeded the EQS of 1.2µgL-1 after accounting for bioavailability. The data showed that ambient background concentrations of lead across Europe are unlikely to influence general compliance with the EQS, although there may be isolated local issues. The waters showing the greatest sensitivity to potential lead exposures are characterized by relatively low DOC (< 0.5mgL-1), regardless of the pH and calcium concentrations.

Assessment of ambient background concentrations of elements in soil using combined survey and open-source data.

Understanding ambient background concentrations in soil, at a local scale, is an essential part of environmental risk assessment. Where high resolution geochemical soil surveys have not been undertaken, soil data from alternative sources, such as environmental site assessment reports, can be used to support an understanding of ambient background conditions. Concentrations of metals/metalloids (As, Mn, Ni, Pb and Zn) were extracted from open-source environmental site assessment reports, for soils derived from the Newer Volcanics basalt, of Melbourne, Victoria, Australia. A manual screening method was applied to remove samples that were indicated to be contaminated by point sources and hence not representative of ambient background conditions. The manual screening approach was validated by comparison to data from a targeted background soil survey. Statistical methods for exclusion of contaminated samples from background soil datasets were compared to the manual screening method. The statistical methods tested included the Median plus Two Median Absolute Deviations, the upper whisker of a normal and log transformed Tukey boxplot, the point of inflection on a cumulative frequency plot and the 95th percentile. We have demonstrated that where anomalous sample results cannot be screened using site information, the Median plus Two Median Absolute Deviations is a conservative method for derivation of ambient background upper concentration limits (i.e. expected maximums). The upper whisker of a boxplot and the point of inflection on a cumulative frequency plot, were also considered adequate methods for deriving ambient background upper concentration limits, where the percentage of contaminated samples is <25%. Median ambient background concentrations of metals/metalloids in the Newer Volcanic soils of Melbourne were comparable to ambient background concentrations in Europe and the United States, except for Ni, which was naturally enriched in the basalt-derived soils of Melbourne.

The Impact of an Anti-Idling Campaign on Ambient Air Quality Near Schools

Background: Exposure to air pollution and diesel exhaust may be elevated at schools due to nearby traffic and buses. School bus idling, in particular, has been associated with an increase of fine particulate matter (PM2.5) and elemental carbon (EC) concentrations near schools. Aims: To determine the impact of an anti-idling campaign on outdoor air quality at four schools with varying exposure to school buses. Methods: Outdoor air sampling for PM2.5 and EC was conducted at four schools for five days before and after an anti-idling campaign. Sampling began each day 30 minutes before the morning arrival of buses and concluded 30 minutes after their departure in the afternoon. Sampling was conducted simultaneously at four corresponding community sites to represent ambient background concentrations. Differences in PM2.5 and EC levels at school and community sites for each sampling day were calculated before and after the campaign. Results: Prior to the anti-idling campaign, the average concentration of PM2.5 at 3 of the 4 schools exceeded the community background levels and the difference was greatest (4.1 µg/m3, p &lt; 0.01) at the school with the most buses (n = 39). The largest difference in EC between school and community site was also observed at the school with the greatest number of buses (0.40 µg/m3, p &lt; 0.01). Following the anti-idling campaign, the average difference in PM2.5 at the school with the most buses decreased from 4.1 µg/m3 to 1.0 µg/m3 (p &lt; 0.05). Similarly, at this school the difference in EC level decreased from 0.4 µg/m3 to 0.1 µg/m3 (p &lt; 0.05). Concentrations of PM2.5 and EC at schools with fewer buses (n = 5–12) were not significantly reduced. Conclusions: The concentration of PM2.5 and EC at schools may exceed community background levels, particularly in the presence of idling school buses. An anti-idling campaign was effective at reducing the concentrations of PM2.5 and EC at the school with the greatest number of buses.

Geogenic control on soil chemistry in urban areas: A novel method for urban geochemical mapping using parent material classified data

The purpose of the study reported here is to assess whether it may in some circumstances be useful and appropriate to use a parent material (PM) soil chemistry mapping method developed for national soil chemistry data to portray spatial variation in urban soil chemistry data in Great Britain. Analysis of variance (ANOVA) of the urban soil data suggests that spatial interpolation of soil ambient background concentrations (ABCs) using PM classified soil data may be justified for those elements with strong geogenic control. The PM soil chemistry mapping method for urban soil data is demonstrated using data from the Northampton urban area, in the English Midlands. Geometric mean (GM) and inverse distance weighting (IDW) interpolations based on the nearest four topsoil samples were evaluated. Independent validation indicated that for As, Cr, Fe and to a lesser extent K, which all exhibit relatively strong geogenic control in the Northampton urban area: (i) the PM soil chemistry mapping method is more accurate and effective than the conventional IDW grid mapping and (ii) PM soil chemistry mapping based on the average of the nearest four Lne element concentrations is more accurate than mapping based on IDW values calculated from the nearest four Lne element concentrations. The variation in effectiveness of the methods can be explained by the fact that PM exerts a significant control on As, Cr, Fe and K in the Northampton area whereas anthropogenic inputs appear to be the dominant control on the spatial variation of Pb, especially at high concentrations. The PM mapping method would be expected to work efficiently in other urban areas and for those elements where a significant proportion of the variation can be explained by PM.

Results of a Long-Term Study of Vapor Intrusion at Four Large Buildings at the NASA Ames Research Center

Most of the published empirical data on indoor air concentrations resulting from vapor intrusion of contaminants from underlying groundwater are for residential structures. The National Aeronautics and Space Administration (NASA) Research Park site, located in Moffett Field, CA, and comprised of 213 acres, is being planned for redevelopment as a collaborative research and educational campus with associated facilities. Groundwater contaminated with hydrocarbon and halogenated hydro-carbon volatile organic compounds (VOCs) is the primary environmental medium of concern at the site. Over a 15-month period, approximately 1000 indoor, outdoor ambient, and outdoor ambient background samples were collected from four buildings designated as historical landmarks using Summa canisters and analyzed by the U.S. Environmental Protection Agency TO-15 selective ion mode. Both 24-hr and sequential 8-hr samples were collected. Comparison of daily sampling results relative to daily background results indicates that the measured trichloroethylene (TCE) concentrations were primarily due to the subsurface vapor intrusion pathway, although there is likely some contribution due to infiltration of TCE from the outdoor ambient background concentrations. Analysis of the cis-1,2-dichloroethylene concentrations relative to TCE concentrations with respect to indoor air concentrations and the background air support this hypothesis; however, this indicates that relative contributions of the vapor intrusion and infiltration pathways vary with each building. Indoor TCE concentrations were also compared with indoor benzene and background benzene concentrations. These data indicate significant correlation between background benzene concentrations and the concentration of benzene in the indoor air, indicating benzene was present in the indoor air primarily through infiltration of outdoor air into the indoor space. By comparison, measured TCE indoor air concentrations showed a significantly different relationship to background concentrations. Analysis of the results show that indoor air samples can be used to definitively define the source of the TCE present in the indoor air space of large industrial buildings.