Chemical mass balance source apportionment for combined PM2.5 measurements from U.S. non-urban and urban long-term networks

The Minnesota Particulate Matter 2.5 (PM_2.5) Source Apportionment Study was undertaken to explore the utility of PM_2.5 mass, element, ion, and carbon measurements from long-term speciation networks for pollution source attribution. Ambient monitoring data at eight sites across the state were retrieved from the archives of the Interagency Monitoring of Protected Visual Environments (IMPROVE) and the Speciation Trends Network (STN; part of the Chemical Speciation Network [CSN]) and analyzed by an Effective Variance – Chemical Mass Balance (EV-CMB) receptor model with region-specific geological source profiles developed in this study. PM_2.5 was apportioned into contributions of fugitive soil dust, calcium-rich dust, taconite (low grade iron ore) dust, road salt, motor vehicle exhaust, biomass burning, coal-fired utility, and secondary aerosol. Secondary sulfate and nitrate contributed strongly (49–71% of PM_2.5) across all sites and was dominant (≥60%) at IMPROVE sites. Vehicle exhausts accounted for 20–70% of the primary PM_2.5 contribution, largely exceeding the proportion in the primary PM_2.5 emission inventory. The diesel exhaust contribution was separable from the gasoline engine exhaust contribution at the STN sites. Higher detection limits for several marker elements in the STN resulted in non-detectable coal-fired boiler contributions which were detected in the IMPROVE data. Despite the different measured variables, analytical methods, and detection limits, EV-CMB results from a nearby IMPROVE-STN non-urban/urban sites showed similar contributions from regional sources – including fugitive dust and secondary aerosol. Seasonal variations of source contributions were examined and extreme PM_2.5 episodes were explained by both local and regional pollution events.     

Inferring coastal processes from regional-scale mapping of Radon and salinity: examples from the Great Barrier Reef, Australia

The radon isotope ²²²Rn and salinity in coastal surface water were mapped on regional scales, to improve the understanding of coastal processes and their spatial variability. Radon was measured with a surface-towed, continuously recording multi-detector setup on a moving vessel. Numerous processes and locations of land-ocean interaction along the Central Great Barrier Reef coastline were identified and interpreted based on the data collected. These included riverine fluxes, terrestrially-derived fresh submarine groundwater discharge (SGD) and the tidal pumping of seawater through mangrove forests. Based on variations in the relationship of the tracers radon and salinity, some aspects of regional freshwater inputs to the coastal zone and to estuaries could be assessed. Concurrent mapping of radon and salinity allowed an efficient qualitative assessment of land-ocean interaction on various spatial and temporal scales, indicating that such surveys on coastal scales can be a useful tool to obtain an overview of SGD locations and processes.     

Distribution of radionuclides in the guano sediments of Xisha Islands, South China Sea and its implication

Several natural and anthropogenic radionuclides (²¹⁰Pb, ²²⁶Ra and ¹³⁷Cs) in guano-phosphatic coral sediments and pure guano particles collected from Ganquan, Guangjin, Jinqing and Jinyin Islands of the Xisha archipelago, South China Sea, were analyzed. The Constant Initial Concentration (CIC) model and the Constant Rate of Supply (CRS) model were applied for age calculation. The average supply rate of ²¹⁰Pb was 126 Bq m⁻² a⁻¹, very close to the flux of northern hemisphere average (125 Bq m⁻² a⁻¹). The activities of anthropogenic radionuclides in the sediments were very low, indicating that human nuclear tests did not notably impact this region. The main source of radionuclides in the sediments was from atmospheric precipitation, and the organic matter derived from plant and produced by nutrient-rich guano could further enhance them.     

Comprehensive assessment of toxic metals in urban and suburban street deposited sediments (SDSs) in the biggest metropolitan area of China

A set of toxic metals, i.e. As, Hg, Pb, Cd, Cu, Zn, Ni and Cr, in urban and suburban SDSs were investigated comparatively in the biggest metropolitan area of China, Shanghai. Results showed that all of the metals except As were accumulated greatly, much higher than background values. Geo-accumulation index indicated that metal contamination in urban SDSs was generally heavier than that in suburban SDSs. Potential ecological risk index demonstrated that overall risks caused by metals were considerable. Cd contributed 52% to the overall risk. Multivariate statistical analysis revealed that in urban SDSs, Zn, Ni, Cd, Pb, Cu and Cr were related to traffic and industry; coal combustion led to elevated levels of Hg; soil parent materials controlled As contents. In suburban SDSs, Pb, Cu, As and Cd largely originated from traffic pollution; Zn, Ni and Cr were associated with industrial contaminants; Hg was mainly from domestic solid waste.     

Dietary exposure of juvenile common sole (Solea solea L.) to polybrominated diphenyl ethers (PBDEs): Part 2. Formation, bioaccumulation and elimination of hydroxylated metabolites

The uptake, elimination and transformation of six PBDE congeners (BDE-28, -47, -99, -100, -153, -209) were studied in juvenile common sole (Solea solea L.) exposed to spiked contaminated food over a three-month period, and then depurated over a five-month period. Methoxylated (MeO-) and hydroxylated (OH-) PBDEs were determined in fish plasma exposed to PBDEs and compared to those obtained in control fish. While all MeO- and some OH- congeners identified in fish plasma were found to originate from non-metabolic sources, several OH- congeners, i.e., OH-tetraBDEs and OH-pentaBDEs, were found to originate from fish metabolism. Among these, 4′-OH-BDE-49 was identified as a BDE-47 metabolite. Congener 4′-OH-BDE-101, identified here for the first time, may be the result of BDE-99 metabolic transformation. Our results unequivocally showed that PBDEs are metabolised in juvenile sole via the formation of OH- metabolites. However, this was not a major biotransformation route compared to biotransformation through debromination.     

The impact of ambient ozone on mountain spruce forests in the Czech Republic as indicated by malondialdehyde

Malondialdehyde (MDA), a product of lipid peroxidation and biomarker of oxidative stress, is measured over the long term in spruce Picea abies needles under real conditions in three Czech mountain border areas. The trends presented collate the MDA content in spruce needles with ambient ozone, temperature and precipitation as casual, and defoliation as a subsequent factor for the period 1994-2006. We have found the overall decreasing trends in MDA and defoliation. The highest MDA and defoliation are recorded in the Jizerske, the lowest in the Krusne hory Mts. Out of the examined variables the MDA is predicted best by mean temperature in vegetation season, median of O₃ concentrations and AOT40; these three variables account for 34% of MDA1 and 36% of MDA2 variability. Our hypothesis that higher ambient O₃ exposure results in higher MDA contents in P. abies needles under real conditions has not been approved.     

Comparison among model estimates of critical loads of acidic deposition using different sources and scales of input data

The critical load (CL) of acidic atmospheric deposition represents the load of acidity deposited from the atmosphere to the earth’s surface at which harmful acidification effects on sensitive biological receptors are thought to occur. In this study, the CL for forest soils was estimated for 27 watersheds throughout the United States using a steady-state mass balance approach based on both national and site-specific data and using different approaches for estimating base cation weathering. Results suggested that the scale and source of input data can have large effects on the calculated CL and that the most important parameter in the steady-state model used to estimate CL is base cation weathering. These results suggest that the data and approach used to estimate weathering must be robust if the calculated CL is to be useful for its intended purpose.     

The Efficacy of a Programme of Landslide Risk Reduction in Areas of Unplanned Housing in the Eastern Caribbean

Poor countries are disproportionately affected by the cost of disasters. Yet there is evidence of the benefits of seeking to mitigate the impact of a disaster, compared with the costs incurred in ‘making good’ after a major event has occurred. This article reviews a programme of landslide risk reduction in unplanned communities in the Eastern Caribbean. The construction of appropriate surface water management measures, based on the application of scientific and engineering principles, has been demonstrated to reduce the hazard from rainfall-triggered landslides. Adopting a community-based approach additionally delivers social and environmental benefits relating to employment generation, improvements in the environmental conditions within the community, and improvements slope management practices. The sustained implementation of the community-based projects has provided the necessary evidence-base for these practices to influence Government policy and practice, and gain recognition from regional development agencies. The strategic and incremental uptake of the community-based methodology is demonstrated to be an effective means for delivering physical landslide risk reduction measures in the most ‘at risk’ areas of unplanned housing.