In Reply to Drs Lipman and Hackett

Publication date: Available online 28 October 2017
Source:Wilderness & Environmental Medicine
Author(s): Nicholas C. Kanaan, Alicia L. Peterson, Matiram Pun, Ghan B. Thapa, Aditya Tiwari, Bikash Basyal, Peter S. Holck, Jennifer Starling, Thomas F. Freeman, Jessica R. Gehner, Linda Keyes, Dana R. Levin, Catherine J. O'Leary, Katherine E. Stuart, Jared L. Velgersdyk, Ken Zafren, Buddha Basnyat




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The influence of continental air masses on the aerosols and nutrients deposition over the western North Pacific

Publication date: January 2018
Source:Atmospheric Environment, Volume 172
Author(s): Jiangping Fu, Bo Wang, Ying Chen, Qingwei Ma
The air masses transported from East Asia have a strong impact on the aerosol properties and deposition in the marine boundary layer of the western North Pacific (WNP) during winter and spring. We joined a cruise between 17 Mar. and 22 Apr. 2014 and investigated the changes of aerosol composition and size distribution over the remote WNP and marginal seas. Although the secondary aerosol species (SO4²⁻, NO3⁻ and NH4⁺) in remote WNP were influenced significantly by the continental transport, NH4⁺ concentrations were lower than 2.7 μg m⁻³ in most sampling days and not correlated with non-sea-salt (nss)-SO4^2- suggesting that the ocean could be a primary source of NH4⁺. Moderate Cl⁻ depletion (23%) was observed in remote WNP, and the inverse relationship between Cl⁻ depletion percentages and nss-K⁺ in aerosols suggested that the transport of biomass burning smoke from East Asia might be a vital extra source of Cl⁻. Both Asian dust and haze events were encountered during the cruise. Asian dust carried large amounts of crustal elements such as Al and Ti to the WNP, and the dusty Fe deposition may double its background concentration in seawater. Differently, a dramatic increase of dry deposition flux of dissolved particulate inorganic nitrogen was observed during the haze event. Our study reveals that the transport of different continental air masses may have distinct biogeochemical impacts on the WNP by increasing the fluxes of different nutrient elements and potentially changing the nutrient stoichiometry.



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Assessment of the impact of climate change on flow regime at multiple temporal scales and potential ecological implications in an alpine river

Abstract

The source region of Yellow river is an alpine river sensitive to climate changes, but the potential effects of climate change on hydrological regime characteristics and ecological implications are less understood. This study aims to assess the response of the alterations in the flow regimes over the source region of Yellow river to climate change using Soil and Water Integrated Model driven by different Global Circulation Models (GFDL-ESM2M, IPSL-CM5A-LR and MIROC-ESM-CHEM) under three Representative Concentration Pathway emission scenarios (RCP2.6, RCP4.5 and RCP8.5). Indicators of hydrological alteration and River impact index are employed to evaluate streamflow regime alterations at multiple temporal scales. Results show that the magnitude of monthly and annual streamflow except May, the magnitude and duration of the annual extreme, and the number of reversals are projected to increase in the near future period (2020–2049) and far future period (2070–2099) compared to the baseline period (1971–2000). The timing of annual maximum flows is expected to shift backwards. The source region of Yellow river is expected to undergo low change degree as per the scenarios RCP2.6 for both two future periods and under the scenarios RCP4.5 for the near future period, whereas high change degree under RCP4.5 and RCP8.5 in the far period on the daily scale. On the monthly scale, climate changes mainly have effects on river flow magnitude and timing. The basin would suffer an incipient impact alteration in the far period under RCP4.5 and RCP8.5, while low impact in other scenarios. These changes in flow regimes could have several positive impacts on aquatic ecosystems in the near period but more detrimental effects in the far period.

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Source apportionment and health risk assessment of potentially toxic elements in road dust from urban industrial areas of Ahvaz megacity, Iran

Abstract

This study investigates the occurrence and spatial distribution of potentially toxic elements (PTEs) (Hg, Cd, Cu, Mo, Pb, Zn, Ni, Co, Cr, Al, Fe, Mn, V and Sb) in 67 road dust samples collected from urban industrial areas in Ahvaz megacity, southwest of Iran. Geochemical methods, multivariate statistics, geostatistics and health risk assessment model were adopted to study the spatial pollution pattern and to identify the priority pollutants, regions of concern and sources of the studied PTEs. Also, receptor positive matrix factorization model was employed to assess pollution sources. Compared to the local background, the median enrichment factor values revealed the following order: Sb > Pb > Hg > Zn > Cu > V > Fe > Mo > Cd > Mn > Cr ≈ Co ≈ Al ≈ Ni. Statistical results show that a significant difference exists between concentrations of Mo, Cu, Pb, Zn, Fe, Sb, V and Hg in different regions (univariate analysis, Kruskal–Wallis test p < 0.05), indicating the existence of highly contaminated spots. Integrated source identification coupled with positive matrix factorization model revealed that traffic-related emissions (43.5%) and steel industries (26.4%) were first two sources of PTEs in road dust, followed by natural sources (22.6%) and pipe and oil processing companies (7.5%). The arithmetic mean of pollution load index (PLI) values for high traffic sector (1.92) is greater than industrial (1.80) and residential areas (1.25). Also, the results show that ecological risk values for Hg and Pb in 41.8 and 9% of total dust samples are higher than 80, indicating their considerable or higher potential ecological risk. The health risk assessment model showed that ingestion of dust particles contributed more than 83% of the overall non-carcinogenic risk. For both residential and industrial scenarios, Hg and Pb had the highest risk values, whereas Mo has the lowest value.

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Risk assessment and ranking of heavy metals concentration in Iran’s Rayen groundwater basin using linear assignment method

Abstract

Groundwater is an important source of freshwater for domestic, agricultural and industrial uses in Iran. Groundwater quality assessment and environmental evaluation are considered as critical issues in recent years. Intensive human activities have resulted in significant changes in environment leading to serious groundwater contamination. This research proposes a two-part systematic approach to tackle heavy metals contamination problem in Rayen Basin (southeast Iran). The first part consists of determining geochemical characteristics and evaluating groundwater quality through application of water quality index and heavy metal pollution indices (i.e. HPI and MI). The second part includes ranking sampling stations based on heavy metals concentration in groundwater using linear assignment method. Six types of water could be identified according to the dominant cations and anions in samples: Ca–HCO₃, Ca–SO₄, Na–Cl, Na–HCO₃, Na–SO₄ and mixed water type. Calculation of indices revealed that natural and anthropogenic activities are playing a vital role in degrading groundwater quality in the study area. The proposed methodology can help in groundwater resource management and preventative activities by identifying risk factors and recognizing their pollution level. The results of this research provide useful and effective information for water pollution control and management and can be used in environmental studies in order to protect groundwater resources in the future.

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UPTAKE AND DISSIPATION OF NEONICOTINOID RESIDUES IN NECTAR AND FOLIAGE OF SYSTEMICALLY–TREATED WOODY LANDSCAPE PLANTS

Abstract

Systemic neonicotinoid insecticides used in urban arboriculture could pose a risk to bees and other pollinators foraging on treated plants. We measured uptake and dissipation of soil–applied imidacloprid and dinotefuran in nectar and leaves of two woody plant species, a broadleaf evergreen tree (Ilex × attenuata) and a deciduous shrub (Clethra alnifolia) to assess concentrations to which pollinators and pests might be exposed in landscape settings. Three application timings, autumn (post–bloom), spring (pre–bloom), or summer (early post–bloom), were evaluated to see if taking advantage of differences in the neonicotinoids' systemic mobility and persistence might enable pest control while minimizing transference into nectar. Nectar and tissue samples were collected from in–ground plants and analyzed for residues by HPLC–MS/MS in two successive years. Concentrations found in nectar following autumn or spring applications ranged from 166–515 ng/g for imidacloprid, and from 70–1235 ng/gg for dinotefuran, depending on plant and timing. These residues exceed concentrations shown in to adversely affect individual and colony–level traits of bees. Summer application mitigated concentrations of imidacloprid (8–31 ng/g), but not dinotefuran (235–1191 ng/g), in nectar. Our data suggest that dinotefuran may be more persistent than is generally believed. Implications for integrated pest and pollinator management in urban landscapes are discussed. This article is protected by copyright. All rights reserved

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DEVELOPMENT AND APPLICATION OF A BIOTIC LIGAND MODEL FOR PREDICTING THE CHRONIC TOXICITY OF DISSOLVED AND PRECIPITATED ALUMINUM TO AQUATIC ORGANISMS

Abstract

Aluminum (Al) toxicity to aquatic organisms is strongly affected by water chemistry. Toxicity modifying factors such as pH, dissolved organic carbon (DOC), hardness, and temperature have a large impact on the bioavailability and toxicity of Al to aquatic organisms. The importance of water chemistry on the bioavailability and toxicity of Al suggests that interactions between Al and chemical constituents in exposures to aquatic organisms can affect the form and reactivity of Al thereby altering the extent to which it interacts with biological membranes. These types of interactions have previously been observed in the toxicity data for other metals where they have been well-described by the biotic ligand model (BLM) framework. In BLM applications to other metals (including cadmium, cobalt, copper, lead, nickel, silver, and zinc), these interactions have focused on dissolved metal. A review of Al toxicity data shows that concentrations of Al that cause toxicity are frequently in excess of solubility limitations. Aluminum solubility is strongly pH dependent, with a solubility minimum near pH 6 and increasing at both lower and higher pH values. For the Al BLM, the mechanistic framework has been extended to consider toxicity resulting from a combination of dissolved and precipitated Al to recognize the solubility limitation. The resulting model can effectively predict toxicity to fish, invertebrate, and algae over a wide range of conditions. This article is protected by copyright. All rights reserved

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