Affiner votre recherche
Résultats 1-10 de 23
Urban metabolism: A review of research methodologies
2013
Zhang, Yan
Urban metabolism analysis has become an important tool for the study of urban ecosystems. The problems of large metabolic throughput, low metabolic efficiency, and disordered metabolic processes are a major cause of unhealthy urban systems. In this paper, I summarize the international research on urban metabolism, and describe the progress that has been made in terms of research methodologies. I also review the methods used in accounting for and evaluating material and energy flows in urban metabolic processes, simulation of these flows using a network model, and practical applications of these methods. Based on this review of the literature, I propose directions for future research, and particularly the need to study the urban carbon metabolism because of the modern context of global climate change. Moreover, I recommend more research on the optimal regulation of urban metabolic systems.
Afficher plus [+] Moins [-]Fiproles in urban surface runoff: Understanding sources and causes of contamination
2019
Cryder, Zachary | Greenberg, Les | Richards, Jaben | Wolf, Douglas | Luo, Yuzhou | Gan, Jay
Urban-use pesticides present a unique risk to non-target organisms in surface aquatic systems because impervious pavement facilitates runoff that may lead to serious contamination and ensuing aquatic toxicity. Fipronil is an insecticide used at high rates in urban environments, especially in regions such as California. This compound and its biologically active degradation products have been detected in urban runoff drainage and downstream surface water bodies at concentrations exceeding toxicity thresholds for sensitive aquatic invertebrates, necessitating a better understanding of the runoff sources and causes of this contamination at sites of application. In this study, we evaluated sorption of fipronil, fipronil desulfinyl, fipronil sulfide, and fipronil sulfone in urban dust, soil, and concrete, matrices commonly associated with the perimeter of a residential home. Samples were also collected from five single family homes treated with fipronil in Riverside, California, for five months to determine the occurrence of fipronil and its degradates in runoff water, urban dust, soil, and on concrete surfaces. Statistical analysis was performed to determine which urban matrices contributed more significantly to the contaminant levels in runoff water. Freundlich sorption coefficients for fipronil and its degradation products in dust were 3- to 9-fold greater than their values in soil. Fipronil and its degradates were detected in 100% of runoff samples and their presence was observed in dust, soil, and concrete wipe samples for 153 d after the treatment. Linear regression analysis showed that concrete surfaces were a primary source of all four compounds to runoff, and loose dust on concrete pavement also served as an important contributor. This study represents the first comprehensive investigation of the sources and causes for surface runoff contamination by fipronil and its degradation products. Findings highlight the importance to reduce fipronil residues on concrete surfaces through improved application methods and other mitigation practices.
Afficher plus [+] Moins [-]Evaluating the mobility of polymer-stabilised zero-valent iron nanoparticles and their potential to co-transport contaminants in intact soil cores
2016
Chekli, L. | Brunetti, G. | Marzouk, E.R. | Maoz-Shen, A. | Smith, E. | Naidu, R. | Shon, H.K. | Lombi, E. | Donner, E.
The use of zero-valent iron nanoparticles (nZVI) has been advocated for the remediation of both soils and groundwater. A key parameter affecting nZVI remediation efficacy is the mobility of the particles as this influences the reaction zone where remediation can occur. However, by engineering nZVI particles with increased stability and mobility we may also inadvertently facilitate nZVI-mediated contaminant transport away from the zone of treatment. Previous nZVI mobility studies have often been limited to model systems as the presence of background Fe makes detection and tracking of nZVI in real systems difficult. We overcame this problem by synthesising Fe-59 radiolabelled nZVI. This enabled us to detect and quantify the leaching of nZVI-derived Fe-59 in intact soil cores, including a soil contaminated by Chromated-Copper-Arsenate. Mobility of a commercially available nZVI was also tested. The results showed limited mobility of both nanomaterials; <1% of the injected mass was eluted from the columns and most of the radiolabelled nZVI remained in the surface soil layers (the primary treatment zone in this contaminated soil). Nevertheless, the observed breakthrough of contaminants and nZVI occurred simultaneously, indicating that although the quantity transported was low in this case, nZVI does have the potential to co-transport contaminants. These results show that direct injection of nZVI into the surface layers of contaminated soils may be a viable remediation option for soils such as this one, in which the mobility of nZVI below the injection/remediation zone was very limited. This Fe-59 experimental approach can be further extended to test nZVI transport in a wider range of contaminated soil types and textures and using different application methods and rates. The resulting database could then be used to develop and validate modelling of nZVI-facilitated contaminant transport on an individual soil basis suitable for site specific risk assessment prior to nZVI remediation.
Afficher plus [+] Moins [-]Transfer of methyl chloroform, trichloroethylene and tetrachloroethylene to milk, tissues and expired air following intraruminal or oral administration in lactating goats and milk-fed kids
1995
Hamada, T. | Tanaka, H. (National Institute of Animal Industry, Tsukuba Norindanchi PO Box 5, Ibaraki 305 (Japan))
Evaluation of ammonia emission abatement on the basis of measurements and model calculations
1998
Erisman, J.W. | Bleeker, A. | Jaarsveld, J.A. van (ECN, P.O. Box 1, 1755 ZG Petten (Netherlands))
Focus on emission factors: a sensitivity analysis of ammonia emission modelling in the Netherlands
1998
Leneman, H. | Oudendag, D.A. | Hoek, K.W. van der | Janssen, P.H.M. (Agricultural Economics Research Institute [LEI-DLO], The Hague (Netherlands))
Retention and distribution of heavy metals in mangrove soils receiving wastewater
1996
Tam, N.F.Y. | Wong, Y.S. (Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China))
Effects of pulpmill effluent irrigation on the distribution of elements in the profile of an arid region soil
1999
Howe, J. | Wagner, M.R. (2301 E 8th Street, Tucson, AZ 85719 (USA))
Measured and predicted volatilisation fluxes of PCBS from contaminated sludge-amended soils
1997
Cousins, I.T. | Hartlieb, N. | Teichmann, C. | Jones, K.C. (Environmental Science Division, Institute of Environmental and Biological Sciences, Lancaster University, Lancaster LA1 4YQ (United Kingdom))
Accumulation of Cr, Pb, Cu, Ni, Zn and Cd in soil following irrigation with treated urban effluent in Australia
1996
Smith, C.J. | Hopmans, P. | Cook, F.J. (CSIRO Division of Soils, GPO Box 639, Canberra, ACT, 2601 (Australia))