Please cite this article in press as: Wang, P., et al., Indicators for environmental dispersion in a three-layer wetland: Extension of Taylor’s classical analysis. Ecol. Indicat. (2014), http://dx.doi.org/10.1016/j.ecolind.2014.04.041 ARTICLE IN PRESS G Model ECOIND-1930; No. of Pages 16 Ecological Indicators xxx (2014) xxx–xxx Contents lists available at ScienceDirect Ecological Indicators j o ur na l ho me page: www.elsevier.com/locate/ecolind Indicators for environmental dispersion in a three-layer wetland: Extension of Taylor’s classical analysis P. Wang a , Z. Li a,∗ , W.X. Huai b,∗ , B. Chen c,d , J.S. Li a , T. Hayat d,e , A. Alsaedi d , G.Q. Chen a,d a College of Engineering, Peking University, Beijing 100871, China b State Key Laboratory of Water Resources and Hydropower Engineering Science, Dong hu Nan rd, Wuhan University, Wuhan 430072, China c State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China d NAAM Group, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia e Department of Mathematics, Quaid-i-Azam University 45320, Islamabad 44000, Pakistan a r t i c l e i n f o Article history: Received 7 January 2014 Received in revised form 21 April 2014 Accepted 24 April 2014 Keywords: Urban indicators Wetland Environmental dispersion Environmental impact assessment Water quality a b s t r a c t The rapid growth of population in cities places great pressure on urban ecosystem health and man- agement, especially on urban water supply and disposal of wastewater. To cope with urban water degradation, indicators are needed for predicting and evaluating anthropogenic impacts on wetlands. Presented in this paper is a analytical study of the environmental dispersion in a three-layer wetland in terms of the longitudinal evolution of the lateral mean concentration. An environmental dispersion model for the mean concentration in the three-layer wetland is devised as an extension of Taylor’s classical for- mulation. The analytical results illustrate the effect of dimensionless parameters on the environmental dispersivity. Other related indicators for urban water quality assessment in three-layer wetlands, i.e., the critical length and duration of the contaminant cloud of typical contaminant constituents are illustrated and characterized. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction Cities are characterized as complex dynamic systems (United Nations, 2008). According to the projections of the United Nations (UN) Population Division, by 2050 two-thirds of inhabitants of the developing world are likely to live in urban areas (United Nations, 2005). Current estimates indicate that the trend toward an urbanized world will continue well into the twenty-first century as that in the past century (Brockerhoff, 2000). While the rapid growth of anthropogenic activity has led to urban sprawl and increase of urban conurbations, the ongoing urbanization consequentially consumes large amounts of resources and causes severe waste discharge, putting increasing pressures on ecosystem management to cope with ecological degradation within urban environments. A survey by the US Department of Agriculture indicated that urbanization resulted in wetland loss in nearly all surveyed watersheds (96%) and may comprise as much as 58% of the total wetland loss (United States, 1997; Opheim, 1997). Constrained by water resources shortage, the green-space coverage rate will be limited in urban area (Yuan et al., 2008). Anthropogenic and ubiquitous ecological and environmental problems, such as pollution, congestion, noise annoyance, shortages of fresh water and energy, ecological degradation, contribute to a serious threat to urban ecosystem health and development (Van Dijk and Mingshun, 2005; Jiang, 2008; Moussiopoulos et al., 2010; Han et al., 2014b). Emphasis should be, therefore, given to developing indicator systems for ‘health’ assessment of urban ecosystems. Considering the different aspects of urban ecosystem health as well as various priorities and objectives, various indicators and systems modelling approaches have been developed. Among these indicators, environment or environmental quality is absolutely indispensable since it is a significant component of urban ecosystem health assessment. Environment indicator represents the effect of human activity on urban environment and vice versa the sustainment of urban environment to city life. Environment indicator was employed to compare urban and rural health by Harpham (1996). Takano and Nakamura (1998) established 459 indicators of a healthy urban ecosystem involved environmental quality. Urban fresh water supply and wastewater disposal determine the urban environment quality and further urban ecosystem health to a large extent. Water scarcity and water pollution are serious urban problems, particularly in arid and semi-arid ∗ Corresponding authors. E-mail addresses: wangping@pku.edu.cn (P. Wang), zhili@pku.edu.cn (Z. Li), wxhuai@whu.edu.cn (W.X. Huai). http://dx.doi.org/10.1016/j.ecolind.2014.04.041 1470-160X/© 2014 Elsevier Ltd. All rights reserved.