Ecological Footprint

Various tools have been developed to quantify sustainability of cities and countries. Berger (2014) listed six aspects of sustainability as aesthetic, environmental, financial, functional, political and social. Environmental Sustainability of urban or rural area can be measured with ecological footprint. Calcott and Bull (2007) defined ecological footprint as “the amount of bio productive land and sea required supporting a person’s lifestyle”.

 Ecological footprint of a city can be calculated using individual’s requirement of productive land and sea using their current expenses in housing, transport, food, consumer items, private services, public services, capital investment and miscellaneous sectors (Calcott and Bull, 2007). Ecological footprint can be expressed in global hectares. Human consumption of resources equivalent to average productivity of global hectares is expressed in ecological footprint (IIED, 2006).

In 2007, global ecological footprint was about 1.5 times the earth’s bio-capacity (Lee and Peng, 2014). Significant difference can be observed between the ecological footprints of the continents. North America has an ecological footprint of 8.7 global hectares (gha) per person. In contrast, Africa has a footprint of 1.4 gha per person (Lee and Peng, 2014).

Urbanization has been identified as a triggering factor for larger ecological footprint as it increases resource consumption (WWF, 2014).  Calcott and Bull (2007) studied the ecological footprint of British cities and ranked them based on the number of plants required to meet current consumption trend. Newport and Plymouth have been ranked as number 1 requiring less resources (2.78 planets), London was ranked as 44 (3.05 planets) and Winchester was ranked as 60 (3.62 planets).


Berger, M. (2014) The Unsustainable City. Sustainability, Vol 6, pp. 365-374.

Calcott, A. and Bull, J. (2007) Ecological Footprint of British City Residents [Online] Available at [Accessed on 14 April 2014].

International Institute for Environment and Development (2006) Environment and Urbanization [Online] Available at [Accessed on 14 April 2004].

Lee, Y and Peng, L (2014) Taiwan’s Ecological Footprint. Sustainability, Vol 6, pp 6170-6187.

World Wildlife Fund (WWF) (2014) Ecological Footprint and Sustainable Consumption in China. [Online] Available at [Accessed on 24 October 2014].

Microbial Transport in Groundwater

Microbial contamination of groundwater could induce waterborne diseases such as hepatitis A, viral gastroenteritis, cholera, typhoid fever and giardiasis. Microbes being living organism, their transport in the groundwater is different than abiotic materials (Ginn et al., 2002). Physical processes such as advection, dispersion, straining, filtration, electrostatic and chemical process are responsible for microbial transport in groundwater (Ginn et al., 2002).

Microbial transport has been found to be controlled by hydrogeological heterogeneity of subsurface sediments (AGU, 2001). Various factors such as adhesion processes, filtration effects, physiological state of the cells, porous medium characteristics, water flow rates and intrinsic mobility of the cells determine the microbial transport activities (Newby et al., 2000).

Microbial transport is affected by the availability of pore space between soil particles. Size of the microbes should be smaller than micro pores for the filtration to occur. Nutrient availability affects the size of the microbes influencing microbial movement (Newby et al., 2000). Properties of cell surface and microbial adhesion influences microbial transport in the soil particles. pH value of the porous medium matrix solution has impacts on microbial transport (Newby et al., 2000). Viral adsorption and transport has been found to be affected by pH (Newby et al., 2000).

Ionic strength or the concentration of cations and anions in solution affects microbial transport. Decrease in ionic strength of the solution facilitates increased bacterial transport (Newby et al., 2000). Availability of cellular appendages such as pili, flagella, or fimbria and hydrological factors such as soil texture, soil structure, porosity, water content, and water movement affects microbial transport (Newby et al., 2000).  Pore water velocity and bacterial attachment to grain surface and detachment from grain surface controls the rate and extent of bacterial movement in groundwater (AGU, 2001).


American Geophysical Union (2001) Breakthroughs in Field Scale Bacterial Transport, Eos, Transaction, Vol 82(38), pp. 417, 423-425.

Ginn, T.R., Wood, B. D., Nelson, R. E., Scheibe, T.D., Murphy, E.M. and Clement, T.P. (2002) Processes in Microbial Transport in the Natural Subsurface, Advances in Water Resources, Vol 25, pp 1017-1042.

Newby, D.T., Pepper, I.L. and Maier, R.M. (2000) Microbial Transport [Online] Available at [16 August 2014]