Deteriorating soil quality and decrease in vegetation abundance are grave consequences of open waste dumping which have resulted in growing public concern. The focus of this study is to assess the contribution of open waste dumping in soil contamination and its effect on plant diversity in one of the renowned green cities of Pakistan. Surface soil samples (n = 12 + 12) were collected from both the open waste dumping areas allocated by Capital Development Authority (CDA) and sub- sectors of H-belt of Islamabad city (representative of control site). The diversity of vegetation was studied at both sampling sites. Significant modifications were observed in the soil properties of the dumping sites. Soils at the disposal sites showed high pH, TDS and EC regime in comparison to control sites. Various heavy metal concentrations i.e., Lead (Pb), Copper (Cu), Nickel (Ni), Chromium (Cr) and Zinc (Zn) were also found to be higher at the dumping sites except for Cadmium (Cd) which had a higher value in control site. A similar trend was observed in plant diversity. Control sites showed diversified variety of plants i.e., 44 plant species while this number reduced to only 32 plant species at the disposal sites. This is attributed to changes in soil characteristics at disposal sites and in its vicinity areas.
The menace of environmental pollution has been haunting the human world since early times and is still growing due to excessive growth in developing countries. Municipal solid waste (MSW) normally termed as “garbage” or “trash” is an inevitable byproduct of human activity. Population growth and economic development lead to enormous amounts of solid waste generation by the dwellers of the urban areas (Karishnamurti and Naidu, 2003). Urban MSW is usually generated from human settlements, small industries and commercial activities (Singh et al., 2011). An additional source of waste that finds its way to MSW is the waste from hospitals and clinics. In majority of countries most of the smaller units do not have any specific technique of managing these wastes. When these wastes are mixed with MSW, they pose a threat for health and also they may have long term effect on environment (Pattnaik and Reddy, 2009).
In developing countries open dumpsites are common, due to the low budget for waste disposal and non-availability of trained manpower. Open dumping of MSW is a common practice in Pakistan. It also poses serious threat to groundwater resources and soil. The contamination of soil by heavy metal can cause adverse effects on human health, animals and soil productivity (Smith et al., 1996). Over the last many years, heavy metals have considerably damaged the soil quality and fertility in consequence of increased environmental pollution from industrial, agricultural and municipal sources (Adriano, 1986). Metals cause physiological disorders in soils as absorption through root system consequently retards plant growth and deprives it of vigour (Moustakas et al., 1994). Waste carries different metals which are then transferred to plants by different ways (Voutsa et al., 1996). Depending on the tendency of the contaminants they end up either in water held in the soil or leached to the underground water. Contaminants like Cd, Cu, Ni, Pb and Zn can alter the soil chemistry and have an impact on the organisms and plants depending on the soil for nutrition (Shaylor et al., 2009).
Diversity of vegetation is directly influenced by soil characteristics. Many studies show evidence of seriousness of hazards caused by open waste dumping ultimately affecting the plant life on the planet leading towards an irreversible erosion trend unless the present land use pattern is checked (Phil-Eze, 2010). Solid waste pollutants serve as an external force affecting the physico-chemical characteristics of soil ultimately contributing towards the poor production of vegetation (Papageorgiou, 2006). The pollutants, in the first place, hinder the normal metabolism of plants which is an invisible injury and owing to which the visible injury appears in the aftermath (Ahmed et al., 1986). It is depriving our ecosystem of the natural balance and bear result beyond any repair. Assessment of soil pollution becomes difficult when contaminants belong to different sources and their products are variably distributed (Partha et al., 2011). Chemical properties of soil serve as main reason of vegetation changes (Neave et al., 1994). In plants accumulation of chemical elements depends not only on their absolute content in a soil but also on the level of fertility, acidic–alkaline and oxidative-reductive conditions and on the presence of organic matter (Subbiah and Asija, 1976). The disturbances of higher intensity sometimes endanger the survival of some species and yield to low richness (Hussain and Palmer, 2006). In this regard, developing countries are even deeper into the chaos as having poor financial resources to upgrade their disposal facilities and turned out to be more vulnerable to the hazards of dumping for their environment (Hazra and Goel, 2009).
Pakistan is generally faced with rapid deterioration of environmental conditions due to the conventional system of collection and dumping of solid wastes. Therefore urban waste management has become a major concern in cities. Little efforts have been made in order to improve the waste collection and disposal facilities. This has some grave consequences ranging from deterioration of soil quality to reduced plant diversity. The present study has been conducted in order to assess the prevailing condition of soil physico-chemical characteristics and its impact on vegetation.
Municipal Solid waste Management services in most of the countries come as a third priority in municipal commitments, after water supply and sanitation. Soils of the study area allocated by the CDA in H-10 Sector of Islamabad city for open waste dumping are located in the residential area and are extensively investigated in terms of physico-chemical properties of soil. However they are under pressure from their own legislation to move away from the current disposal practices of open dumping to sanitary land filling. Such a change is unlikely to occur in the nearest future due to limitations on finance, shortage of technical resources and lack of institutional arrangements. The main environmental problem associated with the disposal sites is the potential risk posed to the soil. Since the waste was disposed directly onto surface of soil, a number of contaminants including heavy metals readily penetrate and eventually they contaminate the soil and affect vegetation abundance of the area.
