The soil system is an important part of the carbon, water and sediment cycles and there is a need to research different aspects of the soil and land degradation that affect the fate of the Earth system (Keesstra et al., 2012a; Mandal and Sharda, 2013; Zhao et al., 2013; Ganjegunte et al., 2014; Mukhopadhyay and Maite, 2014; Brevik et al., 2015). The loss of vegetation, degradation of soil and pollution of water, soil and air are seen as signs of land degradation and reduced soil quality, and solutions to these problems need to be found (Giménez Morera et al., 2010; Novara et al., 2011, 2013; Keesstra et al., 2012b; Batjes et al., 2014; Olang et al., 2014; Srinevasarao et al., 2014). Land and soil degradation processes can be seen in landfills. In developing countries it is necessary to develop efficient waste management systems due to increased waste production as a consequence of population growth. Despite developments that have improved waste management systems, the disposal of solid waste in landfills is still the most commonly used method in developing countries (Leao et al., 2004; Mahini and Gholamalifard, 2006; Sumathi et al., 2007; Donevska et al., 2013). Sanitary landfilling is one of the best ways to decrease the volume of waste products (Wang et al., 2009); nevertheless the lack of effective environmental laws and enough suitable land for landfill sites in most developing countries is a major issue that causes many problems (Hagerty et al., 1997). Unfortunately, in most Iranian cities, the primary method of waste disposal is still confined to pile-up and open dumping. An open dumpsite is an environmental hazard which causes natural resource (soil, water, air) degradation and environmental pollution. Previous works found that leachates from landfills contaminated groundwater (Mor et al., 2006; Dimitrio et al., 2008; Nema et al., 2009) and soil (Raman and Narayanan, 2008; Shaylor et al., 2009; Hernandez et al., 1997). One of the main problems with open dumping is open air burning due to gases emitted from waste degradation processes; some researchers have investigated the effects of fire on soil (Guenon et al., 2013; Leon et al., 2014). The other serious threat to soil in landfill sites is salinity, which causes soil degradation and promotes groundwater salinization (Iwai et al., 2013). All of these impacts from landfills represent threats to human health (Brevik and Burgess, 2013); landfilled e-waste represents a particular hazard (Brevik and Sauer, 2015).

One of the major causes of land degradation is improper land use, which has already been examined (Mohavesh et al., 2015). There are many research investigations that have emphasized the negative impacts of improper land use and management (Biro et al., 2013; De Souza et al., 2013; Pallavicini et al., 2014). One of these unsuitable land management systems in developing countries is municipal solid waste management when the landfill sites are not chosen appropriately. To protect the environment and natural resources in developing countries, a system for proper solid waste site selection should be developed (Rao et al., 2007). In Iran, the environmental evaluation of landfills must be improved and this paper will contribute with the assessment of two methods. Despite the increasing advances in modern methods of locating landfills, 49 % of the total solid waste disposal in Iran is achieved by piling up the waste products (Abdoli, 2005a). These systems have not been adequately improved in Iran and so the open dumping of solid waste is seen as the only solution by most people. Although numerous efforts to reuse municipal solid waste have been undertaken around the world (Morugan et al., 2013; Al-Karaki et al., 2011), unfortunately in Iran waste is dumped without any treatment. In Iran individual municipalities are responsible for municipal solid waste (MSW) management systems and there is no federal oversight for landfill siting. Due to poor planning, insufficient financial resources, inefficient collection systems, lack of data and experience, unsuitable disposal facilities, insufficient laws, guidelines and regulations, lack of knowledge of new municipal solid-waste management options in municipalities, and increasing needs to remove waste from cities, the disposal method that most municipalities select is uncontrolled dumping (Abdoli, 2005b). The most common way of waste disposal in humid regions such as the southern coast of the Caspian Sea has also been open dumping (Monavari and Shariat, 2000). The quality and quantity of municipal solid waste created along the southern coast of the Caspian Sea in Iran has changed during recent years, but unfortunately the methods of collection, transportation, and disposal have remained the same, leading to many serious environmental problems. For example, some of the rivers, forests, and coastal regions in Iran have been contaminated and destroyed and have been converted into dumping sites (Abdoli, 2005b). Therefore, it is both essential and useful to understand the suitability of current municipal landfill sites for waste disposal.

Some evaluations of municipal landfill sites have been done in Iran and the other parts of the world using different methods. For example, Monavari et al. (2007) evaluated all the landfill sites in Tehran province in Iran using the Oleckno method, and also Salimi et al. (2013) evaluated the suitability of the new sanitary landfill site location in Isfahan with the Oleckno method. Assessment of a Maine landfill site had been done with the DRASTIC method (Wang, 2007) and USEPA method (Christensen et al., 1992). In other research projects in Iran, two municipal solid waste landfills – Rasht in Gilan province in the north of Iran and Andisheh, in Karaj Province, which are, respectively, located in humid and arid areas – were evaluated by the Monavari 95–2 method (Ghanbari et al., 2011), and the Karaj municipal landfill site has been evaluated by local and the regional screening methods (Aliowsati et al., 2013). Davami et al. (2014) evaluated the municipal solid waste landfill site in Ahvaz city by local screening incorporating geographic information systems (GISs). The first step to improve MSW management is evaluation of the state and suitability of current landfill sites in the country. The objective of this work was to evaluate the suitability of the Tonekabon landfill site using two methods: Minnesota Pollution Control Agency and regional screening method.

After analyzing the study area with maps and field checks (see tables and figures) it was found that the Tonekabon landfill site is suitable based on the MPCA determinative guidelines (see Table 3), but it is unsuitable according to the regional screening method (see Table 4). Our study shows a conflict between the two methods. About 1555.4507 km2, equivalent to 95.32 % of the entire study area, was rated as suitable for landfill development by the MPCA. About 949.3758 km2 of the Tonekabon city, equivalent to 58.2 % of the entire study area, was rated as suitable for landfill development based on the regional screening criteria (Figs. 6 and 7). Although the Tonekabon landfill site is acceptable according to the MPCA method, due to lack of machinery and necessary equipment, poorly maintained walls around the site, insufficient guards and lack of a guard house, a lack of gas and leaching controls and open air burning are some of problems at this landfill site. It is clear that the main problem at the Tonekabon landfill is non-compliance with landfill site selection standards, engineering frameworks, and design as well as lack of appropriate waste management and sanitary landfill. The problems include open-air waste burning, open-pit dumping, and uncontrolled waste disposal in landfills, which can result in negative impacts on human health and on the environment (Brevik and Burgess, 2013; Brevik and Sauer, 2015). Unfortunately hardly any of the applicable criteria are applied to the Tonekabon landfill site.

Landfills contribute to land degradation as they remove vegetation and damage the soil (loss of structure, loss of soil biodiversity, introduction of contaminants including heavy metals and organic chemicals, etc.), and this will change the water cycle and the soil sustainability (Keesstra, 2007; Keesstra et al., 2009), and this requires special policies that are in existence in many developed countries, to recover the soil properties. Soil conservation is an important and fundamental issue of this century (Mekonnen et al., 2014). Humid areas are vulnerable and sensitive towards environmental impacts of landfills, due to their special physical and biological conditions (Monavari and Shariat, 2000). As it has already been mentioned, municipal solid waste landfills are evaluated by methods such as the Oleckno method, DRASTIC method, USEPA method, Monavari 95–2 method and local and regional screening. Each system evaluates waste sites for one or more hazard migration route(s), namely groundwater, surface water, soil and public health. In the MPCA method, surface water resources – such as rivers, pools, lakes, and wetlands – and geological conditions are determinative criteria to evaluate municipal landfill sites, but in the regional screening method, landfill sites are evaluated in three categories (natural, economic and land use) with additional criteria that may be considered. Identifying the impacts of different parameters around the landfill at Tonekabon and considering the implementation of different standards will help to control existing landfill problems. Paying more attention to current unsanitary landfill sites will change weak points in the current landfill management system to strong points. It is important to note that the criteria utilized in the MPCA method and regional screening guidelines are for sanitary landfill site evaluation and selection, but the evidence at the Tonekabon landfill site suggests open dumping, not sanitary landfill management. In municipal solid waste landfill site selection, there are many criteria which must be considered such as prevailing wind direction, distance from sensitive ecosystems, slope of the land, soil texture and infiltration. Comparisons between the regional screening and the MPCA method showed that the regional screening method has more evaluation criteria to assess. As a result, fewer suitable areas were identified in the study area. Since each of the two methods has some dos and don'ts to evaluate landfill sites, we standardized the map layers based on Boolean logic. The primary feature of this logic is speed and easiness in performance, but at least the suitable and unsuitable locations will be differentiated. Also this logic is appropriate and useful, but it has some defects. The result of Boolean logic gives only two options – appropriate or inappropriate – and it is therefore not able to prioritize between locations. To achieve the desired final result in site selection it would be better to use other multi-criteria decision-making methods and to weight the criteria according to their relative importance based on ecological, economic and social features in each region. The evaluation of the current unsanitary landfill sites and their implications for land degradation can open a new way to start restoration of these regions and convert them to self-sustaining and productive ecosystems in developing countries, including better management approaches for sanitary landfills to decrease land degradation. Restoration of sanitary and non-sanitary landfills is necessary to minimize adverse impacts on the environment (Do et al., 2013). To provide scientific data for future restoration management, Chen et al. (2015) compared the ecological performances between natural sites and revegetated landfill sites and showed that, during the study period, there was a gradual change in the plant communities at restored sites and an increase in biodiversity. Research has also shown that exotic plant species may be more suitable for use as pioneer species in the restoration of sanitary landfills (Wong et al., 2015b) and also pioneer native species were much better than other native species (Wong et al., 2015a). Many research projects have been conducted that can be used to recover the degraded lands at this site and convert this degraded forest to a productive ecosystem in the future (Iwai et al., 2013; Courtney and Harrington, 2012; Mahmoud and El-kader, 2014; Paz-Ferreiro et al., 2014; Mekonnen et al., 2014). This requires a multidisciplinary view of the soil system (Brevik et al., 2015) and also applied methodologies to restore soil quality (van Leeuwen et al., 2015; Zornoza et al., 2015).

Open dumping is an important cause of land and soil degradation in Iran. According to the regional screening method the Tonekabon landfill site is not acceptable, while according to the MPCA method the Tonekabon landfill site is acceptable. About 949.3758 km2, equivalent to 58.2 % of the entire study area of Tonekabon city, was determined to be suitable for sanitary landfill development based on the regional screening criteria, while about 1555.4507 km2, equivalent to 95.32 % of the entire study area, was determined to be suitable using the MPCA method. The study showed fewer suitable areas for landfill development in Tonekabon city based on the regional screening method as compared to the MPCA method. Field research confirmed that inappropriate management techniques were being used at the Tonekabon landfill site and the urgent need for a restoration program. Edited by: A. Cerdà