Application AHP-PROMETHEE Technic for Landfill Site Selection on Based Assessment of Aquifers Vulnerability to Pollution

Choosing a suitable location for the disposal of municipal solid waste is an important environmental problem. Thus, locating a municipal solid waste landfill has been very important. Leachate from the solid waste landfill causes the contamination of groundwater. However, the process is complicated and is based on qualitative and quantitative criteria. Therefore, in this paper, a hybrid approach for determining the optimal location of a municipal solid waste landfill has been presented. Additionally, the present study attempts to evaluate the potential of aquifer contamination vulnerability on the proposed landfill sites using a DRASTIC model of Plain Zanjan and provide a zoning map of vulnerable areas. In this study, the DRASTIC model for aquifer vulnerability mapping is used. This model consists of seven hydrogeological parameters effective in contaminating the aquifer. The parameters appear in the GIS software as seven layers on which the analysis is performed. Considering the map of aquifer vulnerability and with regard to the potential aquifer contamination at various areas, it is possible to determine a suitable site for the landfill. At present, about 49.03% of the aquifers are in average vulnerability situation; by considering them, a suitable site for the landfill can be determined. Accordingly, the considered criteria were determined by AHP method; the weights of the layers were determined, and then the appropriate places were classified into three classes, high, moderate or low, using GIS software. Finally, zones located in the high classes were selected as the best locations for waste disposal by the PRPMOTHEE method, by taking into account the scientific limitations and conditions of the area. The results showed that proposed methods in this paper can be suitable to determine appropriate option for waste disposal. In the future, there can be a lot of studies for modeling to choose a suitable landfill due to some soil characteristics and applying other models of pollution to groundwater in the region.

Discovery of a large subsoil nitrate reservoir in an arroyo floodplain and associated aquifer contamination

In an area of elevated nitrate (NO3) groundwater concentrations in the northern Chihuahuan Desert in central New Mexico (United States), a large reservoir of nitrate was found in the subsoil of an arroyo floodplain. Nitrate inventories in the floodplain subsoils ranged from 10,000 to 38,000 kg NO3-N/ha—over twice as high as any previously measured arid region. The floodplain subsoil NO3 reservoir was over 100 times higher than the adjacent desert (59–95 kg NO3-N/ha). Chloride mass balance calculations of subsoils indicate arroyo floodplain subsoils have undergone negative recharge since 2600–8600 yr ago, while the surrounding desert has had negative recharge since 13,000–17,000 yr ago. Compared to the adjacent desert, plant communities are larger and more abundant in the floodplain, though subsoil NO3 is apparently not utilized. We demonstrate that NO3 accumulates in the subsoil of the floodplain through evaporation of monsoon season precipitation funneled into the arroyo. Through a one-dimensional vadose zone model, we show that the NO3 inventories in the arroyo floodplain could be acquired 8 to 75 times faster than through atmospheric deposition through the lateral movement

Supplemental Material: Discovery of a large subsoil nitrate reservoir in an arroyo floodplain and associated aquifer contamination

Additional information on site background, sampling methods, chloride mass balance calculations, and vadose zone modeling.<br>

Supplemental Material: Discovery of a large subsoil nitrate reservoir in an arroyo floodplain and associated aquifer contamination

Additional information on site background, sampling methods, chloride mass balance calculations, and vadose zone modeling.<br>

A portrait of wellbore leakage in northeastern British Columbia, Canada

Oil and gas well leakage is of public concern primarily due to the perceived risks of aquifer contamination and greenhouse gas (GHG) emissions. This study examined well leakage data from the British Columbia Oil and Gas Commission (BC OGC) to identify leakage pathways and initially quantify incident rates of leakage and GHG emissions from leaking wells. Three types of leakage are distinguished: “surface casing vent flow” (SCVF), “outside the surface casing leakage” (OSCL), and “cap leakage” (CL). In British Columbia (BC), the majority of reported incidents involve SCVF of gases, which does not pose a risk of aquifer contamination but does contribute to GHG emissions. Reported liquid leakage of brines and hydrocarbons is rarer. OSCL and CL of gas are more serious problems due to the risk of long-term leakage from abandoned wells; some were reported to be leaking gas several decades after they were permanently abandoned. According to the requirements of provincial regulation, 21,525 have been tested for leakage. In total, 2,329 wells in BC have had reported leakage during the lifetime of the well. This represents 10.8% of all wells in the assumed test population. However, it seems likely that wells drilled and/or abandoned before 2010 have unreported leakage. In BC, the total GHG emission from gas SCVF is estimated to reach about 75,000 t/y based on the existing inventory calculation; however, this number is likely higher due to underreporting.

Integrated Modelling for Groundwater Contamination from Polluted Streams Using New Protection Process Techniques

Evaluating water quality indicators is a crucial issue in integrated water resource management, since potable water is an essential resource for the world's health and sustainable development. The current study was developed using a coupled model of MODFLOW and MT3DMS (Mass Transport 3-Dimension Multi-Species) to integrate two water supply systems, surface water (polluted drains and canals) and ground water, to identify the contamination process of the groundwater from drains as fresh water is polluted and the contamination level exceeds the standard limits. The study was applied to two cases: the first was a hypothetical simulation and the second was the real case of the Nile Delta Aquifer (NDA). Four different scenarios were simulated to first identify groundwater contamination by total dissolved solids (TDS), and then select the more efficient protection process. The first scenario involved changing polluted drain and canal boundary conditions regarding head and concentration; the second consisted of studying the location of the polluted drain in a low permeability layer or a confined aquifer; the third was based on installing a cut-off wall in the polluted drain sides; and the fourth investigated the use of lining materials for polluted drains. The results reveal that aquifer contamination was decreased by increasing the water head of canals by 50 cm and decreasing the drain head by 50 cm and concentration by 25%, whereby large quantities of groundwater were protected. The percentages of salt repulsion in the hypothetical case were +10.66, +12.89, and +24.99%, while in NDA they were +6.29, +8.71, and +25% respectively compared with the base case. Decreasing the aquifer hydraulic conductivity led to decrease in aquifer contamination, in which the confined aquifer pollution was less than the unconfined aquifers due to the clay cap, which plays a significant role in minimizing the solute transport into the groundwater reservoir, and to reduction of the aquifer salt variation by +19.01% for the hypothetical case. The results indicate that the cut-off wall is effective for contamination management in shallow aquifers (hypothetical case) and the reduction in aquifer salt was +28.49%, whereas it had no effect in the deep aquifer (NDA), where the salt was reduced by just +0.34%. Using the drain lining scenario prevented contamination from the polluted drains and protected the freshwater in the aquifer, so that the aquifer salt mass reductions were +91.02 and +70.13% for the hypothetical case and NDA respectively, indicating that this method is more effective for controlling groundwater contamination. Polluted drains should be located in a low permeability layer to minimize the water degradation. This study represents a new contribution to groundwater protection techniques by changing the boundary conditions, installing a cut-off wall and using linings for polluted drains, and shows the way forward for the future treatment of polluted stream networks.