Evaluation The Leachate Characteristics and its Impacts on Groundwater Contamination Around Al-Diwaniyah Open Dumpsite

Groundwater contamination presents an increasing concern for environmental sustainability and human health, especially organic contamination. The effect of leachate percolation on groundwater contamination was investigated at Al-Diwaniyah open dumpsite to assess the groundwater quality of hand-dug observation wells surrounding the dumpsite. Samples of raw leachate and groundwater were collected for laboratory analysis, where they were analyzed using standard methods in order to evaluate any potential seasonal and variations for rainy, and dry seasons. Analytical results of leachate samples indicate that all physiochemical parameters were high revealing that they were highly contaminated with both organic and inorganic materials. High pH value and low BOD5/COD ratio for leachate indicated that dumpsite is old and in the methanogenic stage of anaerobic decomposition. In groundwater, average values of pH, EC, TDS, and major ion concentrations were higher in the dry season as compared to that in the rainy season. In contrast, the variation in TSS, BOD5, and COD showed more in rainy season than in dry season. GW1 and GW2 samples were more impacted by leachate percolation than GW3. The findings further revealed that except for pH, and nitrate all other examined parameters were above the permitted limitations of World Health Organization and Iraqi Quality standards. Relying on pH, EC, and major ions respectively, groundwater adjacent to dumpsite can be described as slightly alkaline, water with health hazards, and Chloride is the dominating ion. Inferred from the preceding, the noticeable influence of climate variation and distance from dumpsite on the extent of groundwater contamination. Continuously monitoring the groundwater resources in the area and constructing engineering landfills subject to the environmental limitations to control leachate infiltration into groundwater is recommended.


Introduction
Solid waste disposal particularly municipal solid waste (MSW) constitutes a major and emerging issue, particularly in emerging nations where impoverishment, population expansion, and rapid urbanization may hinder effective, sustainable waste management [1].Food waste makes up the largest portion of municipal garbage, and the proportion of organic waste is greater in the wet season than in the dry season due to the higher value of moisture content in waste during the rainy months [2].Common techniques for disposing of and treating MSW include sanitary landfills, open landfills, composting and thermal treatments.Generally, both developed and developing nations use open dumps and/or landfills as common and economical methods of disposing of MSW [3].Currently, Al-Diwaniyah Governorate Iraq has seven open dumpsites and landfills [4].Unfortunately, an environmental and social impact assessment are typically not conducted prior to the establishment of these "wild" landfills.As a result, they could pose threats to the human health and the natural environment through the release of biogas and particularly producing leachates.The formation of leachate and the variety of its characteristics rely on age and the nature of landfill, composition solid waste, particle size, degree of compaction, weather conditions, and availability of oxygen [5].
Good groundwater quality is essential for the attainment of a number of sustainable development objectives, although the achievement of those goals most impacted by groundwater pollution is often hampered by a lack of adaptive resources [6].Groundwater located close to landfills or dumpsites is severely contaminated due to percolation of landfill leachate making it undesirable for drinking, and other household purposes.Many researches have been conducted to limit leachate percolation or improve its qualities; such as those undertaken by Hussain, and other researchers to improve the hydraulic characteristics of surface soil for landfill liner, using silica fume to fill pore space between soil particles which led to limiting leachate migration [7].Abud et al. focused on modifying leachate characteristics using a lime and sawdust waste mixture that assisted in enhanced solid waste stabilization [8].In their research to examine the impact of leachate recirculation on the biological stability of MSW, Hussain, and Al-Ameen found that bioreactor landfills with leachate recirculation are superior to sanitary landfills at removing organic matter [9].The amount of leachate and chemical composition, as well as the distance of the pollutant from the source of water, will affect the pollution level [10].Therefore, it is necessary to continue to monitor the area around the dump site.Furthermore, the influences of leachate on the water sources such as surface and groundwater have been conducted in numerous research on recently.For example, Srivastava et al. examined the influence of leachate seepage on groundwater quality at the Bandhwari sanitary dump site utilizing physicochemical, heavy metal, and organic pollutants and found that landfill contaminants degraded local water quality [11].In their research on evaluating the environmental hazard of dumpsites on the quality of surface water, groundwater, and wastewater, in Baiji city, Hammash and Abed showed Tigris River, groundwater, and wastewater, were contaminated but in varying extents [12].Another investigation in 2021, given by Alghamdi et al. to assess possible environmental hazards relating to MSW landfill leachate currently located in AlMadinah City, Saudi Arabia indicated extreme soil contamination and the most of groundwater in the study area were unacceptable for use as drinking water [13].Studies on the properties of leachate and its influences on the environment in the area around the dumpsites in Iraq are very few, especially in Al-Diwaniyah.Thus, In the current research, an open dumpsite at Al-diwaniyah, Iraq, was used to evaluate the effect of leachate infiltration on the quality of groundwater.It was considered a basic study due to the lack of previous data about the leachate characteristics and the groundwater in the site, The investigation particularly included certain physicochemical water quality parameters in the samples of leachate and groundwater to evaluate the probable groundwater contamination connection and to determine if they satisfy the drinking quality requirements of IQS [14], and WHO [15].also focused on the effect of seasonal variation and distance from the source of pollution.

Description of the study area
The studied Dumpsite is situated in Qadisiyah province, southeast of Al-Diwaniyah city, close to Qadhaa Afak and Diwaniyah city borders Figure 1, at a distance of (11 km) from Al-Diwaniyah city center, at the intersection of latitude 31° north and longitude 45° east (Diwaniyah-Basra) (32.002484, 45.055134).It was established in 1995, and the current area of the site is (13 hectares).The site serves of Al-Diwaniyah district with a population of around 534,000 inhabitants in 2019 [16].Generally, it is distinguished by a desert climate, long, hot, dry summers, and cooler winters.Rainfall only occurs throughout the winter, with an average yearly rainfall of (120.3 mm) and an average annual temperature ranging between (16.57-31.6C°) in 2019 [17].This open dumpsite receives various MSW, ranging from simple domestic waste to construction rubble waste and industrial waste.The daily amount of waste reaches the site (450) tons per day [18], and the high of waste is 4 m above ground level.This dumpsite has been chosen as a case study as it is not subject to environmental limitations like many other dumpsites in Iraq.The disposal process could be categorized as a un engineered process due to dumping the MWS without a suitable sorting process.However, a number of scavengers were seen separating the recently dumped trash to gather glass, cans, metals, and plastic for selling as recyclables.

Field and analytical procedures
Maps and geolocations of monitoring well points were plotted after the reconnaissance tours using Google Earth software that offers clear satellite photos of the research area, so as to investigating the groundwater contamination level.Then three hand-dug 4'' diameter wells according to the gradient of the study area to a depth ranging from (5-13) m below the ground level within the distance of 100 m, 500 m, and 750 m respectively around the dump.However, there are some restrictions to take additional points from other directions around dumpsite Figure 2. Table 1 shows the details of the sampling points.
Since the dumpsite lacked a leachate collector system, raw leachate that had been gathered in November 2022 at the dump's base was randomly sampled from three random sites at (3) m depth and carefully mixed to create a homogenous representative sample before being analyzed.whereas three samples from groundwater were taken GW1, GW2, and GW3 once a fortnight during the period (September 2022 to December 2022) and collected in plastic bottles of one liter according to the standard protocols and methods.Before collecting, bottles were washed with detergent, rinsed with deionized water, and afterward rinsed with water of samples.In order to prevent any interference that might result from utilizing polluted sample containers.
Bottled water samples were immediately stored in a refrigerator (4°C), and delivered to the laboratory where they were kept in a refrigerator at 4°C and samples were analyzed within 6 hours.
The analyses covered the physicochemical parameters of collected leachate and groundwater samples in accordance with the procedures outlined in "the Standard Methods for the Examination of Water and Wastewater" (APHA, 2017) [19].The qualitative analyses were conducted at the Laboratory of U Science, and Environmental Laboratory of college of engineering, Al-Qadisiyah University.

Analysis of Groundwater and Leachates
Leachate and groundwater samples were examined for Various physicochemical parameters, including (pH, total dissolved solids, total suspended solids, electrical conductivity, BOD, COD, NO3-, SO42-, Cl-).The pH, TDS, and EC of the samples were recorded using HydroMaster Portable meter (Model HM-200) on the spot.TSS was measured according to Gravimetric (evaporation) method.Cl was measured by Titration method whereas a UV-VIS spectrophotometer was used to analyze NO3(UVmini-1240).SO4-2 was measured using Turbid Meter.By using incubation at 20 °C for five days, BOD was measured.COD Estimation was achieved via Colorimetric Method Photo multimedia (Lovibond, MD 2000).

Physical and chemical characteristics of leachate
Physicochemical analysis results of leachate samples collected from Al-Diwaniyah Dumpsite are presented in Table 2.As shown in the table, the mean pH of the leachate sample was 8.07, which can be related to anaerobically decomposition that reduces free volatile acids concentration, as Fatty acids can partially ionizable, which raises pH levels.Additionally, it was discovered that the leachate was in the methane production phase, which is in agreement with the presence of burnt gas at the dumpsite.Similar high pH with average value of 8.11 was observed by Amangabara et al for the Eliozu dumpsite in Nigeria which has been around for over 20 years [20].High value of conductivity were recorded in the leachate (45.350 mS/cm), this may be due to the leachate's high concentrations of cations and anions such as sulfate, nitrate, and chloride.The high TDS concentration (27900 mg/L) in the leachate sample was attributed to the existence of inorganic substances in the sample.Leachate containing a high proportion of dissolved and suspended solids can be hurtful to aquatic organisms when released into the aquatic environment.This occurs as a result of the reduced quality of water, inhibit photosynthesis, and ultimately resulting in more bottom sediment and reduction in depth of water [21].Rashid et al showed higher electrical conductivity and total dissolved solids values when they examined the leaching behavior in three leachate samples from the Tanjaro dumpsite in Sulaymaniyah City [22].High amount of total suspended solids in leachate 1328 mg/L reflect the presence of organic matter, inorganic matter, mud, microorganisms, etc.However, the levels of total dissolved solids concentrations were lower than those found in leachate samples from sanitary landfills in Alexandria, Egypt [23].The value of COD is 3,454 mg/l and the BOD is 342 mg/L.It is well-known that the biodegradability of the organics in leachate varies due to the buried materials in landfills being decomposed.This is integrated with the existence of coliform in leachate is described by lower DO values which encourage the anaerobic biota proliferation [24].BOD5/COD ratio (0.09) less than 0.1 evidence that leachate has settled and the dump is in the methanogenic stage of anaerobic decomposition.On the other hand, Higher BOD5/COD ratios of more than 0.6 were observed by Rashid et al for Open Dumpsites in Sulaymaniyah City, indicating High biodegradability for leachate during an anaerobic phase [22].Leachate sample was also examined for the presence of major anions like Cl -, SO4 -2 , and NO3 -.The concentration of chloride was 12626 mg/L.This was significantly high in the leachate.Abd El-Salam and Abu-Zuid also observed leachates with high chloride concentrations [23].The high nitrate and sulfate concentrations 5732 mg/L and 625 mg/L, respectively in the current study indicating the oxidization of environment so that sulphate reduction did not occur.Chofqi et al. also found high average concentrations of nitrates and sulfates in Morocco [25].However, they were lower than the values obtained in our study.

Physical and chemical characteristics of groundwater
Table 2. summarizes the analytical results of various physical and chemical parameters of observation wells samples collected from handy digging wells vicinity of the MSW dump.The comparison of groundwater quality parameters with the permissible limits recommended by the Iraqi Standard IQS [14] and WHO [15] in Table 3. to ascertain the extent of groundwater contamination from leachate percolation for the study period from (September-December) 2022.

pH
The mean values of pH for (GW1, GW2, and GW3) were (7.64, 7.43, and 7.44) respectively based on Table 2. GW.1 and GW.2 registered the highest and lowest pH values through September and December, respectively Figure 3.The values of pH indicating neutral to moderate alkaline behaviour of groundwater.This may be due to rainfall combined with carbon dioxide during the wet season, which can alter the water's acidity, temperature, TDS levels, ion exchange capacity, and adsorption processes.[26].pH results lie within the permissible limit of IQS [14], and WHO s [15] guideline limit prescribed for drinking water Table 3.  2, with the maximum value recorded in GW2 in September and minimum value in GW.3 in December Figure 4. High EC values in the majority of the wells indicate that the leachate pollution has resulted in a significant amount of dissolved ions [27].The current study recorded EC values higher than that found in El Jadida dump in Morocco [25].EC value of all samples exceeded the permissible standard for IQS [14], and WHO [15] for drinking water, Table 3.Using salinity classification Table 4, it was established that groundwater in studied area falls within the Health Hazard category water.

Total Dissolved Solid
The average TDS values of water samples (GW1, GW2, GW3) were (9994, 16136.67,and 1774) mg/L, respectively Table 2.The highest TDS value was in GW2, 500 m away from the dumpsite during September while it reached the lowest value during the wet season in December for sample GW3 750 m away from the dump site Figure 4.This demonstrates how leachate percolation affects the groundwater close to dumpsites and increased in dry season.In addition to geological status of the area, due to the surface nature on which the solid waste landfill site was constructed, represented by areas rich in salts.High concentrations of TDS were also obtained by Abd El-Salam and Abu-Zuid in groundwater [23].Groundwater samples recorded concentrations far above the limit prescribed by IQS [14], and WHO [15] Table 3.

Total Suspended Solid
The data in Table 2. indicates a discrepancy in suspended solids concentrations, as the mean values ranged for three samples (500.67,283, 44.67) mg/L through the observation period.The highest concentration was recorded in GW1 during December, and the lowest value in GW3 during September Figure 5, it was observed that there is a discrepancy in the concentration of wells, especially during December, and may be the reason for the increase in some values due to the large number of pollutants that are thrown in the dumpsite, in addition to being affected by the rain factor in winter because the rains wash away the suspended solids as a result of leaching operations, this pollutes groundwater and increases its concentrations.In contrast, Rashid et al obtained a high concentration of TSS in groundwater around the Tanjaro dump of Sulaymaniyah City [22].According to WHO [15], all wells are located outside the validity of drinking water except GW3, Table 3.  2, mean BOD values for GW1, GW2, and GW3 were (33.67, 13.167, and 7.36) mg/L, respectively.The maximum BOD5 concentration was registered in GW1 in December.Whereas the minimum concentration was in GW3 in September Figure 6.The biodegradable organic matter infiltration and percolation, as well as the organic iron and perhaps leaching of manganese into the groundwater, due to the waste dumpsite, may be responsible for BOD levels established in the groundwater sources [29].Similar concentrations of high BOD recorded by Abd El-Salam and Abu-Zuid ranged between 45-60 mg/L [23].Generally, the BOD levels were higher at all the samples through the wet season in comparison with the dry season.The BOD levels of groundwater samples during the study period were above the WHO [15] limitations Table 3.Therefore, all samples are considered contaminated.

Chemical oxygen demand (COD)
COD is an indication of organic contamination, resulting from the inflowing of municipal waste, stocks of living, and manufacturing waste which mainly consists of high levels of organic contaminants [30].Study investigations showed that BOD in the three groundwater samples varied (121.33,31.33, and 13.66) mg/l for GW1, GW2, and GW3 during dry and wet seasons with a maximum average concentration of 133 mg/L for GW1 in November, and a minimum average concentration of 7 mg/L for GW3 in September Table 2, Figure 6.This may have happened as a result of the effects of household chemical products, preservatives, and dyes present in the dump due to the act of rainfall.High rates of COD compared to low BOD5 confirms that the groundwater samples had comparatively significant concentrations of organic compounds that are not biodegradable.When comparing this results with other studies we can see the COD level in this research shows lower than COD level obtained in groundwater pollution evaluation in Mpape community, Nigeria by Uwem et al [31].It seems that the values of COD for seasons studied exceeded the WHO [15] guideline allowable limitations Table 3.

Chloride ion
The average chloride concentrations of monitoring wells were (6062.53,5756.13, and 724.63) mg/L for GW1, GW2, and GW3 respectively as clarified in Table 2, maximum concentration was recorded in GW1 in September and minimum concentration in GW3 in December Figure 7. High concentration is due to high evaporation values, in addition to the dumping of large quantities of organic waste and chemical compounds.In dumpsite which increased in decomposition during the dry season.However, in wet, especially in the nearby wells to dumpsite, the rising the concentration of chloride ions is due to rain that leaches into soil and groundwater that carries with it solid waste compounds.Abd El-Salam and Abu-Zuid also obtained high Cl -concentrations in groundwater sample reached to 6890 mg/L [23].All of the samples were over the IQS [14], and WHO [15] acceptable limits Table 3.

Sulfate ion
The data in Table 2. indicate that the concentration of this ion vary spatially and temporally.The mean values of the sulfate ion is (4457.56,3993.18 and 546.4) mg/L for GW1, GW2,and GW3, respectively, recording the highest concentration in GW1 in September, and the lowest in GW3 In December Figure 7. Generally, in dry season the high GW1and GW2 sulfate concentration attributed to the amount of waste thrown in dumpsite with high concentrations of sulfate ions, in addition to low groundwater levels and high values of evaporation, which leads to increase its concentrations in shallow groundwater.On another hand, GW3 recorded low concentrations of sulfate due to its distance from dumpsite and locate 1232 (2023) 012006 IOP Publishing doi:10.1088/1755-1315/1232/1/01200610 in an agricultural area that decreases the total dissolved substances concentration in groundwater.All The studied wells exceeded the permissible limit for drinking purposes according to IQS [14], and WHO [15] Table 3.  2. The highest value was recorded in GW3 during September, and the lowest value was recorded in GW2 during December Figure 8. High concentration in GW3 may be due to its location in an agricultural area, rich in fertilizers that increase the concentration of this ion.However, the disposal of organic waste at dumpsite is the cause of groundwater nitrate levels nearby the dumpsite [32].All nitrate ion concentrations below (50 mg/L) standard set by IQS [14], and WHO [15], Table 3.

Conclusion
In current study, Major concerns are leachate characteristics and their serious influence on groundwater quality, and the assessment of seasonal and spatial variations on groundwater properties around Al-Diwaniyah open dump from September 2022 to Late December 2022.The leachates were primarily characterized by Significant levels of organic, and inorganic substances.The pH and BOD5/COD results indicated that dumpsite is old.Furthermore, the study confirmed that leachate has settled and the dump is in the methanogenic stage of anaerobic decomposition and the majority of the organic compounds present are not biodegradable.Observation well results revealed that groundwater in the vicinity of the dumps was seriously contaminated, which contains high organic and inorganic matter.High rates of COD compared to low BOD5 implying that the groundwater samples had comparatively high levels of non-biodegradable organic matter.The seasonal variation clarified that mean values of pH, EC, TDS, and major ion concentrations were higher during the dry season as compared to that during the wet season.On the contrary, the variation in the concentrations of TSS, BOD, and COD showed increasing in wet season higher than in dry season.On one hand, the spatial variation of the locations of groundwater samples confirmed that GW1 and GW2 samples were significantly impacted by contaminants percolated from leachate while GW3 was least affected by contaminants.Despite this contrast, most of the examined parameters exceeded IQS [14], and WHO [15] standards, with the exception of pH and Nitrate.The general quality of the groundwater can be described as slightly alkaline (based on the mean pH value), health hazard water (based on the electrical conductivity value), and dominant ion is Chloride.

Recommendations
1. Proper solid waste management for the open dump in the area must be implemented by Aldiwaniyah Municipality Directorate as a long-term policy.

Figure 2 .
Figure 2. location of open dumpsite and observation wells.

Figure 3 .
Figure 3. Variation of pH in groundwater

Figure 4 .
Figure 4. Variation of EC and TDS in groundwater3.2.2.Electrical ConductivityEC represents the content of ionisable solids in a solution.The results of the analysis revealed that the electrical conductivity of the three observation wells (GW1, GW2, and GW3) all recorded high values, and the average values were (12.793, 21.7967, and 3.09) mS/cm respectively Table2, with the maximum value recorded in GW2 in September and minimum value in GW.3 in December Figure4.High EC values in the majority of the wells indicate that the leachate pollution has resulted in a significant amount of dissolved ions[27].The current study recorded EC values higher than that found in El Jadida dump in Morocco[25].EC value of all samples exceeded the permissible standard for IQS[14], and WHO[15] for drinking water, Table3.Using salinity classification Table4, it was established that groundwater in studied area falls within the Health Hazard category water.

Figure 5 .
Figure 5. Variation of Total suspended Solid in groundwater

Figure 6 .
Figure 6.Variations of BOD and COD in groundwater

Figure 7 .
Figure 7. Variations of Chloride and Sulfate in groundwater

Figure 8 .
Figure 8. Variations of Nitrate in groundwater 3.2.9.Nitrate ion Mean concentrations of nitrate ion (6.98,7.81and10.216) mg/L for GW1, GW2 and GW3 respectively Table2.The highest value was recorded in GW3 during September, and the lowest value was recorded in GW2 during December Figure8.High concentration in GW3 may be due to its location in an agricultural area, rich in fertilizers that increase the concentration of this ion.However, the disposal of organic waste at dumpsite is the cause of groundwater nitrate levels nearby the dumpsite[32].All nitrate ion concentrations below (50 mg/L) standard set by IQS[14], and WHO[15], Table3.

Table 1 .
Details of sampling wells.

Table 2 .
Mean Physicochemical parameters of groundwater and leachate samples during two seasons.