A case study of environmental pollution by pathogenic bacteria and metal(oid)s at Soran Landfill Site, Erbil, Iraqi Kurdistan Region

Environmental pollution is a serious issue all around the world, especially when it is caused by metal(oid)s and pathogenic microorganisms. This study reports here for the first time on the contamination of soil and water with metal(oid)s and pathogenic bacteria directly resulting from the Soran Landfill Site. Soran landfill is a level 2 solid waste disposal site that lacks leachate collection infrastructure. The site is potentially an environmental and public hazard caused by metal(oid)s content and significantly dangerous pathogenic microorganisms through leachate release into the soil and nearby river. This study reports on the levels of the metal(oid)s content of As, Cd, Co, Cr, Cu, Mn, Mo, Pb, Zn, and Ni obtained by inductively coupled plasma mass spectrometer in soil, leachate stream mud, and leachate samples. Five pollution indices are used to assess potential environmental risks. According to the indices, Cd and Pb contamination is significant, whereas As, Cu, Mn, Mo, and Zn pollution is moderate. A total of 32 isolates of bacteria were defined from soil, leachate stream mud, and liquid leachate samples: 18, 9, and 5, respectively. Moreover, 16 s rRNA analysis suggested that the isolates belong to three enteric bacterial phyla of Proteobacteria, Actinobacteria, and Firmicutes. The closest GenBank matches of 16S rDNA sequences indicated the presence of the genera: Pseudomonas, Bacillus, Lysinibacillus, Exiguobacterium, Trichococcus, Providencia, Enterococcus, Macrococcus, Serratia, Salinicoccus, Proteus, Rhodococcus, Brevibacterium, Shigella, Micrococcus, Morganella, Corynebacterium, Escherichia, and Acinetobacter. The identity percentage was mostly between 95%–100%. The results of this study show the levels of microbiological and geochemical contamination of soils, surface and potentially ground water with harmful microorganisms and toxic metal(oid)s originating specifically from Soran landfill leachate which subsequently incorporated into the surrounding environment, creating thus a considerable health and environmental risk.


Introduction
Solid Waste Management (SWM) becomes a various issue comprising political, socio-economic, institutional, and environmental aspects. Due to the exponential growth of population and cities, the solid waste disposal has become one of the most significant issues in allocating urban spaces in developing countries. The disparity in environmental awareness between young and older generations in developing countries points out to difficulties in understanding the environmental issues and concerns related to waste management, which can lead to unsustainable development and would have significant ecological effects in low-income countries (Debrah et al., 2021).
The waste disposal issue has worsened in the twenty-first century as a result of consumerism, the expanding global population, and the linear industrialization process (D'Amato et al., 2016;De Feo et al., 2019;Stoeva & Alriksson, 2017). As people's lives become more affluent, the amount of waste increases (Malinauskaite et al., 2017). Global solid waste generation is expected to triple by 2100 (Nguyen, 2016). The reduction of waste contributes to the natural resource depletion, environmental pollution, for which treatment in recent years is paid so much attention (Huang et al., 2018;Liu et al., 2018;Zeng et al., 2016;Zhang et al., 2017). Furthermore, globally, and even in European Union (EU) countries, landfill rates are still high; meanwhile, waste prevention and recycling rates are too low (Pietzsch et al., 2017;Samadder et al., 2017).
Municipal waste material (MWM) includes wastes, collected from households, markets, and nonhazardous wastes of factories. MWM comprises different organic and inorganic materials, mostly made up of paper, food, wood, plastics, glass, metals, yard waste…etc. (Desa, 2019;Murtaza et al., 2017;Palmisano & Barlaz, 2020). The MWM type and quantity of the refuse can vary depending on the location, community, and culture with many other factors such as socioeconomic factors, methods of waste collection, sampling, and sorting procedures. MWM can be disposed of and treated in several ways, such as recycling, composting, incineration, and dumping in landfills. Among these methods, landfilling is the worldwide adopted treatment to dispose of waste (Palmisano & Barlaz, 2020;Sharma & Jain, 2020).
The composition of the MSW has a great effect on the degeneration process in landfills based on the amount of organic matter present in the component of MSW in the landfill. Cellulose and hemicellulose are the major biodegradable components of the collected trash. It was estimated that 91% of methane gas was generated from the degradation of these components during anaerobic degradation by microorganisms and protein and soluble sugars such as pectin are present in a smaller concentration (El-Fadel & Khoury, 2000;Hoornweg & Bhada-Tata, 2012;Palmisano & Barlaz, 2020).
Even in cases of well-engineered landfill sites which come with important environmental advantages, they have disadvantages that are negatively impacting the environment and public health (Sharma & Jain, 2020). The main problems of any landfill site are microbiological and chemical ones associated with leachate production through the biogeochemical-biodegradation processes inside the landfill. Leachates can contain metal(oid)s and microbial pathogens, which are serious hazards to public health and the environment (Bartkowiak et al., 2016;Shaharoona et al., 2019).
The buildup of metal(oid)s in soil may result in their release into the ecosystem, where they may contaminate natural or groundwater as well as crops, which may in turn be hazardous to both people and the environment. It is possible to conduct an environmental risk assessment to evaluate the likelihood of adverse consequences brought on by the presence of metal(oid)s pollution in soil. Pollution indices are often employed for this purpose. A significant number of research has focused on the metal(oid)s pollutants found in the soil, as well as the possible pollution sources and ecological risks posed by these contaminants (Doležalová Weissmannová et al., 2019;Jia et al., 2018;Klinsawathom et al., 2017;Sun & Chen, 2018;Thongyuan et al., 2021). There are numerous pathways of human exposure to metal(oid)s pollution in the soil, including ingestion, inhalation, and dermal contact via various transporter media such as food, water, air, and skin, which might allow these pollutants to enter the human body. Studies have been conducted to investigate the potential dangers to human health posed by direct, longterm exposure to metal(oid)s in contaminated soil or by eating agricultural products like fruits and vegetables grown in that soil. (Adamcová et al., 2015;Afrifa et al., 2015;Hu et al., 2017;Rinklebe et al., 2019).
Moreover, the microbial pathogens that can infiltrate the soil from the landfill include bacteria, fungi, and viruses, and they can survive in the soil for a long time based on the growth factors such as pH, moisture, temperature, and nutrients (Bartkowiak et al., 2016). Certain dangerous genera of bacteria can be transferred to soil from human waste, such as diapers, that can potentially contain enteric pathogens of Pseudomonas, Enterococcus, Serratia, Proteus, Shigella, Escherichia, Page 3 of 20 811 Vol.: (0123456789) and Acinetobacter. Those bacterial pathogens can be isolated and cultured using molecular techniques for their identification (Boothe et al., 2001;Moynihan et al., 2015;Shaharoona et al., 2019). Infections caused by bacteria found in soils and leachate include typhoid fever (Salmonella), dysentery (Shigella), diarrheal disease (Escherichia coli), urinary tract infections (Proteus), and the multidrug resistant bacteria (Pseudomonas aeruginosa) (Armbruster et al., 2018;Braz et al., 2020;Nyandjou et al., 2018;Shad & Shad, 2021;Tuon et al., 2022).
Similar to the rest of the globe, the Iraqi Kurdistan area has issues with garbage collection and landfills due to inappropriate garbage disposal. The landfills in Kurdistan, especially in the Erbil province, including the Soran landfill, are classified as level II because of the absence of gas and leachate collector systems (Aziz & Mustafa, 2018;Gardi, 2017). Soran landfill, lacking an environmentally engineered solution for these problems, can always cause serious pollution of the environment by dispersing leachate and gases into the environment water, soil, and air. In substantial quantities of biologically hazardous items, including household and abattoir waste, are routinely dumped at this landfill.
Soran city landfill bears all elements related to the environmentally dangerous sites. Therefore, it was vital to analyze the metal(oid)s level and microbiological infections inside the site that might provide a sanitary danger to landfill employees, people of surrounding areas (less than 700-800 m away), and domestic animals that feed and drink water within the range of meters of the dump. As the leachates are immediately released into the surrounding river, the most obvious concern is the pollution of surface and underground water. The plentiful wild birds that flourish on this trash may potentially play a role in the dispersal of dangerous microorganisms, such as viruses, bacteria, fungi, and parasites.
However, this study's goal was limited to searching for pathogenic bacteria and metal(loid)s including As, Cd, Cr, Co, Cu, Mn, Mo, Pb, Zn, and Ni in soil, mud, and leachate samples from Soran landfill, located outside of Soran City, Iraqi Kurdistan, using advanced techniques to determine the metal(loid) s and to identify isolated bacteria and estimate the health risk mainly for the landfill staff and frequent visitors.

Study area
The study area is the landfill site of Soran city within Erbil province. It is located on the Bapshtian road near Kawlokan village, about 5 km south of Soran city, covering about 0.56 km 2 . The study area has a hot-summer Mediterranean climate (Csa) with and cold with humid winters which its average temperature, humidity, and precipitation ratio are 24 °C, 50-60%, and 681 mm annually, respectively. The soil type of the study is calcic clay. The operation of Soran landfill started in 2010. Currently, it receives an average quantity of about 120 tons of all types of solid waste, mainly household waste but also animal remains from slaughterhouses and butcher shops. Kitchen garbage, paper, newsprint, cartoons, iron, plastic, dyes, wood, medical waste, glass, ceramics, leather, fabrics, electrical devices, and batteries are the most common types of domestic waste. These forms of waste may spontaneously burn and generate a terrible fume odor, which differs based on trash structure and poses a bigger danger to the operational management personnel. This is one of the environmental risks that occurs often. Bricks and concrete blocks are some of the materials that make up the debris from construction and demolition projects that are discarded.
The garbage was first thrown over the boundary of the site. that was the initial step in the dumping process, which began at the highest point on the site. Some potential hazardous or toxic components of the waste, such as liquid solvents, are observed flowing along the valley from the east of the Soran landfill until entering the Kawlokan river, which is a main water source and fishing for city inhabitants (Fig. 1). In addition, a potentially hazardous but common activity is observed at the site, which consists of the dumping of wastewater from septic tanks.
In recent years, there has been a shift in the processes of production and consumption that has led to an alarming rise in the amount of garbage produced as a result of the dramatic population expansion in Soran City. It is getting more challenging and costly to dispose of household garbage, which makes up the majority of the waste that is dumped in the Soran landfill due to the absence of waste recycling programs and the growing expenses associated with waste disposal that it has led to the present trash dumpsite quickly reaching its capacity. In addition, the prices associated with waste disposal are always rising. In light of this, any industry that produces food waste is going to encounter a problem in disposing of this type of waste, and this is especially true for establishments that provide catering on a large scale, like hospitals, schools, colleges, jails, restaurants, shopping centers, and parks, as well as homes. The wastes that are dumped in the Soran landfill undergo continuous decomposition, and the sludge of degraded soup that is known as leachate is produced in volumes that create long streams that flow from the base of the landfill into the Kawlokan river (Fig. 1).

Sample collection
On September 18, 2021, eight sample stations were created in order to examine the chemical and microbiological characteristics of the landfill and its surroundings. These sampling locations were positioned both on the perimeter of the dump as well as in the neighboring populated regions, as shown in Fig. 1 and detailed in Table 1. Soil samples, mud samples, and leachate samples were obtained in October 2021. All the soil samples and mud samples were collected with a sterilized steel spatula and kept in clean polyethylene bags, and the leachate samples were collected in a sterilized plastic bottle. Finally, all the samples were transferred to the Biogeoscience laboratory at the scientific research center at Soran University, and the samples were kept at 4 °C until the starting of the analysis process.

Microbial analysis: soil, mud, and leachate
Isolation of the bacteria 1 g of the soil and mud samples were mixed with 9 ml of sterilized distilled water to prepare a serial dilution for 6 factors. For the leachate samples, 1 ml of the leachate was diluted in 9 ml of sterilized distilled water for four dilution factors, and then 100 µl of the last three dilution factors were cultured on the nutrient agar and incubated at 35 °C for 24-48 h. The culture plates were purified in order to get a single type of bacteria on each plate.

DNA extraction and amplification
Following the guidelines provided by the manufacturer, the DNA extraction was performed using the AddPrep genomic DNA extraction kit (AddBio Inc. Ltd., Korea) (Ferdous et al., 2021;Khan et al., 2021). The extract product was checked by gel electrophoresis in 5X TBE buffer (20 ml of 5X TBE buffer per 80 ml of distilled water) with safety dye.
Amplification of bacterial 16 s V4 areas was achieved by the use of locus-specific sequencing primers during the DNA amplification process. The names and sequences of the primers are 515fB, G T

G Y C A G C M G C C G C G G T A A, and 806rB, G G A C T A C N V G G G T W T C T A A T. The
Master mix was used in the PCR reactions was Add-Taq 2X PCR master mix with the PCR protocol in the thermal cycler at 95 _°C for 5 min, followed by 30 cycles at 95 _°C for 30 s, 55 _°C for 30 s, and 72 _°C for 2 min, and a final extension at 72 _°C for 10 min. It was then held at 4 _°C (Chukwuma et al., 2021). The PCR product was analyzed with gel electrophoresis to observe the bands of the DNA related to the 16S rRNA-V4 gene. It was 254 base pairs in 20 ml of 5X TBE buffer per 80 ml of distilled water and 1.5% (w/v) of agarose (Apprill et al., 2015;Cuevas et al., 2020;Francioli et al., 2021;Parada et al., 2016).

Gene sequencing
After the recognition of the band related to the V4 region of the 16 s rRNA, the sequencing of all the PCR products was run using an ABI 3730xl DNA analyzer (Applied Biosystems) by Macrogen Inc, a biotechnology company, south Korea as in (Tao et al., 2014).

Sequence analysis
The program called Bio Edit Sequence Alignment Editor (v. 7.2.5) was used in order to display the sequences that were acquired. It was possible to assess the Phred quality of the sequences. After that, the first and last parts of the sequences were taken out, leaving only the high-quality fragment. Following the trim operation, the sequences were saved in FASTA format. The sequences that were collected over the course of this research were submitted to NCBI GenBank with accession numbers ranging from ON681607 to ON681640. A phylogenetic diagram was created for proof of the sequencing data using all the isolates. In addition, we used 16 sequences obtained from the GenBank database as a reference. The 33 FASTA sequences were aligned using the Molecular evolutionary genetic analysis software version 11.0.11 (Mega × 11 software) (Kumar et al., 2016). Mega × 11 software was used to determine the best substitution model, as a result of the preliminary analysis, a neighbor-joining phylogenetic tree was constructed, using the Kimura 2-parameter model with uniform rates. Bootstrap analysis with a total of 1000 repetitions was used to evaluate the consistency of the internal nodes. (Felsenstein, 1985;Krishnamurthi & Chakrabarti, 2013;Saitou & Nei, 1987;Tao et al., 2014).

Plate counting method
For enumeration of those bacteria transferred to the environment through leachate from landfills, the plate counting method was used by performing a serial dilution and culturing of bacteria on the plate followed by incubating culture plates at 37 °C for 24 h. The bacteria number was calculated using the following equation: relation to solid mineral residue mass in the leachate samples.
The following indices were calculated for the purpose of determining the potential environmental dangers and levels of pollution. These indices are very necessary in order to assess the level of contamination in the soil and sediment as well as the possible ecological dangers caused by metal(oid)s in landfills. (Aja et al., 2021;Akanchise et al., 2020;Mavakala et al., 2016Mavakala et al., , 2022Xie et al., 2019).

Leachate liquid samples
The leachate samples were air dried, crushed and ground into powder in a clean mortar and pestle. The powders were sieved using a 0.65-micron sieve (Akanchise et al., 2020). The assessment of metal(oid)s presence of (As, Cd, Cr, Co, Cu, Fe, Mn, Mo, Pb, Zn, Ni, and Al) was performed by

SEM analysis
Scanning electron microscope (FEI Model QUANTA 450) was used for imaging of dry leachate concentrate obtained through rotary evaporation followed by air drying at 25 °C. The solid samples, which represent a mixture of mineral matrix, organic matter, bacteria and other microorganisms (fungi and parasites), were gold coated and examined under the SEM for microbial community morphology and ICP-MS (Azimov et al., 2020;Fitamo et al., 2007;Francioli et al., 2021;Mao et al., 2017;Monged et al., 2018;Xiang et al., 2020).

Enrichment factor (EF)
In order to determine the enrichment factor (EF) in the soil samples, the following equations were utilized in the calculation process (Gu et al., 2022; Page 7 of 20 811 Vol.: (0123456789) Zhang et al., 2007). Normalization was conducted with aluminum (Al), as recommended by the prior investigation that was carried out (Din, 1992

Geoaccumulation Index (Igeo)
In 1969, Muller first proposed the idea of using a geoaccumulation index as a means of determining and defining metal(oid)s contamination in soil and sediments (Muller, 1969). This was accomplished by contrasting the current concentrations with the levels that existed before to industrialization. Geoaccumulation index (Igeo) was found with the following equation: The use of a factor of 1.5 is necessary due to the possibility of variations in the background values for a particular metal(oid)s found in the environment, in addition to the extremely modest anthropogenic influences. (Mavakala et al., 2016;Mwanamoki et al., 2015).

Contamination Factor (CF)
CF is a technique for assessing the pollution status of contaminants in the soil. This method takes into account the concentrations of the pollutants in the sample as well as the concentrations of the pollutants in the background. It is a crucial index for monitoring the amounts of pollutants that have been present over a considerable amount of time. Moreover, the calculation goes as below (Gu et al., 2022;Martin & Meybeck, 1979;Soumahoro et al., 2021).

M sample Concentration of metal in samples
M background Concentration of metals in background samples (uncontaminated sample).

Contamination Degree (CD)
The degree of contamination makes it possible to make a priori estimate of the amount of poly-metallic contamination at each sampling location and was computed by the following equation according to Mavakala et al. (2022): i count of the metal(oid)s species (CF As , CF Cd , CF Co ……. etc.)

Ecological risk factor (Eri)
It has been utilized in the assessment of the potentially dangerous impacts that pollutants have on both humans and the environment. Additionally, it is a reflection of the ecological sensitivity as well as the toxicity of the concentration of contaminants. It has been utilized effectively for the purpose of conducting risk assessments of soils, dust, and air (Gu et al., 2022;Hakanson,  1980). The ecological risk factor is determined by the following equation: Tri toxic-response factor of a single element CFi contamination factor of element i.
Tri 10 for As, 30 for Cd, 5 for Co, 5 for Cu, 1 for Mn, 5 for Pb, 2 for Cr, 1 for Zn, and 5 for Ni (Gu et al., 2022) The potential ecological risk index (RI) For the many different metal(oid)s that were found in the soil, RI was comparable to the degree of contamination that was defined as the total of a single possible ecological risk factor. This method takes into account all relevant aspects, including the synergy between metal(oid)s, the hazardous level of those metal(oid)s, the concentration of those metal(oid)s, and the ecological sensitivity of those metal(oid)s (Hakanson, 1980;Singh et al., 2002). It is a representation of the vulnerability of a variety of biological communities as well as the potential dangers posed by metal(oid) s (Al-Anbari et al., 2015; Gu et al., 2022;Pan & Li, 2016). RI was computed using the below equation: i count of the metal(oid)s species Eri single index of ecological risk factor.

Results and discussion
In the study, the plate counting method was used to enumerate the number of bacteria that were released from landfill through the leachate. The number of bacteria was estimated by using Eq. (1) based on the colony forming unit (Waste, 2018). The number of bacteria in the leachate from the borehole is 1.2*10 10 cfu/ml, which is more than the number of bacteria in the leachate sample from the stream, which is 5.84*10 9 cfu/ml due to the precipitation of the bacteria into the stream mud and sediment layer. The SEM images show the morphology of the bacteria community in the leachate samples. According to the SEM images, there are different species of bacteria with different shapes and arrangement, which supports to our result in the identification of different species of bacteria from the samples (Fig. 2). The highest number of isolated bacteria were isolated from soil and mud samples. A few bacteria were obtained from leachate due to the reduction condition because of the presence of a significant toxic substance and strict anaerobic conditions (Flores-Tena et al., 2007;Hilger & Barlaz, 2007).
Page 9 of 20 811 Vol.: (0123456789) Some of the isolated bacteria are potentially human pathogens, and the occurrence of the pathogenic bacteria and other gram-negative bacteria in the Soran landfill site suggests a potential risk to public health. E. coli is an indicator for fecal coliform, which is responsible for many human infections such as bloody diarrhea, chronic gut inflammation, and some asymptomatic cases (Braz et al., 2020). Other gram-negative pathogenic bacteria such as Pseudomonas aeruginosa can cause many infections such as: ventilator-associated pneumonia, urinary tract infection, keratitis, and otitis media (Tuon et al., 2022). Morganella morgani is the cause of infections such as: cellulitis, sepsis, diarrhea, and bacteremia (Li et al., 2018). Shigella is the main cause of shigellosis and bloody diarrhea (Shad & Shad, 2021). Proteus mirabilis is responsible for the development of bladder and kidney stones (Armbruster et al., 2018). Serratia marcescens causes urinary tract infection (UTI), pneumonia, bloodstream infection, and meningitis in newborns (Cristina et al., 2019). In addition to the isolated gramnegative bacteria, the gram-positive are equally harmful to humans such as Enterococcus faecalis that cause UTI, endocarditis, bacteremia, and pelvic infections (Bolocan et al., 2019). Corynebacterium sp. which is responsible for respiratory infections and Micrococcus sp. that causes hepatic and brain abscess (Otshudiema et al., 2021).
The presence of these potential human pathogens causes a health risk for the landfill site operators' staff ( Fig. 4) in addition to the fact that this risk is easily transferable to the community through personto-person contact, birds and other wild animals that feed on the landfill waste (Fig. 4). Soran landfill has no leachate collection system, most of the survival pathogenic bacteria can contaminate the underground water as well as the nearby Kawlokan river with bacteria and metal(oid)s released from the landfill (Fig. 1) (Bartkowiak et al., 2016).

Metal(oid) content in leachate
Metal(oid)s can frequently be discovered in the garbage produced by households in the form of used electronic gadgets, chargers, pigments, various plastics, etc., where metal(oid)s compounds can be emitted into the surrounding environment. When garbage is buried in landfills, some of the metal(oid)s in the waste may leak into the soil, which can then deposit a significant quantity of those metal(oid)s. A high metal(oid) content can concentrate in a landfill leachate (Soumahoro et al., 2021). Our results show a similar trend (Table 3). Alloway (2013a) and Ishchenko (2018) showed that the sources of the most widespread metal(oid)s originating from Soran municipal waste material and delivered into the environment are summarized as in Table 4.

Heavy metal content in soil and mud
The concentration of metal(oid)s in the soil and leachate stream mud samples is shown in Table 5. Generally, the heavy metal concentration in samples shows varied levels. It is noted that the concentration of metal(oid)s including Pb, Zn, As, Cd, and Cu were found to be moderately higher in most of the samples compared to background (soil control) values in mg/ kg (Bartkowiak et al., 2016). The concentration of the metal(oid)s in mg/kg for As was 10.2, 6.7, 6.6, 11.1, and 9.3, for Cd was 0.4, 0.6, 0.4, 0.3, and 0.3, for Pb was 6, 1, 11, 2, and 1, for Zn was 162,310,205,182,and 188 in BHS,BLS,LSS,LSM,and LSM2,respectively,compared to the metal(oid)s concentration in control samples as the background of the soil was 4.7, 0.1, < 1, and 120 for As, Cd, Pb, and Zn, respectively. The highest concentration of As and Mn was detected in sample LSM (11.1 mg/kg and 985 mg/kg, respectively). While the highest concentration of Pb was found in LSS (11 mg/kg) and BLS showed the highest concentration of Zn and Cd (310 mg/kg and 0.6 mg/kg, respectively). Co, Cr, Mo, and Ni have the highest levels in the BHS (35 mg/kg, 500 mg/kg, 2.4 mg/kg, and 304 mg/kg, respectively). The Al concentration was measured to be used as a background metal(oid) in some index equations (Din, 1992).
The concentration of some elements is more than acceptance level to discharge to the surface water as shown in (Table 6) for comparison of the study's results and standards. Pb, Cd, As, Zn, and Mo are toxic metal(oid)s whose concentration were very high compared to those thresholds were set discharge and Irrigation (Van Der Merwe et al., 2013).
Explicitly, this is an alarm to treat the leachate before mixed with rivers or natural sources of water. When the leachate enters the river, it leads to the changes in the water quality that is becoming healthy risks for humans and ecological risks for plants and animals. In Soran landfill city, the leachate is directly entered into the Kawlokan river which increases the concentrations of the metal(oid)s more than standards for aquatic animals especially fishes that causes the accumulation of the metal(oid)s in the fish's bodies and the contaminated fishes will be the main source of the food for many peoples around the rivers that they cause many disorders in the organs of the bodies as liver and kidney. Humans run the risk of ingesting metal(oid)s when they consume contaminated plant food containing metal(oid)s. Metal(oid)s are known to have a number of negative effects on human health, including those that are related to the neurological system, kidneys, liver, and respiratory systems. This is in addition to the fact that they are known to lower Fig. 3 The phylogenetic tree was performed using the Neighbor-Joining method. The optimal tree with the sum of branch lengths = 1.97187253 is shown. The bootstrap consensus tree performed from 1000 replicates is taken to represent the evolutionary analysis. The accession numbers ON681607 to ON681640 are the isolates from landfill samples. BHS: Borehole soil, BLS: Base of landfill soil, LSS: Leachate stream soil, LSM: Leachate stream mud the quality of natural waterways (Alengebawy et al., 2021;Mahurpawar, 2015;Morais et al., 2012).

Pollution indices
EF and Igeo are both commonly used to assess the level of anthropogenic pollutants in soils (Braz et al., 2020). Igeo and EF values for selected metal(oid)s in soil samples from the Soran landfill are given in Tables 7 and  8. Based on the Igeo values, the toxicity of metal(oid) s was divided as follows: Pb > Cd > Mo > Zn > As > Cu > Mn > Co > Cr > Ni. Pb pollution was determined as moderately polluted at BHS, while Pb pollution was estimated as moderately to heavily polluted at LSS. Cadmium pollution was measured as moderately polluted at BLS. All samples were shown to be unpolluted to moderately polluted for As, Co, Cr, Cu, Mn, Mo, Zn, and Ni (Table 7). Overall, most samples have no enrichment for Co, Cr, and Ni, while having minor enrichment for As, Cu, Mn, Mo, and Zn. Cd, Pb, and Mo have moderate enrichment in BHS. In LSS, LSM, and LSM2 are found to have moderate enrichment. While Cd has moderate to severe enrichment in BLS. LSS has severe enrichment for Pb (Table 8). The contamination factors and ecological risk are shown in Tables 9 and 10. Based on the contamination factor, all samples have low pollution for Co, Cr, and Ni; they have moderate pollution for As, Cu, Mn, Mo, and Zn; and they have considerable pollution for Cd. While BLS has very high pollution for Cd, BHS and LSS also have very high Pb pollution (Table 9). Regarding the ecological risk, all samples showed a low ecological risk for As, Co, Cr, Cu, Mn, Zn, and Ni, and they presented a considerate ecological risk for Cd, except for the BLS site that showed a high ecological risk (Gu et al., 2022). The LSS sample is shown to be at moderate ecological risk for Pb (Table 10).
The contamination degree level of the sample is between 12 and 23, or moderate to high contamination. This high level of polymetallic contamination is mostly due to Cd but also, with a smaller contribution of As, Co, Mn, Mo, Pb, and Zn are participating to a lesser degree in this high polymetallic contamination.    (Alloway, 2013b;Ishchenko, 2018) Cd, Ni, and Cr Electrical materials, chargers, cement, pesticides and fertilizers, PVC-plastic, colored glass (Alloway, 2013b;Ishchenko, 2018) Zn Cement, pesticides, paints, waste medicines, batteries (Alloway, 2013b;Ishchenko, 2018) Cu Electrical materials, cement, pesticides, dyes, sewage sludge, agriculture waste (livestock) (Alloway, 2013b;Ishchenko, 2018) As Paints, waste medicines, pesticides, printing products (Alloway, 2013b;Ishchenko, 2018)  BHS and LSS are shown to have highly contaminated degrees because of the high level of Pb pollution based on the contamination factor (Fig. 5). The potential ecological risk results ranged from 131-216, which indicates a potential ecological risk between low and moderate (Fig. 6). BHS, BLS, and LSS have a high level of the RI of 192.6,216.99,and 205.42, respectively, indicating a moderate ecological risk for the environment for those samples close to the landfill (Fig. 6). (Mavakala et al., 2016) reported similar case where dumpsites containing a diverse collection of waste types, the distribution of metals in the soil might experience large variations, and the pollution level caused by the metal(oid)s varies greatly throughout the various locations of a certain landfill site.

Conclusions
The current case study offers the results of a comprehensive analysis of the geochemical and microbiological indicators that demonstrate the potential environmental and public health hazards stemming from improperly managed landfills located in urban areas that have experienced rapid population growth and urbanization, and resulting in significant solid waste generation. The research highlights a representative example of the transformation of rural regions into urban settings, particularly in developing countries.
Here, the landfill leachate is identified as the principal contributor to environmental pollution, whereby it presents a formidable risk to contiguous ecosystems such as surface waters and soils. The contamination emanates from hazardous bacterial agents and metal(loid)s, which have deleterious effects on the environment and public health. The geochemical analyses of leachate samples, leachate stream mud, and soil analyzed for metal(loid)s concentrations and their various risk indices factors showed a dangerous level of Cd and Pb that are produced directly from the landfill solid waste, while As, Co, Cr, Cu, Mn, Mo, Zn, and Ni showed low-risk concentrations.
These findings emphasize the importance of engineering upgrades to landfill sites and the implementation of proven solutions and international standards and designs for leachate recycling to promote environmental    Vol.: (0123456789) sustainability. Regular geochemical and microbiological monitoring of solid waste, soil, and leachates is essential to ensure optimal environmental conditions. Further research should prioritize the investigation of the environmental impact of landfills to achieve a better understanding of the dynamics and spread of toxic metal(loid)s and bacteria in natural environments.