1. Introduction
The concept of sustainability emerged due to environmental problems brought about by rapidly increasing industrialization after the Industrial Revolution [
1]. While production increased with industrialization, the uncontrolled increase in waste caused pollution, disrupting the natural balance of air, water, soil, noise, and electromagnetic pollution. For example, pollutants such as nitrogen oxides, sulfur oxides, acidic gases and heavy metals create cumulative pollution in the atmosphere [
2]. In addition, Potentially Harmful Elements (PHEs), led by heavy metals, are an important pollution threat to water resources, soil and living things [
3].
Numerous studies have shown that industrial wastes from a variety of sectors, including from sugar processing, energy and power generation, cement manufacture and petrochemicals, are the primary contributors to environmental degradation, including water, soil, and food contamination [
4,
5]. Although the sugar industry, which is among these sectors, is seasonal and does not operate more than 150/160 days a year, a large amount of waste material is produced during sugar production, including many xenobiotics such as heavy metals [
6,
7]. Heavy metals can easily accumulate in water and soil and can accumulate in the edible parts of vegetables at high rates as they are easily absorbed by plant roots [
8]. As a result of the uncontrolled discharge of wastes to the environment, especially, heavy metals are transmitted to the food production chain because pollutants in polluted soil, air and water are absorbed by plants. In general, heavy metals are not biodegradable and therefore also penetrate important human organs [
9,
10]. Contamination with heavy metals is of great importance for human health due to the metals’ capacity to enter the food chain. These substances can remain in ecosystems at dangerous concentrations for long periods of time, accumulating in living organisms and circulating through food chains. The products obtained due to these concentrations are extremely dangerous in terms of health [
11].
Vegetables are indispensable for people’s nutrition programs because they contain many nutrients, including protein, carbohydrates, vitamins and minerals [
12]. In places where water scarcity and land degradation occur, such as Pakistan, it is especially necessary to increase vegetable production to meet people’s nutritional needs [
13,
14,
15]. Sugar beet (
Beta vulgaris L.) is one of the plants that has an important place in terms of nutrition. Sugar Beet is a plant with rosette and flat leaves and a fleshy root. The sugar produced in the leaves by photosynthesis is intensely stored in the roots. The root of the sugar beet contains 5% pulp, 20% sugar and 75% water. Sugar Beet is an important cash crop worldwide due to the primary value of sugar. Water-insoluble sugar beet pulp is mainly composed of cellulose, hemicellulose, pectin and lignin and is used in animal nutrition. Molasses and pulp are by-products of sugar beet and constitute 10% of the harvest value due to their place in animal nutrition [
16,
17].
In Pakistan, wastewater such as industrial and urban wastewater is widely used for agricultural irrigation despite its chemical and pollutant content [
18,
19,
20]. In this respect, it is important to determine the risks of heavy metal accumulation in various agricultural products and the risks to human health. The aims of this study were to assess the heavy metal(loid)s contamination in soil and sugar beet samples and to assess the health risks of heavy metal(loid)s to the population via the consumption of sugar beet.
2. Materials and Methods
2.1. Study Area
The Sargodha District is bordered to the north by the District of Jhelum, to the east by the Chenab River, and beyond that by the District of Mandi Bahauddin (
Figure 1). The District of Hafizabad is bordered to the south by Jhang District and to the west by Khushab District, with the Jhelum River dividing the two Districts. The Sargodha District’s highest recorded temperatures are 450 °F in the summer and 0 °F in the winter. Sargodha currently has 24 husking units, 12 flour mills, 4 sugar mills, 7 textile mills, and 4 sugar mills in operation. Sargodha is also famous for handicrafts, citrus processing, agricultural machinery, light oven electrical industry, homemade fabrics and various agricultural and industrial products.
2.2. Sample Collection
For the research, the region in the Chishtia Sugar Mill Limited domain was selected as the sampling area. It is situated in the village of Sillanwali, tehsil Farooka.
A total of 100 mL of each source’s groundwater and wastewater from the sugar industry that was used to irrigate Site 1 (groundwater irrigated site) and Site 2 (wastewater irrigated site) was sampled to determine their metal concentrations. To prevent microbial growth, acid polypropylene was used to wash the bottles, and 1 mL of HNO3 was added. Before further analysis, the samples were chilled.
Each of Sites 1 and 2, which are irrigated by groundwater and wastewater from the sugar industry, respectively, had 25 soil samples taken. A stainless-steel drill was used to drill the planned locations for the soil samples to a depth of 10–15 cm, and all soil layers were partially cleaned. All materials were compressed into 2 mm crush strainers after being dried and crumpled. Soil samples were stored on croft paper until analysis.
In the same locations where soil samples were obtained, sugar beet samples were also taken. During sampling, 25 samples of these vegetables were collected from Sites 1 and 2. Samples of sugar beet were cleaned with deionized water to get rid of any particles, and they were then dried at 80 degrees centigrade until a consistent weight was obtained.
2.3. Sample Preparation
For digestion, one gram of soil was collected and combined with nitric acid (HNO3) in a beaker. The next day, hydrogen peroxide (H2O2) was added to the left-overnight combination and it was cooked in the digestive tube for an hour at 750 degrees Celsius until the solution was clear. After digestion was finished, the material was taken out of the digestion tube, filtered through filter paper, and then combined with distilled water to form a volume of 50 mm.
Nitric acid (HNO3) was added to a digestion tube along with a sample of 1 g of each vegetable. The following day, the digestive tube was placed on a hot plate set to 750 degrees. Hydrogen peroxide (H2O2) was added to the tube after 35 min, and the ensuing solution was boiled until clear. When digestion was finished, the digested material was taken out of the digestion tube, filtered using Whatman No. 42 filter paper, and then given a 50 mm volume raise with deionized water.
2.4. Analysis of Physicochemical Properties of Soil Samples
The electrical conductivity (EC), pH, and organic matter (OM), which are physical and chemical properties of soil, were studied. A pH meter was used to measure the pH of the soil [
18]. A calculation of electrical conductivity was made based on Richard [
19]. By using the Walkley and Black acid digestion technique, the OM of the soil was determined [
20].
2.5. Metal(loid) Analysis
A PerkinElmer AAS-300 atomic absorption spectrophotometer was used to conduct a metal analysis on soil and vegetable samples. Lead (Pb), Cadmium (Cd), Manganese (Mn), Nickel (Ni), Copper (Cu), Iron (Fe), Chromium (Cr), Zinc (Zn) and Cobalt (Co) were the metals and metalloids that were the subject of the current research. Limit of Detection (LOD) values were assessed in accordance with the accepted procedures outlined in the literature [
21]. The blank solution’s standard deviation (SD) and signal-to-noise ratio were both found to be 10; the value was therefore identified as LOD.
Table 1 provides the detection thresholds for the pertinent heavy metals. The extremely sensitive hydride method was used to find the presence of nickel (Ni) and chromium (Cr).
2.6. Quality Control
Diagnostic marker standardization data from Merck (Darmstadt, Germany) were utilized to calibrate the device. The crystalline pupillages were methodically cleaned throughout the study using deionized water. Specialized Position Quantifiable assessments (SRM-2711 for soil and SRM NIST 1577b for vegetables) were used to complete the statement of value and ensure that the results were consistent. The mean SRM recoveries for Pb, Cu, Co, Mn, Cd, Cr, Zn and Fe in soil were 102%, 95%, 101%, 97%, 97%, 95% and 98%, respectively. The mean SRM recoveries for these metals in sugar beet were 95%, 95%, 98%, 102%, 102%, 96% and 99%, respectively.
2.7. Statistical Analysis
Using IBM SPSS 24.0 (Statistical Package for Social Sciences), a one-way analysis of variance (One-way ANOVA) was utilized to estimate the significant difference in metal/metalloid values between irrigation zones. The differences between values were tested statistically at the 0.05, 0.01 and 0.001 levels [
22,
23,
24,
25,
26]. Furthermore, using IBM SPSS 24.0 software’s Hierarchical Clustering Analysis, the relationships between metal/metalloid values in the samples were compared and contrasted.
2.8. Bioconcentration Factor
The BCF values for each metal in this study were computed using the formula:
Metal values in plant tissues are denoted by the acronym C
veg (mg/kg, dry weight), whereas the term C
soil (mg/kg, dry weight) refers to metal concentration in soil [
27,
28,
29].
2.9. Enrichment Factor
The enrichment factor (EF) was computed using the following formula:
Standard reference amounts of Co, Zn, Cd, Fe, Pb, Cu, Ni, Mn and Cr for soil were employed in this study as 9.1, 44.19, 1.49, 56.9, 8.15, 8.39, 1.5 and 9.07 mg/kg, respectively [
30,
31]. Standard metal concentrations of 0.01, 0.6, 2.02, 20, 2, 10, 9.06, 80 and 1.3 mg/kg were used for the plant [
32].
2.10. Daily Intake of Metals
The DIM values in this study were determined in accordance with Sajjad’s [
33] definition:
The average body weight is indicated by B
average weight, where C
metal stands for the concentration of metal ingrains, D
food intake for daily caloric intake, and C
metal for the concentration of metals. The average daily vegetable intake rate for adults was calculated using 0.345 kg/person/day and an average body mass of 55.9 kg, from the literature [
34].
2.11. Health Risk Index
The ratio of the oral reference dose (RfD) to the daily intake of metals (DIM) in food products is known as the HRI [
35]:
The RfD values for Cd, Co, Cr, Cu, Fe, Ni, Pb, Zn and Mn, as reported by the USEPA [
36], were 0.001, 0.04, 1.5, 0.04, 0.7, 0.02, 0.003, 0.3 and 0.04 mg/kg/day, respectively.
4. Conclusions
The goals of this study were to analyze the levels of heavy metal(loid)s in the soil–sugar beet system in regions that were irrigated with industrial effluent, to evaluate the heavy metal(loid)s contamination of sugar beet samples using pollution indices and to estimate the health hazards of heavy metal(loid)s to the local people from eating sugar beet. Firstly, except for Mn, the heavy metal(loid) values in the water samples in the area were higher than the maximum permitted limits. However, it was found that, except for Cd, the heavy metal levels in the soil and sugar beet samples watered with these waters were lower than the maximum allowed limits. From this perspective, there is a risk associated with the irrigation of vegetables like sugar beet, cauliflower, radish, lettuce and cabbage using water from the sugar sector that contains a certain level of heavy metals. According to the findings of the Health Risk Index evaluation carried out for this study, the accumulations of Co, Cu, Fe, Mn, Cr, Zn and particularly Cd provide a health risk when consumed. Wastewater irrigation is widely employed throughout the world, especially in underdeveloped countries. Therefore, it is suggested that wastewater treatment facilities be built and used effectively to reduce the risk. In locations where these opportunities are uncommon, the use of appropriate bioremediation techniques and the cultivation of plants with decreased accumulation may be beneficial. The potential health concerns linked to exposure to heavy metals through diverse pathways should be the main topic of future study in any case.