Study of Spatial Distribution and Health Risk Assessment due to Arsenic Contamination in Bihar, India, for its Detection and Bioremediation

Abstract

The shortage of drinking water is a matter of concern in today’s world. Arsenic (As) is a naturally occurring and highly toxic environmental impurity found in rocks, soil, and water in contact with them. Natural As concentrations above their permissible limits (>10 μg/L) is an environmental crisis all over the globe and one of the biggest in India. Arsenic toxicity and human health are intensely connected. Human health risks associated with acute As toxicity include DNA damage, mutations, neurological disorders, respiratory diseases, and cancer in the liver, kidney, and skin. India's middle Gangetic plains, which make up 89% of the state of Bihar and have potential alluvial aquifers, are severely damaged. One of the hardest impacted places by geogenic As is the Bhojpur district of Bihar, which is situated in the center of the Gangetic plains in the flood-prone Sone- Ganga interfluvial zone. The present investigation starts with a study that evaluated the amounts of geogenic As and other heavy metals influencing the release of As in the aquifers inside the drinking water sources in the Bhojpur district of Bihar, India. In six nearby villages near the River Ganga, namely Bakhorapur, Gaziapur, Parasrampur (or Kanhachhapara), Saraiya, Paiga, and Gundiinin, hand-dug wells were used to collect 18 water samples in triplicate. Arsenic, zinc, manganese, and iron contamination levels in the area were found to be extremely high according to the physicochemical parameters, ionic content, and heavy metal analyses of the water samples that were collected. Iron and As concentrations ranged from 0.17 to 1.16 mg/L and 24.3 to 168.07 μg/L, respectively, indicating high groundwater removal for irrigation and domestic use with a strong link between the two elements. The heavy use of chemical fertilizers and pesticides in the area is blamed for the elevated zinc concentration there. Manganese concentrations were also higher, ranging from 0.05 to 1.15 mg/L, mostly as a result of the industrial activities that are concentrated in metropolitan areas. The overall water quality in the region is slightly contaminated, but the risk associated with it is modest, according to an assessment of the human health risk among two population groups. The range of the water quality index, from 29 to 48, indicated poor water quality. From the previous study, it was revealed that a high concentration of As in groundwater exists, which is the sole source of drinking water for the villagers. The toxicity associated with acute As poisoning is well-known and established. Because of this toxicity, it is crucial to find and identify these As-rich aquifers in order to protect human health. As a result, individuals unknowingly eat As, a colourless, tasteless, and odourless heavy metal, through drinking water that contains it as well as through irrigational operations, which has an impact on the food chain. Therefore, there is a need for a quick, simple, and affordable As detection kit so that any regular person, at any time, can do so at a very low cost without the need for special training or laboratory conditions and protect themselves from the toxic and carcinogenic effects of this infamous heavy metal (As). Inductively coupled plasma mass spectrometers (ICPMS) and atomic absorption spectrometers (AAS) are two systems that can be used to detect As and provide both qualitative and quantitative data. These systems have shortcomings, such as larger equipment that makes them difficult to move about. Additionally, because to the high cost of the equipment, they can only be found in advanced research labs and require trained employees to run the instruments in order to carry out the intricate and time-consuming analytical procedure. To ensure that the general public can detect the presence of As in the water sample at any time and at a very reasonable cost without any special training or lab requirement, there is a need for a quick, user-friendly, and cost-effective As detection kit. This will protect them from the carcinogenicity and toxic effects of As. The goal of the current project is to create a low-cost kit for paper-based As detection. Despite the availability of As paper-based field test kits, the majority of methods for the detection of As rely on the production of arsine gas. Due to the fact that gas mobility is significantly higher than that of liquid mobility, the emission of this arsine gas is extremely harmful to human health. The currently available paper-based test kit was developed using the silver nitrate immobilization method (AgNO3). The kit was examined for factors such as colour development for various As forms (As3+ and As5+) and concentrations, test strip storage conditions, the impact of various interfering agents on colour development, and optimization of AgNO3 solution. Potassium permanganate (KMnO4) was used as the oxidant for oxidizing As3+ to As5+. A colour gradient scale was created from the colour established for various As concentrations to roughly measure the concentration of As. The kit will cost Rs. 3.92 per sample, which is 70 to 100 times less than the cost of current procedures, according to the cost study, which was conducted. Under Intellectual Property Rights India, the current method for creating the kit and the kit itself have both been applied for patent with the application number 202231027806. The presence of As in groundwater and its associated toxicity is very much harmful to human health. Therefore, the next study aimed at the removal of this As along with other heavy metals using plant-based biosorbents and microorganism-based biofilm-mediated remediation. In the plant-based approach, biosorbents prepared from novel Colocasia esculenta stem and Artocarpus heterophyllus (jackfruit) seed biomass were studied for the removal of As and other heavy metals. Biosorbents from the stems of the Colocasia esculenta plant and Artocarpus heterophyllus (jackfruit) seed biomass were able to successfully and efficiently remove As along with other heavy metals from individual and as well as from heavy metal mixture solution. The adsorption of As and other heavy metals happened via endothermic and spontaneous processes and followed the pseudo-second-order kinetics model for both biosorbent experiments, according to the findings of the thermodynamic and kinetic study. In order to analyze the equilibrium data for both biosorbent studies, eight different isotherm models were used. Zeta potential and a CHNS analyzer were used to characterize the biosorbents. Utilizing SEM-EDX, FTIR, and XRD analyses, further characterization of the biosorbents both before and after adsorption was investigated. In the microorganism-based approach, a biofilm-mediated bioremediation study of As and other heavy metals was studied. This was carried out using a multi-metal resistant, gram-positive, non-virulent bacterial strain, Bacillus sp. GH-s29 strain isolated from the As-contaminated groundwater of Bhojpur district, Bihar, India. The strain's biofilm mode was able to remove heavy metals not only from individuals but also from multi-metal solutions. These findings were further supported by the results of the strain characterization using SEM-EDX and FTIR analysis. The maximum removal of As5+, Cd2+, and Cr6+, was observed to be 73.65%, 57.37%, 61.62%, and 48.92%, 28.7%, and 35.46%, from individual metal solutions and multi-metal solutions, respectively. The effective sequestration of the positively charged metal ions from solutions is facilitated by the presence of various negatively charged functional groups on the EPS, including hydroxyl, phosphate, sulphate, and carboxyl. This hypothesis was supported by the results of the FTIR study. The final study aimed at the development of a bio-filter column to remove As from the groundwater. In the prior investigation, two plant-based strategies and a biofilm-mediated strategy for As removal were validated. Both biosorbents were mixed in equal parts and used as a result of the plant-based system's high removal efficiency and availability. In order to remove total As from the groundwater, a small-scale plant-based bio-filter column has been devised and developed in the current work while considering its possible applications in the urban, rural, and industrial sectors. After testing the effectiveness of oxidation with three different oxidants, it was discovered that chlorine, at an ideal concentration of 0.3 mg/L, had the maximum efficacy in oxidizing As (III) to As (V). The study also discovered that when the initial As concentration was 250 μg/L, the X bio-filter column was capable of filtering 96.29% of the total As over the course of 60 days at a flow rate of 1.5 L/h. According to the research, the bio-filter column was capable of filtering out As up to a concentration of 1000 μg/L, but after that, its ability to do so started to decline. With the AAS inquiry, interference analysis of several anions and cations was performed. The analysis's findings showed that PO4 3- had the greatest inhibitory effect, followed by CO3, 2- and Cl-. The possibility of PO4, 3- and CO3, 2- ions competing for the As binding sites in the biosorbent could be the reason for decline in As adsorption. However, it was established that a rise in Ca2+ and Mg2+ concentrations was closely related to a rise in As adsorption strength. This might be because the hydration reaction on the biosorbent is aided by the presence of Ca2+ and Mg2+ ions. The bio-filter column's best removal performance was noted at a capacity of 1000 L volume. This shows that the bio-filter column can remove total As from water that is polluted with As up to a maximum volume of 1000 L before its removal efficiency starts to drastically decline. Therefore, it may be stated that the developed bio-filter column can remove total As from water that is polluted with As for a maximum of 1000 L volume.