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Introduction
In this systematic review, we delve into the factors influencing the uptake of arsenic in the food chain, with a specific focus on its presence in rice. Arsenic (As) is naturally occurring and is present in various types of soil, water, and food. In most cases, arsenic is usually present in soils on which agriculture or farming is applicable because it is an essential element that facilitates vegetation growth to produce vegetables and fruits (Abdul et al., 2015).
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However, it is crucial to comprehend that arsenic in the soil must be present in limited amounts to ensure that the grown product is not contaminated with excessive arsenic, leading to arsenic poisoning (Li et al., 2016). Furthermore, even if the concentration of arsenic in the soil is low, farmers who add fertilizers to enhance the plant's growth must ensure that they add arsenic in low amounts to prevent arsenic poisoning (Jain and Chandramani, 2018). Lindsay and Maathuis (2017) explain that there are two forms of arsenic: organic and inorganic. The author further describes that organic arsenic is naturally occurring and is present in the soil, water, and air and during farming, the organic arsenic is absorbed in the crops as per their concentration in the soil. However, Rahman et al. (2018) shed light that the inorganic arsenic compound is considered detrimental to health.
According to Shrivastava et al. (2017), the absorption of arsenic and contamination of food like vegetables, fruits, and grains are one of the key causes of arsenic poisoning in major parts of the world where arsenic is not present naturally in drinking water. Shakoor et al. (2016) explain that due to the high toxicity of arsenic, leads to individuals suffering from high chronic and prolonged pain in their stomach, kidneys, and liver and leads to coronary heart diseases and diabetes. The International Agency for Research on Cancer (IARC) has categorized arsenic as a carcinogen because of its prolonged health effects on the skin, bladder, and lungs, leading to the formulation of cancer cells in the body (Ruíz-Huerta et al., 2017). According to an experiment conducted by Shi et al. (2016) to measure the levels of arsenic in rice, the researchers found that within the soil where the rice was being cultivated, arsenic was present in the soil, equating to 5.60mg/kg. This was because the water being used to irrigate the soil already contained toxic substances, which increased the levels of arsenic within the soil, thereby increasing its overall limit and being absorbed by crops in greater amounts (Hojsak et al., 2015). In the study of Davis et al. (2017), the researcher tested 223 rice samples to find out the concentration of arsenic in those rice. After testing all the samples, the researchers revealed that the highest concentration of arsenic was found in brown rice, followed by basmati brown, whole grain brown rice, and aromatic brown rice. The researchers further tested out brown rice by removing its hull and described that with the bran removed to produce white rice during the milling process, it contained 20 times more arsenic levels than normal (Davis et al., 2017). Additionally, a high risk is posed to those individuals who only consume ground food since ground food does not undergo an authentic purification process, owing to which much of the arsenic component is retained. Moreover, Implementing sustainable agricultural practices, such as cover cropping and organic matter incorporation, is essential for enhancing soil quality in rice cultivation, fostering improved fertility, water retention, and overall ecosystem health.
Research Rationale
There are many research articles and published data available reporting the uptake of arsenic in rice (Ma et al., 2016; Seyfferth et al., 2016; Suriyagoda, Dittert, and Lambers, 2018) and discuss the factors that contribute to the addition of arsenic in soil, water or air. Various studies discuss factors that impact arsenic uptake in rice and explain how each factor affects the uptake.
These studies also discuss the potential adverse health effects of ingesting rice containing high levels of arsenic, which leads to cancer development. Wang et al. (2016) describe that during arsenic stress, the production of reactive oxygen species is increased, leading to membrane damage in rice plants along with non-specific oxidation of proteins and lipid membranes and causing damage to the DNA. Furthermore, the study of Althobiti, Sadiq, and Beauchemin (2018) highlights that since rice is an efficient accumulator of silica as compared to other crop plants, the concentration of arsenic in the plant increases due to increased accumulation of silicic acid in the crop which leads to a higher concentration of arsenic exceeding the safe limit. In the study of Otero et al. (2016), the author describes that uncertainties can be noticed in experiments concerning the investigation of inorganic arsenic in rice, as pointed out by the FDA and the US Food and Drug Administration. The uncertainties are seen in the consumption level regarding the contamination of rice and rice products, along with the lower impact on the uncertainty of risk estimates, which is compared with the uncertainty linked with the dose-response relationship. The main factors that determine the increase of arsenic in soil and consequently in rice pertain to the location of where it was planted along with the methods that have been employed to process the rice and the overall plant physiology (Mishra, Mattusch, and Wennrich, 2017). Numerous studies have carried out different factors and different varieties of rice in different geographical locations to analyze the soil conditions that affect the uptake of rice. However, there is a gap in assessing the factors that affect the influence of uptake in rice. Hence, conducting a systematic review of arsenic in the food chain and the factors that influence the uptake in rice in this study allows the researcher to be knowledgeable of all the factors and review appropriate recommendations facilitating a reduction in arsenic levels in rice.
Aim and Objectives
This research aims to conduct a systematic review of arsenic in the food chain and identify the factors that influence the uptake of arsenic in rice. The objectives of this research are as follows:
To assess the challenges in the food chain due to the presence of arsenic
To analyze the role of arsenic in the contamination of soil
To evaluate the impact of arsenic in the food chain and identify the factors related to arsenic that influence the uptake in rice. To provide recommendations for reducing Arsenic in the food chain that influences the uptake of rice
Research Questions
The research questions of this research are as follows:
What are the challenges for the food chain due to the presence of arsenic?
What is the role of arsenic in the contamination of soil?
What are the impacts of arsenic in the food chain and the factors related to arsenic that influence the uptake in rice?
What recommendations can be provided to reduce arsenic in the food chain influencing the uptake of rice?
Research Structure
The structure of this research pertains to the execution of this research throughout five chapters, whereby chapter one introduces the research and background for a better understanding of this study. In this chapter, the aim and objectives of the study are developed and noted to ensure that subsequent chapters of the study conform to the objectives developed and are being fulfilled during the execution. The research problem has also been identified and described as why it was necessary to research the selected topic of the study.
Chapter two of this research consists of a literature review, whereby different studies will be reviewed for data collection, arguments will be developed, and facts and figures regarding arsenic in the food chain and the aspects that impact its uptake in rice. This chapter explains the different factors influencing the uptake of arsenic in rice and provides a theoretical framework as well.
Chapter three of this study conforms to providing an explanation and justification of the methodology that has been adopted for the successful execution of this research. It includes information regarding the research philosophy adopted, the research approach, the methods of data collection, and data analysis, and justifications are provided to depict why it was necessary to adopt a philosophy or research approach.
Chapter four includes the analysis of the data and their results and discussion. In this chapter, data collected with the method mentioned in chapter three is analyzed as per the method also mentioned. After the data analysis, the results are obtained and discussed based on the study's objectives.
Chapter 5 is the final chapter of this research and provides the researcher's conclusion and final thoughts on this research. The findings of the data that were analyzed are summarized, and appropriate recommendations are given to reduce the uptake of arsenic in rice.
CHAPTER 2: Literature Review
Learn from what others have written about Arsenic;
Introduction
Arsenic is one of the toxic metalloids for animals and plants as it is used in large amounts of food and soil. Arsenic is released into the arable soil through the use of contaminated irrigation water, some anthropogenic activities, and mining (Li et al., 2014). Moreover, in many countries, rice is one main food whose annual production is extremely high. As analyzed from the report of The United States Department of Agriculture in 2014, the production of rice was observed as 474.86 million tons by the major producers of the world, such as India, China, Bangladesh, and Vietnam (Bastías, and Beldarrain, 2016). As reported, some of these countries use groundwater contaminated with arsenic naturally present in the water, thus resulting in soil contamination with high levels of arsenic (Awasthi et al., 2017).
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Additionally, it has been observed that rice, because of the biochemical characteristics of agricultural soils, is known to be an efficient arsenic accumulator (Bastías and Beldarrain, 2016). It has been estimated that worldwide, more than 150 million people have been affected due to the increased concentrations of arsenic, as one of the routes to arsenic exposure in humans is Oral ingestion. Thereby, Li et al. (2014) analyzed and reported in their research that arsenic contamination is greatly visible in countries, especially those having huge populations such as China, India, Turkey, Columbia, Chile, and Argentina.
Moreover, the soil also can transport or absorb arsenic. The International Agency for Cancer Research Arsenic has reported that arsenite (AsIII) and arsenate (AsV) are determined carcinogenic agents (Bastías and Beldarrain, 2016). Therefore, increasing rice production also increases arsenic harm and has become an important concern for the scientific community (Bastías and Beldarrain, 2016). Furthermore, according to Azam, Sarker, and Naz (2016), the foods that are produced on soils are impacted by the mining activities of the Pb-Zn, and due to the uptake of arsenic, the mining activities related to these foods are determined to crucial for the health. A survey was taken, and the results showed that the concentration of arsenic in all the rice does not satisfy the national food standards, whereas the least arsenic is observed in the rice cultivators “SY-89” and “DY-162” (Li et al., 2014). Additionally, it has been analyzed that the arsenic accumulation within rice plants is strongly related to the properties of soil, such as phosphorous, silicon, pH, organic matter, and clay ((Awasthi et al., 2017; Bastías and Beldarrain, 2016).
This chapter of the research has assessed the critical literature review of the previous studies to analyze their results related to the arsenic in the food chain and the factors associated with arsenic that influence the uptake of rice. Further, it also presents the impact of arsenic on the food chain, followed by a literature gap and an important point to be concluded in the chapter summary.
Theoretical Framework
Florence Nightingale developed this theory and described the methods to increase the well-being of individuals and enhance their health. The use of this theory aids in this research because a systematic review is being conducted to evaluate the factors that influence the uptake of arsenic in rice, and since arsenic is considered toxic and promotes the development of cancer cells in the body, this theory would allow understanding the methods to ensure the reduction of arsenic in rice. The environmental theory describes the act of utilizing the resources of an environment to enhance the health of the individual (de Florence Nightingale and Crítica, 2015). Utilizing natural resources to promote the well-being of a person would allow for an enhanced recovery process; however, Pirani (2016) highlights that many factors affect the natural resources of the environment, polluting them and consequently reducing the effectiveness of these resources in facilitating the health of the individual. The theory further describes the environmental factors that promote an individual’s health, including the intake of fresh environmental air. Clean and fresh environmental air would allow people to inhale an increased amount of clean oxygen, which is free from any carcinogenic elements, thereby increasing the efficiency of their lungs and the purity of their blood (Mughal and Irshad Ali, 2017). By drinking pure and clean water, an individual's internal organs will always remain healthy since the body does not need to extract all the poisonous material being ingested (Kamau, 2015). Cleanliness of the environment: the overall cleanliness of the environment allows for the reduction of diseases developed in that environment, which would affect the person's health.
Assessing the Water Quality and Mineral Footprint
Since it has been stated that arsenic is a compound that can be found in soil, water, and air, the nightingale theory allows for a better understanding of the adverse health effects of arsenic in the food chain. The theory helps comprehend the adverse effects on health effects by ensuring that one realizes that arsenic consumption needs to be controlled or it can lead to significant adverse effects on health. This allows for the development of appropriate recommendations where different methods and procedures can be employed to provide people with clean water, clean air, and safe amounts of arsenic ingestion into the body.
The theory of National Planning policy framework describes that it is impossible to eliminate pollution that is emanating from a process. Smith (2018) highlights that no process in the world produces no waste products, thereby not harming the environment. With the aid of this theory, an extensive understanding of the processes can be done to determine the processes that retain arsenic compounds in the food chain. Since arsenic is a toxic compound and higher levels of arsenic are poisonous, it is important to note that the process employed during the extraction of rice retains much of the arsenic within the rice, which results in it being unsafe for consumption. According to this theory, people need to identify the sources of pollution and research methods to reduce the levels of pollution contaminating their daily consumable products and damaging their environment (Rowe et al., 2016). Furthermore, all consumable goods need to have well-defined property rights, which allow for the safe trading of these goods and are safe for consumption as well. Without having such rights, it is possible that goods being traded may not be at par with safety standards of consumption and can affect the well-being of the individual who consumes such products (Åström, 2017). Hu and McKitrick (2016) explain that with the use of the theory of pollution policy, the sources or processes which produce the highest waste or contaminate food sources and the environment can be identified along with other factors of influence as well and can allow individuals to work on processes that reduces as much pollution as possible. However, de Vries and Hanley (2016) have pointed out that in some cases, this theory can be difficult to implement because it is difficult to measure, and the damage is done to the environment by certain sources. Furthermore, it is also difficult to monitor and enforce pollution policies in certain areas and difficult to add taxes on pollution considering the political and financial costs. Pope III et al. (2015) shed light that market-based instruments provide some level of flexibility to polluters in the sense that regarding agriculture, a certain amount of toxic substance within the product has been indicated, and the products should not cross the specified limit. Ebenstein et al. (2017) depict that adopting a command and control approach allows an enhanced level of control regarding the pollution of consumable products by inducing a specific limit. Consumable goods being transported to different areas provide a classic example that allows the government to control the level of pollution or the level of toxic substances in the products and enables them to have full control. Failing to comply with the safe levels of toxic substances in the products allows the stakeholders to destroy the products or resend them to reduce their toxicity levels for safe consumption (Mohai and Saha, 2015).
Arsenic in the Food Chain
In the food chain, arsenic is considered to be of high severity. Bakhat et al. (2017) have stated that food is the easiest form of ingesting arsenic. The author further states that the Joint FAO/WHO Expert Committee on Food Additives (JECFA) studied arsenic consumption through food. The meeting resulted in the committee eradicating the Provisional maximum Tolerable Weekly Intake (PTWI) perimeter for ingesting 15mg/kg of body weight (BW) arsenic.
Zia et al. (2017) assert that arsenic enters the food chain through irrigation water, which is usually contaminated. The author further states that groundwater is the main cause of drinking water in numerous countries, which is usually mixed with groundwater.
| Country | Area sq. mile | Population | Proportion of groundwater |
| Denmark | 16,639 | 5,450,661 | 98% |
| Hungary | 35,919 | 9,981,334 | 95% |
| Portugal | 35,672 | 10,605,870 | 80% |
| Switzerland | 15,942 | 7,523,934 | 83% |
| UK | 94,525 | 60,609,153 | 28% |
| Spain | 194,896 | 40,397,842 | 21% |
| Netherlands | 16,033 | 16,491,461 | 68% |
| Bangladesh | 55,589 | 147,356,352 | 90% |
| Finland | 130,558 | 5,231,372 | 37% |
| France | 211,208 | 60,876,136 | 56% |
| Greece | 50,942 | 10,688,058 | 50% |
| Italy | 116,305 | 58,133,509 | 80% |
| Germany | 137,846 | 82,422,299 | 72% |
| Norway | 125,181 | 4,610,820 | 13% |
| Czech Republic | 30,450 | 10,235,455 | 43% |
Table 1 - Groundwater used by countries (Zia et al., 2017)
From Table 1, it can be seen that around one-third of the world’s population makes use of groundwater for drinking purposes. The World Health Organization (WHO) guideline strictly states that the maximum consumable threshold of arsenic in drinking water is 10 µg/L. However, Kumarathilaka et al. (2018) believe that numerous developing countries use 50 µg/L of arsenic in their drinking water as a standard. This is relevant to the food chain because it shows how people consume arsenic for drinking.
Dietary arsenic intake is also an aspect that must be considered in the food chain. Majumdar, Kumar, and Bose (2020) assert that dietary arsenic is most of the population's main basis of arsenic exposure. People who are high consumers of fish would consume a high quantity of arsenic of organic arsenic from this specific food group. Data related to the absorption of total arsenic show that arsenic in foods is mainly a combination of inorganic species and oranosenicals comprising arsenobetaine (Punshon et al., 2017). The factual total arsenic absorptions in different foodstuffs vary from to nation, depending on the food type, the rising conditions surrounding it (which are a type of soil, water, geochemical activity, using arsenical pesticides), and the processing methods.
| Country | Sampling method/ Other info | Arsenic intake (µg/kg BW per day) | |
| Total | Inorganic | ||
| Bangladesh | Average food intake without water | 3.01 | 0.88 |
| Five scenarios (including water) | 2.68-5.07 | - | |
| Small community without water | - | 1.68-3.00 | |
| India | Urine Analysis in arsenic-contaminated areas (DD) | - | 3.32-12.9 |
| China | Total Dissolved Solids (including water) | - | 0.24-0.76 |
| China (Taiwan) | Small community without water (adult) | - | 0.91 |
| Japan | Total Dissolved Solids, including water (Adult) | - | 0.36-0.46 |
| Europe | Adult (European Food Safety Authority) | - | 0.21-0.61 |
| Canada | Total Dissolved Solids (All without water) | - | 0.29 |
| USA | TDA (adult, water included in some studies | - | 0.08-0.20 |
| 1-6 years | - | 0.12-0.32 | |
| Infant<12 months | - | 0.24-1.19 | |
| Australia | >17years (MB) not per Kg BW | 41 | - |
| 13-16 years | 37 | - | |
| 6-12 years | 25 | - | |
| 2-5 years | 25 | - | |
| 9 months | 8.8 | - |
Table 2 - Dietary Intake (Azam, Sarker, and Naz, 2016)
From the figure above, it can be seen that there are variations in dietary intake of the total arsenic in adults, which imitates mainly the inconsistency in the consumption forms of arsenic-rich food groups (fish, shellfish, and meats) (Azam, Sarker and Naz, 2016). Moreover, it confirms regional differences in arsenic intake that occur when human health is assessed for any effects of arsenic.
Mukherjee et al. (2017) believe that arsenic-contaminated water's abrupt and long-term influence on irrigating paddy soils is the root through which arsenic transmits from water to the soil and eventually into the food chain. The people and government must control this alarming situation at all levels. Bastías and Beldarrain (2016) state that soil arsenic level is usually increased by 1 µg/g per annum due to the constant use of irrigation with arsenic-contaminated water. This notion was further supported by Kwon, Nejad, and Jung (2017), who mentioned in their study that irrigation water that is rich in arsenic could increase the levels of arsenic in agricultural soil up to five times. Although arsenic is not a crucial element for plants and animals, it plays a vital role in food crops' growth factor. In their study, Suriyagoda, Dittert, and Lambers (2018) state that food crops, which are vegetables and cereals, become the path through which arsenic enters the food chain. However, a key aspect to note here is that for fishes, the phytoplanktons are the cause through which fishes can consume arsenic and make their way to the food chain. The author further states that the food crops reflect the levels of arsenic existing in the environment, in which they have been cultivated through soil and irrigation water. This is the point where the build-up of arsenic in rice field soil and its role in the food chain through uptake by the rice plant is seen as a key issue.
Role of Arsenic in Contamination of Soil
Arsenic is seen as a universal chemical element in the biosphere that transpires naturally in both inorganic and organic forms. Awasthi et al. (2017) are of the view that the significant inorganic arsenic composites are sodium arsenite, arsenic trioxide, arsenic acid and arsenates, arsenic trichloride, and arsenic pentoxide (which are lead and calcium arsenates). The author further states that organic arsenic compounds are methylmalonic acid, dimethylarsinic acid, arsanilic acid, and arsenobetaine (AB). AB is seen as the leading organoarsenic in marine biota. Afzal, Hussain, and Farooqi (2018) mention other organoarsenicals, which comprise arsenocholine, dimethloxyarsylethanol, trimethylammonium lactate, arsenic, which comprises sugars, and phospholipids, which are found in fish. The author further states that arsenites and arsenates are available in water, even though methylmalonic and dimethylarsinic acids are at low stages.
Factors Related to Arsenic that Influences the Uptake in Rice
Zecchin et al. (2017) assert that numerous factors expose rice plants to arsenic. The author further states that rice plants accumulate arsenic, which naturally exists in the soil or is added through groundwater irrigation or contaminated soil additives, as seen in the figure below.
Groundwater Irrigation - (Bakhat et al., 2019)
Bakhat et al. (2019) are of the view that combined evidence proves that high rice product nations, which are India, Bangladesh, Taiwan, and China, tend to exceed the usual absorption of arsenic in soil (10.0 mg/kg) and the extreme standard allowed by the United States Environmental Protection Agency which is 20.0mg/kg as shown in the figure below.
| Region/Country | Agricultural soil (mg arsenic/kg) | Groundwater (µg arsenic/L) |
| Bangladesh | 3.1-42.5 | >50 |
| Bangladesh | 10-70 | 130 |
| Bangladesh | 4-138 | - |
| India | 5.70-9.71 | 318-643 |
| China | 1.29-25.28 | - |
| Taiwan | 11.8-112 | - |
| Taiwan | 67-438 | - |
| 6-12 years | 25 | |
| 2-5 years | 25 | |
| 9 months | 8.8 |
Table 3 - Arsenic Concentration
In China and Taiwan, the organic arsenic composite roxarsone exists in poultry brood, which is usually utilized as a fertilizer for rice at sea-level rise and immersed by the plants. Chatterjee, Sharma, and Gupta (2017) believe that the rice grain yield is decreased by arsenic absorption of the soil where the limit of the roxarsone/kg soil which killed rice plant was 200mg. It can be seen clearly that the arsenic absorption in the rice grain surpassed the statutory acceptable limit that has been set by the WHO (Wang et al., 2020).
Costa et al. (2016) assert that rice plants uptake arsenic largely in arsenic III, arsenic V, dimethylarsinic acid (DMA), and monomethyl arsenic acid (MMA) types via the roots. Of these elements, arsenic III is considered to be the major type. The author further states that after accumulation, different forms of arsenic species do not change throughout translocation to diverse plant parts, mainly shooting, root, and grain. Arsenic III and DMA are the main species that were noticed in the United States rice (Boye, Lezama-Pacheco, and Fendorf, 2017).
He et al. (2020) believe that agricultural condiments, such as fertilizers, desiccants, and pesticides, are the key causes of arsenic in the soil. The author further states that low stages of arsenic in nitrogen and potassium fertilizers, along with lime, also play a significant role in the uptake of rice. The possible arsenic accumulation level, which is increased in soils, is mainly due to the repeated application of arsenic that comprises fertilizers. Ma et al. (2017) assert that sources of drinking and irrigation water pollution from Concentrated Animal Feeding Operations (CAFOs) comprise absolute expulsions, open feedlots, action and stowage lagoons, land usage of compost to the fields, and manure stocks. The CAFOs from the animals’ wastes can cause arsenic pollution in different parts of the world due to the extensive use of feed additives with organoarsenic.
The bioavailability of arsenic present in the soil is another factor that influences the arsenic uptake of rice. Bakhat et al. (2017) believe that arsenic's origin and type of bioavailability can vary significantly. The author further states that the water-soluble arsenic level is more efficiently connected with the arsenic substance in the plant than in the soil. The parameters of soil possibly affect arsenic accumulation in rice: arsenic content, soil texture, plant-available silicon, plant-available phosphorous, and absorption of poorly crystalline iron-(hydro)oxides.
Du et al. (2019) focus on the soil properties and components that influence the solubility of arsenic and its toxicity. The organic carbon content, pH, ionic robustness of the soil solution, cation conversation capacity, and iron oxides are the vital aspects that affect arsenic availability in soils. Pokhrel et al. (2020) mention in their study that soil environments can differ from one site to another. This means that the phytoavailability of nutrients and contaminants can differ via the rhizosphere. It should be noted here that the influence of limits, which are iron, manganese, phosphorous, organic matter contents, pH value, the occurrence of microorganisms, and flood, tends to clarify the arsenic concentrations in the soil of the rice plants (Di et al., 2019).
Impact of Arsenic in the Food Chain: Factors Influencing the Uptake in Rice
The factors affecting iron absorption in rice are paramount and encompass several key elements to be analyzed within a presentation. These factors include the influence of manganese and iron levels, the impact of pH, the role of phosphate, the contribution of microorganisms, the presence of organic substances, and the consequences of flooding.
1. Effect of Manganese and Iron
Bakhat et al. (2017) state in their study that manganese and iron precipitate as iron and manganese oxides in a toxic atmosphere. The author further states that there is a rising similarity between iron and manganese oxides and arsenic, along with residue redox. The firmness of iron and iron (hydro)oxides mainly depends on the pH of the deposit (Awasthi et al., 2017). Afzal, Hussain, and Farooqi (2018) believe that iron transpires in soluble procedures in an acidic atmosphere. In a non-aligned power of hydrogen (pH), the iron can persist in a solution that has low redox or is considered to be a soluble organic compound in oxic soils. Zia et al. (2017) believe that iron and manganese (hydro)oxides decrease the arsenic flexibility in deep soil horizons. This leads to iron acting as a vigorous purpose in the arsenic circulation on the rice field. The mobility of arsenic takes place through adsorption on iron oxides, which substitutes the surface hydroxyl groups with arsenic ions, and through the creation of unsolvable secondary oxidation minerals and shapeless iron III arsenates (Kumarathilaka et al., 2018).
Majumdar, Kumar, and Bose (2020) have explored the rice stowage factor by investigating the spatial distribution of arsenic absorption in soil, irrigation water, and rice plants within a tube-well command area, with a particular focus on its relationship with iron and manganese levels, as indicated in various studies. In this context, the concentration of arsenic in water typically ranges from 68 to 136 µg/L in 110m extensive irrigation channels, with variations observed as one moves closer to the shallow tube-well point (Punshon et al., 2017). Notably, there is a decreasing trend in iron concentrations. Furthermore, concerning soil arsenic, its concentration exhibits a declining gradient as one moves away from the tube well pump, and there is a positive correlation between soil arsenic levels and the arsenic content in rice grains.
2. Influence of PH
Azam, Sarker, and Naz (2016) state that the pH of the soil contributes to the activity of flexibility and bioavailability of arsenic. The author further states that arsenic has elevated similarity for oxide surfaces. The specificity of arsenic immersion of specific soil elements is affected by the pH and pH depending on the organic matter, soil texture, and the nature and parts of minerals (Mukherjee et al., 2017). Compared with other elements, which can be cadmium and zinc, the low pH of the extractant is held responsible for having low extractability of arsenic.
Bastías and Beldarrain (2016) focus on the bauxite residue (red mud) as the fine fraction excess once the arsenic extraction from the bauxite occurs through the Bayer process. The author further states that the remobilization of red mud-related arsenic V is known to be extremely pH-reliant, and the accumulation of phosphate in red mud suspensions is linked to arsenic discharge for the solution.
3. Effects of Phosphate
Kwon, Nejad, and Jung (2017) believe that under aerobic environments, arsenic V is known to be the key type of arsenic in soils and views with the nutrient phosphorous of plants in the form of phosphate (PV). The author further states that this aspect is not only for sorption sites on mineral sides in soil but is also applicable for root membrane transporters. Moreover, the arsenic V and PV allocate the comparable transport pathway in rice roots by inhibiting rice plants' high-similarity arsenic V/PV accretion system. This rapidly reduces to arsenic III (Suriyagoda, Dittert, and Lambers, 2018).
4. Microorganisms
Zecchin et al. (2017) assert that research shows that arbuscular mycorrhizal fungi (AMF) can upsurge the arsenic lenience in plants. The author further states that AMF is known to reduce the proportions of inorganic and organic arsenic in rice grains. The rice injected with AMF under aerobic soils can expand the soil nutrients, which are nitrogen and phosphate. Moreover, it also helps with the growth factors, affecting the arsenic translocation to the root system. Bakhat et al. (2019) state that the effects of AMF (which are glomus georporum and G. intraradices) on arsenic by lowland (Guangyinzhan) and upland rice were assessed in the soil. The result of this experiment was that there was a spike with and without 60mg arsenic/kg. The author further states that in arsenic-contaminated soil, Guanghizhanincoluated with G. intraradices or Handao 502 inoculated with G. georporum, which improved the acceptance of arsenic elements. There were also the AMF/rice mixtures, which had a striking (p<.05) role in grain arsenic absorption (Chatterjee, Sharma, and Gupta, 2017). The link between rice cultivars and mycorrhizal inoculation had significant outcomes on root biomass (p<.001), straw (p<.0001), grain yield (p<.001), grain arsenic concentration (p<.0001), root, straw, and grain arsenic uptake (p<.05) showing that arsenic uptake can be restricted through the rice/AMF mixtures.
5. Organic Substances
Wang et al. (2020) believe that organic material is a complicated matter of practical organic acids, which is attained from the decay of water and terrestrial plants and animals. The author additionally adds that organic matter is robustly linked to arsenic adsorption, which depends on numerous factors of redox capability, pH, arsenic absorption, and speciation, along with complexing ligands and opposing ions, aquifer mineralogical properties, and reaction kinetics.
6. Flooding
Costa et al. (2016) mention that flooding is the main factor in arsenic uptake in rice plants. The author further states that extensive repetition of rice farming comprises endless flooding in the irrigated land. This leads to soil decreasing during cultivation, which leads to an increase in the bioavailability of arsenic in the soils. The result is the accretion of arsenic in rice grains. Boye, Lezama-Pacheco, and Fendorf (2017) state that under the flood and aerobic environments, the dynamics of arsenic speciation in the soil solution and association arsenic build-up in rice gain and shoot in a greenhouse were analyzed. The result attained by the authors was that flooding caused a rapid mobilization of arsenic, mainly arsenic III, in the soil solution. Moreover, in the active rice growth period, which is 12 to 97 days, the arsenic absorption in the soil solution was seen to be 4-13 times greater under the flooded condition (He et al., 2020). It is important to note here that arsenic concentration changes according to the conditions that are present in the soil, causing the rice plants to react accordingly in the flooded condition. There is a need for further analysis in this area that the authors have not studied.
Literature Gap
In this study, the literature review carried out focused on the factors that are related to arsenic in influencing the uptake in rice, along with analyzing their impact on the uptake in rice. These factors are mainly the irrigated contaminated water, as well as the soil that is used for the rice plants. The bioavailability of arsenic present in the soil is another area that has been analyzed in the literature review, specifically focusing on the effects of manganese and iron, the influence of pH, and the effects of phosphate, microorganisms, and organic substances. The researcher has analyzed how arsenic impacts the soil content, which affects the rice plants. However, the literature gap exists in a few areas that would be analyzed in this study. The first literature gap is that the study will focus on identifying those issues that specifically impact the uptake of rice. The second literature gap will focus on observing and evaluating the effect of arsenic in the uptake of rice that can assist in linking the gap existing between society and the scientific public regarding environmental health hazards, along with managing exposure to arsenic. The third literature gap exists in the research related to doubts in the study of inorganic arsenic in rice, along with observing the effect of arsenic on crops due to the level of arsenic growing from time to time. The researcher will focus on fulfilling the literature gaps that have been identified and provide complete research for the future purpose of other analysts.
Chapter Summary
To summarize this chapter, the developed theoretical framework comprises Nightingale’s Environmental Theory and the Theory of Pollution Policy. The employment of both of these theories for the execution of this research allows the researcher to know the various processes and sources that increase the level of arsenic and determine the basic source from which an increased amount of arsenic is being added to the soil, water, and air. Both theories provide concepts that are employed to reduce the levels of arsenic uptake in rice. Furthermore, to reduce the levels of arsenic in soil, the water that is being used to irrigate the crops must be clean and pure since higher levels of arsenic in water also increase the uptake of arsenic in rice, which then leads to arsenic poisoning in the individual who consumes rice with higher levels of arsenic.
Numerous developing countries, such as Bangladesh, Taiwan, and China, use high concentrations of arsenic despite strict limitations set by the WHO and US food authorities to keep arsenic levels limited in food usage. Various factors are related to arsenic in influencing the uptake of rice, which also leads to having an impact on the food chain, eventually causing an influence on the uptake of rice. These factors are mainly the irrigated contaminated water and the soil elements that significantly influence the rice plants. The impact of factors has been analyzed in light of the effects of manganese and iron, the influence of pH, the effects of phosphate, microorganisms, organic substances, and flooding. Each factor is vital in affecting the rice plants with a high concentration of organic arsenic available in each condition.
CHAPTER 3: Research Methodology
In this chapter of the research, there is a detailed analysis of the methods used to identify and process the related information for the study.
Introduction
Research methodologies are the specific procedures that are essential to analyze the research objectives and yield an effective result. Therefore, this chapter presents the selected tools appropriate for the study the research design, research philosophy, research approach, and the method for data collection and analysis. Later, it assesses the research limitations and ethical considerations that were put into consideration while conducting this research.
Research Philosophy
According to Pham (2018), the research philosophy is an important part while carrying out any research which is classified into three major categories namely positivism, interpretivism, and realism. Moreover, these approaches are essential as they make the researchers able to decide the appropriate research approach derived for the research questions (Antwi and Hamza, 2015). Positivism is an approach for quantitative studies in which a hypothesis is developed, realism analyses the experience by our senses whereas interpretivism emphasizes the interpretation of research from multiple perspectives used for the qualitative research (Mack, 2010).
Therefore, in this research interpretive philosophy was used to focus on the meaning and reflect the different aspects of the topic selected for the study i.e. arsenic in the food chain. The interpretive research philosophy was selected for this research as in the words of (Antwi and Hamza (2015), the philosophy is rooted in the understanding of knowledge through facts related to human behavior. Additionally, this philosophy by adopting the realist ontology provides multiple interpretations with a deeper level of understanding and gain of information through the evaluation of complexity from its unique context (Antwi and Hamza, 2015). Interpretivist research philosophy was beneficial for this research since it provides reliable information through qualitative research and explanation of the topic to a certain extent that provides a high level of validity and multiple viewpoints for the critical analysis (Pham, 2018).
Research Design
Research design is broadly classified into quantitative and qualitative methods and the selection of methods depends upon the underlying research philosophy. Quantitative research methods produce data that is always numerical to determine the impact through surveys or observational research (Jason and Glenwick, 2016; Silverman, 2016). Whereas, qualitative research methods investigate the research question through a rich and in-depth analysis particularly useful for the exploration of the “WHY” question (Hennink, Hutter, and Bailey, 2020). Therefore, in this research, a qualitative method was implied to assess the data through secondary sources such as Academic Info, Google Scholar, I seek Education, etc. The method was effective for the research to determine the different factors related to Arsenic and their impact on the food chain industry.
Moreover, according to Pathak, Jena, and Kalra (2013), qualitative research is known to be multi-method as it focuses on the naturalistic and interpretive approach to data analysis. Researchers apply this method as it is extremely creative for the wide disclosure of the research topic such as the empirical analysis from the findings of the multiple literature studies (Jason and Glenwick, 2016; Silverman, 2016). Additionally, events and factors through this method are understood more adequately as seen in several contexts, also it is less time-consuming and cost-effective in which the observer needs to analyze the existing data by an understanding an idealistic or humanistic approach (Antwi and Hamza, 2015).
Research Approach
The two approaches of reasoning used by the researchers are inductive and deductive (Soiferman, 2010). The deductive approach begins from the general points and moves towards specifications, the arguments here are based on the rules, laws, or principles that are accepted widely. Whereas, the inductive method of reasoning moves from specific to general and the arguments here depend upon observation and experiences (Soiferman, 2010). Deductive is a top-down approach however inductive is a bottom-up approach as this research has been conducted through a qualitative method, therefore, the approach selected for the study was inductive in which themes are broadly interconnected to generate a theory for the aim of the research (Zalaghi and Khazaei, 2016).
Inductive reasoning was beneficial for the research as it detects patterns and explores the research questions in a more open-ended way which especially at the beginning of the research is helpful for the broad exploration of the topic (Armat et al., 2018). Furthermore, the learners are benefited from this approach as it involves learning through rules of generalization and becomes more interesting when the topic is viewed from the different experiences (Soiferman, 2010). The biggest advantage is that by the use of inductive reasoning the researcher gets to work with the various probabilities and an idea regarding the research is developed at the starting point which provides a better understanding of the topic (Zalaghi and Khazaei, 2016). In this study, the inductive approach was used.
Data Collection Method
The data in this research was collected through secondary sources which are readily available and collected from various sources. Moreover, secondary data was used in this research as according to Trinh (2018), this type of data is obtained more quickly and it is also economical which saves expenses as well as extra effort. In this study, the data was collected from the previously published studies on arsenic in the food chain and the factors influencing the uptake in rice. Additionally, the resources from the Cochrane database of systematic reviews comprised literature from the National Health Service, National Library of Medicine, Science Direct, PubMed, Central, etc.
Moreover, as stated by Johnston (2017) secondary data is effective as it helps to make the collection of primary data more specific such that it enables the researcher to find out the literature gap and other deficiencies in the existing literature to improve the understanding of the research problem. Therefore, it was selected for this research to evaluate the current data and compare the existing literature and their results (Johnston, 2017). In addition, since the data collected through primary sources is already stored in the electronic format the researcher gets more time to analyze the data instead of making it ready for their research. Secondary data also offers a level of expertise and professionalism with the exploration of the current changes and trends over time within the research topic (Trinh, 2018).
Data Analysis
The data in this research has analyzed through the tool of content analysis which was beneficial for the evaluation of certain themes, words, or concepts from the data collected through secondary sources (Vaismoradi et al., 2016). Moreover, with the use of content analysis researchers can analyze the meanings, relationships, and the influence of the factors determined during the data collection for the research. Content analysis was extremely useful for this research as it provided valuable insights through the analysis of results of the previous studies (Vaismoradi et al., 2016).
Additionally, it also allows the researcher to study human thoughts and analyze the complex thought related to the research aims by providing several pieces of evidence from multiple perspectives (Erlingsson and Brysiewicz, 2017). Content analysis is a tool for transparent research, by the use of this method the researcher can follow up the study in feasible ways and set out the results examined for the research purpose. Furthermore, content analysis allows a certain amount of longitudinal analysis and involves no reactivity which allows the information to be studied from various contexts (Erlingsson and Brysiewicz, 2017).
Ethical Consideration
Ethical considerations are specified as one of the essential parts while the research is carried out. The research has ensured the follow-up of all the principles and rules during the execution of the study according to the ethical considerations for the secondary data collection. All the data that has been employed for the research has been cited properly with the name and year of the research, also proper referencing has been done in which the respective authors were credited for their work by the style of referencing suggested by the school. Additionally, the results of the multiple types of research are mentioned as identified by the authors of the studies accurately.
Research Limitations
The research was limited to qualitative research as the data was collected only from secondary sources. Additionally, the research has evaluated the multiple perspectives of the researcher through previously published articles. The study was limited to the analysis of Arsenic only and its influence on the uptake of rice, whereas it could be explored in several food chains other than rice.
Chapter Summary
This chapter has analyzed the research method and approach used for this study to explore the impact of arsenic in food chains and the factors related to Arsenic that influence the uptake in rice. The research philosophy that was used in this study was interpretivism which was effective here as it analyzed the data collected through secondary sources. Moreover, the qualitative research method was used by collecting the data through published research articles and official websites of the health and food sectors. Further, the data collected was analyzed through the tool of content analysis to explore the themes in the research. Lastly, the ethical considerations while conducting the study were discussed followed by research limitations.
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