A critical review on the separation of heavy metal(loid)s from the contaminated water using various agricultural wastes.

Wastewater contamination with heavy metal(loids)s has become a worldwide environmental and public health problem due to their toxic and non-degradable nature. Different methods and technologies have been applied for water/wastewater treatment to mitigate heavy metal(loid)-induced toxicity threat to humans. Among various treatment methods, adsorption is considered the most attractive method because of its high ability and efficiency to remove contaminants from wastewater. Agricultural waste-based adsorbents have gained great attention because of high efficiency to heavy metal(loids)s removal from contaminated water. Chemically modified biosorbents can significantly enhance the stability and adsorption ability of the sorbents. The two mathematical models of sorption, Freundlich and Langmuir isotherm models, have mostly been studied. In kinetic modeling, pseudo-second-order model proved better in most of the studies compared to pseudo-first-order model. The ion exchange and electrostatic attraction are the main mechanisms for adsorption of heavy metal(loid)s on biosorbents. The regeneration has allowed various biosorbents to be recycled and reused up to 4-5 time. Most effective eluents used for regeneration are dilute acids. For practical perspective, biosorbent removal efficiency has been elucidated using various types of wastewater and economic analysis studies. Economic analysis of adsorption process using agricultural waste-based biosorbents proved this approach cheaper compared to traditional commercial adsorbents, such as chemically activated carbon. The review also highlights key research gaps to advance the scope and application of waste peels for the remediation of heavy metal(loid)s-contaminated wastewater.

This review provides new information and insights on the potential utilization of agriculture-based biosorbents for the removal of contaminants, especially heavy metal(loid)s from toxic water/wastewater, as well as their mechanisms, adsorption efficiency, and regeneration ability. For practical perspective, biosorbent adsorption efficiency was elucidated by using various types of wastewater and economic analysis studies.

Environmental implications of phosphate-based fertilizer industrial waste and its management practices.

During the green revolution in the mid-twentieth century, the consumption of inorganic phosphorous and phosphate-based fertilizers (P-fertilizers) in the developing world skyrocketed, resulting in a proliferation of P-fertilizer industries. Phosphate-based fertilizer industries are ranked among the most environment-polluting industries. The worldwide phosphorus market, which was 68.5 million metric tons in 2020, is expected to increase at a compound annual growth rate (CAGR) of 2.5% to 81 million metric tons by 2027. The release of untreated hazardous pollutants from these fertilizer industries into the soil, water, and atmosphere has resulted in severe environmental health issues. Excessive surface runoff of phosphorus from agricultural fields and its deposition in water promote the growth of algae and macrophytes and lower dissolved oxygen concentration through eutrophication, which is detrimental to aquatic life. Fluorides (F-) and sulfur dioxide (SO2) and/or heavy metals (potentially toxic elements, PTEs) are also detected in the emissions from these fertilizer industries. The main solid waste generated from the phospho-gypsum plant produced up to 5 tons of di-hydrogen phosphate (H2PO4), including PTEs and radioactive substances. Phosphates and fluorenes from these industries are usually disposed of as sludge in storage ponds or trash piles. Humans inhaling poisonous gases released from the P-fertilizer industries can develop hepatic failure, autoimmune diseases, pulmonary disorders, and other health problems. The objectives of this review are to provide guidelines for eliminating the bottleneck pollutions that occur from the phosphate-based fertilizer industries and explore the management practices for its green development.

Arsenic concentrations in soil, water, and rice grains of rice-growing areas of Punjab, Pakistan: multivariate statistical analysis.

Arsenic (As), a class-A human carcinogen, is ubiquitously present in the earth's crust and soil and may enter the air, water, and surface environments through different natural and anthropogenic sources. In this experiment, soil, irrigation water, and rice grains were sampled from conventional rice-growing areas of Punjab, Pakistan. Soil samples were collected from 0 to 15 cm surface soil of rice growing fields, and rice grains were collected from the same field at crop maturity. Irrigation water samples were collected from the source used to irrigate the respective rice fields. Coordinates of sampling locations were noted using a global positioning system, and a locations map was made using ArcGIS. Soil samples were digested in a microwave digester using aqua regia, and plant samples were block digested using nitric acid. Arsenic concentration was determined using an inductively coupled plasma mass spectrometer coupled with an auto-sampler and integrated samples introduction system. The mean concentration of As in rice grains, soil, and water samples was found within the safe limit set by WHO except for a sample from Narowal (148.54 µg l-1) that exceeded the irrigation water standard limit, i.e., 100 µg l-1 for irrigation water. Principal component analysis was performed to reduce the multidimensional space of variables and samples. Through the calculations of estimated daily intake, it has been revealed that the As levels measured in this study would only contribute a small amount (less than 5%) of the total recommended daily intake allowance.

Biomagnification of potentially toxic elements in animals consuming fodder irrigated with sewage water.

Globally, sewage water is considered a cheap and effective alternative source of irrigation and nutrient supplement. For example, in Faisalabad, Pakistan untreated sewage water loaded with potentially toxic elements (PTEs) is being routinely used to grow fodder crops in the peri-urban areas, where PTEs accumulate at different trophic levels and contaminate the food chain. Trophic transfer, bioaccumulation, and biomagnification of hazardous metals in food chains had toxic implications for human health. Currently, the major concern is associated with the consumption of PTEs contaminated fodder by animals and the subsequent translocation into humans via consumption of milk and meat from these animals. This study thus analyzed the concentration of Cd, Cu, Pb and Zn in sewage water, sewage irrigated soil, fodder is grown on such soils and the milk of cows and buffalos to calculate the transfer through water and fodder to animal milk. Overall, concentrations and bioaccumulation factors of Cd and Cu in buffalo milk were higher than the cow milk, whereas it was inverse for the concentration of Zn. Non-significant difference in the bioaccumulation factor for Pb in both buffalo and cow milk was observed. Calculation of the estimated daily intake indicated that there was no health risk associated with the consumption of tested milk samples. However, given the widespread exposure of infants to milk, continuous monitoring of milk quality is recommended to preclude a child's exposure to elevated levels of PTEs.

Health risks from trace elements in muscles of some commonly available fish in Australia and India.

The levels of trace elements (As, Hg, Cr, Cd, Pb, Co, Ni, Cu, Mn and Zn) in commercially important fish species sampled from fish markets of Adelaide, Australia; canned fish from South Australian supermarkets; and fish markets of West Bengal, India were determined by inductively coupled plasma mass spectrometry (ICP-MS) after microwave digestion. Mercury was determined by using triple quadrupole ICP-MS. The accuracy of the methods was assessed with a certified standard reference material (NRCC-DORM-3 dogfish protein), and the results were compared with values reported in the literature. The results indicated considerable variations in the accumulation of trace elements among the fish species. The relationship between species with respect to trace element concentrations was examined using cluster analysis, which showed Indian fish species forming distinct groups from the others. Other than As in sardines, whiting and snapper and Hg in swordfish and snapper, the trace element concentrations were within permissible limits recommended by various standards. Based on the estimated daily intake (EDI), fish samples analysed in this study can be considered safe for human consumption as per the recommended daily dietary allowance limit fixed by various agencies. Continuous monitoring and assessments of fish metal(loid) content are needed to generate more data and safeguard human health.

Assessment of trace elements in urban topsoils of Rawalpindi-Pakistan: a principal component analysis approach.

Assessment of trace elements is inevitable to reduce stress on environment due to urbanization and industrialization. Rawalpindi, the fourth largest city of Pakistan, rapidly moving towards industrialization and has a large number of automobiles. In the present study, the urban area of Rawalpindi was divided into five parts: Gawal Mandi, Pir Wadhai, Soan Adda, Chah Sultan, and Central Ordinance Depot (COD), to determine distribution of trace elements. Soil samples were collected from 5 to 20 cm depth. After drying and sieving, samples were digested using di-acid (HNO3 and HClO4 at 2:1). Concentrations of heavy metals were determined using atomic absorption spectrophotometer (AAS). Principal component analysis (PCA) was performed to reduce multidimensional space of variables and samples. Observed mean concentrations of Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn were 164, 33.4, 295, 336, 634, 236, 1572, and 546 mg kg-1, respectively. Mean concentrations of all the heavy metals in urban area soil were higher than the WHO permissible limits. Correlation coefficient analysis showed positive correlation among Cd, Co, Cu, Ni, and Pb, whereas no obvious correlation for Cr and Mn was found with any other heavy metal. Zn was positively correlated with Co, Ni, and Mn, whereas negative correlation was found with Cr. Results showed that Pir Wadhai and COD were the most and least contaminated parts of the city, respectively, and this is attributed to the presence and absence of heavy traffic loads and industrial effluents. Graphical abstract ᅟ.