Determination of Heavy Metals in Surface Water, Sediments and Planktons at the Junction of Multiple Rivers (Punjnad Headworks) and Their Impact on Human Health

: 28 This study was conducted to calculate the burden of heavy metals i.e., aluminium (Al), arsenic 29 (As), barium (Ba) and lead (Pb) in the river water of Punjnad Headworks, Bahawalpur, 30 Pakistan. For this purpose, samples were collected from surface water, bed sediments and 31 planktons during autumn, winter and spring seasons (September 2018 to May 2019). The 32 results showed that in surface water Pb concentration was highest (453.87 mg L -1 ), while in 33 sediments and plankton, Al concentration was highest (370.24 µg g -1 and 315.05 µg g -1 , 34 respectively). A significant difference ( p < 0.000) in metal concentrations was found among 35 surface water, bed sediments and plankton at different sampling stations during various 36 seasons. However, findings of this study showed no adverse effects of heavy metal 37 concentrations on human health. This study provided better understanding of various pollutants 38 and their concentrations in water sources at the studied location.

Abstract: 28 This study was conducted to calculate the burden of heavy metals i.e., aluminium (Al), arsenic 29 (As), barium (Ba) and lead (Pb) in the river water of Punjnad Headworks, Bahawalpur, 30 Pakistan. For this purpose, samples were collected from surface water, bed sediments and

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The higher discharge of numerous metallic compounds into the rivers of Pakistan has 101 adversely affected the freshwater ecosystem (Qadri and Faiq 2020). Being junction of multiple 102 rivers, Punjnad Headworks receives a variety of pollutants from different rivers. Major 103 pollutants include agricultural, domestic and industrial wastes from different cities e.g., 104 Gujarat, Faisalabad, Jhang, Multan etc., which drain out their waste from textile, dying, 105 petrochemical, hosiery, oil refineries, sugar and flour mills, distilleries, tannery industries, heavy metals contamination in a junction of different water sources, therefore, the current study 109 was designed to assess heavy metal concentration and to conduct multivariate relationships 110 among water, sediments and plankton for the flow of heavy metals at three different stations 111 of Punjnad headworks. Based on the results an assessment of the health risk to humans was 112 carried out using some risk assessment parameters.

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Study area 115 The Punjnad Headworks is located about 99 m above the sea level. The average annual rainfall, 116 average annual temperature and annual average relative humidity (%RH) were recorded as 3.56 117 mm, 29.49 ºC and 27.64%, respectively. Surface water, bed sediments and plankton samples 118 were collected from three different locations of Punjnad Headworks during three seasons 119 (autumn, winter, and spring). The sampling stations were visited monthly for the study period.

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Sample collection and processing 126 Water samples for heavy metals determination were collected from each study site in acid-127 washed polyethylene bottles. In the field, the bottles were rinsed several times with the 128 river water and 100 ml of water sample was then collected from 150 cm below the water 129 surface. After that, the water samples were acidified with concentrated hydrochloric acid   The plankton samples were collected by filtering nearly 100 ± 10 L of water using the 151 plankton net of 10 μm pore capacity and 30 cm in diameter. Sampled plankton was acidified 152 by using HCl and then transferred to the laboratory for analysis. Plankton samples were   Concentrations of As and other heavy metals including Pb, Al, and Ba were assayed using 183 AAS with the standard analytical protocol (Table 1)   Where Exping is the ingestion exposure from the sediment or water; C represents the 195 measured concentration in the sediment or water; IR is the ingestion rate (114 mg/day); CF 196 represents the unit conversion factor (10 -6 kg/mg); EF is the exposure frequency (350 197 days/year); ED represents the exposure duration (30 years); BW is the body weight (70 kg); AT represents the average day (10,950 days); Expderm is the dermal uptake; SA is the exposed 199 skin surface area (5700 cm 2 ); AF represents the adherence factor from sediment to the skin 200 (0.07 mg/cm 2 ); ABS is the dermal absorption from sediment (0.001 cm/h); ET is the exposure 201 time (assumed to be 2 h/day); KP is the dermal permeability coefficient (0.001 cm/h).

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Hazardous quotients (HQs) are used to assess the noncarcinogenic health risks Punjnad Headworks were much higher than the WHO and USEPA standards for the same 249 metals (Table 1). 250 Heavy metals levels in the bed sediments were in the orders of Al ˃ Pb ˃ As > Ba 251 (Table 2)  The concentration level (µg g -1 ) of different As and heavy metals in plankton were 265 studied in different seasons and at different sampling stations (Table 3). The trend of 266 accumulation of As and heavy metals in plankton were similar to the trend in sediments, so it 267 was found that the metals levels were Al ˃ Pb ˃ As ˃ Ba, respectively. Also, the highest and 268 lowest concentrations of metals in the fall were attributed to Al (349.06±5.92 µg g -1 ) and Ba

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(1.64±0.35µg g -1 ), respectively. The highest concentrations of As and Pb were at station 1, 270 while the lowest concentrations of these pollutants were at stations 2 and 3, respectively. An  We found a significant amount of heavy metals and As at different sampling sites (station I, 297 station II and station III) of the Punjnad headworks. A significant variations in the number of 298 metals were present at different sampling sites. This study concluded that the river water at this 299 location exhibited a significantly higher level of Pb followed by Al, Ba and As. The quality of 300 drinking water has been regarded as a major factor to influence human health. The The human health risk of Al, As, Ba and Pb were determined in the current study. The 370 human health risk assessment and HQ(ing/derm) values for As and Pb in water were higher than 371 1, indicating obvious health risk from these pollutants in water over a lifetime of exposure.

Consent for publication 417
Not applicable 418

Availability of data and material 419
Do not wish to share.  The different letters (a, b, and c) in the same row, show significant difference among stations (I, II, and III) for the same heavy metal and season (p < 0.05)

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The different letters (x, y, and z) in the same column, show significant difference among seasons (autumn, winter, and spring) for the same heavy metal and station (p < 0.05)

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The different letters (a, b, and c) in the same row, show significant difference among stations (I, II, and III) for the same heavy metal and season (p< 0.05)

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The different letters (x, y, and z) in the same column, show significant difference among seasons (autumn, winter, and spring) for the same heavy metal and station (p< 0.05)