Freely dissolved organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) along the Indus River Pakistan: spatial pattern and risk assessment

Legacy and new chlorinated persistent organic pollutants in the rivers of south India: Occurrences, sources, variations before and after the outbreak of the COVID-19 pandemic

“…It is to be noted that the current range of PCBs in surface water of south India has been found to be much higher than levels reported nearly a decade and a half back from the coastline of Chennai city along the Bay of Bengal, India (PCBs: 1.934–4.458 ng/L) ( Rajendran et al, 2005 ). However, the PCB levels were in line with the observation from River Chenab, Pakistan (Σ 24 PCBs:7.7–110 ng/L) ( Eqani et al, 2012 ) but several times higher than levels observed from the Himalayan Riverine Network (Σ 33 PCBs: 0.031–0.175 ng/L) ( Ullah et al, 2020 ) and Indus River, Pakistan (Σ 21 PCBs:0.003–0.2 ng/L) ( Sohail et al, 2022 ), Yangtze River Delta (Σ 38 PCBs:1.23–16.6 ng/L) ( Zhang et al, 2011 ), Yellow River (average Σ 33 PCB:0.2 ng/L) ( Chen et al, 2021 ) and Songhua River (Σ 43 PCBs:0.26–9.7 ng/L) ( You et al, 2011 ) in China and Hudson River Estuary, USA (average Σ 90 PCB:1.1 ng/L) ( Yan et al, 2008 ).

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“…Highest TEQ was observed at PR-02 (30.396 pgTEQ/L) due to the high contribution of the most toxic PCB congener, PCB−126. Excluding this outlier, the range of TEQ levels reported in this study seems to be comparable with Ravi, Indus and the Himalayan river network of Pakistan ( Baqar et al, 2018 , Sohail et al, 2022 , Ullah et al, 2020 ), River Songhua in China ( You et al, 2011 ) and River Udu, Nigeria ( Iniaghe and Kpomah, 2022 ) before the outbreak of the pandemic. Reduced TEQ values of CR during the COVID-19 pandemic were lower than Hooghly, Brahmaputra, and Yamuna rivers in India ( Chakraborty et al, 2016a , Kumar et al, 2012 ) and coastal Bangladesh ( Habibullah-Al-Mamun et al, 2019 ).…”

“…Tropical riverine ecosystems in developing economies are considered a conduit for POPs. Despite the ban on most of the legacy POPs, several studies from the recent past reported chlorinated POPs in surface water samples from major rivers in India such as Ganga ( Sharma et al, 2015 ), Brahmaputra and Hooghly ( Chakraborty et al, 2016a ), Chenab and Indus in Pakistan, ( Eqani et al, 2012 , Sohail et al, 2022 ), Yangtze, Pearl, Minjiang, and Jiulongjiang in China ( Han and Currell, 2017 ), Syr Darya in Kazakhstan ( Snow et al, 2020 ), Danube, Tisza, Begej and Krivaja in Serbia ( Škrbić et al, 2018 ), Pangani in Tanzania ( Hellar-Kihampa et al, 2013 ), Talar, Babolrood and Haraz in Iran ( Behrooz et al, 2020 ) and Volturno in Italy ( Montuori et al, 2020 ) indicated historical/on-going usage as the prevalent source in the riverine environment.…”

Gaseous and soil OCPs and PCBs along the Indus River, Pakistan: spatial patterns and air–soil gradients

“…The Gulibagh Swat and Gilgit sites in the FMZ exhibited the highest concentration of DDTs (50-343 ng g −1 ), which highlighted the current illegal application of these banned pesticides for crop protection (i.e., fruits and vegetables). 1,4,17 Another reason for the high DDT concentrations in the FMZ could be LRAT from the low altitude areas to these high altitude valleys. A possible justication of POP build-up levels in the soils of these colder areas is the very high temperature and low organic matter content in the low altitude arid/semi-arid areas, which emitted most of the OCPs through volatilization and short and long term dust transportation to colder areas where they deposited into organic matter rich soils for longer times.…”

“…A possible justication of POP build-up levels in the soils of these colder areas is the very high temperature and low organic matter content in the low altitude arid/semi-arid areas, which emitted most of the OCPs through volatilization and short and long term dust transportation to colder areas where they deposited into organic matter rich soils for longer times. 4,17,34 It is also worth mentioning that the high levels of various DDT metabolites, which indicated high transformation rates of DDT isomers into their metabolites, are due to the subtropical climatic conditions of Pakistan. Higher particulate OCP and PCB levels in urban areas might be due to rapid urbanization, and the existence of demolished DDT manufacturing units and pesticide stockpiles in the cities of Lahore, Nowshera and Islamabad, respectively.…”