Evidence of economic development revealed in centennial scale sedimentary records of organic pollutants in Huguangyan Marr Lake

Sedimentary records of polycyclic aromatic hydrocarbons (PAHs) and phthalates could reflect energy consumption and industrial production adjustment. However, there is limited knowledge about their effects on variations of PAH and phthalate compositions in the sediment core. The PAH and phthalate sedimentary records in Huguangyan Maar Lake in Guangdong, China were constructed, and random forest models were adopted to quantify the associated impact factors. Sums of sixteen PAH (∑₁₆ PAH) and seven phthalate (∑₇ PAE) concentrations in the sediment ranged from 28.8 to 1110 and 246–4290 μg/kg dry weight in 1900–2020. Proportions of 5–6 ring PAHs to the ∑₁₆ PAHs increased from 32.0 %–40.7 % in 1900–2020 with increased coal and petroleum consumption, especially after 1980. However, those of 2–3 ring PAHs decreased from 30.7 % to 23.6 % due to the biomass substitution with natural gas. The proportions of bis (2-ethylhexyl) phthalate to the ∑₇ PAEs decreased from 52.3 %–29.1 % in 1900–2020, while those of di-isobutyl phthalate increased (13.7 % to 42.3 %). The shift from traditional plasticizers to non-phthalates drove this transformation, though the primary plastic production is increasing. Our findings underscore the effectiveness of optimizing energy structures and updating chemical products in reducing organic pollution in aquatic environments.