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The three most representative areas of petroleum pollution on the Loess Plateau are the research subjects of this study. In this study, 16 priority polycyclic aromatic hydrocarbons (PAHs) were determined by the QuEChERS method combined with gas chromatography-tandem mass spectrometry (GC-MS/MS). The total concentrations of ∑16PAHs in top layer soils (0–10 cm), middle layer soils (10–30 cm), and bottom layer soils (30–50 cm) ranged from 1010.67 to 18,068.80, 495.85 to 9868.56 and 213.16 to 12,552.53 μg/kg, with an average of 5502.44, 2296.94 and 2203.88 μg/kg, respectively. The 3-ring and 4-ring PAHs were the most prominent components in all soil samples. Meanwhile, the average value of ∑16PAHs decreased with the depth, from 5502.44 μg/kg (0–10 cm) to 2203.88 μg/kg (30–50 cm). The PAHs levels in the studied soils were heavily polluted (over 1000 μg/kg) according to the Soils Quality Guidelines and 95% of PAHs come from petroleum sources. Moreover, the total of PAHs in petroleum-contaminated soils was assigned a high ecological risk level. Toxic equivalency quantities (TEQs) indicated that PAHs in petroleum-contaminated soils presented relatively high toxicity.

Waste pickers (WPs) play an indispensable role by helping to control municipal solid waste (MSW). However, they constitute the entry-level workforce of the waste recycling industry and receive little attention from the general public. In China, approximately 4 million WPs make their living by collecting MSW recyclable materials. To assess the role of WPs, an extensive social survey including urban management decision-makers, recycling industrial circle insiders, WPs, as well as common citizen respondents has been conducted in the city of Nanjing, China. The results confirmed that 70-80% of recyclable MSW materials were collected by WPs in the informal sector, which are an integral component of the waste recycling system. In Nanjing, the recyclable material collected annually by WPs is about 505,000 tons, which creates annual economic value of about 78.6-84.7 million USD. However, WPs account for only 6.8-7.3% of the entire industrial chain of the recycling economy. In Nanjing, WPs are able to save an annual MSW disposal cost of about 17.6-22.0 million USD. The resource recovery rate is also increased by 1.9-8.0%. The survey results support the experience of establishing a community-based semi-official picker organizational framework, accompanied by relevant laws, regulations, and preferential policies that would improve the resource recovery rate and pickers' living and working conditions in order to achieve more effective and hazard-free MSW resource utilization. It is anticipated that the results of this research will be instrumental for the improvement of the MSW recycling system and WP management in other cities in China and other developing countries.

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