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.

Microorganisms are the driving force behind the circulation and transformation of the soil substance. The development of soil bacterial communities is critical for ecosystem restoration and evolution. In the Loess Plateau, coal mining activities have aggravated the deterioration of the fragile local ecological environment. The adaptive development of soil bacterial communities in response to different ecological processes caused by coal mining activities was explored through high-throughput sequencing technology and an ecological network analysis of the mining subsidence area of the Daliuta Coal Mine and vegetation rehabilitation area of the Heidaigou Coal Mine in the Loess Plateau. The results showed that while mining subsidence was inhibited, vegetation rehabilitation promoted the soil physicochemical properties. Soil organic matter, available phosphorus and available potassium in the subsidence area decreased significantly (P < 0.05), while soil organic matter, soil water, pH and EC in the vegetation rehabilitation area increased significantly (P < 0.05). The diversity index in the subsidence area decreased by about 20%, while that in the vegetation rehabilitation area increased by 63%. Mining subsidence and vegetation rehabilitation had a distinct influence on the molecular ecological networks of the soil bacteria, which tended to be more complex after the mining subsidence, and the number of connections in the network increased otherwise significantly enhanced interactive relationships. After the vegetation rehabilitation, the number of modules in the ecological network increased, but the contents of modules tended to be simpler. Soil bacterial communities adapted to the changes by changing the relationships between bacteria in response to different ecological processes. This study provides new insights into the monitoring and abatement of the damaged ecological environment in mines.

Secondary lead smelting is a widespread industrial activity which has exacerbated Pb or Cd contamination of soil and water across the world. Soil physicochemical properties, soil enzyme activities, heavy metal concentrations, and bacterial diversity near a secondary lead plant in Xuzhou, China were examined in this study. The results showed that secondary lead smelting activities influenced nearby soils. Soil acidification decreased one order of magnitude, with a mean value of 7.3. Soil organic matter also showed a downward trend, while potassium and nitrogen appeared to accumulate. Soil urease and protease activity increased in samples with greater heavy metal pollution, but overall the soil microbial biodiversity decreased. Soil heavy metal concentration—especially Pb and Cd—greatly exceeded the concentrations of Chinese Environmental Quality Standard for Soils (GB 15618-1995). Some environmental factors—such as pH, organic matter, enzyme activity, and the concentration of heavy metals—significantly affected bacterial diversity: compared with the control site, the Chao1 estimator decreased about 50%, while the Shannon diversity index dropped approximately 20%. Moreover, some genera have significant relationships with heavy metal concentration—such as Ramlibacter with Zn and Steroidobacter with Cd—which might act as bio-indicators for soil remediation. These results will provide a new insight in the future for reclaiming soil contaminants caused by secondary lead smelting.

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