Heavy metal-organic pollutants compound pollution at industrial legacy sites and have caused damage to the ecological environment and human health during recent decades. In view of the difficulty and high cost of post-contamination remediation, it is worth studying, and practically applying, cutoff walls to reduce the spread of pollution in advance. In this study, field-scale studies were carried out at e-waste dismantling legacy sites in Taizhou, Zhejiang Province of China, through the process of site investigation, numerical simulation, and cutoff wall practical application. Firstly, the concentrations and spatial distributions of Pb, Cd and polychlorinated biphenyls (PCBs) and poly brominated diphenyl ethers (PBDEs) were identified in both soil and groundwater. Then, potential dispersal routes of key combined contaminants (Pb and PCBs) at the soil-groundwater interface were systematically studied through numerical simulation applying Visual MODFLOW-MT3DMS. One site was chosen to predict the barrier effect of differently sized cutoff walls based on the migration path of compound pollutants. A protocol for a cutoff wall (50 m length x 2 m width x 3 m height) was finally verified and applied at the real contaminated site for the blocking of compound pollutant diffusion. Further, the groundwater quality of the contaminated site was monitored consecutively for six months to ensure the durability and stability of barrier measures. All pollutant indicators, including for Pb and PCB complex pollutants, were reduced to below the national Grade IV groundwater standard value, achieving environmental standards at these polluted sites and providing possibilities for land reuse. In summary, this field-scale test provided new ideas for designing cutoff walls to block the diffusion of complex pollutants; it also laid a basis for the practical application of cutoff walls in pollution prevention and control of complex contaminated sites and for soil-groundwater environmental protection at industrial heritage sites.

Accurately applying engineered nanoparticles (NPs) in farmland stress management is important for sustainable agriculture and food safety. We investigated the protective effects of four engineered NPs (SiO2, CeO2, ZnO, and S) on pakchoi under arsenic (As) stress using pot experiments. The results showed that CeO2, SiO2, and S NPs resulted in biomass reduction, while ZnO NPs (100 and 500 mg kg- 1) significantly increased shoot height. Although 500 mg kg- 1 S NPs rapidly dissolved to release SO42-, reducing soil pH and pore water As content and further reducing shoot As content by 21.6 %, the growth phenotype was inferior to that obtained with 100 mg kg- 1 ZnO NPs, probably due to acid damage. The addition of 100 mg kg- 1 ZnO NPs not only significantly reduced the total As content in pakchoi by 23.9 % compared to the As-alone treatment but also enhanced plant antioxidative activity by increasing superoxide dismutase (SOD) and peroxidase (POD) activities and decreasing malondialdehyde (MDA) content. ZnO NPs in soil might inhibit As uptake by roots by increasing the dissolved organic carbon (DOC) by 19.12 %. According to the DLVO theory, ZnO NPs were the most effective in preventing As in pore water from entering plant roots due to their smaller hydrated particle size. Redundancy analysis (RDA) further confirmed that DOC and SO42- were the primary factors controlling plant As uptake under the ZnO NP and S NP treatments, respectively. These findings provide an important basis for the safer and more sustainable application of NP-conjugated agrochemicals.

One year of online total gaseous mercury (TGM) measurements were carried out for the first time in Lanzhou, a city in northwest China that was once seriously polluted. Measurements were made from October 2016 to October 2017 using the Tekran 2537B instrument, and the annual mean concentration of TGM in Lanzhou was 4.48 +/- 2.32 ng m(-3) (mean +/- standard deviation). TGM concentrations decreased during the measurement period, with autumn 2017 average concentrations 2.87 ng m(-3) lower than autumn 2016 average concentrations. Similar diurnal variations of TGM were obtained in different seasons with low concentrations observed in the afternoon and high concentrations at night. The principal component analysis and conditional probability function results revealed that the sources of mercury were similar to the other atmospheric pollutants such as SO2, CO, NO2 and PM2.5, and were mainly from industrial combustion plants in urban districts. Concentration weighted trajectory analysis using backward trajectories demonstrated that higher mercury concentrations were related to air masses from adjacent regions, indicating the importance of influences from local-to-regional scale sources. A synthesis of multi-decadal atmospheric mercury measurements in Lanzhou and other Chinese megacities revealed that atmospheric mercury concentrations were either generally stable or experienced a slight decrease, during a time when China implemented control measures on atmospheric pollution. Long-term atmospheric mercury observations in urban and background sites in China are warranted to assess mercury pollution and the effectiveness of China's mercury control policies. (C) 2020 Elsevier B.V. All rights reserved.

The uncertain, future development of emissions of short-lived trace gases and aerosols forms a key factor for future air quality and climate forcing. The Representative Concentration Pathways (RCPs) only explore part of this range as they all assume that worldwide ambitious air pollution control policies will be implemented. In this study, we explore how different assumptions on future air pollution policy and climate policy lead to different concentrations of air pollutants for a set of RCP-like scenarios developed using the IMAGE model. These scenarios combine low and high air pollution variants of the scenarios with radiative forcing targets in 2100 of 2.6 W m(-2) and 6.0 W m(-2). Simulations using the global atmospheric chemistry and transport model TM5 for the present-day climate show that both climate mitigation and air pollution control policies have large-scale effects on pollutant concentrations, often of similar magnitude. If no further air pollution policies would be implemented, pollution levels could be considerably higher than in the RCPs, especially in Asia. Air pollution control measures could significantly reduce the warming by tropospheric ozone and black carbon and the cooling by sulphate by 2020, and in the longer term contribute to enhanced warming by methane. These effects tend to cancel each other on a global scale. According to our estimates the effect of the worldwide implementation of air pollution control measures on the total global mean direct radiative forcing in 2050 is +0.09 W m(-2) in the 6.0 W m(-2) scenario and -0.16 W m(-2) in the 2.6 W m(-2) scenario. (C) 2013 Elsevier Ltd. All rights reserved.