Historical trends of PCBs and PBDEs as reconstructed in a lake sediment from southern Tibetan Plateau

High-altitude lake sediment can be used as a natural archive to reconstruct the history of pollutants. In this work, the temporal distribution of polychlorinated biphenyls(PCBs) and polybrominated diphenyl ethers(PBDEs) were determined using a high-resolution gas chromatography coupled with high-resolution mass spectrometer(HRGC/HRMS) in an alpine lake sediment core collected from the southern Tibetan Plateau(TP) to examine whether the expected decreasing trends due to the implementation of the international Conventions could be observed. The concentrations of PCBs and PBDEs in the sediment core were in the range of 11.8–142 pg/g dw and ND-457 pg/g dw, and their fluxes were in the range of 2.51–31.7 ng/(m^2 ·yr) and ND-43.2 ng/(m^2 ·yr), respectively. The prevalence of low-chlorinated(tri-CB) PCBs and low-brominated(tri-to tetra-) PBDEs in most sections of the sediment profiles was observed, suggesting that the light molecular weight PCBs and PBDEs have most likely reached lake sediments by long-range atmospheric transport from distant sources. Despite the restrictions on their applications, the sediment records for the concentrations and fluxes showed no corresponding decreasing trend with restrictions for PCBs, which suggested that these POPs(e.g., PCBs) were still emitted to the environment owing to the influence of primary or secondary emissions. To our knowledge, this is the first report on input history of atmospheric PCBs and PBDEs recorded in TP Lake sediment.

China's agriculture green development: from concept to actions

China has initiated a green transformation plan in 2015, which was soon applied to agriculture, known as the agriculture green development(AGD)initiative, with the goals of achieving food security, high resource use efficiency, and an ecofriendly environment. To assess the agricultural transformation from 1997 to 2020, this paper proposes a national-scale indicator system consisting three dimensions(socioeconomic, food production and eco-environmental) and ten sub-dimensions to quantify the AGD score.This study showed that AGD score in China was at a moderate level during 1997–2010, scoring 40 out of 100. During this stage, decreased scores in the sub-dimensions of resource consumption, environmental quality, and environmental cost have offset the improvement in the socioeconomic dimension, resulting in fluctuated scores around 40. In the second stage(2011–2020), China's AGD score improved but still at moderate level, scoring an average of 46.3, with each dimension increasing by 5.3%–25.0%. These results indicate that China has made progress in the agricultural transformation, transitioning from conceptualization to actions through the implementation of various policies and projects. However, the study emphasizes the need for more effort to address the insufficient and unbalanced development, along with the growing eco-environmental challenges, especially the trade-offs among dimensions.