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Abstract. Developing a big data analytics framework for generating the Long-term Gap-free High-resolution Air Pollutant concentration dataset (abbreviated as LGHAP) is of great significance for environmental management and Earth system science analysis. By synergistically integrating multimodal aerosol data acquired from diverse sources via a tensor-flow-based data fusion method, a gap-free aerosol optical depth (AOD) dataset with a daily 1 km resolution covering the period of 2000–2020 in China was generated. Specifically, data gaps in daily AOD imageries from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard Terra were reconstructed based on a set of AOD data tensors acquired from diverse satellites, numerical analysis, and in situ air quality measurements via integrative efforts of spatial pattern recognition for high-dimensional gridded image analysis and knowledge transfer in statistical data mining. To our knowledge, this is the first long-term gap-free high-resolution AOD dataset in China, from which spatially contiguous PM2.5 and PM10 concentrations were then estimated using an ensemble learning approach. Ground validation results indicate that the LGHAP AOD data are in good agreement with in situ AOD observations from the Aerosol Robotic Network (AERONET), with an R of 0.91 and RMSE equaling 0.21. Meanwhile, PM2.5 and PM10 estimations also agreed well with ground measurements, with R values of 0.95 and 0.94 and RMSEs of 12.03 and 19.56 µg m−3, respectively. The LGHAP provides a suite of long-term gap-free gridded maps with a high resolution to better examine aerosol changes in China over the past 2 decades, from which three major variation periods of haze pollution in China were revealed. Additionally, the proportion of the population exposed to unhealthy PM2.5 increased from 50.60 % in 2000 to 63.81 % in 2014 across China, which was then reduced drastically to 34.03 % in 2020. Overall, the generated LGHAP dataset has great potential to trigger multidisciplinary applications in Earth observations, climate change, public health, ecosystem assessment, and environmental management. The daily resolution AOD, PM2.5, and PM10 datasets are publicly available at https://doi.org/10.5281/zenodo.5652257 (Bai et al., 2021a), https://doi.org/10.5281/zenodo.5652265 (Bai et al., 2021b), and https://doi.org/10.5281/zenodo.5652263 (Bai et al., 2021c), respectively. Monthly and annual datasets can be acquired from https://doi.org/10.5281/zenodo.5655797 (Bai et al., 2021d) and https://doi.org/10.5281/zenodo.5655807 (Bai et al., 2021e), respectively. Python, MATLAB, R, and IDL codes are also provided to help users read and visualize these data.

The utilization of reclaimed water is a reliable and sustainable approach to enhance water supply in water-deficient cities. However, the presence of micro-organic pollutants (MPs) in reclaimed water has potential adverse effects on aquatic ecosystems and human health. In this study, we investigated the occurrence of 12 target MPs in the influent and reclaimed water collected from a local wastewater treatment plant, and the ultraviolet (UV)-chlorine process was applied to analyze its ability to remove MPs. The results showed that all 12 MPs were detected in both the influent and the reclaimed water, with the concentrations ranging from 25.5 to 238 ng/L and 8.6 to 42.5 ng/L, respectively. Over 52% of all the target MPs were readily degraded by the UV-chlorine process, and the removal efficiency was 7.7% to 64.2% higher than the corresponding removal efficiency by chlorination or UV irradiation only. The degradation efficiency increased with the increasing initial chlorine concentration. The pH value had a slight influence on the MP degradation and exhibited different trends for different MPs. The formation of known disinfectant byproducts (DBPs) during the UV-chlorine process was 33.8% to 68.4% of that in the chlorination process, but the DBPs' formation potentials were 1.3 to 2.2 times higher. The toxicity assay indicated that UV-chlorine can effectively reduce the toxicity of reclaimed water.

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