Foregroundness-Aware Task Disentanglement and Self-Paced Curriculum Learning for Domain Adaptive Object Detection.

Unsupervised domain adaptive object detection (UDA-OD) is a challenging problem since it needs to locate and recognize objects while maintaining the generalization ability across domains. Most existing UDA-OD methods directly integrate the adaptive modules into the detectors. This integration procedure can significantly sacrifice the detection performances, though it enhances the generalization ability. To solve this problem, we propose an effective framework, named foregroundness-aware task disentanglement and self-paced curriculum adaptation (FA-TDCA), to disentangle the UDA-OD task into four independent subtasks of source detector pretraining, classification adaptation, location adaptation, and target detector training. The disentanglement can transfer the knowledge effectively while maintaining the detection performance of our model. In addition, we propose a new metric, i.e., foregroundness, and use it to evaluate the confidence of the location result. We use both foregroundness and classification confidence to assess the label quality of the proposals. For effective knowledge transfer across domains, we utilize a self-paced curriculum learning paradigm to train adaptors and gradually improve the quality of the pseudolabels associated with the target samples. Experiment results indicate that our method achieves state-of-the-art results on four cross-domain object detection tasks.

How do drying-wetting cycles influence availability of heavy metals in sediment? A perspective from DOM molecular composition.

Investigating the influence mechanism of drying-wetting cycles on the availability and mobility of heavy metals in sediment from the perspective of the molecular composition of dissolved organic matter (DOM) may gain a new understanding, but little current information exists. Here, we used spectral technologies, high-resolution mass spectrometry, and elemental stoichiometry method to trace the change rules of the molecular composition of DOM in the riparian sediment of the river. Results showed that the drying-wetting cycles could benefit the degradation of labile fractions (e.g., proteins, aliphatics, and lipids) of DOM and retain the fractions with high aromaticity and molecular size (e.g., lignin). The decrease in the availability of Cd after drying-wetting alternation processes was highly related to these changes in DOM composition. However, the availability of Zn and Cu remained almost unchanged, which probably resulted from the release and depletion of N and S in sediment-derived DOM under drying-wetting alternation conditions. As for Cr, its exchangeable fraction was unchanged during the drying-wetting alternation process, likely due to its high stability in the sediment. These results have implications on the environmental geochemical cycling of heavy metals in the riparian sediment with frequent drying-wetting alternation.

Recent advances in the application of water-stable metal-organic frameworks: Adsorption and photocatalytic reduction of heavy metal in water.

Heavy metals pollution in water is a global environmental issue, which has threatened the human health and environment. Thus, it is important to remove them under practical water environment. In recent years, metal-organic frameworks (MOFs) with water-stable properties have attracted wide interest with regard to the capture of hazardous heavy metal ions in water. In this review, the synthesis strategy and postsynthesis modification preparation methods are first summarized for water-stable MOFs (WMOFs), and then the recent advances on the adsorption and photocatalytic reduction of heavy metal ions in water by WMOFs are reviewed. In contrast to the conventional adsorption materials, WMOFs not only have excellent adsorption properties, but also lead to photocatalytic reduction of heavy metal ions. WMOFs have coupling and synergistic effects on the adsorption and photocatalysis of heavy metal ions in water, which make it more effective in treating single pollutants or different pollutants. In addition, by introducing appropriate functional groups into MOFs or synthesizing MOF-based composites, the stability and ability to remove heavy metal ions of MOFs can be effectively enhanced. Although WMOFs and WMOF-based composites have made great progress in removing heavy metal ions from water, they still face many problems and challenges, and their application potential needs to be further improved in future research. Finally, this review aims at promoting the development and practical application of heavy metal ions removal in water by WMOFs.

Chronological records of sediment organic carbon at an entrance of Dongting Lake: Response to historical meteorological events.

Lake sediments are the products of soil erosion and are strongly influenced by climate variability, particularly extreme meteorological events. Sediment organic carbon (SOC) can reflect environmental changes that affect sediment transport. However, the response of SOC chronological records to major meteorological events is relatively unknown. This study explored the chronological regularity of SOC and verified its variations using major historical meteorological events. Based on three sediment profiles with a depth of 230 cm at the Yuan River entrance to the West Dongting Lake (Hanshou entrance), the SOC chronology was reconstructed by employing the sedimentation rates calculated by 137Cs and 210Pb. The sedimentary environment then was interpreted via comparisons and quantitative analysis. The grain distribution and the S-shaped distribution of SOC reflected the general deposition regularity of organic carbon in lake sediments, which gradually stabilized with depth. The average sedimentation rates based on 137Cs and 210Pb were 1.310 and 1.319 cm a-1, respectively. Accordingly, SOC records covered the past 76 years via dating (0-100 cm), during which the SOC content first increased and subsequently stabilized. By comparing the data with the occurrence of 11 major historical meteorological events, we found that SOC generally increased after these events. Moreover, the frequent occurrence of meteorological events stabilized the SOC content. Severe floods had a greater impact on SOC content than severe droughts, causing SOC to change by up to 20.24% and 8.77%, respectively. Our findings suggest that major historical meteorological events can verify SOC chronological records, thereby highlighting their significant impacts on organic carbon variations in sediments.

Spatiotemporal dislocation of urbanization and ecological construction increased the ecosystem service supply and demand imbalance.

The spatiotemporal dislocation of urbanization and ecological construction may lead to differences in the spatiotemporal pattern and matching of the ecosystem service supply and demand, which are significantly important in altering the ecosystem service supply and demand equilibrium. This study quantified and mapped the supply and demand of carbon sequestration services in the Xiangjiang River Basin (XRB) from 1990 to 2015 using the InVEST and population distribution models and identified the spatial distribution characteristics and changes in the supply and demand relationship on the sub-basin scale using the spatial autocorrelation method and Z-scores. The results show that the expansion of land urbanization greater than 50% was concentrated in the midstream and downstream, while the ecological construction was mainly distributed in the upstream. On the whole-basin scale, the supply of carbon sequestration services slightly decreased by 21.62%, while the demand sharply increased by 376.86%. The carbon sequestration services supply-demand ratio (CSDR) reduced from 0.16 (1990) to -0.03 (2015). This meant that the status of the supply and demand in the XRB had changed from oversupply to overdemand, and this tide turned in 2005 (-0.01). Furthermore, the spatial distribution pattern of the sub-basins' CSDR in the upstream was the High-High cluster, while it was the Low-Low cluster in the downstream. These results revealed the high spatial distribution consistency between the CSDR and urbanization and ecological construction. The slight increase in the carbon sinks caused by the ecological construction in the upstream could not offset the rapidly increased carbon emissions from the downstream for urbanization. Meanwhile, the lack of ecological concern during the urbanization process had led to a persistent reduction in the carbon sinks in the downstream, which also exacerbated the disequilibrium of the ecosystem service supply and demand in the XRB. Consequently, this study suggests that the scale and speed of the urbanization of land should be reasonably controlled and that the ecological construction in rapid urbanization regions should be strengthened to meet the demand for ecosystem services.