ABSTRACT
Nitrogen oxides (NOx ≡ NO + NO2) play a central role in air pollution and are targeted for emission mitigation by environmental protection agencies globally. Unique challenges for mitigation are presented by super-emitters, typically with the potential to dominate localized NOx budgets. Nevertheless, identifying super-emitters still challenges emission mitigation, while the spatial resolution of emission monitoring rises continuously. Here we develop an efficient, super-resolution (1 × 1 km2) inverse model based on year-round TROPOMI satellite observations over China. Consequently, we resolve hundreds of super-emitters in virtually every corner of China, even in remote and mountainous areas. They are attributed to individual plants or parks, mostly associated with industrial sectors, like energy, petrochemical, and iron and steel industries. State-of-the-art bottom-up emission estimates (i.e., MEICv1.3 and HTAPv2), as well as classic top-down inverse methods (e.g., a CTM coupled with the Ensemble Kalman Filter), do not adequately identify these super-emitters. Remarkably, more than one hundred super-emitters are unambiguously missed, while the establishments or discontinuations of the super-emitters potentially lead to under- or over-estimates, respectively. Moreover, evidence shows that these super-emitters generally dominate the NOx budget in a localized area (e.g., equivalent to a spatial scale of a medium-sized county). Although our dataset is incomplete nationwide due to the undetectable super-emitters on top of high pollution, our results imply that super-emitters contribute significantly to national NOx budgets and thus suggest the necessity to address the NOx budget by revisiting super-emitters on a large scale. Integrating the results we obtain here with a multi-tiered observation system can lead to identification and mitigation of anomalous NOx emissions.
ABSTRACT
BACKGROUND: Combined effects of intrinsic and extrinsic ageing factors on skin tissue and the therapies have been rarely studied before. ADSCs have gained popularity in anti-ageing field, which may provide promising methods to fight against skin ageing. OBJECTIVE: To find out the fate of HDFs exposed to intrinsic or extrinsic ageing factors or both of them and further examine the impacts of ADSC-CM on the damaged HDFs. METHODS: We irradiated HDFs with UVB at different senescent levels, and then treated them with ADSC-CM. After 48 h, we detected cellular proliferative activity, morphology, SA-ß-Gal expression, apoptosis, mRNA expression of collagen I, collagen III and elastin. RESULTS: Intrinsic ageing factors inhibited cellular proliferation, increased senescent ratio and reduced mRNA expression of collagen I, collagen III and elastin, so did UVB, except for its induction of elastin mRNA expression. Furthermore, ADSC-CM treatment can slightly or significantly improve cellular proliferative activity and restore functions both in irradiated and non-irradiated HDFs. Besides, ADSC-CM treatment decreased cellular apoptosis and senescence induced by UVB but had no obvious effect on cellular senescence induced by intrinsic ageing factors. The results were similar in three generations of HDFs, yet in different degrees. CONCLUSIONS: The results suggest that ADSCs secretome protect HDFs from ageing damages but with some limitations.
