氢冶金的发展历程与关键问题

在“双碳”(碳达峰碳中和)战略背景下，以氢代碳的氢冶金成为钢铁企业优化能源结构和工艺流程、实现绿色低碳可持续发展的有效途径之一。以《联合国气候变化框架公约》和《京都议定书》的通过为时间节点，梳理和追溯了氢冶金的发展历程。从“以煤代焦、以气代焦”到“以氢代碳、以氢减碳”，铁矿石冶炼工艺由以减少焦炭和焦煤依赖为初衷，转变为以降低碳排放为重心，再到以净零碳排放为最终目标，逐渐形成高炉富氢冶炼和全氢直接还原工艺两大技术路线。从目前中国钢铁生产结构以及降碳目标来看，长流程产钢量占90%，高炉炼铁碳排放占比大、基数大。高炉低碳冶炼是规模化实现中国钢铁工业低碳的重要路径，而高炉富氢冶炼对“双碳”过渡时期的炼铁工业应用具有重要意义。从未来钢铁行业发展及能源结构转变来看，全氢直接还原工艺是实现钢铁行业净零碳排放的重要路线。发展氢冶金的关键问题包括如何解决绿色经济化制氢和安全规模化用氢。

Research progress of microplastic pollution in the global rivers

Microplastics are ubiquitous in the environment. As an emergent pollutant, microplastics are potentially harmful to the ecosystems and human health. Rivers play an irreplaceable role in the transmission of microplastics pollution. They are not only a temporary sink of microplastics, but also an important pathway for microplastics from land to the ocean. Through the overview of the previous studies on riverine microplastics globally, we found that the highest abundance of microplastics was from the Sinos River in Brazil, while for the riverine sediments, results from the Suzhou creek in China and the Jedara River in Tunisia were relatively higher. The microplastics in the rivers were mainly white fibers with a particle size of less than 1 mm. The microplastic pollution was significantly affected by human activities and land use types especially in industrial areas. The selection of sampling methods and experimental reagents will affect the concentration of microplastics, and result from large flow sampling were identified with more microplastics. However, the current researches on microplastics in rivers are mostly focused in urban areas, the related studies in remote areas should be strengthened. Meanwhile, due to the continuous changes of microplastic pollution in rivers, it is necessary to study the temporal and spatial variability of river microplastic pollution and establish a long-term real-time monitoring mechanism in order to grasp the status of microplastic pollution.