Dehalococcoides-Containing Enrichment Cultures Transform Two Chlorinated Organophosphate Esters.

Although chlorinated organophosphate esters (Cl-OPEs) have been reported to be ubiquitously distributed in various anoxic environments, little information is available on their fate under anoxic conditions. In this study, we report two Dehalococcoides-containing enrichment cultures that transformed 3.88 ± 0.22 µmol tris(2-chloroethyl) phosphate (TCEP) and 2.61 ± 0.02 µmol tris(1-chloro-2-propyl) phosphate (TCPP) within 10 days. Based on the identification of the transformed products and deuteration experiments, we inferred that TCEP may be transformed to generate bis(2-chloroethyl) phosphate and ethene via one-electron transfer (radical mechanism), followed by C-O bond cleavage. Ethene was subsequently reduced to ethane. Similarly, TCPP was transformed to form bis(1-chloro-2-propyl) phosphate and propene. 16S rRNA gene amplicon sequencing and quantitative polymerase chain reaction analysis revealed that Dehalococcoides was the predominant contributor to the transformation of TCEP and TCPP. Two draft genomes of Dehalococcoides assembled from the metagenomes of the TCEP- and TCPP-transforming enrichment cultures contained 14 and 15 putative reductive dehalogenase (rdh) genes, respectively. Most of these rdh genes were actively transcribed, suggesting that they might contribute to the transformation of TCEP and TCPP. Taken together, this study provides insights into the role of Dehalococcoides during the transformation of representative Cl-OPEs.

XRD and TEM analyses of a simulated leached rare earth ore deposit: Implications for clay mineral contents and structural evolution.

The types, contents, and microstructures of clay minerals play important roles in controlling the adsorption and desorption of ion-absorbed type rare earth ores and heavy metals. By selecting a typical rare earth ore profile, we conducted a leaching experiment and used XRD (X-ray diffraction) and TEM (Transmission electron microscopy) analyses to determine the clay mineral types and microstructural changes after various leaching periods. The XRD phase analyses showed that the main minerals in the simulated rare earth ore were quartz, potassium feldspar, kaolinite, and illite. TEM images showed that the mineral aggregates were broken, disintegrated, and transformed by the leaching process, and a large number of moire fringes were visible. With continuous leaching, REEs (Rare Earth Elements) were gradually re-solved and leached. The results of the leaching experiment indicate that fine-grained minerals in rare earth ores, such as potassium feldspar and clay minerals, migrated downward with the leaching solution. Leaching also promoted the alteration of potassium feldspar to clay minerals, as well as mutual alteration of clay minerals. Under acidic or neutral conditions during the early stage, potassium feldspar was altered to kaolinite or illite, whereas during the middle and late stages of leaching it was altered as follows: illite → mixed-layer illite-kaolinite → kaolinite → mixed-layer kaolinite-illite → illite. This transformation has an important effect on the release of REEs and heavy metals and provides insights into improving the leaching process and explaining heavy metal pollution in rare earth mining areas.

Assessing habitat quality at Poyang Lake based on InVEST and Geodetector modeling.

Poyang Lake is an essential natural wetland in the Yangtze River basin and plays a vital role in maintaining the ecosystem function and ecological security in the middle and lower reaches of the Yangtze River. However, the relative importance and spatial heterogeneity of the impacts of human activities and land use changes on ecological security needs to be further explored. Here, we analyzed the habitat quality level around Poyang Lake in 2022 and explored the factors of habitat quality change from a geographical perspective. The land use structure changes around the Poyang Lake basin from 2000 to 2022 were quantitatively analyzed, and then the relative importance and spatial heterogeneity of each factor on ecological security changes were investigated using geographic probes. The results show that (1) The worst quality habitat (0-0.1) consists mainly of construction land (1624.9 km2) with an area of 1634.64 km2; (2) Construction land continues to increase with the most significant change, and the dynamic land use attitude is 0.47. Grassland and mudflats have the greatest decrease. The increase in cultivated land in different periods is mainly due to the shift of water surface and forest land; (3) The drivers of habitat quality in Poyang Lake were significantly influenced by the interaction of socioeconomic factors. The explanatory power of population density interacting with the total year-end population and population density interacting with administrative area exceeded 0.84. These values were higher than the explanatory power of each individual factor, indicating that habitat quality was primarily associated with population density, total year-end population, and administrative area. These results suggest that human activities contribute to the degradation of wetlands around Poyang Lake. This study has significant reference value for coordinating human-land relationships in Poyang Lake, optimizing land management policy, and improving the sustainable development of cities.