土地利用方式对喀斯特山区土壤养分及有机碳活性组分的影响

通过对喀斯特山区5种土地利用方式(林地、 花椒林、 火龙果林、 退耕草丛和旱地)土壤养分和活性组分含量的比较研究,探讨了土壤质量对土地利用变化的响应。结果表明,林地土壤养分和活性组分含量最高,其中土壤有机碳、 微生物生物量碳、 氮、 磷、 易氧化有机碳和可溶性有机碳含量分别为44.80 g·kg^-1、 477.86 mg·kg^-1、 102.87 mg·kg^-1、 17.54 mg·kg^-1、 7.72 g·kg^-1和166.43 mg·kg^-1,土壤养分和活性组分含量总体按花椒林、 火龙果林、 退耕草丛和旱地依次下降。除旱地与经自然恢复15 a的退耕草丛土壤养分和活性组分含量较为接近,大多未达显著差异水平外,其他土地利用方式间土壤养分和活性组分均存在显著差异。冗余分析表明,土壤有机碳是影响活性组分变化的主要影响因子;花椒林对土壤养分和活性组分的累积效应仅次于林地,且明显高于火龙果林和旱地。研究阐明了喀斯特土壤的自然修复是一个非常缓慢的过程,需辅以必要的造林措施加速其恢复,花椒林可以作为喀斯特山区农业生产或生态恢复过程中优先考虑的植被类型。     

电镀污泥中铜和镍的回收

采用硫酸酸浸#x02014;铜镍分离#x02014;净化除杂#x02014;沉淀制取硫酸镍的工艺从电镀污泥中回收铜和镍，分别采用硫化钠沉淀法和铁粉置换法研究电镀污泥酸浸液中铜和镍的分离效果。实验结果表明，硫化钠沉淀法对铜和镍的分离效果较好，其最优工艺条件为：硫化钠加入量为理论需求量的1.2倍，硫化钠沉淀温度60℃，硫化钠沉淀时间30min。利用本回收工艺制得的硫酸镍产品中镍的质量分数为18%，镍的回收率达80%以上，铜的回收率达90%以上。     

A comparison of microplastic contamination in freshwater fish from natural and farmed sources

Contamination of aquatic systems mainly by urbanization and poor sanitation, deficient or lack of wastewater treatments, dumping of solid residues, and run off has led to the presence of particles, including manmade polymers, in tissues of many marine and freshwater species. In this study, the prevalence of microplastics (MPs) in freshwater fish from farmed and natural sources was investigated. Oreochromis niloticus from aquaculture farms in the Huila region in Colombia, and two local species (Prochilodus magdalenae and Pimelodus grosskopfii), naturally present in surface waters were sampled. Of the particles identified, fragments were the predominant type in the three tissue types (stomach, gill, and flesh) derived from farmed and natural fishes. MicroFT-IR spectroscopy was conducted on 208 randomly selected samples, with 22% of particles identified as MPs based on spectra with a match rate ≥ 70%. A total of 53% of identified particles corresponded to cellophane/cellulose, the most abundant particle found in all fish. Not all fish contained MPs: 44% of Oreochromis farmed fish contained MPs, while 75% of natural source fish contained MPs in any of its tissues. Overall, polyethylene terephthalate (PET), polyester (PES), and polyethylene (PE) were the prevalent MPs found in the freshwater fish. A broader variety of polymer types was observed in farmed fish. The edible flesh part of fish presented the lower prevalence of MPs compared to gill and stomach (gut), with gut displaying a higher frequency and diversity of MPs. This preliminary study suggests that the incidence and type of MPs varies in farmed verses natural fish sources as well as across different tissue types, with significantly less detected within the edible flesh tissues compared with stomach and gill tissues.