Electrochemical degradation of p-nitrophenol with different processes

The electrochemical degradation of p-nitrophenol (PNP) under di erent conditions was investigated. The electrochemical behavior of PNP and its reduction product p-aminophenol (PAP) on stainless steel cathode and Ti/Pt anode through cyclic voltammetry were observed. Electrochemical degradation process was performed in an undivided cell and 92% PNP was removed corresponding to a 22% total organic carbon removal. A divided cell was also used and it was found that PNP degradation was mainly attributed to cathodic reduction, while anodic oxidation was responsible for PNP removal due to the reaction with hydroxyl radicals and surface oxide generated on the anode. The sequential electrolytic processes, reduction-oxidation and oxidation-reduction, were compared in the divided cell. In the case of reduction-oxidation process, the total organic carbon removal reached 40%, but PNP removal was the same with the undivided cell. A black deposit was found in the e uent and identified by Fourier transform infrared spectroscopy as a polymer of PAP produced by the 1,4-addition reaction of quinoneimine. Intermediates left in the solution such as hydroquinone, p-benzoquinone and PAP were determined by high performance liquid chromatography. Whereas, the oxidation-reduction process proved unsatisfying.     

An evaluation of the bioavailability and bioaccumulation of selected metals occurring in a wetland area on the volcanic island of Guam, Western Pacific Ocean

This initial research examined the presence, distribution and bioavailability of Cu, Cr, Ni, Mn and Fe in a wetland area of southern Guam. The research sites are within an area covered with saporite, a soil type derived from volcanic deposits on the island. Leaf tissue of Pandanus tectorius was extracted and analysed to determine the bioaccumulation of the target metals. Metal accumulation at sites considered aerobic and anaerobic was investigated together with an attempt to correlate actual accumulation of the target metals in the plant tissue with a recognised bioavailability indicator, in this case, three step sequential extraction scheme. Manganese was found to be accumulated in relatively high concentrations and to a lesser extent Cu was also accumulated. Chromium, Ni and Fe however exhibited very low accumulation factors. Accumulation of Mn in particular was significantly a ected by aerobic conditions whereas the converse e ect was experienced by Cu. Significant correlation between various steps of a Sequential Extraction Scheme and actual accumulation was not achieved although the degree of aerobic conditions at each site and soil pH did a ect concentrations of metals extracted by di ering steps of SES. Results obtained suggest that further research in the area should be undertaken using di erent plant species and tissues.     

Lipid peroxidation rates in <Emphasis Type="Italic">Taraxacum officinale</Emphasis> Wigg. and <Emphasis Type="Italic">Vicia cracca</Emphasis> L. from biotopes with different levels of soil pollution with heavy metals

The rates of lipid peroxidation (LPO) have been studied in Taraxacum officinale Wigg. (Asteraceae) and Vicia cracca L. (Fabaceae) from urban ecosystems with different levels of soil pollution with heavy metals (HMs), including Pb, Zn, Cu, and Cr. The former species responds to the increased HM contents by intensification of LPO processes, with their parameters correlating with the concentrations of Pb, Zn, and Cu in the soil. In the latter species from the same biotopes, conversely, LPO homeostasis remains actually undisturbed.     

Aquatic ecological health assessment of Shaying River Basin based on indices of physico-chemistry and aquatic organisms北大核心CSCD

With a variety of ecosystem services, river ecosystem plays an important role in the process of human society development. On the other hand, health condition of most aquatic ecosystems is seriously threatened by human activities. Restoring and maintaining a healthy ecosystem has already become a vital goal of river management. As a basis of river management, river health assessment is therefore particularly important. Based on indices of physics, chemistry and aquatic organisms, this research tried to establish a comprehensive evaluation system of aquatic ecological health suitable for the situation of Shaying River Basin. The system included 6 factors including riparian zone, river morphology, nutrients, oxygen balance, periphyton and benthic macroinvertebrates, which were defined into 19 indices reflecting the aquatic ecological health from different aspects. The assessment results indicated that the health condition of overall basin was normal, varying among different parts of the region, with Shahe River, Lihe River and Beiru River in the upper part sub-healthy, and Jialu River in the same part sub-sick. The middle region was generally in normal or sub-sick level; the health condition of the lower part was comparatively better due to a good condition. Within the indices, the nutrients and benthic macroinvertebrates were the major constraining factors to the health condition of Shaying River Basin for their poor health condition. The health conditions showed significant differences among the rivers (P < 0.01), with Jialu River being the worst. The result indicated that the aquatic ecological health of Shaying River Basin is affected by many factors, with urban and industrial sewage being the main ones, And that different protective measures should be employed for rivers of different conditions. The result can provide theoretical basis for the ecological restoration of Shaying River Basin and reasonable exploitation and conservation of the water resource of the whole Huaihe River Basin.     

湖泊沉积物有机质的连续提取与荧光光谱特征分析

采用化学连续提取与三维荧光光谱相结合的方法研究了蠡湖沉积物中可提取有机质的组成、结构和空间分布特征,并探讨了可提取态有机质组分与可交换态氮和弱吸附态磷之间的相关关系.结果表明,蠡湖沉积物中有机质含量为5.59~22.11 g·kg~(-1)(以C计),均值为12.28g·kg~(-1),其中水可提取态有机质(WSOM)、富里酸(FA)、胡敏酸(HA)和胡敏素(HM)的比例分别为5.14%、11.81%、9.63%和73.42%,空间上呈现由西向东逐渐递增,湖岸大于湖心的分布趋势.WSOM鉴别出3个荧光组分,以类氨基酸荧光峰(W-C1)占优势,占总荧光强度的比例为42.49%;FA鉴别出2个荧光组分,以富里酸荧光峰(F-C2)为主,比例为67.63%;HA的3个荧光峰中,以类胡敏酸荧光峰(H-C1和H-C3)为主,两者之和的比例为71.55%.多元回归统计表明,可提取有机质组分与游离态氮和易解析态磷含量之间均显著正相关,且与氮的相关性系数大于与磷,反映了可提取有机质与可交换态氮的关系更为密切,可用于指示沉积物生物可利用性氮磷的污染状况.     

Red-list status and extinction risk of the world's whales,dolphins, and porpoises

To understand the scope and scale of the loss of biodiversity, tools are required that can be applied in a standardized manner to all species globally, spanning realms from land to the open ocean. We used data from the International Union for the Conservation of Nature Red List to provide a synthesis of the conservation status and extinction risk of cetaceans. One in 4 cetacean species (26% of 92 species) was threatened with extinction (i.e., critically endangered, endangered, or vulnerable) and 11% were near threatened. Ten percent of cetacean species were data deficient, and we predicted that 2–3 of these species may also be threatened. The proportion of threatened cetaceans has increased: 15% in 1991, 19% in 2008, and 26% in 2021. The assessed conservation status of 20% of species has worsened from 2008 to 2021, and only 3 moved into categories of lesser threat. Cetacean species with small geographic ranges were more likely to be listed as threatened than those with large ranges, and those that occur in freshwater (100% of species) and coastal (60% of species) habitats were under the greatest threat. Analysis of odontocete species distributions revealed a global hotspot of threatened small cetaceans in Southeast Asia, in an area encompassing the Coral Triangle and extending through nearshore waters of the Bay of Bengal, northern Australia, and Papua New Guinea and into the coastal waters of China. Improved management of fisheries to limit overfishing and reduce bycatch is urgently needed to avoid extinctions or further declines, especially in coastal areas of Asia, Africa, and South America.     

珠江三角洲近地层CO2通量模拟分析与评估验证

利用能分别代表珠江三角洲草地、城市绿地及地带性森林植被生态系统的番禺站、东莞站和鼎湖山站CO2净通量资料对CT-2010碳源汇反演模式系统进行了验证,并利用该模式初步分析了区域净碳通量的时空分布及不同生态系统的碳汇特征.结果表明: CT-2010模式模拟的珠江三角洲城市绿地、地带性植被、以及草地生态系统碳通量与站点观测结果具有较好的一致性,其拟合相关系数(r)高于0.60(P<0.01),小时、逐日、日变化的残差均值低于2.0μmol/(m2?s);模式一定程度上能反映3种生态系统碳通量的季节分布特征,但各月的模拟值均高于观测值,其中对城市绿地生态系统的模拟最接近,残差年均值为0.964μmol/(m2?s),对草地和地带性森林植被生态系统的模拟效果相当,残差年均值分别为 2.056,2.100μmol/(m2?s);2004~2005年期间珠江三角洲地区近地层净碳通量为3.43μmol/(m2?s),其中冬季最强,为1.4μmol/(m2?s),春季次之,为1.35μmol/(m2?s),秋季和夏季最低,分别为0.51和0.18μmol/(m2?s);在冬、春两季,珠江三角洲区域为强的碳源区,而在夏、秋季,粤北和粤东大部分地区为较弱碳汇区;2004~2005年期间珠江三角洲地区陆地生态系统的碳汇为-6.5×10-3PgC,其中农作物,草地/灌木,常绿针叶/阔叶混合林是吸收CO2的主要生态系统,其净通量占陆地生态系统的比率分别为42.01%,31.46%和26.53%.     

氮素在河流生态系统中的滞留研究进展

河流是陆地生态系统和水生生态系统物质循环的主要连接通道,氮素在河流生态系统中发生复杂的物理、化学、生态过程,氮素的滞留影响输出形态、负荷,人为活动改变滞留过程,加剧水体富营养化。总结了国内外河流生态系统中的氮素滞留方面研究。滞留主要受控于生物因素和非生物因素,需要恢复河流生态系统的结构和功能,加强氮素滞留,改善区域水环境。     

生态系统对酸沉降相对敏感性评价原理与方法

介绍了敏感性及生态系统对酸沉降的绝对敏感性和相对敏感性的概念,概念了水体和土壤对酸沉降绝对敏感性评价的方法。通过分析比较生态系统中各生态子对酸沉降的缓冲能力,担子同建立生态系统对酸沉降相对敏感性评价的基本原理,并介绍了建立的评价才近期的发展。     

一维修正弹任务可靠度的序贯截尾检验方法

目的 研究并提出一种基于序贯截尾检验方法的任务可靠度评定方法.方法 将序贯截尾检验方法引入一维修正弹任务可靠度评定过程中,建立检验方法数学描述模型,并结合工程实例,综合应用Monte-Carlo法,给出数值算例和任务可靠度检验方案,验证方法的有效性和可行性.结果 与二项式经典假设检验方法(所需试验样本量N=54)相比,...