Comparative study of humic acids of the mound of a wood-feeding termite and of the litter directly below in the Amazon river delta

In order to determine the role of termites in the recycling of organic matter and in humification processes, organic matter from the mound of a wood-feeding termite (Nasutitermes sp.) and from the litter directly below has been studied in secondary forest on the campus of Belem University, in Brazil. The carbon content was slightly lower in the litter (just beneath the mound) than in the mound, but nitrogen was much more abundant in the mound. As a consequence, the C/N ratio of fragmented litter total organic matter is very high, which shows that the humification process is not complete. Therefore, plant debris seemed to be more degraded in the mound than in the litter, indicating a humification gradient from mound to litter. Humic acid extracted from the mound and from the litter was compared by using elemental, E4/E6 ratio, spectroscopic (FTIR) analyses, and Sephadex gel chromatography. First, humic acids were more abundant in the mound than in the litter, showing that humification processes were more advanced in the mound than in the litter. Gel-permeation chromatography showed that the humic acids of the mound contained more low-molecular-weight fractions than those of the litter. In addition, the results of infrared spectra, E4/E6 ratio and elemental composition can confirm the fulvic character of mound material and the humic character of litter material. Therefore, the plant debris seems to follow two different humification pathways in the two environments, as long as the mound is alive.     

Experimental study of chromium adsorption on minerals in the presence of phthalic and humic acids

The effect of phthalic acid (benzene 1,2 dicarboxylic acid), a surrogate compound for natural organic matter, and of humic acid, on the adsorption of chromium to the surface of minerals was observed. In ternary systems involving phthalic acid, chromium(III) adsorption decreases on clays, probably because of aqueous Cr(III)-phthalate complexation, preventing ionic-exchange. Phthalic acid was also found to reduce chromium(VI) adsorption onto alumina, because of a competitive effect. In ternary systems involving humic acid, Cr(III) adsorption is increased in the low pH range because of the formation of surface ternary complex S-L-Cr(III) and is decreased in the high pH range because of aqueous Cr(III)-humate complexation.     

Light-induced variation in environmentally persistent free radicals and the generation of reactive radical species in humic substances

• Light irradiation increased the concentration of free radicals on HS. • The increased spin densities on HS readily returned back to the original value. • The “unstable” free radicals induced the formation of reactive radical species. • Reactive radicals’ concentration correlated strongly with EPFRs’ concentration. Environmentally persistent free radicals (EPFRs) in humic substances play an essential role in soil geochemical processes. Light is known to induce EPFRs formation for dissolved organic matter in aquatic environments; however, the impacts of light irradiation on the variation of EPFRs in soil humic substances remain unclear. In this study, humic acid, fulvic acid, and humin were extracted from peat soil and then in situ irradiated using simulated sunlight. Electron paramagnetic resonance spectroscopy results showed that with the increasing irradiation time, the spin densities and g-factors of humic substances rapidly increased during the initial 20 min and then gradually reached a plateau. After irradiation for 2h, the maximum spin density levels were up to 1.63 × 10¹⁷, 2.06 × 10¹⁷, and 1.77 × 10¹⁷ spins/g for the humic acid, fulvic acid, and humin, respectively. And the superoxide radicals increased to 1.05 × 10¹⁴–1.46 × 10¹⁴ spins/g while the alkyl radicals increased to 0.47 × 10¹⁴–1.76 × 10¹⁴ spins/g. The light-induced EPFRs were relatively unstable and readily returned back to their original state under dark and oxic conditions. Significant positive correlations were observed between the concentrations of EPFRs and reactive radical species (R² = 0.65–0.98, p<0.05), which suggested that the newly produced EPFRs contributed to the formation of reactive radical species. Our findings indicate that under the irradiation humic substances are likely to be more toxic and reactive in soil due to the formation of EPFRs.     

Species of Trace Metals, Organic Residues and Humic Substances in Sediments From the Taiwan Erhjin River and Coastal Areas

Total organic carbon, humic substances, and the species of trace metals (including Cu, Zn, Pb, Cd, Cr, Mn and Fe) in six and seven phases, such as bioexchangeable (P1), skeletal (carbonates, P2), easily reducible (Fe and Mn oxides, P3), moderately reducible (crystalline Mn oxides, P4), organic matters with sulphides (P5), and detritus with minerals (P6) as well as organic with humic substances (PB4) and organic residues (PB6), were analyzed in sediments from the Taiwan Erhjin coastal (including river and estuarine) area, where places we found the copper pollution. Results indicate that higher percentages of P1 and P2 for copper, zinc, lead, cadmium and manganese in samples collected in March and September of 1990 were much higher than those in P3-P6. High percentages of chromium and iron in samples respectively collected in March and September of 1990 were found in P6. for the seven phase analysis, higher percentages of copper species in PB4 and PB6 as well as iron species in PB7 were observed. On the other hand, purified humic acid with the high contents of manganese and iron in humic acid as well as purified fulvic acids were generally found at the upstream stations; and low values at coastal stations. However, extremely high copper (as high as 1750μg g^-1, dry weight in fulvic acid and 820μg g^-1 in humic acid) and lead (821μg g^-1 in humic acid) concentrations with relatively high manganese and iron concentrations were observed in humic substances from the station near the copper recycling area. Comparing the results obtained from the Antarctic Ocean sediments with those from the Taiwan Erhjin Chi coastal sediments, the human impacts on the latter are evaluated.     

Species of Trace Metals,Organic Residues and Humic Substances in Sediments From the Taiwan Erhjin River and Coastal Areas

Abstract

Total organic carbon, humic substances, and the species of trace metals (including Cu, Zn, Pb, Cd, Cr, Mn and Fe) in six and seven phases, such as bioexchangeable (P1), skeletal (carbonates, P2), easily reducible (Fe and Mn oxides, P3), moderately reducible (crystalline Mn oxides, P4), organic matters with sulphides (P5), and detritus with minerals (P6) as well as organic with humic substances (PB4) and organic residues (PB6), were analyzed in sediments from the Taiwan Erhjin coastal (including river and estuarine) area, where places we found the copper pollution. Results indicate that higher percentages of P1 and P2 for copper, zinc, lead, cadmium and manganese in samples collected in March and September of 1990 were much higher than those in P3-P6. High percentages of chromium and iron in samples respectively collected in March and September of 1990 were found in P6. for the seven phase analysis, higher percentages of copper species in PB4 and PB6 as well as iron species in PB7 were observed. On the other hand, purified humic acid with the high contents of manganese and iron in humic acid as well as purified fulvic acids were generally found at the upstream stations; and low values at coastal stations. However, extremely high copper (as high as 1750μg g^?1, dry weight in fulvic acid and 820μg g^?1 in humic acid) and lead (821μg g^?1 in humic acid) concentrations with relatively high manganese and iron concentrations were observed in humic substances from the station near the copper recycling area. Comparing the results obtained from the Antarctic Ocean sediments with those from the Taiwan Erhjin Chi coastal sediments, the human impacts on the latter are evaluated.     

珠江三角洲典型地区蔬菜重金属污染现状研究--以中山市和东莞市为例

以珠江三角洲典型地区中山市与东莞市为研究对象，通过对其大型蔬菜生产基地中10种蔬菜76个样品中重金属元素铬、铅、镉和汞的含量进行分析，初步摸清了珠江三角洲典型地区中山市与东莞市蔬菜中的重金属污染状况，并在不同城市不同蔬菜品种之间的污染程度进行了比较。结果表明，蔬菜中铬、铅、镉、汞的平均含量分别为0．1719、0．0962、0．0257和0.0014mg/kg，其中铬、铅、镉含量超出了国家卫生标准的允许量的蔬菜样品分别有1．3％、13，2％与13．2％；4种重金属在10种蔬菜中的平均残留量由大到小依次为：铬→铅→镉→汞；铅、镉是珠江三角洲典型地区中山市与东莞市蔬菜中的主要污染元素。     

Comparative study of plasma lead levels in the staff of Dandy Zinc Factory of Zanjan and in normal individuals

Pollution is a global problem which affects various human population functions. Despite the decline in plasma lead (Pb) levels among the general population during the past 20 years, this metal continues to be a public health concern for individuals with past and present exposures. The objective of this study was to determine blood lead levels (BPbL) in the staff of Dandy Zinc Company and compare them to control subjects. The test group included 40 staff of Dandy Zinc Company of Zanjan, while controls were selected from general population. Five milliliters of blood and plasma was sent to Atomic Energy Organization of Iran (AOEI) reference lab to measure BPbL by Flameless Atomic Absorption. BPbL in test group (16.6 + 8.18 µg dL^?1) was significantly higher than control (10.47 + 2.10 µg dL^?1). In both groups BPbL was significantly higher in smokers than non-smokers. Blood lead levels in molding workers were significantly higher than other workers. BPbL in exposed workers were directly related to duration of work and age. Data indicate Pb exposure was of significant magnitude to be a public health concern especially in zinc-and Pb-related industries.     

Spatial variations in the N2O emissions and denitrification potential of riparian buffer strips in a contaminated urban river

Spatial variations in the N₂O emissions and denitrification potential of riparian buffer strips (RBS) in a polluted river were examined. The river received large pollutant inputs from urban runoff and wastewater discharge, resulting in impaired water quality in the river and downstream reservoir. The potential for nitrogen removal by RBS was evaluated by measuring in situ N₂O emission fluxes in static closed chambers and sediment denitrification potentials with acetylene inhibition techniques. The results showed that N₂O emission fluxes decreased from the upstream (16.39 μg/(m²·h)) to downstream (0.30 μg/(m²·h)) sites and from the water body to upland sites. The trend in decreasing N₂O emission fluxes in the downstream direction was mainly associated with sediment/soil textures (clay loam→sandy soil) and sediment/soil water contents and was also related to the vegetation along the RBS and nutrients in the sediments/soils. The correlation coefficient was highest (r=0.769) between the N₂O emission flux and sediment/soil water content. Sediment/soil denitrification potentials under N-amended and ambient conditions were higher (highest 32.86 mg/(kg·h)) for the upstream sites, which were consistent with in situ N₂O flux rates.     

广西喀斯特和红壤地区桉树人工林土壤理化性质对比研究

喀斯特地区种植桉林是恢复和改善岩溶地区生态环境及推进脱贫致富的重要措施,但其生态环境影响也是广泛关注的科学问题。选择广西桂林、扶绥两处地点,对比分析了红壤和喀斯特土壤种植桉树对土壤结构和土壤养分的影响,结果表明：（1）喀斯特地区桉林土壤容重略大于红壤、毛管孔隙度不发达,非毛管孔隙度较发达,总孔隙度小于红壤;（2）喀斯特地区桉林土壤非毛管含水量显著低于红壤,但饱和含水量基本相当;（3）喀斯特桉林土壤的全量养分多高于红壤,而一些速效养分低于红壤,尤其是钾的含量显著偏低;（4）喀斯特桉林土壤的pH值和有机质含量高于红壤。研究表明喀斯特地区种植桉树人工林并未引起土壤结构的破坏和土壤养分含量的显著降低,相反在某些方面喀斯特地区种植桉树相对于红壤还有其优势。最后,结合研究结论,该文还就喀斯特地区和红壤地区桉树人工林管理提出了一些针对性建议。     

Calculation of the minimum ecological water requirement of an urban river system and its deployment: A case study in Beijing central region

The minimum ecological water requirements of an urban river system and water deployment are key elements in integrated water resources planning and urban ecological construction. Based on a review of ecological water requirement calculation methods and considering the different ecological functions of an urban river system, the ecological function method was used in this paper to calculate the components of the ecological water requirements of an urban river. An envelope curve-based method was proposed for assessing the minimum ecological water requirements of an urban river system. Water resources deployment strategies designed to meet the minimum ecological water requirements were described. Then, the minimum ecological water requirements of the urban river system in Beijing central region, selected as a case study, were investigated. The key parameters for assessing the minimum ecological water requirement in the Beijing urban river system were determined. Based on the ecological objectives and the current status of the different urban river systems within the Beijing central region, the minimum ecological water requirements were calculated. Different types of water sources, including rainwater, upstream water, and reclaimed water, were deployed to meet the ecological water requirements for the urban river system in the Beijing central region.     

平原河网地区滨岸带外来植物入侵现状及影响研究——以上海青浦区为例

河流滨岸带作为一种典型的开放系统,在受到外界干扰的条件下极易被外来植物所入侵并受到严重影响。以上海青浦区为例,通过对河流滨岸带生态系统入侵植物分布及现状调查,以及对两种入侵植物：白花三叶草（Trifolium repens）和加拿大一枝黄花（Solidago canadensis）群落的物种多样性及其土壤特性的实证研究,探讨外来植物入侵对河流滨岸带生态系统造成的影响。结果表明：目前该地区河流滨岸带外来入侵植物共有14科24种,其科、种数分别占到该生态系统所有植物的48．3％与26．1％。入侵植物白花三叶草与加拿大一枝黄花在春、秋两季均显著降低了河流滨岸带植物群落的物种多样性。此外,两种人侵植物也对当地河流滨岸及土壤特性造成了不同程度的影响,其中对土壤含水量、pH值的影响最为显著。该研究填补了平原河网地区河流滨岸带生态系统外来植物入侵研究的空白,有助于今后开展对该生态系统的评价、恢复及管理工作。     

Comparative study of the age and location dependence of some heavy metals in human hair from two Nigerian cities

The concentration of some heavy metals (lead, zinc and copper) were determined in the scalp hair of children (1–15 year) and active adults (16–40 year) in two Nigerian cities. The levels of zinc were found to be higher in children than in the adult population. There was a significant difference (P?=?0.05) between the two age groups. The levels of copper were all within the same range for the two age groups and independent of location. The levels of lead were generally higher in adults than in children. However, there was no significant difference (P?=?0.05) in the average concentrations of lead between the children and adult populations of the two cities. The regression analysis indicated a strong correlation (r?=?0.86) between zinc and copper.     

The possible association between selected sediment characteristics and the occurrence of benthic macroinvertebrates in a minimally affected river in South Africa

Forty-two families of which the vast majority associated with particles >2000?µm were found. Sediment particle sizes <2000?µm had a detrimental effect on biodiversity. The highest biodiversity was recorded at sites characterised by riffle and run habitats. Although relatively high concentrations of selected metals were present in the sediment, it was largely from geological origin and most probably not bioavailable. No significant correlation was demonstrated between variation in temperature, pH, and electrical conductivity and diversity and abundance of macroinvertebrates. Therefore, it can be concluded that, under these conditions, sediment particle size and biotope availability played a decisive role on the distribution and abundance of macroinvertebrate taxa.     

微孔曝气与覆盖对城市重污染河道底泥磷形态分布及释放过程的影响

采用自行研发的泥-水界面微孔曝气系统,开展了底泥表面曝气和覆盖对城市重污染河道底泥磷释放及形态分布规律的影响研究.结果表明,微孔曝气能够有效提高上覆水的溶解氧(DO)和沉积物的氧化还原电位(Eh),能够将泥-水界面Eh维持在-100 m V左右,DO提高到6 mg·L-1以上.与对照比较,原位覆盖处理的上覆水DO和Eh有一定提高,但仍明显低于微孔曝气处理.与对照相比较,微孔曝气处理均有效降低上覆水中总磷(TP)和溶解性正磷酸盐(PO3-4)的含量.试验结束时,微孔曝气(A)和微孔曝气+原位覆盖处理(A+C)上覆水中TP含量由初始的0.201 mg·L-1分别降至0.062 mg·L-1和0.050 mg·L-1;上覆水中PO3-4含量由0.086 mg·L-1和0.078 mg·L-1分别降至0.026 mg·L-1和0.023 mg·L-1.与对照相比,微孔曝气处理明显降低了底泥间隙水中TP的浓度,在整个培养期间,其TP含量平均下降38.8%(A)和47.9%(A+C).底泥原位覆盖处理对抑制泥-水界面磷释放能力要弱于微孔曝气处理,而且在试验后期(50 d),上覆水中TP和PO3-4的含量均有所反弹.不管有无覆盖,泥-水界面微孔曝气处理均显著改变了表层底泥磷形态分布特征,显著降低了底泥中铁铝结合态磷(Fe/Al-P)组分比例,而钙结合态磷(Ca-P)含量比例却出现明显增加.单一的表面覆盖处理对底泥磷形态分布特征没有显著影响(P0.05).研究表明,与单一的处理效果相比较,泥-水界面纳米微孔曝气处理,并结合底泥原位覆盖,更有利于抑制城市重污染河道泥-水界面中磷的释放风险.     

Framing the ecosystem concept through a longitudinal study of developments in science and policy

This paper examines how scientific literature and policy documents frame the ecosystem concept and how these frames have shaped scientific dialogue and policy making over time. This was achieved by developing a frame typology, as a basis for organizing relevant value expressions, to assess how different frames have altered perspectives of the ecosystem concept. The frame typology and analysis is based on a semi‐grounded and longitudinal document analysis of scientific literature and policy documents using the ecosystem concept. Despite changing discourses and public priorities (e.g., cultural constructs of biodiversity) both science and policy documents are characterized by stable value systems that have not changed substantially since the 1930s. These value systems were defined based on ethical principles that delineate 6 core frames: humans first, dual systems, eco‐science, eco‐holism, animals first, and multicentrism. Specific crises (e.g., climate change) and cross‐disciplinary uptake and re‐uptake of, for example, the ecosystem services concept, have brought new perspectives to the forefront of public discourse. These developments triggered changes in the core frames that, rather than being value based, are based on how the ecosystem is conceptualized under fixed value systems and over time. Fourteen subframes were developed to reflect these longitudinal changes. There are as such clear framing effects in both scientific literature and in policy. Ecosystem research is for instance often characterized by unstated value judgments even though the scientific community does not make these explicit. In contrast, policy documents are characterized by clear value expressions but are principally management driven and human centered.     

Exploring the risks and benefits of flexibility in biodiversity offset location in a case study of migratory shorebirds

Biodiversity offsets aim to counterbalance the residual impacts of development on species and ecosystems. Guidance documents explicitly recommend that biodiversity offset actions be located close to the location of impact because of higher potential for similar ecological conditions, but allowing greater spatial flexibility has been proposed. We examined the circumstances under which offsets distant from the impact location could be more likely to achieve no net loss or provide better ecological outcomes than offsets close to the impact area. We applied a graphical model for migratory shorebirds in the East Asian–Australasian Flyway as a case study to explore the problems that arise when incorporating spatial flexibility into offset planning. Spatially flexible offsets may alleviate impacts more effectively than local offsets; however, the risks involved can be substantial. For our case study, there were inadequate data to make robust conclusions about the effectiveness and equivalence of distant habitat-based offsets for migratory shorebirds. Decisions around offset placement should be driven by the potential to achieve equivalent ecological outcomes; however, when considering more distant offsets, there is a need to evaluate the likely increased risks alongside the potential benefits. Although spatially flexible offsets have the potential to provide more cost-effective biodiversity outcomes and more cobenefits, our case study showed the difficulty of demonstrating these benefits in practice and the potential risks that need to be considered to ensure effective offset placement.     

Decentralization and people's participation in conservation: a comparative study from the Western Terai of Nepal

Nepal formally embarked on decentralized participatory conservation programmes in 1990. To assess who participates in and benefits from such programmes, stratified random questionnaire surveys of 234 households and interviews with 29 user group chairs were conducted in the buffer zones of two protected areas of the Nepalese Terai: Bardia National Park and Suklaphanta Wildlife Reserve. The Poisson regression shows that gender, education, household affluence, and conservation attitudes were significant predictors of people's participation in decentralized conservation programmes, while family size, ethnicity and resource dependency were not. The benefits of participation outweighed the costs based on respondents' estimates. The performance of grassroots organizations and levels of participation were correlated. Nepal's decentralized participatory conservation has achieved efficiency, relative equity and effectiveness to some extent. Yet the central government should devolve more power to local communities to sustain the achievements as well as to provide more equitable benefits to residents to ensure the effectiveness and sustainability of conservation programmes.     

Dynamics and driving forces of agricultural landscapes in Southern Ethiopia – a case study of the Chencha and Arbaminch areas

Agricultural landscapes in Ethiopia have undergone unprecedented changes. The direction of change, however, is unsustainable as manifested in land degradation, biodiversity loss, and low agricultural productivity. The objective of this study is to examine the patterns and trends of agricultural landscape development and responses of the local people within the framework of the dynamics of demography, socioeconomic conditions, politics, and natural resources in the Chencha and Arbaminch areas, Southern Ethiopia, during the last century. Information on cultivated and grazing land areas was acquired by satellite image interpretation. Interviews and group discussions provided important information on agricultural land use systems. A review and an analysis of secondary sources and documents of past studies were also used for trend analysis as a baseline and a supplement to oral history. The results show that cultivated land was expanded by 39% from 1973 until 2006, but per capita farming land holdings decreased enormously. In the same period of time, grassland shrank by 69% thus causing a significant decrease in livestock. Cultivated land scarcity can mostly be related to demographic pressure, which was exacerbated by government policy, land tenure, and the nature of subsistence agriculture. The farmers, however, were resourceful and developed skills over millennia to cope with the problems associated with population density and scarce resources. However, these traditional land use activities and land management practices have been deteriorating recently. Land use planners and environmental managers should take local knowledge and innovation into account in order to make sound decisions for the future.     

Contamination of lead (Pb) in the coastal sediments of north and south of Iran: a review study

Coastal areas of Iran are heavily affected by urbanisation, industrialisation, and maritime activities. One consequence of this environmental pressure is the contaminants accumulation, as heavy metals, into the marine ecosystem. In this review, the coastal areas in the north and south of the country were assessed for lead (Pb) contamination of, one of the most toxic metals found in the environment. All studies conducted during 2006–2016 with at least 10 specimens that reported the mean and standard deviation of Pb were considered in this review. Heterogeneity between studies was assessed using the Q and I² statistics. The Pb mean concentration overall studies was estimated to be 21.88?µg/g (95% CIs: 16.25–27.50). Random effect model showed no statistical difference in mean Pb concentration levels between south and north coasts. However, the variability in Pb mean concentrations within southern coasts was considerable and statistically significant. Moreover, the Pb concentrations in the northern coasts of Persian Gulf and Oman Sea, in south of Iran, decreased in the following order Hormozgan > Khuzestan > Sistan-VA-Balluchestan > Bushehr while in the southern coasts of Caspian Sea, in north of Iran, decreased in the order Guilan > Mazandaran > Golestan.     

我国中亚热带人工林水热通量对干旱差异响应的模拟研究

季节性干旱现象在我国中亚热带地区时有发生,为了研究该区域大气-生态系统之间的相互作用关系及其碳水收支状况,2002年起在江西省千烟洲（26.7°N,115.1°E）人工林生态系统建立了通量观测塔。2003年7月该人工林生态系统遭遇了历史上少有的高温少雨天气,本研究应用基于生理生态学过程的EALCO（Ecological Assimilation of Land and Climate Observation）模型及2003和2004年通量观测数据对该生态系统的水热通量进行了模拟,同时分析了干旱胁迫对它们产生的影响。结果显示,模型能够很好的模拟该生态系统的能量通量的日变化,净辐射、显热和潜热通量模拟值与实测值相关系数的平方（R2）及标准差分别为0.99和8.05 W.m-2;0.81和41.02 W.m-2;0.90和31.49 W.m-2,模型可以解释87%的日蒸散量的变化。从模拟结果看,2003年7月下旬（发生较严重干旱胁迫）较2004年同期（干旱程度轻）相比,冠层及土壤水势下降约2倍,植物蒸腾的日变化形式改变,根系吸水滞后冠层蒸腾的时间缩短约半小时,冠层导度下降40%～60%。模拟与观测结果均表明,2003年7月下旬每天正午的波文比大都介于1～2.2,而2004年同期正午的波文比则介于0.2～0.6。EALCO模型通过Ball模型将植物碳水过程耦合在一起,从而可以很好的模拟植物的气孔行为,进而准确的模拟植物水热过程对干旱的响应。土壤水分匮乏对冠层导度的限制是2003年干旱期间冠层潜热通量模拟值下降的根本原因。