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931.
A study was performed selecting one protected forest and an adjacent degraded forest ecosystem to quantify the impact of forest
degradation on soil inorganic nitrogen, fine root production, nitrification, N-mineralization and microbial biomass N. There
were marked seasonal variations of all the parameters in the upper 0–10 and lower 10–20 cm depths. The seasonal trend of net
nitrification and net N-mineralization was reverse of that for inorganic nitrogen and microbial biomass N. Net nitrification,
net N-mineralization and fine root biomass values were highest in both forests during rainy season. On contrary, inorganic
nitrogen and microbial biomass N were highest during summer season.
There was a marked impact of forest degradation on inorganic nitrogen, fine root production nitrification, N-mineralization
and microbial biomass observed. Soil properties also varied with soil depth. Fine root biomass, nitrification, N-mineralization
and microbial biomass N decreased significantly in higher soil depth. Degradation causes decline in mean seasonal fine root
biomass in upper layer and in lower depth by 37% and 27%, respectively. The mean seasonal net nitrification and N-mineralization
in upper depth decreased by 42% and 37%, respectively and in lower depth by 42.21% and 39% respectively. Similarly microbial
biomass N also decreased by 31.16% in upper layer 33.19% in lower layer. 相似文献
932.
Alexander L. Bond 《Environmental pollution (Barking, Essex : 1987)》2010,158(5):1182-1184
Stable isotopes of carbon (δ13C) and nitrogen (δ15N) are used frequently in ecotoxicological investigations of birds to relate contaminant levels to trophic position (δ15N) or foraging location (δ13C) and many researchers using avian feathers in such investigations use δ13C or δ15N as a predictor of contaminant concentrations. Contaminants, especially mercury, however, are integrated into feathers over different time periods than are stable isotopes, resulting in spurious relationships that have no biological meaning. I show the fundamental principles behind the conclusion that relating δ13C or δ15N to contaminant concentrations in feathers is not appropriate in light of the number of recent studies that have employed this approach, and make recommendations for those wishing to investigate the relationship between contaminants and stable isotope ratios. 相似文献
933.
Clémentine Fritsch 《Environmental pollution (Barking, Essex : 1987)》2010,158(3):827-840
We investigated how host factors (species, age, gender) modulated Cd, Pb, Zn, and Cu concentrations, metallothionein levels (MTs) and their relationships in 7 sympatric small mammal species along a pollution gradient. Cd concentrations in liver and kidneys increased with age in all species. Age effect on other metals and MTs differs among species. Gender did not influence metal and MT levels except in the bank vole. Three patterns linking internal metal concentrations and MTs were observed along the gradient: a low metal accumulation with a (i) high (wood mouse) or (ii) low (bank vole) level of MTs accompanied by a slight or no increase of MTs with Cd accumulation; (iii) an elevated metal accumulation with a sharp increase of MTs (common and pygmy shrews). In risk assessment and biomonitoring perspectives, we conclude that measurements of MTs and metals might be associated because they cannot be interpreted properly when considered separately. 相似文献
934.
Christopher K.H. Guay Alexander V. Zhulidov Daniel A. Zhulidov Robert M. Holmes John V. Headley 《Environmental pollution (Barking, Essex : 1987)》2010,158(2):624-630
Concentrations of dissolved and particulate Cd, Cu, Pb and Zn were determined in samples collected in summer 1998 from the lower reaches of six major Eurasian arctic rivers: the Onega, Severnaya Dvina, Mezen, Pechora, Ob and Yenisey. These data comprise some of the earliest measurements of trace metals in Eurasian arctic rivers above the estuaries using recognized clean techniques. Significant (α = 0.05) differences were observed among mean concentrations of particulate metals in the individual rivers (F ≤ 0.006), with highest levels overall observed in the Severnaya Dvina and Yenisey. No significant differences were observed among mean concentrations of dissolved metals in the individual rivers (F = 0.10-0.84). Contributions from anthropogenic sources are suggested by comparison of trace metal ratios in the samples to crustal abundances. These results establish a baseline for assessing future responses of Eurasian arctic river systems to climate-related environmental changes and shifting patterns of pollutant discharge. 相似文献
935.
Christine Lors Jean-François Ponge Maite Martínez Aldaya 《Environmental pollution (Barking, Essex : 1987)》2010,158(8):2640-2647
Five bioassays (inhibition of lettuce germination and growth, earthworm mortality, inhibition of springtail population growth, avoidance by springtails) were compared, using four coke factory soils contaminated by PAHs and trace elements, before and after biotreatment. For each bioassay, several endpoints were combined in an ‘ecoscore’, a measure of test sensitivity. Ecoscores pooled over all tested bioassays revealed that most organisms were highly sensitive to the concentration of 3-ring PAHs. When four soils were combined, behavioural tests using the springtail Folsomia candida showed higher ecoscores, i.e. they were most sensitive to soil contamination. However, despite overall higher sensitivity of behavioural tests, which could be used for cheap and rapid assessment of soil toxicity, especially at low levels of contamination, some test endpoints were more sensitive than others, and this may differ from a soil to another, pointing to the need for a battery of bioassays when more itemized results are expected. 相似文献
936.
Day and night period sampling programs were carried out using a versatile air pollutant system to collect fine particulate matter (PM2.5) and coarse particulate matter (PM2.5–10) simultaneously at a traffic junction that is only 60 m from HungKuang University located in Central Taiwan. Therefore, HungKuang University is regarded as the traffic sampling site in this study. Similar measurements were carried out in a previous 2013 study by Fang and colleagues during October 2012 to November 2012. Determination of metallic element composition of fine and coarse particulates collected during the day and the night was accomplished with inductively coupled plasma atomic emission spectrometry (ICP-AES). The results indicated that there were no significant differences in composition of metallic elements Zn, Cu, Cr, Mn, Fe, Pb, and Cd in either coarse or fine particles for both day and night sampling periods. The statistical results indicated no significant differences for metallic elements in the PM2.5–10 particulates for day and night sampling periods. Also, no significant differences were noted for metallic elements in the PM2.5 particulates for day and night sampling periods at this traffic sampling site. The proposed reason is the limited sampling period employed in this study. Another potential reason is the presence of traffic that runs heavily both day and night being a major contributor to the ambient air metallic pollutants in this region. 相似文献
937.
A systematical approach based on hierarchical eco-restoration system for the simultaneous removal of COD and dissolved nutrients was proposed and applied in a complex residential-cropland area in Kunming, China from August 2006 to August 2008, where the self-purifying capacity of the agricultural ecosystem had been lost. The system includes four main parts: (1) fertilizer management and agricultural structure optimization, (2) nutrients reuse, (3) wastewater treatment, and (4) catchment restoration. The results showed that the average removal efficiencies were 90% for COD, 93% for ammonia, 94% for nitrate and 71% for total dissolved phosphorus (TDP) when the hierarchical eco-restoration agricultural system was in a relatively steady-state condition. The emergence of 14 species of macrophytes and 4 species of zoobenthos indicated that the growth conditions for the plankton were improved. The results demonstrated that this promising and environmentally benign hierarchical eco-restoration system could decrease the output of nutrients and reduce downstream eutrophication risk. 相似文献
938.
939.
940.
Agricultural landscapes illustrate the impact of human actions on physical settings, and differential human pressures cause
these landscapes to change with time. Our study explored changes in the terraced landscapes of Nisyros Island, Greece, focusing
on the socioeconomic aspects during two time periods using field data, cadastral research, local documents, and published
literature, as well as surveys of the islanders. Population increases during the late 19th to early 20th centuries marked a significant escalation of terrace and dry stone wall construction, which facilitated cultivation on 58.4%
of the island. By the mid-20th century, the economic collapse of agricultural activities and consequent emigration caused the abandonment of cultivated
land and traditional management practices, dramatically reducing farm and field numbers. Terrace abandonment continued in
recent decades, with increased livestock grazing becoming the main land management tool; as a result, both farm and pasture
sizes increased. Neglect and changing land use has led to deterioration and destruction of many terraces on the island. We
discuss the socioeconomic and political backgrounds responsible for the land-use change before World War II (annexation of
Nisyros Island by the Ottoman Empire, Italy, and Greece; overseas migration opportunities; and world transportation changes)
and after the war (social changes in peasant societies; worldwide changes in agricultural production practices). The adverse
landscape changes documented for Nisyros Island appear to be inevitable for modern Mediterranean rural societies, including
those on other islands in this region. The island’s unique terraced landscapes may qualify Nisyros to become an archive or
repository of old agricultural management techniques to be used by future generations and a living resource for sustainable
management. 相似文献