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981.
Marino Martini Luciano Giannini Antonella Buccianti Laura Maggi Franco Prati Paola Cellini Legittimo Paolo Iozzelli Bruno Capaccioni 《Chemistry and Ecology》1991,5(3):139-147
A major influence on the environment of active volcanic areas is expected from continuous input of chemical species pertaining to fumarolic activities occurring during inter-eruptive intervals.
The systematic investigations carried out during thirteen years in the island of Vulcano (Italy) showed also substantial contributions to phreatic waters and soils of minor constituents and trace metals from volcanic rocks with no negligible influence on growing crops.
Greater extents of these phenomena have been observed for products of hydromagmatic volcanic activity or of long-lasting weathering processes. 相似文献
The systematic investigations carried out during thirteen years in the island of Vulcano (Italy) showed also substantial contributions to phreatic waters and soils of minor constituents and trace metals from volcanic rocks with no negligible influence on growing crops.
Greater extents of these phenomena have been observed for products of hydromagmatic volcanic activity or of long-lasting weathering processes. 相似文献
982.
Iodine Deficiency Disorders (IDD) are a common health problem prevalent in the wet zone of Sri Lanka with a prevalence of >25 of the population. In comparison, in the dry zone of Sri Lanka IDD occurs in <10 of the population. Seventy soil samples from 14 villages selected on the basis of the incidence of goitre, were collected and analysed for 13 trace elements using ICP-MS. In order to identify any prevailing differences in antecedent chemical environments, soil samples from each pre-selected village were classified into three groups in terms of their geographical location. Among the elements investigated, the total soil concentrations of Rb, Sr, Ba, Mn and Co are lower in the wet zone of Kalutara. In contrast, total soil Rb, Sr, Ba and Mn contents are higher in the dry zone of Anuradhapura. Further soil total Mo and Nb levels are relatively similar in all pre-selected study locations. The high endemic goitre regions (IDD >25 of the population) show low levels of Rb, Sr, Ba, and Mn and higher levels of V, Cr, Co, Ni, Cu, Zn and Pb as compared with moderate and non-goitre areas. Factor analysis was used to exploit the correlation structure present in data and yielded three groups in all cases. This indicated that most transition group elements and iodine are associated with the Mn phase in the low IDD areas whereas iodine shows a high affinity for the organic phase in high IDD regions. The variable distribution of trace elements, therefore, must be due to differences in mobility and capacity for incorporation into the structure of secondary minerals or organic phases. 相似文献
983.
长江中游潜沼化土壤的限制因子及其对策研究 总被引:2,自引:0,他引:2
研究表明,地下水和单一的种植结构与利用方式,是长江中游地区潜沼化土壤生产力的主要限制因子,在调查和田间试验的基础上,在国家目前难以实现配套水利工程设施的条件下,提出了以生物措施为主,结合小型工程措施进行综合改良利用,治渍改土的切实可行的方案,在优化农业结构的前提下,比较了诸多优化模式,通过田间试验,筛选出诸如退田还湖,种植水生经济植物,垄稻沟鱼及各种轮作方式,同时适当引进耐潜作物品种,实行配方施肥 相似文献
984.
V.?Krishna?PrasadEmail author Ben?Stinner Deb?Stinner John?Cardina Richard?Moore Prabhat?K.?Gupta Harao?Tsuruta Kiyoto?Tanabe K.?V.?S.?Badarinath Casey?Hoy 《Regional Environmental Change》2003,3(4):154-161
We studied trends in food production and nitrous oxide emissions from India's agricultural sector between 1961 and 2000. Data
from Food and Agricultural Statistics (FAO) have been gathered covering production, consumption, fertilizer use and livestock
details. IPCC 1996 revised guidelines were followed in studying the variations in N2O-N emissions. Results suggest that total N2O-N emissions (direct, animal waste and indirect sources) increased ~6.1 times from ~0.048 to ~0.294 Tg N2O-N, over 40 years. Source-wise breakdown of emissions from 1961–2000 indicated that during 1961 most of the N2O-N inputs were from crop residues (61%) and biological nitrogen fixation (25%), while during 2000 the main sources were synthetic
fertilizer (~48%) and crop residues (19%). Direct emissions increased from ~0.031 to ~0.183 Tg. It is estimated that ~3.1%
of global N2O-N emissions comes from India. Trends in food production, primarily cereals (rice, wheat and coarse grains) and pulses, and
fertilizer consumption from 1961–2000 suggest that food production (cereals and pulses) increased only 3.7 times, while nitrogenous
fertilizer consumption increased ~43 times over this period, leading to extensive release of nitrogen to the atmosphere. From
this study, we infer that the challenge for Indian agriculture lies not only in increasing production but also in achieving
production stability while minimizing the impact to the environment, through various management and mitigation options. 相似文献
985.
986.
珠江三角洲粘质水稻土的肥力水平和产量水平与土壤结构特性密切相关。中低产水稻土产量偏低的原因主要是5—2、2—1、1—0.5mm水稳性团聚体、1—0.01mm粗粒微团聚体和非毛管孔隙都较少,从而导致土壤通透性差,水稻生长不良。水旱轮作、犁冬晒白和增施有机物料都能在一定程度上改善土壤结构孔隙。因而促进水气循环、土壤活化、产量提高。特别是水旱轮作与施用有机物料相结合,对改善粘质中低产水稻土结构的效果最为显著。犁冬晒白对改善土壤结构和促进水稻生长发育,当季效果也很明显,但其作用不能持久,宜与其它两种措施配合使用。 相似文献
987.
Martin Pichler Georg Guggenberger Robert Hartmann Wolfgang Zech 《Environmental science and pollution research international》1996,3(1):24-31
The behavior of 20 PAH in the organic layers of a L mull, an Of mull and a mor was assessed by a combined approach of a soil
profile study, and the analysis of particle-size separates. Increasing PAH concentrations with depth in the mor profile (L,
866 μg kg−3; Of, 2902 μg kg−1; Oh, 10489 ug kg−1) were assigned to selective enrichment during organic matter decomposition. PAH were further highly enriched within the finer
separates. For the L horizons, significant positive correlations were established between the enrichment of individual PAH
(as observed from the decomposition gradient between the >2-mm fraction and the < 0.05-mm fraction), and the KOW for each compound. The slope of the regression line, m, described the degree of differentiation between low- and high-molecular
PAH during litter decomposition. Since m was greatest in the most biologically active humus type (L mull, 0.33) and smallest
in the most inactive (mor, 0.20), microbial breakdown was assumed as the dominating process for this differentiation. The
results also indicated that decomposition processes had already taken place in the L horizons, leading to morphological and
chemical changes of organic matter, and to an enrichment of high molecular PAH. 相似文献
988.
我国农村耕地利用及保护对策 总被引:2,自引:0,他引:2
论述了当前我国土地资源利用中存在的耕地数量减少、耕地质量下降、土地利用结构和布局不合理、土地资源未能得到有效配置等问题,分析了这些问题产生的原因,并在此基础上提出了相应的耕地保护对策。 相似文献
989.
Cecilia Akselsson Olle Westling Harald Sverdrup Johan Holmqvist Gunnar Thelin Eva Uggla Gunnar Malm 《Water, Air, & Soil Pollution: Focus》2007,7(1-3):201-210
The effects of harvesting on the long-term mass balances of calcium (Ca), magnesium (Mg) and potassium (K) were evaluated
on a regional level in Sweden. A new high-resolution weathering database was used together with estimates of total deposition,
losses through harvest and leaching. Estimates were made for pine and spruce separately and for two harvesting intensity scenarios:
stem harvesting and whole-tree harvesting. The mass balance calculations showed net losses of Ca and Mg in almost the whole
country for both scenarios. The losses were smaller for pine than for spruce. The K balances were mainly positive for pine
but negative for spruce. Leaching was a main factor in the mass balances, especially for Ca and Mg. Whole-tree harvesting
in spruce forests led to substantially higher net losses of K and Ca than stem harvesting, according to the calculations.
In the whole-tree harvesting scenario in spruce forests the estimated yearly net losses of Ca, Mg and K corresponded to at
least 5%, 8% and 3% of the pools of exchangeable base cations, respectively, at 25% of the analysed sites. If losses of this
magnitude continue the depletion of the pools of Ca, Mg and K may lead to very low base saturation of the soils, possibly
accompanied by negative effects on soil fertility, runoff water quality, tree vitality and tree growth within a forest rotation
in parts of Sweden. Avoiding whole-tree harvesting can improve the situation substantially for K, but the losses of Ca and
Mg will still be significant. 相似文献
990.
Methane emission from rice paddy soils, aerotolerance of methanogens and global thermal warming 总被引:3,自引:0,他引:3
In vitro methane emissions from different rice paddy soils and algal mats were studied under anoxic and atmospheric conditions. Methane production from rice paddy soils cultivating different strains of rice was found to be appreciable under anoxic conditions, but considerably reduced under atmospheric conditions, and dependent on rice cultivars (strains). A contradictory result was obtained with a Gobindabhog cultivated rice field (a strain of rice with aroma), where methane yield under anoxic was greater than that under atmospheric conditions. The results indicated aerotolerance of methanogens or the possible existence of microaerophilic methanogens. The results from algal mats corroborated these findings.Methane has been considered to be an important greenhouse gas contributing significantly to global thermal warming (GTW). Flooded rice paddy fields have been considered to be a most prominent source of abiogenic methane emission, though considerable uncertainty exists regarding the true estimates of methane emission. Factors affecting methane emission and its abatement have been examined. In spite of increasing methane emission, rice cultivation leads to enormous utilization of the green house gas carbon dioxide and release of oxygen to the atmosphere. Thus, the contribution of methane to GTW (from rice paddy cultivation) is more than compensated by carbon dioxide absorption.Appropriate steps have been suggested for the reduction of methane emissions, the most important of which is the restoration of methane sinks. 相似文献