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361.
江汉平原农田土壤有机碳分布与变化特点:以潜江市为例 总被引:8,自引:2,他引:6
以地处江汉平原腹地的潜江市农田土壤(水田、旱地)为研究对象,于2011年实地采样分析表层土壤(0~20 cm)有机碳的分布现状,并对比第二次土壤普查(1983年)资料,探讨28 a来江汉平原农田土壤有机碳的分布与变化特点.结果表明,2011年潜江市农田表层土壤有机碳密度为30.50 t·hm-2,碳储量为452.82×104t,与1983年相比有明显下降,下降速率分别为0.10 t·(hm2·a)-1和1.53 t·a-1,碳储量共损失了9%.两个时期水田土壤有机碳密度均明显高于旱地土壤,分别是旱地土壤的1.6倍和1.3倍,但是经过28年的常规耕作管理,水田土壤有机碳密度呈下降趋势,下降速率为0.23 t·(hm2·a)-1,导致的有机碳损失为52.83×104t,损失比例达16%;而旱地土壤有机碳则以0.05 t·(hm2·a)-1的速率缓慢增长,碳储量共增加了8.57×104t,增加比例为5%,远不能抵消水田土壤的有机碳损失.水田土壤碳储量的损失主要来自于低产潜育型水稻土碳密度的大幅下降所致(尽管其所占面积比例较小),其碳损失量占水田碳损失量的比例达80%;其次为占水田面积比例最大的潴育型水稻土,其碳损失量占水田碳损失量的15%.旱地土壤碳储量增长缓慢,完全来自于面积占96%的灰潮土有机碳密度的增长.因此,江汉平原区水田土壤有机碳的变化决定了农田土壤有机碳的整体动向,今后需着力提升有机碳下降迅速的低产水田以及面积较大的土壤类型的有机碳积累和固持能力. 相似文献
362.
363.
Distribution of Al-, Fe- and Mn-pools and their correlation in soils from two acid deposition small catchments in Hunan, China 总被引:2,自引:0,他引:2
Distribution of Al-, Fe- and Mn-pools was investigated in five forest soil profiles (consisting of four horizons) in each of two Hunan catchments (BLT and LKS) where acid deposition has been considered critical. Al- and Fe-pools were higher in BLT than those in LKS, but Mn-pools much lower in BLT. Mn-pools vary from topsoils to bottom soils, but there are different trends for different Mn speciation. Al- and Fe-pools, except amorphous Feox, were positively correlated to contents of soil organic matter (OM) showed by the loss on ignition in the two catchments. Accumulation of Al- and Fe-pools may occur in the area where soil organic matter was enriched (e.g. in top soil and rhizosphere soil). However, no direct correlation is observed between Mn and OM. Acidic atmospheric deposition may affect transforming among speciations of Al-, Fe- and Mn-pools and leaching of soil Al, Fe and Mn through formation of soluble organo-metal dissolved Al which was potentially toxic, increased. There were significant correlations between Al-pools complexes or change of oxidation–reduction conditions. Mnex (exchangeable Mn) and Mnox (amorphous and organic Mn) were highly linearly correlation with soil pH values at LKS but at BLT. Under acid deposition, the availability of the nutrient Fe increased with the amount of dissolved Al, which was potentially toxic, in the two catchments. There are no significant correlations between Alex (exchangeable Al) and Mnex, Feex (exchangeable Fe) and Mnex in this work, indicating potentially toxic Mn increase seldom accompanying with Al increase in the two catchments. 相似文献
364.
Reza M. Khanbilvardi Andrew S. Rogowski Arthur C. Miller 《Journal of the American Water Resources Association》1983,19(4):585-593
ABSTRACT A rill-interrill erosion model was applied to a mined and reclaimed area. Soil loss from the interrill areas was estimated by the Universal Soil Loss Equation (USLE). The model considers the fate and ultimate disposition of the sediment from interrill areas along with the fate and destination of soil materials detached by the rill flow. The net sediment loss was predicted by comparing, for a given flow, the amounts of eroded soil to rill transport capacity. When applied to a selected stripmined and reclaimed site the model displayed the location of contributing areas and the amount of erosion and deposition. The predicted areal distribution of erosion and deposition was compared to measured data. Agreement between the predicted and measured values was within 25 percent. 相似文献
365.
Hosung Ahn 《Journal of the American Water Resources Association》1998,34(3):583-593
ABSTRACT: The total phosphorous (TP) concentrations in the South Florida rainfall have been recorded in weekly intervals with a detection limit (DL) of 3.5 μg/L. As a large amount of the data is reported as below the DL, appropriate statistical methods are needed for data analysis. Thus, an attempt was made to identify an appropriate method to estimate the mean and variance of the data. In particular, a method to separate the statistics for the below DL portion from the estimated population statistics is proposed. The estimated statistics of the censored data are compared with the statistics of the uncensored data available from the recent years’ laboratory records. It was found that the one-step restricted maximum likelihood method is the most accurate for the wet TP data, and that the proposed method to combine the estimated statistics for TP < DL portion and the sample statistics for TP ≥ DL portion improves estimates compared to the conventional maximum likelihood estimates. 相似文献
366.
Space shuttle launches produce localized hydrochloric acid deposition. The interaction of solid rocket motor exhaust and deluge
water released on the pad at the time of launch results in the formation of an exhaust cloud. The spatial pattern and extent
of deposition from the launch cloud are predicted by the rocket exhaust effluent diffusion (REED) model. The actual pattern
of deposition has been mapped by field surveys for each shuttle launch since 1981. In this paper we use a geographical information
system (GIS) to compare model predictions with ground patterns for 49 shuttle launches. We also compile cumulative maps of
deposition patterns needed to consider long-term impacts. The direction of launch cloud movement did not differ significantly
from model predictions. The REED model overpredicted both the area that received deposition and the maximum distance from
the launch pad that deposition occurred. Severe vegetation damage was restricted to near-field deposition areas within 1980
m north of each launch pad. Total area impacted from launches has been 87.0 ha around pad 39A and 52.9 ha around pad 39B.
Far-field deposition has caused leaf spotting from acid droplets or aluminum oxide over a wider and more variable area than
near-field. A total of 19,397 ha has received deposition, but 63.6% of this area has received deposition only one time and
92.2% not more than three times. GIS techniques provide means to test spatial models and compile information useful for assessing
cumulative impacts. 相似文献
367.
368.
The governments of British Columbia, Alberta, Saskatchewan, Manitoba, Northwest Territories, and Canada held joint consultations in 1980 to review the available information on acid rain from Western and Northern Canada. It was concluded that acid rain might become a problem in the future and, hence, a research, monitoring, and management strategy for acidic deposition was needed. An overview of the joint governments' management strategy, organization of research and monitoring programs, and accomplishments to date are discussed in this article.The authors are members of the Technical Committee for the Long Range Transport of Atmospheric Pollutants (LRTAP)/Acid Deposition in Western and Northern Canada, and represent Alberta and British Columbia, respectively. 相似文献
369.
William L. Jackson Robert L. Beschta 《Journal of the American Water Resources Association》1984,20(4):527-533
ABSTRACT A flume study was conducted to examine (1)changes in the particle-size distribution of sediments in riffles due to the proportion of sand in transport and the total rate of bedload transport at the time the riffle is deposited and (2) the effect of high sand transport rates on the stability of gravel riffles. The median particle size of sediment deposited in the riffle was larger than that of the sediment in transport. Small but significant (a = 0.05) decreases in the median particle size of riffle sediments resulted as the sand-to-gravel ratio. Increased concentrations of sand in transport caused previously stable gravel riffles to undergo scour. These results, in combination with information from other studies, suggest that an alluvial channel with pool-riffle sequences and with sand and gravel beds may respond to an increased delivery of sand by reducing form roughness. Form roughness can be reduced by degrading riffles and filling pools. Subsequent responses may be increases in width-to-depth ratio and slope. 相似文献
370.
废旧干电池的环境污染防治及回收利用 总被引:5,自引:0,他引:5
介绍了各种干电池的基本化学组成,分析了废旧干电池污染环境的主要途径及对人类的危害,并就回收利用问题提出建议。 相似文献