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排序方式: 共有289条查询结果,搜索用时 31 毫秒
281.
Hongxing Zhang Xiaoke Wang Zongwei Feng Junzhu Pang Fei Lu Zhiyun Ouyang Hua Zheng Wenzhao Liu Dafeng Hui 《环境科学学报(英文版)》2011,23(1):79-86
As a conventional farming practice, tillage has lasted for thousands of years in Loess Plateau, China. Although recent studies show
that tillage is a prominent culprit to soil carbon loss in croplands, few studies have investigated the influences of tillage on the responses
of soil CO2 e ux (SCE) to soil temperature and moisture. Using a multi-channel automated CO2 e ux chamber system, we measured
SCE in situ continuously before and after the conventional tillage in a rain fed wheat field of Loess Plateau, China. The changes in soil
temperature and moisture sensitivities of SCE, denoted by the Q10 value and linear regression slope respectively, were compared in the
same range of soil temperature and moisture before and after the tillage. The results showed that, after the tillage, SCE increased by
1.2–2.2 times; the soil temperature sensitivity increased by 36.1%–37.5%; and the soil moisture sensitivity increased by 140%–166%.
Thus, the tillage-induced increase in SCE might partially be attributed to the increases in temperature and moisture sensitivity of SCE. 相似文献
282.
2005年4月-2006年3月年间对军山湖河蚬进行了周年逐月采集,对河蚬的种群动态进行了分析,并采用Brey经验公式测算了军山湖河蚬周年生产量。结果表明,河蚬周年平均生物量为115.84 g/m2,平均密度为51.93 ind./m2。种群密度及生物量峰值出现在58、月5,月分别为90.67 ind./m21,87.39 g/m2;8月分别为72 ind./m2,170.67 g/m2。密度及生物量在次年3月份为最低值,分别为27.2 ind./m2,58.88 g/m2。河蚬周年生产量(AFDW)为10.86(g/m2.yr),P/B系数为0.52,结果较为合理。P/B系数较低,说明这一资源日趋贫乏,需要合理的保护利用。 相似文献
283.
气溶胶地基观测数据和颗粒物浓度数据的同步定量评估可为了解长安区大气污染的垂直分布特征,制定合理的大气污染控制提供更有效的依据.基于CE-318太阳光度计观测数据,分析了2018年10月~2021年4月西安市长安区月均和季均气溶胶光学特性分布和变化特征,结合近地面颗粒物浓度数据,分析了不同季节、不同污染程度下气溶胶光学厚度(AOD)对颗粒物浓度的响应.结果表明:(1)观测期间长安区AOD季节变化分明:秋季(1.02)>冬季(1.00)>夏季(0.63)>春季(0.47); AOD月度、年际差异大,2019年AOD(0.51)略高于2020年(0.48).(2)整个观测期间长安区气溶胶主控模态存在明显的季节、月度差异,从春季到冬季气溶胶主控模态逐渐从粗模态向细模态转变;2019年气溶胶主控模态的季节变化与整个观测时段类似,2020年各季节气溶胶Angstrom波长指数(Angstrom)分布稳定,气溶胶粒子均以粗模态的形式存在;整个观测时段来看长安区气溶胶类型以混合型气溶胶为主.(3)AOD和Angstrom的关系存在明显的季节差异,春季大气污染以粗模态的气溶胶粒子为主导... 相似文献
284.
中国森林生态系统的异戊二烯排放研究 总被引:3,自引:4,他引:3
植被的非甲烷碳氢化合物(non-methane hydrocarbon,NMHC)排放对大气环境变化有重要的影响,异戊二烯是对流层最主要的NMHC之一.本文应用Guenther的光温影响模型,对1993年中国森林生态系统的异戊二烯排放量进行了估算.结果发现:中国森林生态系统异戊二烯总的排放量约为0.03~8.6Tg/a,对全球碳的贡献量以碳计为0.026~7.589Tg/a,年最大可能排放量约占全球年排放总量的1.5%~4.3%;排放有较大的空间(地域)差异,年排放大值区分布在南方多林区和东北地区,以云南和黑龙江2省最大,对全国排放的贡献率分别为22%和11%;不同植被对总排放量的贡献率有较大差异,贡献率较大的杨树和栎类分别达到52.28%和44.29%. 相似文献
285.
286.
Nonpoint Source Pollution Responses Simulation for Conversion Cropland to Forest in Mountains by SWAT in China 总被引:1,自引:0,他引:1
Several environmental protection policies have been implemented to prevent soil erosion and nonpoint source (NPS) pollutions
in China. After severe Yangtze River floods, the “conversion cropland to forest policy” (CCFP) was carried out throughout
China, especially in the middle and upper reaches of Yangtze River. The research area of the current study is located in Bazhong
City, Sichuan Province in Yangtze River watershed, where soil erosion and NPS pollution are serious concerns. Major NPS pollutants
include nitrogen (N) and phosphorus (P). The objective of this study is to evaluate the long-term impact of implementation
of the CCFP on stream flow, sediment yields, and the main NPS pollutant loading at watershed level. The Soil and Water Assessment
Tool (SWAT) is a watershed environmental model and is applied here to simulate and quantify the impacts. Four scenarios are
constructed representing different patterns of conversion from cropland to forest under various conditions set by the CCFP.
Scenario A represented the baseline, i.e., the cropland and forest area conditions before the implementation of CCFP. Scenario
B represents the condition under which all hillside cropland with slope larger than 25° was converted into forest. In scenario
C and D, hillside cropland with slope larger than 15° and 7.5° was substituted by forest, respectively. Under the various
scenarios, the NPS pollution reduction due to CCFP implementation from 1996–2005 is estimated by SWAT. The results are presented
as percentage change of water flow, sediment, organic N, and organic P at watershed level. Furthermore, a regression analysis
is conducted between forest area ratio and ten years’ average NPS load estimations, which confirmed the benefits of implementing
CCFP in reducing nonpoint source pollution by increasing forest area in mountainous areas. The reduction of organic N and
organic P is significant (decrease 42.1% and 62.7%, respectively) at watershed level. In addition, this study also proves
that SWAT modeling approach can be used to estimate NPS pollutants’ impacts of land use conversions in large watershed. 相似文献
287.
Mengmeng Zheng Hua Zheng Yingxia Wu Yi Xiao Yihua Du Weihua Xu Fei Lu Xiaoke Wang Zhiyun Ouyang 《环境科学学报(英文版)》2015
The nitrogen balance can serve as an indicator of the risk to the environment of nitrogen loss from agricultural land. To investigate the temporal and spatial changes in agricultural nitrogen application and its potential threat to the environment of the Haihe Basin in China, we used a database of county-level agricultural statistics to calculate agricultural nitrogen input, output, surplus intensity, and use efficiency. Chemical fertilizer nitrogen input increased by 51.7% from 1990 to 2000 and by 37.2% from 2000 to 2010, concomitant with increasing crop yields. Simultaneously, the nitrogen surplus intensity increased by 53.5% from 1990 to 2000 and by 16.5% from 2000 to 2010, presenting a continuously increased environmental risk. Nitrogen use efficiency decreased from 0.46 in 1990 to 0.42 in 2000 and remained constant at 0.42 in 2010, partly due to fertilizer composition and type improvement. This level indicates that more than half of nitrogen inputs are lost in agroecosystems. Our results suggest that although the improvement in fertilizer composition and types has partially offset the decrease in nitrogen use efficiency, the environmental risk has still increased gradually over the past 20 years, along with the increase in crop yields and nitrogen application. It is important to achieve a better nitrogen balance through more effective management to significantly reduce the environmental risk, decrease nitrogen surplus intensity, and increase nitrogen use efficiency without sacrificing crop yields. 相似文献
288.
Yaqin Tan Zhemin Shen Weimin Guo Chuang Ouyang Jinping Ji Weili Jiang Haiyun Zhou 《环境科学学报(英文版)》2014,26(3):512-518
289.
Ouyang Shenyang Huang Yanli Gao Huadong Guo Yachao Wu Laiwei Li Junmeng 《Environmental science and pollution research international》2022,29(32):48285-48300
Environmental Science and Pollution Research - The long-term, high-yield production of coal has resulted in the large-scale accumulation of coal gangue on the ground surface, which causes serious... 相似文献