共查询到20条相似文献,搜索用时 62 毫秒
1.
2.
为探究冬、春两季不同植物群落的不同垂直高度处PM_(2.5)浓度的变化,运用垂直梯度法对北京奥林匹克森林公园碳通量塔、鹫峰国家森林公园气象观测塔及对照点(北京林业大学校内)共3处样地进行研究。结果表明:春季样地的PM_(2.5)浓度值呈现为冠层以上(塔上部,12 m处)冠层(塔中部,9 m处)冠层以下、地面以上(塔下部); PM_(2.5)浓度日变化基本呈现06∶00—10∶00早上高峰,10∶00—14∶00降低,18∶00—22∶00又呈现出升高的"倒N"型的变化规律;鹫峰国家森林公园气象观测塔3层PM_(2.5)浓度值表现为塔上层塔中层塔下层; 3处地点同一高度处的PM_(2.5)浓度值表现为北京林业大学奥林匹克森林公园鹫峰国家森林公园; 3处地点的PM_(2.5)值为冬季春季。 相似文献
3.
指出了原油装卸和储存过程的蒸发损耗主要是由饱和烃和芳烃的挥发而引起的,两者共含原油组份的17.4%~22.2%。根据公式计算,原油装船损耗介于0.017%~0.032%,由于装船过程需要伴热,因此按0.03%考虑较为合理,原油储运时的挥发损耗为0.078%~0.217%之间,该过程无需伴热,因此,按0.15%考虑较为合理。装船损耗的排放量明显小于储运工程的损耗量,但由于装船损耗在短时间内集中排放,因此,对下风向地面浓度的影响,装船废气明显大于储运废气。 相似文献
4.
5.
以山葡萄籽为实验材料,通过单因素法提取葡萄籽中的多酚。根据不同浸提剂在540nm处可见光吸收情况的测定,确定70%甲醇溶液为最佳浸提剂。通过单因素试验确定了提取剂浓度、提取时间、提取温度、料液比的适用范围,再利用正交试验法进行工艺优化。确定最佳工艺条件为:体积分数70%的甲醇,料液比1:20(m/v),70℃水浴,浸提20min。山葡萄籽中多酚的含量可达18.981mg/g。 相似文献
6.
《绿色科技》2018,(24)
利用O_3及其前体物在线观测数据,对2016年夏季南京市城区O_3污染特征开展研究。结果表明:南京市城区O_3浓度呈显著单峰变化特征,与NO、NO_2、NOx、CO和VOCs呈负相关关系。白天高温有利于O_3的生成,而高湿环境则会抑制O_3的生成。夏季O_3高值易发生于西北和东北方向。在≤4m/s风速范围内,O_3浓度伴随风速的增加而上升。当风速4m/s时,O_3浓度由于大风扩散作用而降低。南京市大气VOCs中烷烃浓度最高,烯烃和芳香烃O_3生成潜势(OFP)较高。乙烯、丙烯、间/对-二甲苯、甲苯、异戊二烯、异戊烷、正丁烷、丙烷、邻二甲苯和反-2-丁烯是活性最高的VOCs物种。 相似文献
7.
为提高分析效率,对活性炭管对气体中苯的吸附和解吸情况进行了实验改进,结果显示:活性炭管在0.5L/min流量下,吸气10min ,A段吸附了约8mg苯后开始穿透,在满足标准方法要求的吸附效率下,A、B两段共吸附了约8.5mg苯,折算浓度为1700mg/m3,因此,以相同的采样流量和时间,在此浓度以下,可对活性炭管A、B两段合并解吸进行分析测定,若高于此浓度值再分别解吸以判断是否符合解吸效率。改进的解吸方式可减少操作步骤,节省时间和有毒的CS2试剂。 相似文献
8.
9.
《福建林业科技》2022,(1)
采用固体发酵箱进行球孢白僵菌固体发酵中试试验,对菌丝不同生长阶段的温度、CO_2变化进行监测。结果表明,0~24 h为发酵准备期(延滞期),白僵菌菌丝生长慢,固体培养料温度呈小幅上升的趋势,维持在22℃左右,发酵箱内CO_2浓度则呈现逐渐升高的状态,从2000 mg·m(-3)逐渐上升到5000 mg·m(-3)逐渐上升到5000 mg·m(-3);24~48 h为菌丝初始生长期(升温期),菌丝逐步生长,固体培养料温度急剧上升,发酵箱内形成了明显的温度梯度和CO_2梯度,上层与下层温度差异可达5℃以上,上层CO_2浓度从5000 mg·m(-3);24~48 h为菌丝初始生长期(升温期),菌丝逐步生长,固体培养料温度急剧上升,发酵箱内形成了明显的温度梯度和CO_2梯度,上层与下层温度差异可达5℃以上,上层CO_2浓度从5000 mg·m(-3)上升至13000 mg·m(-3)上升至13000 mg·m(-3)左右,下层CO_2浓度从5000 mg·m(-3)左右,下层CO_2浓度从5000 mg·m(-3)升到6500 mg·m(-3)升到6500 mg·m(-3)左右;48~96 h为菌丝旺盛生长期(稳定期),菌丝大量生长,但固体培养料的发酵温度逐渐降低;96 h以后为产孢期,该阶段固体料温度依然呈现缓慢下降的趋势,逐渐下降接近或略高于室温。通过加入空气内循环系统,可消除发酵箱内温度梯度,并降低CO_2浓度梯度,促进发酵箱内菌丝生长均匀。研究结果可为白僵菌规模化生产提供技术参考。 相似文献
10.
研究了留叶片的数量、生根粉浓度、扦插时间等对巨尾桉(32~29)扦插生根率的影响,结果表明:生根粉的浓度对巨尾桉树(32~29)插条生根的影响很大,并且要达到较高的生根率,不同扦插时间要求生根粉的浓度不同,4月份扦插的插条生根粉浓度为800mg/L最佳,生根率为93.3%;6月份扦插的插条生根粉浓度为600mg/L较好,生根率就可以达到96.5%;留4对×1/2叶时,扦插条的生根率最高。 相似文献
11.
《Scandinavian Journal of Forest Research》2012,27(5):427-435
In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads. 相似文献
12.
《Scandinavian Journal of Forest Research》2012,27(3):206-217
The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage. 相似文献
13.
《Scandinavian Journal of Forest Research》2012,27(1):53-61
This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland. 相似文献
14.
《Scandinavian Journal of Forest Research》2012,27(1):15-27
The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions. 相似文献
15.
本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。 相似文献
16.
17.
《Scandinavian Journal of Forest Research》2012,27(5):472-479
Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken. 相似文献
18.
《Scandinavian Journal of Forest Research》2012,27(2):131-138
The effects of soil scarification (mounding), slash removal and clear-cut age on the natural regeneration in clear-cuts was evaluated using data from four sites in southern Sweden. The treatments were carried out during a good seed and establishment year for birch ( Betula pubescens Ehrh. and B. pendula Roth). Scarification had the strongest positive effect on the density of naturally regenerated seedlings, especially in birch, but also in pine ( Pinus sylvestris L.) and spruce [ Picea abies (L.) Karst]. Slash removal had a positive effect on birch density. No statistically significant effect of clear-cut age was found. In addition, no statistically significant interactions between clear-cut age and scarification or slash removal were found. The ingrowth of field vegetation was the fastest in areas that were not scarified, less rapid in areas scarified on old clear-cuts, and the slowest after scarification in fresh clear-cuts. In conclusion, it may be possible to control the density of birch during a good establishment year for birch. If birch is desired, the best combination of treatments is to remove the slash and scarify; otherwise, these treatments should be avoided. 相似文献
19.
Srisuda Thippayarugs Banyong Toomsan Patma Vityakon Viriya Limpinuntana Aran Patanothai Georg Cadisch 《Agroforestry Systems》2008,72(2):137-148
In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic
or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts
(stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea
(Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content
as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest
N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized
to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea,
largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for
N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant
components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N
released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures
were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality
components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in
the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols.
Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest
age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its
components are mixed. 相似文献
20.
A. Rigueiro-Rodríguez M. R. Mosquera-Losada E. Gatica-Trabanini 《Agroforestry Systems》2000,48(3):245-256
The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste
disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization,
(2) milk sewage sludge at 40 kg N ha−1 target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two
pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha−1. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha−1) + Trifolium repens L. group Ladino (4 kg ha−1) + Trifolium pratense L. var. Marino (1 kg ha−1); (2) Lolium perenne L. var. Tove (25 kg ha−1) + Trifolium repens L. group Ladino (4 kg ha−1) + Trifolium pratense L. var. Marino (1 kg ha−1). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea
(Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m2, with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect
on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage
sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but
affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral
systems.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献