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1.
雷琼地区玄武岩发育时间序列土壤中植硅体特征及其发生学意义 总被引：1，自引：1，他引：0
对雷琼地区发育于玄武岩跨度为0.01~6.12 M a时间序列土壤中植硅体的含量和形态进行了研究。结果表明:(1)土壤中植硅体的含量为1.54~21.95 g kg-1,其随着土壤深度的增加而降低;从新成土到富铁土阶段急剧降低,从富铁土到铁铝土阶段降幅明显减少,进入铁铝土阶段则基本趋于稳定。(2)植硅体主要源于禾本科、棕榈科植物,大小在5~130μm之间,形态包括刺球型、哑铃型、扇型、长方型、方型、鞍型、帽型、棒型、尖型、齿型、圆型和其他12种植硅体类型。所有样品中的温暖指数值均大于0.5,说明6.12 M a以来研究区域基本以温暖气候为主。 相似文献
2.
《Soil Science and Plant Nutrition》2013,59(5):551-561
Abstract Chemical properties of hydrophobic acid (HoA) fractions in water-soluble organic matter in soil and water are concerned with its interactions with mineral soil surfaces and organic pollutants. In 2004 we examined the seasonal and vertical changes in chemical properties of the HoA fraction in a Cambisol profile and compared these properties with those in the HoA fraction of an adjacent stream (aquatic humic substances) in a temperate forested watershed using high performance size exclusion chromatography (HPSEC) and 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The HoA fractions from Oi, Oe/Oa, A and B horizon soils in summer had lower O-alkyl C proportions than those recorded in samples in other seasons. The proportions of aromatic C in HoA fractions from A and B horizons were highest in summer. These seasonal variations were less significant than variations with soil depth. O-alkyl C proportions in HoA fractions decreased with increasing soil depth from the Oi to the A horizon. The HoA fractions from the B horizon showed a higher alkyl C proportion than samples from other horizons in winter and spring. These changes with soil depth from the Oi to A horizons might result from selective utilization of carbohydrate carbon by microorganisms, whereas those in the B horizon may result from sorption to mineral surfaces. The HoA fractions in the stream were similar in relative molecular weight, distribution of each type of proton and carbon species in HoA fractions from the B horizon, whereas stream HoA fractions collected in summer would be derived from organic horizons. This indicated that vertical changes in the chemical properties of HoA fractions in soil and pathways of water to the stream would largely affect the chemical properties of HoA fractions in the stream. 相似文献
3.
黄土丘陵区纸坊沟流域60年来土地利用格局变化研究 总被引：8，自引：3，他引：8
以黄土丘陵区纸坊沟流域为研究区,对其60年来的土地利用格局变化进行系统的分析研究,结果表明,土地利用格局变化与人类活动密切相关。农业用地的扩张,是导致林草植被破坏和土地利用格局变化的重要原因。从1938～1958年,坡耕地在土地利用格局中的优势度由低到高,而林草植被的优势度则降至最低点。之后,林草植被随着坡耕地的变化经历了缓慢变化期(1958～1973年)和较快增长期(1973年后)。其中1958年和1995年,是土地利用格局的质变点,也是生态环境变化的重要转折点。而景观形状复杂性变化的转折与景观基质基本一致;景观多样性指数1938年和1958年基本相近,1975年以后,多样性指数逐渐增大,至1995年达到最大值,之后有所降低;由一个利用类型支配(1938年和1958年)的土地利用格局逐渐演变为多个利用类型共同支配的土地利用格局。 相似文献
4.
《Communications in Soil Science and Plant Analysis》2012,43(15):2043-2049
A laboratory experiment was carried out to study the influence of 100 mg phosphorus pentoxide (P2O5) kg–1 soil from various phosphate sources on ammonia losses from soils amended with urea at 200 mg nitrogen (N) kg–1 soil. Irrespective of soil type, ammonia (NH3) loss was significantly greater from untreated soil (control) than from the soil treated with phosphorus (P) sources. A maximum decrease in ammonia loss (56%) was observed by applying phosphoric acid followed by triple and single superphosphate. Ammonia losses were significantly greater from sandy clay loam than from clay. Rate of ammonia volatilization was maximum during the first week of incubation and became undetectable for both soils at 21 days after incubation. The addition of phosphate sources significantly decreased pH in the sandy clay loam, but in the clay a significant decrease was observed only with the phosphoric acid addition. Addition of phosphate fertilizers was beneficial in reducing NH3 losses from urea. 相似文献
5.
安徽省黟县农田耕层土壤中微量元素含量研究 总被引：4，自引：2，他引：2
黟县是皖南黄山市重要的农业县,本文利用黟县测土配方施肥工作获取的农田土壤测定数据,分析其耕作层中量元素硫和微量元素铁、锰、铜、锌、硼的有效态含量及其空间分布,以为区域施肥提供决策支持。结果表明:黟县农田土壤有效铁、锰、铜、锌、硼、硫含量分别介于4.20~348.30、0.60~225.00、0.04~14.74、0~88.00、0~355.00、0.48~87.85 mg/kg,平均值分别为126.10、15.62、2.93、1.78、0.81、16.17 mg/kg。采用克里格插值获取的元素有效态含量空间分布图显示,黟县南部、北部的元素有效态含量较高,中间区域的含量相对较低。该地区有效硼普遍较为缺乏,应广泛补施硼肥;部分地区有效锌缺乏,需酌情喷施硫酸锌叶面肥。 相似文献
6.
珠江三角洲平原不同种植年限土壤铁氧化物特征研究 总被引：4，自引：0，他引：4
珠江三角洲平原具有上千年的围垦历史,其土壤发生演变过程深受人为作用影响,开展此区域不同种植年限土壤中铁氧化物形态特征和分布规律的研究,能够揭示人为耕种下土壤发生演变过程。以珠江三角洲平原不同种植年限的土壤剖面为对象,研究了滨海沉积物、河流冲积物和三角洲沉积物发育的土壤及黏粒中全铁、游离铁含量变化及其影响因素。结果表明:随着种植年限的增加,河流冲积物、三角洲沉积物发育土壤中游离铁(Fe_d)向土体下部淀积深度逐渐增加,黏粒中游离铁(Fe_(d(clay)))含量在水耕氧化还原层中呈减小趋势,而滨海沉积物发育的土壤Fe_d含量及淀积深度均有所减小。随着种植年限的增加,滨海沉积物发育的土壤全铁(Fe_t)和游离铁(Fe_d)在黏粒中的富集程度呈增大趋势,而河流冲积物、三角洲沉积物发育的土壤Fe_t和Fe_d富集程度逐渐减小。土壤Fe_d与Fe_t、黏粒游离铁(Fe_(d(clay)))与黏粒全铁(Fe_(t(clay)))均呈极显著正相关;全铁富集率(Fe_(t(clay))/Fe_t)、游离铁富集率(Fe_(d(clay))/Fe_d)均与Fe_(t(clay))、Fe_(d(clay))、黏粒铁游离度(Fe_(d(clay))/Fe_(t(clay)))呈极显著正相关,与Fe_t、Fe_d、土壤铁游离度(Fe_d/Fe_t)、黏粒含量呈极显著负相关,且Fe_(t(clay))/Fe_t与Fe_(d(clay))/Fe_d呈极显著正相关,表明土壤铁氧化物在黏粒中的富集以Fe_d为主,且铁氧化物的富集程度受土壤黏粒含量的影响。 相似文献
7.
采用磷形态的连续提取法,研究了巢湖沉积物中磷的地球化学形态及间隙水中总溶解性磷（DTP）、可溶性磷酸盐（DIP）、可溶性有机磷（DOP）含量的垂向分布特征。结果表明,西湖区的沉积物总磷含量明显高于东湖区。表层沉积物中活性磷含量占总磷的44％-81％,金属氧化物结合态磷（NaOH—P）作为活性磷的主要存在形式,在西湖区含量比例达到47％-60％,对磷释放起重要贡献;磷形态剖面表明,西湖区的金属氧化物结合态磷、可还原态磷（BD—P）含量高于东湖区。金属氧化物结合态磷、可还原态磷、钙结合态磷（HCl-P）受人类活动影响较大,有机磷（Org—P）受外源磷污染影响很小;BD—P、NaOH—P随深度增加而减小,说明巢湖近期磷负荷有增加的趋势;DTP、DIP、DOP在水-沉积物界面的浓度梯度反映它们有自间隙水向上覆水扩散的趋势;巢湖间隙水不同形态磷与BD—P、NaOH—P显著相关（α=0．01）。这项研究可为巢湖内源污染和富营养化的控制与治理提供理论参考。 相似文献
8.
Microbial succession associated with litter decomposition was studied in the semi-arid western Chaco woodland of Cordoba province, Argentina. Annual rainfall in the area averages 450 mm, concentrated during the summer (October-March). We placed 200 g of freshly shed litter in metallic cages covered with 1 mm mesh divided in four equal size sectors, for 1 year. Cages were sampled at 3-month intervals from the starting date. On each sampling date, we collected the content of one sector from each cage for analysis. Microbial functional groups (ammonifiers, nitrifiers, N-fixing, cellulolytic, and sugar fungi) and litter chemical composition (carbon, nitrogen, insoluble fibre, and phenol concentration) were analysed in the initial litter and litter samples collected at the end of each sampling period. Litter mass remained constant during the dry season (winter and spring), decreasing abruptly in the wet season (summer and autumn). Nitrogen content increased significantly until summer (from 1.52 to 2.18%), whereas phenols and C/N ratio decreased (from 2.48 to 0.67 and from 40 to 20%, respectively). Sugar fungi and ammonifiers increased rapidly since the initial stages and remained stable throughout the year (from log 5.0 to log 6.2 and from log 5.4 to log 20.0, respectively). Cellulolytic bacteria and fungi as well as nitrifiers decreased markedly during winter and spring, peaking in summer. Nitrogen-fixing bacteria increased during the study period (from log 1.6 to log 4.8), showing a significant correlation with ammonifiers, C/N ratio, and N content (r2=0.801, 0.573 and 0.513, respectively). Our results show that microbial successions in litter decomposition are strongly influenced by synergic interaction among functional groups and litter chemical composition. Moreover, they also suggest that biological nitrogen fixation may have an important role in improving the C/N ratio, and therefore favours a higher decomposition rate. 相似文献
9.
Soil erodibility measurements for detachment by raindrop impact were made on samples collected at monthly intervals from forest, pasture and farmland sites. All sites exhibited strong seasonal variations in erodibility with maximum values occurring during the winter and minimum values in the summer. The relative erodibility of the different soils is described and the field and laboratory methods used are compared. The best time for sampling the soil for soil erodibility determinations is indicated. Erodibility is estimated from laboratory simulation experiments on undisturbed samples, from aggregate stability determinations and from field measurements with splash boards. 相似文献
10.
Soil solutions were taken from three forest areas with granite bedrock in Japan (Abukuma, Tateyama and Hiroshima) to investigate pH values, forms of Al and the molar BC/Al ratios. In each area, 10 sites were chosen for study. At each site, a target tree was selected, and two soil solution samples were taken from 10 cm depth at points 10 cm and 100 cm from the trunk of the tree to evaluate the effects of stemflow and throughfall on soil solution chemistry. Values of pH of samples taken 10 cm from the trunks (referred to as S samples) and 100 cm from the trunks (referred to as T samples) ranged from 3.66 to 6.52 and from 4.55 to 6.48, respectively. For Japanese cedar (Cryptomeria japonica) and Japanese cypress (Chamaecyparis obtusa) trees, S samples showed lower pH than T samples, whereas the inverse relation was observed for broadleaf trees. In the Abukuma and Tateyama areas, the concentrations of monomeric Al (Alm) were mostly below 30 µmol L?1. In the Hiroshima area, however, extremely high Alm concentrations (up to 293 µmol L?1) were observed at some sites. The molar ratio of BC (= Ca + Mg + K) to inorganic monomeric Al was higher than 1 for all samples, except for an S sample from the Hiroshima area having a ratio of 0.72. 相似文献
11.
Olle Westling 《Water, air, and soil pollution》1991,56(1):419-426
The concentration of Hg was studied in runoff from drained and undrained peatlands in the south and central parts of Sweden,
from 1987 to 1989. Mercury was speciated into total Hg, water-soluble Hg (Hg II) including reactive Hg (Hg IIa) and non-reactive
Hg (Hg IIb), and methyl Hg. The aim of the study was to investigate if normally low concentrations of different species of
Hg in runoff from peatland were elevated at drained mires with peat-harvesting. Five drained mires with different nutrient
statuses were studied, and compared with undrained controls. The highest concentration of total Hg (5.3 to 21.3 ng L−1) was found in runoff from an undrained, oligotrophic bog with low pH (3.79 to 4.08). Mires in south Sweden showed in general
higher concentrations of all species of Hg in runoff compared to central Sweden. The concentrations of total Hg, Hg IIa and
Hg IIb in runoff from peatland showed similar levels as runoff from forested areas. No data showed that the drained peatland
leached more total Hg than the undrained areas. 相似文献
12.
13.
Rice CP Baldwin Vi RL Abbott LC Hapeman CJ Capuco AV Le A Bialek-Kalinski K Bannerman DD Hare WR Paape MJ McCarty GW Kauf AC Sadeghi AM Starr JL McConnell LL Van Tassell CP 《Journal of agricultural and food chemistry》2007,55(21):8806-8813
Perchlorate has been detected in U.S. milk samples from many different states. Applying data from a recently reported 9-week experiment in which 16 Holstein dairy cows were administered perchlorate allowed us to derive an equation for the dose-response relationship between perchlorate concentrations in feed/drinking water and its appearance in milk. Examination of background concentrations of perchlorate in the total mixed ration (TMR) fed in addition to the variable dose supplied to treated cows as a ruminal infusate revealed that cows receive significant and variable exposure to perchlorate from the TMR. Weekly examination of the TMR disclosed that a change in ingredients midway through the experiment caused a significant (78%) change in TMR perchlorate concentration. Analyses of the ingredients comprising the TMR revealed that 41.9% of the perchlorate came from corn silage, 22.9% came from alfalfa hay and 11.7% was supplied by sudan grass. Finally, USDA Food and Nutrition Survey data on fluid milk consumption were used to predict potential human exposure from milk that contained concentrations of perchlorate observed in our previous dosing study. The study suggests that reducing perchlorate concentration in dairy feed may reduce perchlorate concentrations in milk as well as the potential to reduce human exposure to perchlorate in milk. 相似文献
14.
Chun-xing Hai Chun-shin Yuan Guang-tong Liu Xiao-jia Li Fu Zhang Xiu-jiang Zhang 《Water, air, and soil pollution》2008,190(1-4):27-34
The dust fall in a region is closely related to upwind sources. Dust fall from sandstorms has a strong influence on industry, agriculture, and daily life. Hohhot, the capital of Inner Mongolia Autonomous Region, is downwind of the Inner Mongolia Plateau and experiences frequent sandstorms during the spring monsoon season. This study investigated the relationship between dust fall in the Hohhot area and surface soils on the Inner Mongolia Plateau. Samples of dust fall from Hohhot and surface soils from the plateau were analyzed for major and trace elements. The SiO2 content of dust fall from sandstorms differs from that of the plateau soils by only 2.77%, indicating that the main dust fall source for Hohhot is surface soils from the plateau. Dust samples from coal smoke, roads, and buildings were used for comparison. The As content in dust fall from sandstorms is greater than that found in the plateau soils and in dust from non-sandstorm days. This indicates that As is added to the sand during transport from the plateau by coal factories near Hohhot. The second most important dust source is traffic, as evidenced by Pb contents. Preventing erosion of sand upwind of Hohhot during the spring monsoon is key to improving and managing air quality in the Hohhot region. This can be accomplished through management of the farm grassland areas. 相似文献
15.
江西省农田土壤有效硫现状研究 总被引：6，自引：2，他引：6
采集了江西 1 6个县市 9种主要母质的 6 0 9个农田耕层土样进行了土壤有效硫含量测定 .统计结果表明 :平均值为 2 6 7mg/kg ,缺硫和潜在缺硫样点占 39 1 % .按地区分 ,以赣南、赣东北山区缺硫最严重 ,有效硫小于 1 2mg/kg的样点占 2 6 6 %～ 4 4 7% ,其次是丘陵地区 ,有效硫小于 1 2mg/kg的样点占1 0 0 %～ 1 9 0 % .按母质分 ,以石英岩、花岗岩发育的土壤最缺 ,约占 50 %～ 6 0 % ,其次是红砂岩、泥质岩 ,缺硫为 30 %～ 4 0 % ,这些是江西省急需施用硫肥的土壤 .水稻土以黄砂泥田、麻砂泥田、红砂泥田、鳝泥田等土属有效硫缺乏面积最大 ,全省水稻土有效硫缺乏的面积约为 1 0 3 8万hm2 ,约占水稻土面积的 34 % . 相似文献
16.
《Applied soil ecology》1999,11(2-3):253-259
We investigated seasonal variations in the soil microbial biomass N content (MBN) and the soil neutral sugar composition from April 1995 to September 1996 in cattle-grazed pasture in a Japanese Andisol. MBN showed seasonal variation, gradually increasing from April to August, and decreasing rapidly by the end of August when soil moisture content decreased. Soil inorganic-N increased after fertilization and cattle pasturage. Seasonal variations in seven types of neutral sugar-C contents in the soil were observed. However, the trends in seasonal variation for sugars derived from plant materials were different from one another and from those derived from microbial products. Seasonal variation trends in soil neutral sugar-C were similar to that of MBN, with a sharp decrease in midsummer and a subsequent increase in autumn probably due to dence pasture plant growth. Furthermore, galactose-C (Gal), rhamnose-C (Rham) and ribose-C (Rib) that originated mainly from microbes showed positive correlations with MBN, but the other forms of soil neutral sugar-C did not. It was concluded that the composition of the soil organic matter accumulated in grassland varied seasonally, and that these seasonal variations can be investigated by MBN or by soil neutral sugar composition. 相似文献
17.
18.
The annual changes in the soil erodibility as a function of time can be described by a polynomial of the fourth power. In western Georgia, the soil erodibility varies from 134% of the mean annual value in April to 18% in August within the piedmont hilly zone and from 159% (in April) to 54% (in June) in the mountain-forest zone. It is demonstrated that the soil erodibility during the growing period can be calculated from the polynomial of the fourth power with the use of data on the mean annual and monthly air temperatures and the mean annual soil erodibility (the K factor). 相似文献
19.
通过对洛阳市城区居民区、商业区、工业区、风景区4种功能类型区中的11个采样点中的10～15年生雪松松针（SA）、地面落针（SB）和20～30年生雪松松针（SC）、地面落针（SD）中重金属Pb含量的测定,分析了洛阳市城区大气中Pb污染现状。结果表明：洛阳市城区雪松松针Pb含量平均为1.606mg/kg,属重金属轻度污染;居民区、商业区、工业区、风景区雪松松针Pb含量差异显著,表现为工业区〉居民区〉商业区〉风景区;松针中Pb含量主要受冶炼、工业废气、汽车尾气排放等人为活动因素影响。雪松松针Pb含量分异性可以客观反映城市不同区域内大气Pb污染程度,这为城市环境保护研究提供了新方法,值得推广使用。 相似文献
20.
Hammond BG Campbell KW Pilcher CD Degooyer TA Robinson AE McMillen BL Spangler SM Riordan SG Rice LG Richard JL 《Journal of agricultural and food chemistry》2004,52(5):1390-1397
Fumonisins were monitored in corn grain collected from Bt hybrids grown in 107 locations across the United States in 2000-2002. Bt corn hybrids contain the Cry1Ab protein from Bacillus thuringiensis that controls European corn borers and other stalk-boring pests. Fumonisin levels were frequently lower in grain from Bt hybrids grown in field trials under conditions of natural (FACT trials) or manual insect infestation (university trials). Over three years of FACT trials, there were 126/210 comparisons when fumonisin levels in grain from control hybrids were >2 ppm, exceeding U.S. FDA guidance levels of 2 ppm for human food. Grain from Bt hybrids was at or below 2 ppm of fumonisins for 58 of the 126 comparisons. The use of Bt hybrids can increase the percentage of corn grain that would be suitable for use in food and feed. 相似文献