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1.
LIU Jieyun 《干旱区科学》2016,8(6):910-920
With rapid economic growth in China,anthropogenic reactive nitrogen(Nr) emissions have more than doubled over the last two or three decades.Atmospheric Nr pollution is an environmental concern in China especially in megacities such as Beijing.In order to identify the impact of emission sources on atmospheric Nr pollution,we measured atmospheric Nr concentrations and their isotopic composition(δ~(15)N) dynamics at three typical sites:landfill,pig farm and road traffic sites in Beijing from April 2010 to March 2011.Passive samplers were used for monitoring ammonia(NH_3) and nitrogen dioxide(NO_2),two major Nr species,while their δ~(15)N values were measured by a diffusion method combined with mass spectrometer approach.The raw water pool of the landfill and fattening house of the pig farm were important NH_3 sources with mean NH_3 concentrations being 2,829 and 2,369 μg/m~3,respectively,while the road traffic site was a minor NH_3 source(10.6 μg/m~3).NH_3 concentrations at sites besides the landfill and roads were high in summer and low in winter due to the annual variation of temperature and the change of emission source intensity.In contrast,the NH_3 concentrations inside the pig farm house were high in winter and low in summer,for the barn windows were open in summer and closed in winter.The mean NO_2 concentrations were 89.8,32.9 and 23.0 μg/m~3 at the road traffic,the landfill and pig farm sites,respectively.Due to vehicle fuel combustion,NO_2 concentration at the road traffic was the highest among the three sources,and the road traffic was a main NO_2 emission source.PM10,p NH4+ and p NO3– concentrations in particulate matter were higher in summer than in winter(except PM10 for the pig farm).The δ~(15)NH_3 values ranged from –19.14‰ to 7.82‰,with an average of –0.05‰ for the landfill site,and the lowest values were observed in June and July.The δ~(15)NH_3 values for the pig farm site ranged from –29.78‰ to –14.05‰ with an average of –24.51‰,and the δ~(15)NH_3 values were more negative in summer than in the other seasons.The δ~(15)NO_2 values were –9.63‰ to 7.04‰ with an average of –3.72‰ for the road traffic site.The δ~(15)NO_2 values were more negative in summer than those in the other seasons.The different δ~(15)N values for the various Nr species in different sources may serve as important indicators for identifying atmospheric Nr sources in megacities.The results may also provide the theoretical basis for research on the atmospheric N deposition and its sources. 相似文献
2.
沙地樟子松人工林土壤氮矿化特征 总被引：1，自引：0，他引：1
土壤氮(N)的有效性是沙地林生态系统生产力和稳定性的关键限制因子。本研究以科尔沁沙地樟子松人工林为研究对象，分析测定了10~60 a林龄土壤NH4+-N、NO3--N和矿质N含量、氨化速率、硝化速率和N矿化速率的变化规律。结果表明：樟子松人工林土壤NH4+-N、NO3--N和矿质N含量，随着不同林龄在10~60 a内表现出增加的趋势，其中10~30 a增幅较小，40~60 a显著提高；随着土层深度增加而减小，主要集中在0~20 cm，呈现出表聚性。不同林龄樟子松人工林土壤氨化速率、硝化速率和矿化速率均随林龄增加而增加，随土层深度的增加而降低，其中0~40 cm土层明显大于40~100 cm。通过双因素方差分析，得出林龄与土层对各矿化指标影响显著。土壤矿化指标与人工林地上樟子松株高、胸径、冠幅以及土壤有机碳、全氮、碱解氮有显著的正相关关系。通过冗余分析(RDA)表明，影响不同林龄土壤矿化指标的主要环境因子为全氮、全磷、有机碳；影响不同土层土壤矿化指标的主要环境因子为全氮、碱解氮、有机碳。因此，樟子松人工林能够改善沙地土壤N的有效性，幼龄林和中龄林改善效果较小，近成熟林和成熟林改善效果明显；对表层土的改善效果优于深层土；土壤肥力是影响土壤矿化指标的主要环境因子。 相似文献
3.
Zongjie LI 《干旱区科学》2017,9(6):911-923
Precipitation chemistry analysis is essential to evaluate the atmospheric environmental quality and identify the sources of atmospheric pollutants. In this study, we collected a total of 480 precipitation samples at 6 sampling sites in the northern and southern slopes of Wushaoling Mountain from May 2013 to July 2014 to analyze the chemical characteristics of precipitation and to identify the main sources of ions in precipitation. Furthermore, we also explored the indicative significance for sand dust events in the northern and southern slopes of Wushaoling Mountain based on the precipitation chemistry analysis.During the sampling period(from May 2013 to July 2014), the p H values, EC(electrical conductivity)values and concentrations of cations(Ca~(2+), Mg~(2+), Na~+, K~+ and NH_4~+) and anions(SO_4~(2–), NO_3~–, Cl~–, NO_2~– and F~–) in precipitation were different in the northern and southern slopes at daily and seasonal time scales, with most of the values being higher in the northern slope than in the southern slope. The chemical type of precipitation in the southern and northern slopes was the same, i.e.,SO_4~(2–)-Ca~(2+)-NO_3~–-Na~+. The concentrations of ions in precipitation were mainly controlled by terrigenous material and anthropogenic activities(with an exception of Cl~–). The concentration of Cl~– in precipitation was mainly controlled by the sea salt fraction. The concentrations of Na+ and Cl~– showed an increasing trend after the occurrence of sand dust events both in the northern and southern slopes. In addition, after the occurrence of sand dust events, the concentrations of K~+, Mg~(2+), SO_4~(2–), NO_3~– and Ca~(2+) showed an increasing trend in the southern slope and a decreasing trend in the northern slope. It is our hope that the results may be helpful to further understand the atmospheric pollution caused by sand dust events in the Wushaoling Mountain and can also provide a scientific basis for the effective prevention of atmospheric pollution. 相似文献
4.
密怀顺地区是北京市重要的水源涵养区,直接影响着主城区的供水安全。2014年南水北调盈余水量通过潮白河河道回补地下水,地下水位不断抬升,使常年积累在耕地土壤中NO3--N对地下水环境风险不断增加。通过对地下水中NO3--N和耕地属性地块研究。结果表明:1)2015-2018年研究区地下水NO3--N浓度有升高趋势;2)2015-2018年研究区水质稳定区面积达到164.26km2,占比33.78%;其次为水质略变差区和水质变差区,面积分别为136.76km2和112.74km2,占比分别为28.12%和23.18%。3)耕地属性不变的7个有监测地块地下水NO3--N浓度均有不同程度升高,MW-3和MW-1地块超过地下水Ⅲ类水质标准;4)地下水NO3--N含量变化与地下水回补有一定关联。 相似文献
5.
Soil water repellency and influencing factors of Nitraria tangutorun nebkhas at different succession stages 总被引：1，自引：0，他引：1
Soil water repellency(WR) is an important physical characteristic of soil surface. It is capable of largely influencing the hydrological and geomorphological processes of soil, as well as affecting the ecological processes of plants, such as growth and seed germination, and has thus been a hot topic in recent research around the world. In this paper, the capillary rise method was used to study the soil WR characteristics of Nitraria tangutorun nebkhas. Soil water repellencies at different succession stages of Nitraria tangutorun were investigated, and the relationships between soil WR and soil organic matter, total N, and total P, soil texture, pH, and concentrations of CO3 2-, HCO3-, Cl-, SO4 2-, Na+, K+, Ca2+and Mg2+were discussed. Soil WR may be demonstrated at the following nebkhas dune evolvement stages: extremely degradeddegradedstabilizedwell developednewly developedquick sand. Apart from some soil at the bottom, the WR of other soils(crest and slope of dune) was found to be largest at the topsoil, and decreased as the soil depth increased. The results showed that multiple factors affected soil WR characteristics, e.g. WR increased significantly as the contents of soil organic matter and total N increased, but did not change as the total P content increased. Soil texture was a key factor affecting soil WR; soil WR increased significantly as clay content increased, and decreased significantly as sand content increased. Low pH was shown to be more suitable for the occurrence of soil WR. Four cations(Ca2+, Mg2+, K+and Na+) and two anions(Cl-and SO4 2-) enhanced soil WR, while CO3 2-decreased it. HCO3-did not show any observable effect. Finally, we established a best-fit general linear model(GLM) between soil-air-water contact angle(CA) and influencing factors(CA=5.606 sand+6.496(clay and silt)–2.353 pH+470.089 CO3 2-+11.346 Na+–407.707 Cl-–14.245 SO4 2-+0.734 total N–519.521). It was concluded that all soils contain subcritical WR(0°CA90°). The development and succession of Nitraria tangutorun nebkhas may improve the formation of soil subcritical WR. There exist significant relationships between soils subcritical WR and soil physical or chemical properties. 相似文献
6.
Nitrogen (N) and phosphorus (P) are two essential nutrients that determine plant growth and many nutrient cycling processes. Increasing N and P deposition is an important driver of ecosystem changes. However, in contrast to numerous studies about the impacts of nutrient addition on forests and temperate grasslands, how plant foliar stoichiometry and nutrient resorption respond to N and P addition in alpine grasslands is poorly understood. Therefore, we conducted an N and P addition experiment (involving control, N addition, P addition, and N+P addition) in an alpine grassland on Kunlun Mountains (Xinjiang Uygur Autonomous Region, China) in 2016 and 2017 to investigate the changes in leaf nutrient concentrations (i.e., leaf N, Leaf P, and leaf N:P ratio) and nutrient resorption efficiency of Seriphidium rhodanthum and Stipa capillata, which are dominant species in this grassland. Results showed that N addition has significant effects on soil inorganic N (NO3--N and NH4+-N) and leaf N of both species in the study periods. Compared with green leaves, leaf nutrient concentrations and nutrient resorption efficiency in senesced leaves of S. rhodanthum was more sensitive to N addition, whereas N addition influenced leaf N and leaf N:P ratio in green and senesced leaves of S. capillata. N addition did not influence N resorption efficiency of the two species. P addition and N+P addition significantly improved leaf P and had a negative effect on P resorption efficiency of the two species in the study period. These influences on plants can be explained by increasing P availability. The present results illustrated that the two species are more sensitive to P addition than N addition, which implies that P is the major limiting factor in the studied alpine grassland ecosystem. In addition, an interactive effect of N+P addition was only discernable with respect to soil availability, but did not affect plants. Therefore, exploring how nutrient characteristics and resorption response to N and P addition in the alpine grassland is important to understand nutrient use strategy of plants in terrestrial ecosystems. 相似文献
7.
Groundwater forms the main freshwater supply in arid and semi-arid areas,and contamination of this precious resource is complicated by the slow rate of recharge in these areas.Nitrate contamination of groundwater is a global water quality problem,as it entails threat to human health as well as aquatic ecosystems.Source identification of contamination is the cornerstone and a prerequisite for any effective management program of water quality.Stable isotope composition of the dissolved nitrate(δ15N-NO3-andδ18O-NO3-)has been applied to identify NO3-sources and the main transformation processes in the upper aquifer system(A1/2,A4,and B2/A7 aquifers)in the Wadi Shueib catchment area,Jordan.Moreover,the stable isotope compositions of the groundwater(δ2H-H2O andδ18O-H2O)in conjunction with the groundwater hydrochemistry were integrated to investigate the origin and evolution of the groundwater.Results revealed that groundwater in the study area is fresh and hard-very hard water,and mainly a Ca-Mg-Cl type.NO3-concentration was in the range of 7.0-74.0 mg/L with an average of 37.0 mg/L.Most of the samples showed concentration higher than the natural background concentration of NO3-(5.0-10.0 mg/L).Theδ2H-H2O andδ18O-H2O values indicated that the groundwater is meteoric,and of Mediterranean origin,with a strong evaporation effect.Theδ15N-NO3-values ranged between 6.0‰and 11.3‰with an average of 8.7‰,and theδ18O-NO3-values ranged between 1.6‰and 5.9‰with an average of 3.4‰.These values are in conformity with the stable isotope composition of nitrate derived the nitrification of wastewater/manure,and soil NH4.Nitrification and denitrification are the main transformation processes affecting nitrogen species.Statistical analysis revealed no significant differences in theδ2H-H2O andδ18OH2O values,andδ15N-NO3-andδ18O-NO3-values for the three aquifers(A1/2,A4,and B2/A7),indicating that the groundwater of these aquifers has the same origin,and a common source of pollution. 相似文献
8.
Excessive fertilization combined with unreasonable irrigation in farmland of the Hetao Irrigation Area (HIR), China, has resulted in a large amount of nitrogen (N) losses and agricultural non-point source pollution. Application of soil amendments has become one of the important strategies for reducing N losses of farmland. However, there is still no systematic study on the effects of various soil amendments on N losses in the HIR. In this study, three types of soil amendments (biochar, bentonite and polyacrylamide) were applied in a maize-wheat rotation system in the HIR during 2015-2017. Yields of maize and wheat, soil NH3 volatilization, N2O emission and NO3- leaching were determined and soil N balance was estimated. The results showed that applications of biochar, bentonite and polyacrylamide significantly increased yields of maize by 9.2%, 14.3% and 13.3%, respectively, and wheat by 9.2%, 16.6% and 12.3%, respectively, compared with the control (fertilization alone). Applications of biochar, bentonite and polyacrylamide significantly reduced soil N leaching by 23.1%, 35.5% and 27.1%, soil NH3-N volatilization by 34.8%, 52.7% and 37.8%, and soil N surplus by 23.9%, 37.4% and 30.6%, respectively. Applications of bentonite and polyacrylamide significantly reduced N2O-N emissions from soil by 37.3% and 35.8%, respectively, compared with the control. Compared with application of biochar, applications of bentonite and polyacrylamide increased yields of maize and wheat by 5.1% and 3.5%, respectively. Our results suggest that soil amendments (bentonite and polyacrylamide) can play important roles in reducing N losses and increasing yield for the maize-wheat rotation system in the HIR, China. 相似文献
9.
为探究新疆昌吉州东部平原区地下水水质演化过程，采用数理统计、Piper三线图、Gibbs图和离子比法对昌吉州东部平原区2016年63组地下水水质取样点及54组2012—2015年地下水水质监测数据进行分析。结果表明：昌吉州东部平原区2012年地下水阳离子平均含量总体为Ca2+>K++Na+>Mg2+，阴离子平均含量总体为HCO3->SO42->Cl-；从2013年开始，SO42-逐渐增大，Ca2+逐渐减小；到2016年阳离子平均含量总体为Ca2+>K++Na+>Mg2+，阴离子平均含量总体为HCO3->SO42->Cl-。水化学类型由2012年HCO3—Ca·Mg（Ca·Na、Ca·Na·Mg）型向2016年HCO3·SO4—Ca·Na·Mg（Ca·Mg、Ca·Na）演化，这主要与含水介质的风化作用和蒸发浓缩作用有关，而蒸发浓缩作用更加体现在承压水区的上部潜水中。地下水中Na+、K+、Cl-主要来自岩盐的溶解；Ca2+、Mg2+主要来自蒸发岩溶解；SO42-主要来自石膏（CaSO4·2H2O）和芒硝（Na2SO4·10H2O）的溶解。Cl-、SO42-除来自岩盐的溶解外，还受到人类活动的影响。 相似文献
10.
为探究新疆伊犁河谷西北部地下水化学特征及成因,运用数理统计以及Piper三线图、Gibbs图、离子比图等方法,对2018年伊犁河谷西北部地下水取样监测数据进行分析。结果表明:(1)研究区地下水属于总硬度偏高的弱碱性水,地下水化学组分含量整体变异性不大,主要阳离子为Ca2+,主要阴离子为HCO3-。(2)地下水水化学类型以HCO3-Ca、HCO3·SO4-Ca、HCO3·SO4-Ca·Mg、HCO3·SO4-Ca·Na和HCO3-Ca·Mg型为主。(3)研究区地下水化学组分主要受岩石溶滤作用控制,蒸发-浓缩作用及阳离子交换作用对地下水化学组分有一定的贡献,个别地下水水样点可能受到人为活动的影响。(4)地下水中的Na+、Cl-和SO42-主要来自岩盐、石膏等蒸发岩的溶解,Ca2+和Mg2+主要来自方解石、白云石和石膏等矿物溶解。 相似文献
11.
Saline wetlands are rare ecosystems in Saharan areas, which are important for conservation of many endemic and rare plant species. In this study, we investigated five saline wetland sites of the Oued Righ region, located in the northeastern Algeria, to determine the environmental factors controlling the composition and distribution of plant communities. We established a total of 20 transects to measure the vegetation parameters (density and cover) and soil characteristics (electrical conductivity, moisture, pH, CaSO4, CaCO3, organic matter, Na+, K+, Mg2+, Ca2+, SO42–, Cl–, NO3– and HCO3–). A total of 17 plant species belonging to seven families were identified. The natural vegetation was composed of halophytic and hydro-halophytic plant communities, presented specially by the species of Amaranthaceae family. Soils in the studied wetlands were moist, gypsiferous, alkaline, salty to very salty with dominance of chloride and calcium. Results of the Canonical Correspondence Analysis (CCA) showed that community structure and species distribution patterns of vegetation were mainly dependent on soil characteristics, mainly being soil salinity (CaSO4, K+, Ca2+ and Cl–) and moisture. The distribution of plant species was found to follow a specific zonal pattern. Halocnemum strobilaceum was observed to grow in highly salt-affected soils, thus being the more salt-tolerant species. Phragmites communis plants were widely distributed in the study area with a high density at the edges of accumulated water body. Juncus maritimus, Tamarix gallica and Salicornia fructicosa grew in soils that are partially or completely flooded in winter. Suaeda fructicosa, Traganum nudatum, Arthrocnemum glaucum, Aeluropus littoralis, Cressa cretica and Cynodon dactylon were distributed in salty and moist soils away from the open water body. Plants of Zygophyllum album, Limonastrirum guyonianum, Cornulaca monacantha, Cistanche tinctoria, Mollugo nudicaulis and Sonchus maritimus were found in soils with less salty and moisture. They constituted the outermost belt of vegetation in the studied wetlands. This study will provide a reference on introducing the salt-tolerant plant species as a fodder resource in saline habitats and regenerating the degraded saline wetlands. 相似文献
12.
Soil salinization has adverse effects on the soil physical-chemical characteristics.However,little is known about the changes in soil salt ion concentrations and other soil physical-chemical characteristics within the Qarhan Salt Lake and at different soil depths in the surrounding areas.Here,we selected five sampling sites(S1,S2,S3,S4,and S5)alongside the Qarhan Salt Lake and in the Xidatan segment of the Kunlun Mountains to investigate the relationship among soil salt ion concentrations,soil physical-chemical characteristics,and environmental variables in April 2019.The results indicated that most sites had strongly saline and very strongly saline conditions.The main salt ions present in the soil were Na+,K+,and Cl-.Soil nutrients and soil microbial biomass(SMB)were significantly affected by the salinity(P<0.05).Moreover,soil salt ions(Na+,K+,Ca2+,Mg2+,Cl-,CO32-,SO42-,and HCO3-)were positively correlated with electrical conductivity(EC)and soil water content(SWC),but negatively related to altitude and soil depth.Unlike soil salt ions,soil nutrients and SMB were positively correlated with altitude,but negatively related to EC and SWC.Moreover,soil nutrients and SMB were negatively correlated with soil salt ions.In conclusion,soil nutrients and SMB were mainly influenced by salinity,and were related to altitude,soil depth,and SWC in the areas from the Qarhan Salt Lake to the Xidatan segment.These results imply that the soil quality(mainly evaluated by soil physical-chemical characteristics)is mainly influenced by soil salt ions in the areas surrounding the Qarhan Salt Lake.Our results provide an accurate prediction of how the soil salt ions,soil nutrients,and SMB respond to the changes along a salt gradient.The underlying mechanisms controlling the soil salt ion distribution,soil nutrients,and SMB in an extremely arid desert climate playa should be studied in greater detail in the future. 相似文献
13.
Halimeh PIRI 《干旱区科学》2022,14(11):1274-1292
Water scarcity is the most significant barrier to agricultural development in arid and semi-arid regions. Deficit irrigation is an effective solution for managing agricultural water in these regions. The use of additives such as vermicompost (VC) to improve soil characteristics and increase yield is a popular practice. Despite this, there is still a lack of understanding of the interaction between irrigation water and VC on various crops. This study aimed to investigate the interaction effect of irrigation water and VC on greenhouse cucumber yield, yield components, quality, and irrigation water use efficiency (IWUE). The trials were done in a split-plot design in three replicates in a semi-arid region of southeastern Iran in 2018 and 2019. Three levels of VC in the experiments, i.e., 10 (V1), 15 (V2), and 20 t/hm2 (V3), and three levels of irrigation water, i.e., 50% (I1), 75% (I2), and 100% (I3) of crop water requirement were used. The results showed that the amount of irrigation water, VC, and their interaction significantly affected cucumber yield, yield components, quality, and IWUE in both years. Reducing the amount of irrigation water and VC application rates reduced the weight, diameter, length, and cucumber yield. The maximum yield (175 t/hm2) was recorded in full irrigation using 20 t/hm2 of VC, while the minimum yield (98 t/hm2) was found in I1V1 treatment. The maximum and minimum values of IWUE were recorded for I1V3 and I3V1 treatments as 36.07 and 19.93 kg/(m3?hm2), respectively. Moreover, reducing irrigation amount decreased chlorophyll a and b, but increased vitamin C. However, the maximum carbohydrate and protein contents were obtained in mild water-stressed conditions (I2). Although adding VC positively influenced the value of quality traits, no significant difference was observed between V2 and V3 treatments. Based on the results, adding VC under full irrigation conditions leads to enhanced yield and IWUE. However, in the case of applying deficit irrigation, adding VC up to a certain level (15 t/hm2) increases yield and IWUE, after which the yield begins to decline. Because of the salinity of VC, using a suitable amount of it is a key point to maximize IWUE and yield when applying a deficit irrigation regime. 相似文献
14.
Mixed or chloride salty ions dominate in saline soils, and exert wide-ranging adversely affect on soil biological processes and soil functions. The objectives of this study were to(1) explore the impacts of mixed(0, 3, 6, 10, 20 and 40 g Cl~–/SO_4~(2–)salt/kg dry soil) and chloride(0, 1.5, 3, 5, 8 and 15 g Cl~– salt/kg dry soil) salts on soil enzyme activities, soil physiological functional(Biolog) profiles and microbial community structure by using soil enzymatic, Biolog-Eco microplates as well as denaturing gradient gel electrophoresis(DEEG) methods, and(2) determine the threshold concentration of soil electronic conductivity(EC_(1:5)) on maintaining the functional and structural diversity of soil microbial community. The addition of either Cl~– or mixed Cl~–/SO_4~(2–)salt obviously increased soil EC, but adversely affected soil biological activities including soil invertase activity, soil microbial biomass carbon(MBC) and substrate-induced respiration(SIR). Cl~– salt showed a greater deleterious influence than mixed Cl~–/SO_4~(2–)salt on soil enzymes and MBC, e.g., the higher soil MBC consistently appeared with Cl~–/SO_4~(2–)instead of Cl– treated soil. Meanwhile, we found that SIR was more reliable than soil basal respiration(SBR) on explaining the changes of soil biological activity responsive to salt disturbance. In addition, microbial community structures of the soil bacteria, fungi, and Bacillus were obviously affected by both salt types and soil EC levels, and its diversity increased with increasing of mixed Cl~–/SO_4~(2–)salt rates, and then sharply declined down after it reached critical point. Moreover, the diversity of fungal community was more sensitive to the mixed salt addition than other groups. The response of soil physiological profiles(Biolog) followed a dose-response pattern with Cl~–(R~2=0.83) or mixed Cl~–/SO_4~(2–)(R~2=0.89) salt. The critical threshold concentrations of salts for soil physiological function were 0.45 d S/m for Cl~– and 1.26 d S/m for Cl~–/SO_4~(2–), and those for soil microbial community structural diversity were 0.70 d S/m for Cl~– and 1.75 d S/m for Cl~–/SO_4~(2–). 相似文献
15.
七星瓢虫Coccinella septempunctata Linnaeus和松毛虫赤眼蜂Trichogramma dendrolimi Matsumura作为多种害虫的天敌昆虫，广泛应用于生物防治中。本研究按标准采用药膜法分别测定了37%联苯·噻虫胺悬浮剂、24%溴虫腈·甲维盐悬浮剂、45%吡虫·虫螨腈悬浮剂和20%甲维盐·茚虫威悬浮剂四种杀虫剂对七星瓢虫2龄幼虫和松毛虫赤眼蜂成蜂的急性接触毒性，并进行了安全性评价。结果表明：37%联苯·噻虫胺悬浮剂、24%溴虫腈·甲维盐悬浮剂、45%吡虫·虫螨腈悬浮剂和20%甲维盐·茚虫威悬浮剂对七星瓢虫的LR50分别为0.0327、6.90、5.00和1.25 g a.i./hm2，其中24%溴虫腈·甲维盐悬浮剂对七星瓢虫为高风险性，其余药剂为极高风险；对赤眼蜂的LR50分别为2.35×10-3、0.0129、6.46×10-3和0.127 g a.i./hm2，均属极高风险。本研究为杀虫剂对七星瓢虫和松毛虫赤眼蜂的负效应影响研究提供一定数据支持。 相似文献
16.
抑霉唑的毛细管电泳手性拆分及其在线富集 总被引：1，自引：0，他引：1
采用毛细管电泳法对抑霉唑进行手性拆分，研究了手性选择剂β-环糊精 (β-CD)、有机添加剂、NaH2PO4、NH4H2PO4和分离电压对手性拆分的影响；同时，采用堆积法对抑霉唑进行在线富集，研究了进样压力和进样时间对在线富集的影响。结果表明:在分离电压为20 kV、β-CD浓度为5 mmol/L及缓冲体系为2.5% 异丙醇 + 75 mmol/L NaH2PO4 + 5 mmol/L NH4H2PO4时，抑霉唑获得最佳分离度，分离度可达3.0；在分离电压为20 kV、β-CD浓度为5 mmol/L、缓冲体系为75 mmol/L NaH2PO4 + 5 mmol/L NH4H2PO4 + 50 mmol/L H3PO4及进样条件为13.8 kPa × 99.9 s时获得最高富集倍数，富集倍数达91~92倍。 相似文献
17.
环境养分及其在生态系统养分资源管理中的作用——以大气氮沉降为例 总被引：2，自引：0，他引：2
以大气氮素沉降为例,对环境养分的概念、研究方法、数量及其与人为活性氮排放的关系进行了阐述.总结文献资料发现,大气氮素干湿沉降等环境养分已经成为我国农田及自然生态系统一项重要的养分资源,其数量高达1.8×107t/a,相当于全国氮肥用量的60%.因此,通过养分资源综合管理,充分利用好这一环境养分资源是实现我国农田及自然生态系统可持续发展的关键所在. 相似文献
18.
SHAN Junjie WANG Jianping SHAN Fashou TENG Xueming FAN Qishun LIQingkuan QIN Zhanjie ZHANG Xiangru 《干旱区科学》2020,12(2):331-348
It is widely accepted that hydrogeochemistry of saline springs is extremely important to understand the water circulation and evolution of saline basins and to evaluate the potential of potassium-rich evaporites.The Kuqa Basin,located in the northern part of the Tarim Basin in Northwest China,is a saline basin regarded as the most potential potash-seeking area.However,the origin and water circulation processes of saline springs have yet to be fully characterized in this saline basin.In this study,a total of 30 saline spring samples and 11 river water samples were collected from the Qiulitage Structural Belt(QSB)of the Kuqa Basin.They were analyzed for major(K^+,Ca2^+,Na^+,Mg2^+,SO42-,Cl-and HCO3-)and trace(Sr2^+and Br-)ion concentrations,stable H-O-Sr isotopes and tritium concentrations in combination with previously published hydrogeochemical and isotopic(H-O)data in the same area.It is found that the water chemical type of saline springs in the study area belonged to the Na-Cl type,and that of river water belonged to the Ca-Mg-HCO3-SO4 type.The total dissolved solid(TDS)of saline springs in the QSB ranged from 117.77 to 314.92 g/L,reaching the brine level.On the basis of the general chemical compositions and the characteristics of the stable H-O-Sr isotopes of saline springs,we infer that those saline springs mainly originated from precipitation following river water recharging.In addition,we found that saline springs were not formed by evapo-concentration because it is unlikely that the high chloride concentration of saline springs resulted in evapo-concentration and high salinity.Therefore,we conclude that saline spring water may have experienced intense evapo-concentration before dissolving the salty minerals or after returning to the surface.The results show that the origin of salinity was mainly dominated by dissolving salty minerals due to the river water and/or precipitation that passed through the halite-rich stratum.Moreover,there are two possible origins of saline springs in the QSB:one is the infiltration of the meteoric water(river water),which then circulates deep into the earth,wherein it dissolves salty minerals,travels along the fault and returns to the surface;another is the mixture of formation water,or the mixture of seawater or marine evaporate sources and its subsequent discharge to the surface under fault conditions.Our findings provide new insight into the possible saltwater circulation and evolution of saline basins in the Tarim Basin. 相似文献
19.
Ridge-furrow plastic mulching with a suitable planting density enhances rainwater productivity,grain yield and economic benefit of rainfed maize 总被引：1，自引：0，他引：1
Soil surface mulching and planting density regulation are widely used for effective utilization of limited rainwater resources and improvement of crop productivity in dryland farming.However,the combined effects of mulching type and planting density on maize growth and yield have been seldom studied,especially in different hydrological years.A field experiment was conducted to evaluate the effects of mulching type and planting density on the soil temperature,growth,grain yield(GY),water use efficiency(WUE)and economic benefit of rainfed maize in the drylands of northern China during 2015-2017.Precipitation fluctuated over the three years.There were four mulching types(NM,flat cultivation with non-mulching;SM,flat cultivation with straw mulching;RP,plastic-mulched ridge plus bare furrow;RPFS,plastic-mulched ridge plus straw-mulched furrow)and three planting densities(LD,low planting density,45.0×10^3 plants/hm^2;MD,medium planting density,67.5×10^3 plants/hm^2;HD,high planting density,90.0×10^3 plants/hm^2).Results showed that soil temperature was higher with RP and lower with SM compared with NM,but no significant difference was found between RPFS and NM.More soil water was retained by soil mulching at the early growth stage,but it significantly varied at the middle and late growth stages.Maize growth was significantly improved by soil mulching.With increasing planting density,stem diameter,net photosynthetic rate and chlorophyll content tended to decline,whereas a single-peak trend in biomass yield was observed.Mulching type and planting density did not have significant effect on evapotranspiration(ET),but GY and WUE were significantly affected.There were significant interacting effects of mulching type and planting density on biomass yield,GY,ET and WUE.Compared with NM,RPFS,RP and SM increased GY by 57.5%,50.8%and 18.9%,and increased WUE by 66.6%,54.3%and 18.1%,respectively.At MD,GY increased by 41.4%and 25.2%,and WUE increased by 38.6%and 22.4%compared with those of at LD and HD.The highest maize GY(7023.2 kg/hm^2)was observed under MD+RPFS,but the value(6699.1 kg/hm^2)was insignificant under MD+RP.Similar trends were observed for WUE under MD+RP and MD+RPFS,but no significant difference was observed between these two combinations.In terms of economic benefit,net income under MD+RP was the highest with a 9.8%increase compared with that of under MD+RPFS.Therefore,we concluded that RP cultivation pattern with a suitable planting density(67.5×10^3 plants/hm^2)is promising for rainwater resources utilization and maize production in the drylands of northern China. 相似文献
20.
2013年5-8月按照GB13580.2-92规定的大气降水采样方法,采集了东天山喀尔力克山南坡榆树沟流域32场降水,进行了pH、EC及离子组成的测定,并运用综合描述法、相关性分析、气团来源轨迹、富集因子及端源贡献法探究其来源。结果表明：榆树沟流域夏季降水的pH平均值为6.8,呈弱酸性;电导率在3.79~239 μs·cm-1,受降水量影响明显;阴阳离子质量浓度的平均值分别是SO42->NO3->Cl->F-和Ca2+> NH4+>Na+>K+>Mg2+;SO42-、NO3-、F-和NH4+主要来自于人类活动;Cl-基本来自海盐源,受地壳源的影响甚微;Na+的来源受海盐源和陆源共同影响;Ca2+和K+来自于非海盐源的贡献。 相似文献