Impacts of climate warming on vegetation in Qaidam Area from 1990 to 2003

The observed warming trend in the Qaidam area, an arid basin surrounded by high mountains, has caused land surface dynamics that are detectable using remotely sensed data. In this paper, we detected land-cover changes in the Qaidam Area between 1990 and 2003 in attempt to depict its spatial variability. The land-cover changes were categorized into two trends: degradation and amelioration, and their spatial patterns were examined. Then we estimated the correlation coefficients between growing-season NDVI and several climatic factors with the consideration of duration and lagging effects. The results show that the inter-annual NDVI variations are positively correlated with May to July precipitations, but not significantly correlated with sunshine duration. We observed no obvious trend in precipitation or sunshine duration from 1990 to 2003. Thus, the authors suggest that their slight fluctuations may not be responsible to the decade-scaled land-cover changes. However, our results indicate a good positive relationship between the NDVI trend and climate warming in the ameliorated areas, but a negative one in the degraded areas. By statistical analyses, we found that degradations mainly occurred at the oasis boundaries and at lower elevations in the non-oasis regions where effective soil moisture might have been reduced by the warming-caused increase in evapotranspiration. At higher elevations where thermal condition acts as a major limiting factor, ameliorations were unequivocally detected, which is attributable to the direct facilitation by temperature increases. We suggest that the impacts of the observed climate warming on vegetation are spatially heterogeneous, depending on the combinations of thermal condition and moisture availability.     

Changes in labile soil organic matter fractions following land use change from monocropping to poplar-based agroforestry systems in a semiarid region of Northeast China

Labile fractions of soil organic matter (SOM) respond rapidly to land management practices and can be used as a sensitive indicator of changes in SOM. However, there is little information about the effect of agroforestry practices on labile SOM fractions in semiarid regions of China. In order to test the effects of land use change from monocropping to agroforestry systems on labile SOM fractions, we investigated soil microbial biomass C (MBC) and N, particulate organic matter C (POMC) and N (POMN), as well as total organic C (TOC) and total N (TN) in the 0- to 15-cm and the 15- to 30-cm layers in 4-year-old poplar-based agroforestry systems and adjoining monocropping systems with two different soil textures (sandy loam and sandy clay loam) in a semiarid region of Northeast China. Our results showed that poplar-based agroforestry practices affected soil MBC, POMC, and POMN, albeit there was no significant difference in TOC and TN. Agroforestry practices increased MBC, POMC, and POMN in sandy clay loam soils. However, in sandy loam soils, agroforestry practices only increased MBC and even decreased POMC and POMN at the 0- to 15-cm layer. Our results suggest that labile SOM fractions respond sensitively to poplar-based agroforestry practices and can provide early information about the changes in SOM in semiarid regions of Northeast China and highlight that the effects of agroforestry practices on labile SOM fractions vary with soil texture.     

Assessment of sampling designs to measure riverine fluxes from the Pearl River Delta, China to the South China Sea

The Pearl River Delta (PRD), located in South China and adjacent to the South China Sea, is comprised of a complicated hydrological system; therefore, it was a great challenge to sample adequately to measure fluxes of organic and inorganic materials to the coastal ocean. In this study, several sampling designs, including five-point (the number of sampling points along the river cross-section and three samples collected at the upper, middle, and bottom parts at each vertical line), three-point (at the middle and two other profiles), one-point (at the middle profile), and single-point (upper, middle, or bottom sub-sampling point at the middle profile) methods, were assessed using total organic carbon (TOC) and suspended particulate matter (SPM) as the measurables. Statistical analysis showed that the three- and five-point designs were consistent with one another for TOC measurements (p > 0.05). The three- and one-point sampling methods also yielded similar TOC results (95% of the differences within 10%). Single-point sampling yielded considerably larger errors than the three- and one-point designs, relative to the results from the five-point design, but sampling at the middle sub-point from the middle profile of a river achieved a relatively smaller error than sampling at the upper or bottom sub-point. Comparison of the sampling frequencies of 12 times a year, four times a year, and twice a year indicated that the frequency of twice a year was sufficient to acquire representative TOC data, but larger sample size and higher sampling frequency were deemed necessary to characterize SPM.     

On the intensity and type transition of land use at the basin scale using RS/GIS: a case study of the Hanjiang River Basin

The purpose of this study is to investigate the land use intensity and land use change type at the basin scale in the middle and lower reaches of the Hanjiang River Basin (in Hubei Province, China) by combining the Landsat TM images in 1995 and 2000 with the land use database (in scale 1:10,000) and relative data. In this study, the basic data is acquired from the interpretation of remote sensing (RS) images. The intensity of land use and the rate of change in double-directions of land use dynamics are calculated with the support of software ARC/INFO. The intensity of land use is indicated by the intensity coefficient of land use, and the transition of land use types is quantified as the rate of change in double-direction of land use types and also expressed as the transition matrix of land use types. The results are expressed in space by Geographic Information System (GIS) software. Results of this study show that (1) the intensity of land use is high in the study region, the intensity coefficients of land use in 1995 and 2000 are 260.025 and 290.526, respectively, and the intensity of development and utilization of land is trend to increscent; and (2) the rate of land use change in double directions in the whole study region is 0.52 with great spatial variation and the differentiation of land use types. In the differentiation of land use types, the unutilized land (with the rate to 4.391) is developed fast, the grassland (with 2.836) and water area (with 1.664) are disturbed severely, and these changes will influence the eco-environment in the Hanjiang River Basin and all the Yangtze Basin. The rates of the farmland and the woodland are 0.424 and 0.344, respectively, meaning that the fundamentals of regional human-environmental system are relative stable. With this study, we can conclude that (1) the patterns of land use are increasingly changing in the study region, the environmental impacts are escalated on this stage, and the further outcomes are destined to change the stability of the regional human–environmental system; and (2) the most useful method to study the present land use and its change is through the use of the RS/GIS with the land use database (in scale 1:10,000).     

Labile pools of Pb in vegetable-growing soils investigated by an isotope dilution method and its influence on soil pH

Pollution of Pb in the surface of agricultural soils is of increasing concern due to its serious impact on the plant growth and the human health through the food chain. However, the mobility, activity and bioavailability of Pb rely mainly on its various chemical species in soils. In the present study, E and L values, the labile pools of isotopically exchangeable Pb, were estimated using the method of isotope dilution in three vegetable-growing soils. The experiments involved adding a stable enriched isotope ((206)Pb > 96%) to a soil suspension and to soils in which plants are subsequently grown, the labile pools of Pb were then estimated by measuring the isotopic composition of Pb in soil solutions and in the plant tissues, respectively. In addition, the correlation of E values and soil pH was investigated at the ranges of pH 4.5-7.0. The amount of labile Pb in soils was also estimated using different single chemical extractants and a modified BCR approach. The results showed that after spiking the enriched isotopes of (206)Pb (>96%) for 24 hours an equilibration of isotopic exchanges in soil suspensions was achieved, and the isotope ratios of (208)Pb/(206)Pb measured at that time was used for calculating the E(24 h) values. The labile pools of Pb by %E(24 h) values, ranging from 53.2% to 61.7% with an average 57%, were found to be significantly higher (p < 0.05) than the values estimated with L values, single chemical extractants and the Σ(BCR) values obtained with the BCR approach, respectively. A strong negative correlation (R(2) = 0.984) between E(24 h) values and soil pH was found in the tested soil sample. The results indicate that the %E(24 h) value can more rapidly and easily predict the labile pools of Pb in soils compared with L values, but it might be readily overestimated because of the artificial soil acidity derived from the spiked isotopic tracer and the excess of spiked enriched isotopes. The results also suggest that the amounts of Pb extracted with EDTA and the Σ(BCR) values extracted with the modified BCR approach are helpful to detect the labile pools of Pb in soils. In addition, the negative correlation between soil pH and the labile pools of Pb in soils may be useful for further remediation to reduce the bioavailability of Pb in contaminated soils.     

几种观叶植物对室内污染物的净化效果研究

为了寻求减少室内空气污染物的措施和技术,我们用吊兰、虎尾兰、君子兰和橡皮树做为试材,开展一系列有针对性的试验.结果表明,这4种室内观叶植物都能吸收室内有毒有害气体,但作用效果差异明显.虎尾兰效果最佳,7 d内室内甲醛总量的减少率比对照多64.6%,二甲苯总量的减少率比对照多61.4%,总挥发性有机物(TVOC)总量的减少率比对照多64.8%;而橡皮树的作用效果最差.     

土壤氮磷平衡在评价区域氮磷损失中的应用

土壤氮磷平衡是评价农田生态系统氮磷迁移损失的有效工具。文章从土壤氮磷平衡的定义、分类及模型计算表达出发,结合国内外土壤氮磷平衡研究实例,探讨了土壤氮磷平衡的分析过程,并提出了土壤氮磷平衡研究的新动向。     

废弃线路板的破碎解离和气流分选研究

破碎和材料富集分离是废弃线路板资源化的关键技术。采用冲击破碎和气流分选技术对废线路板的机械分离过程进行了研究。结果表明使用锤式粉碎机破碎,线路板中主要金属在0.8mm以下基本解离,79.65%的金属集中分布在0.125～1.0mm粒级。气流分选得到品位较高的金属富集体,粒级0.125～1.0mm中的总金属回收率超过90%。     

电-Fenton法预处理青霉素废水的降解规律研究

研究电-Fenton法预处理青霉素钠(penicillin G sodium,PGN)模拟废水的降解规律,分析预处理过程中PGN浓度、COD、TOC的变化情况及BOD5/COD改善情况.当T=20℃、pH=3时,投加0.5g/L FeSO4、0.2 mL/L H2O2,于0.3 A电流下降解浓度为100 mg/L的PGN废水,120 min后PGN去除97.9%,COD去除76.7%,TOC去除59.8%,BOD5/COD由0升至0.4,有效提高了废水的可生化性.以红外光谱(infrared spectrogram,IR)和液相色谱-质谱联用(Liquid chromatogramMass chromatogram,LC-MS)检测青霉素钠的降解产物,说明青霉素钠抑菌的关键结构b-内酰胺环被破坏,抗菌性消失,有助于生物处理有效去除.     

滴流床苯酚催化湿式氧化反应动力学及反应器模型

在自制的滴流床反应器中,以苯酚配水溶液为研究对象,采用负载型MnO_x/γ-Al₂O₃作为催化剂,研究了苯酚催化湿式氧化过程.通过实验数据的拟合分析,提出了苯酚催化湿式氧化本征反应速率表达式,计算了液体流率为1.6　L/h时不同温度下催化剂外表面湿润效率以及不同温度下与一定的氧分压相平衡的水中溶解氧浓度;由实验数据拟合得到苯酚催化湿式氧化表观反应动力学模型参数,并建立了关于积分式滴流床苯酚催化湿式氧化的反应器模型,比较了不同氧分压、进液苯酚质量浓度、进液流率下苯酚去除率的计算值与实验值.结果显示:当氧分压大于1.0 MPa时,计算值与实验值能较好吻合,当氧分压较低时,氧气从气相到液相存在一定的传质阻力.在苯酚进液质量浓度为0～5 000 mg/L时,苯酚对催化氧化反应的抑制作用不明显.在进液流率为0～2.05 L/h时,存在一定的外扩散阻力.