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431.
中国2000—2010年耕地低效转化的空间特征 总被引:1,自引:0,他引:1
耕地向经济效益相对较低的用地类型转化具有多重社会及生态效应。论文首先将耕地向草地、灌丛地和裸地的转化定义为“耕地低效转化”,然后以GlobeLand30为基础,提取2000—2010年的低效转化耕地,并结合耕地资源禀赋和地形条件,从多尺度、多角度深入揭示了我国耕地低效转化的空间分布特征。结果表明:1)全国总体的耕地低效转化率仅为1.50%,但区域差异明显,空间分布极不均衡;2)耕地低效转化依照地势的三级阶梯呈现明显的区域分异规律,农牧交错带的耕地转化问题最为严重,但耕作条件好、原有耕地比例高的东部地区,耕地低效转化水平一般较低;3)耕地低效转化率大体随海拔和坡度的增加而增加,但会受到地形复杂度的影响。 相似文献
432.
Yangtze River Delta(YRD) area is one of the important economic zones in China. However,this area faces increasing environmental problems. In this study, we use ground-based multi-axis differential optical absorption spectroscopy(MAX-DOAS) network in Eastern China to retrieve variations of NO_2, SO_2, and formaldehyde(HCHO) in the YRD area. Three cities of YRD(Hefei, Nanjing, and Shanghai) were selected for long-term observations. This paper presents technical performance and characteristics of instruments, their distribution in YRD, and results of vertical column densities(VCDs) and profiles of NO_2, SO_2, and HCHO.Average diurnal variations of tropospheric NO_2 and SO_2 in different seasons over the three stations yielded minimum values at noon or in the early afternoon, whereas tropospheric HCHO reached the maximum during midday hours. Slight reduction of the pollutants in weekends occurred in all the three sites. In general trace gas concentrations gradually reduced from Shanghai to Hefei. Tropospheric VCDs of NO_2, SO_2, and HCHO were compared with those from Ozone Monitoring Instrument(OMI) satellite observations, resulting in R~2 of 0.606, 0.5432, and 0.5566, respectively. According to analysis of regional transports of pollutants, pollution process happened in YRD under the north wind with the pollution dissipating in the southeast wind. The feature is significant in exploring transport of tropospheric trace gas pollution in YRD, and provides basis for satellite and model validation. 相似文献
433.
Ci Zhang Xiaohui Lu Jinghao Zhai Hong Chen Xin Yang Qi Zhang Qianbiao Zhao Qingyan Fu Fei Sh Jing Jin 《环境科学学报(英文版)》2018,30(10):118-132
To investigate formation mechanisms of secondary organic carbon(SOC) in Eastern China,measurements were conducted in an urban site in Shanghai in the summer of 2015. A period of high O_3 concentrations(daily peak 120 ppb) was observed, during which daily maximum SOC concentrations exceeding 9.0 μg/(C·m~3). Diurnal variations of SOC concentration and SOC/organic carbon(OC) ratio exhibited both daytime and nighttime peaks. The SOC concentrations correlated well with O_x(= O_3+ NO_2) and relative humidity in the daytime and nighttime, respectively, suggesting that secondary organic aerosol formation in Shanghai is driven by both photochemical production and aqueous phase reactions. Single particle mass spectrometry was used to examine the formation pathways of SOC. Along with the daytime increase of SOC, the number fraction of elemental carbon(EC) particles coated with OC quickly increased from 38.1% to 61.9% in the size range of 250–2000 nm, which was likely due to gas-to-particle partitioning of photochemically generated semi-volatile organic compounds onto EC particles. In the nighttime, particles rich in OC components were highly hygroscopic, and number fraction of these particles correlated well with relative humidity and SOC/OC nocturnal peaks. Meanwhile, as an aqueous-phase SOC tracer, particles that contained oxalate-Fe(III) complex also peaked at night. These observations suggested that aqueous-phase processes had an important contribution to the SOC nighttime formation. The influence of aerosol acidity on SOC formation was studied by both bulk and single particle level measurements, suggesting that the aqueous-phase formation of SOC was enhanced by particle acidity. 相似文献
434.
海藻糖强化厌氧氨氧化耦合反硝化工艺处理高盐废水的脱氮除碳效能 总被引:2,自引:2,他引:0
采用SBR反应器研究海藻糖强化厌氧氨氧化耦合反硝化工艺(SAD)处理高盐水的脱氮除碳效能及其动力学特性.当海藻糖为0.25 mmol·L~(-1)时反应器具有最佳的脱氮效能,NH_4~+-N、NO_2~--N、NO_3~--N和COD均可以被完全去除,与没有添加海藻糖相比,NH_4~+-N、NO_2~--N和总氮去除率分别提高了50%、43%和46%,氨氮去除速率(ARR)和亚硝氮去除速率(NRR)分别提高了81.25%和75%.当海藻糖浓度进一步提升至0.5 mmol·L~(-1)时,NH_4~+-N去除率(ARE)仅为58.82%,出水NH_4~+-N浓度下降为33.25 mg·L~(-1).相比于Haldane模型和Aiba模型,Luong模型更适合拟合海藻糖添加条件下SAD的脱氮性能.由其得到的NRRmax、KS、Sm和n分别为0.954 kg·(m3·d)-1、0 mg·L~(-1)、184.785 mg·L~(-1)和0.718.与修正的Logistic模型和修正的Boltzman模型相比,修正的Gompertz模型得到的预测值与实验值最为贴近,修正的Gompertz模型更适合描述海藻糖添加条件下单周期内基质的降解过程. 相似文献
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436.
聚苯胺和聚2,5-二甲氧基苯胺具有很好的电化学性能、光学性能等,广泛应用于电致变色显示器、化学传感器、抗静电涂层及太阳能电池等领域。不同于传统的机械化学合成法,首次应用高速气流法低温固相合成了聚苯胺和聚2,5-二甲氧基苯胺,同时用X射线衍射(XRD)、傅里叶红外光谱(FT-IR)、热重分析(TG)、紫外可见吸收光谱(UV-Vis)对两种聚合物进行了表征;此外,测试了两种聚合物的循环伏安特性,结果表明,两者均具有较好的电化学性能。相比于传统的机械化学合成法,高速气流法低温固相合成能够高效快速、连续循环制备聚苯胺类化合物,而且此方法具有操作简便、高效率、低能耗、安全性好和绿色环保等优点,可应用于诸多领域。 相似文献
437.
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439.
QIU Rongliang WANG Shizhong QIU Hao WANG Xuemei LIAO Jin ZHANG Zhentian 《环境科学学报(英文版)》2009,21(8):1108-1118
The current acid deposition critical loads in Guangdong, China were calculated using the PROFILE model with a 3 km × 3 km resolution. Calculations were carried out for critical loads of potential acidity, actual acidity, sulfur and nitrogen, with values in extents of 0–3.5, 0–14.0, 0–26.0 and 0–3.5 kmol/(hm2·year), respectively. These values were comparable to previously reported results and reflected the influences of vegetation and soil characteristics on the soil acid buffering capacity. Simulations of S... 相似文献
440.