Changes of organic acid exudation and rhizosphere pH in rice plants under chromium stress.

The effect of chromium (Cr) stress on the changes of rhizosphere pH, organic acid exudation, and Cr accumulation in plants was studied using two rice genotypes differing in grain Cr accumulation. The results showed that rhizosphere pH increased with increasing level of Cr in the culture solution and with an extended time of Cr exposure. Among the six organic acids examined in this experiment, oxalic and malic acid contents were relatively higher, and had a significant positive correlation with the rhizosphere pH, indicating that they play an important role in changing rhizosphere pH. The Cr content in roots was significantly higher than that in stems and leaves. Cr accumulation in plants was significantly and positively correlated with rhizosphere pH, and the exudation of oxalic, malic and citric acids, suggesting that an increase in rhizosphere pH, and exudation of oxalic, malic and citric acid enhances Cr accumulation in rice plants.     

Diffusion pollution from livestock and poultry rearing in the Yangtze Delta,China

BACKGROUND: The Yangtze Delta is one of the most developed regions in China and includes Shanghai, eight cities in Jiangsu province and eight cities in Zhejiang province. Meat consumption in this region has increased with economic growth, and most of the consumed meat is produced locally. The water quality of surface waters has deteriorated in recent years. An example was the huge blue-green algae bloom in Tai Lake in late May 2007, which affected millions of people's daily drinking water. However, animal husbandry is considered to be one of the main pollution sources. METHODS: Pollutants (NH3-N, total phosphorus (TP), and total nitrogen (TN)) excreted by livestock and poultry, and the resultant COD (chemical oxygen demand) and BOD (biochemical oxygen demand), were estimated using two different methods based on different data sets. RESULTS: The number of livestock and poultry has remained stable in the Yangtze Delta over the four years from 1999 to 2002, with the average number of pigs, cattle, sheep and poultry being 21.1 M, 0.4 M, 7.7 M and 597.6 M, respectively. Pollutants in livestock and poultry excreta estimated by Method I were: 0.12 Mt NH3-N, 0.11 Mt TP and 0.29 Mt TN, resulting in COD and BOD of 1.34 Mt and 1.30 Mt, respectively, while the estimations based on Method II were: 0.18 Mt NH3-N, 0.15 Mt TP and 0.40 Mt TN, resulting in COD and BOD of 1.95 Mt and 1.80 Mt, respectively. DISCUSSION: Pollutants excreted annually by livestock and poultry in the Yangtze Delta are estimated to be: 0.17 Mt NH3-N, 0.16 Mt TP and 0.42 Mt TN, giving rise to a COD of 1.86 Mt and a BOD of 1.72 Mt. Approximately 25% of this pollution was estimated to enter water bodies, which means that the annual pollutant load is 43,700 t NH3-N, 39,400 tTP, 104,600t TN with a COD of 465,000 tand a BOD of 430,100 t. Pollutants from animal husbandry were similar in magnitude to those from industrial wastewater. Pigs produced the most pollution, followed by poultry, cattle and sheep. The pollution load from animal husbandry in the Yangtze Delta is about twice the average level of the whole of China. CONCLUSIONS: Domestic wastewater was the main pollution source in the Yangtze Delta, followed by pollution from raising livestock and poultry and from industrial wastewater. The pollution load in Shanghai and Jiaxing were the greatest, followed by 7 cities of Jiangsu province (except Suzhou) and other cities of Zhejiang province and Suzhou. Pigs and poultry produced about 90% of the total pollutants from animal husbandry. RECOMMENDATIONS AND PERSPECTIVES: The local governments, especially in Shanghai and Jiaxing, should focus their attention on the pollution produced by livestock and poulrry. Controlling pollution from pigs and poultry will have the greatest impact in this region. Control of pollution will be facilitated by the development of large-scale livestock and poultry farming units and a shift away from small scale husbandry.     

Implications of urine-to-feces ratio in the thermophilic anaerobic digestion of swine waste.

Thermophilic anaerobic digestion of swine manure represents a potential waste treatment technology to address environmental concerns, such as odor emissions and removal of pathogenic microorganisms. However, there are concerns relative to the stability of this process when swine manure is the sole substrate. In this study, the potential of biogas production from swine manure as the sole substrate under thermophilic (50 degrees C) conditions was investigated in the laboratory, to determine whether separation of urine and feces as part of the waste collection process would benefit anaerobic digestion. Effluent from a continuously stirred tank reactor was used as the inoculum for batch tests, in which the substrate contained three different concentrations of urine (urine-free, as-excreted urine-to-feces ratio and double the as-excreted urine-to-feces ratio). Inocula were acclimated to these same urine-to-feces ratios to determine methane production. Results show that both urine-free and as-excreted substrates were not inhibitory to anaerobic inocula. Anaerobic microorganisms can be readily acclimated to substrate with double the as-excreted urine concentration, which contained nitrogen concentrations up to 7.20 g/L. Cumulative methane production reached similar levels in the batch tests, regardless of the substrate urine concentration.     

Surface functional characteristics (C, O, S) of waste tire-derived carbon black before and after steam activation

The effects of steam activation on the surface functional characteristics of waste tire-derived carbon black were investigated. Two carbon-based materials, powdered carbon black (PCB) and PCB-derived powdered activated carbon (PCB-PAC), were selected for this study. A stainless steel tubular oven was used to activate the PCB at an activation temperature of 900 degrees C and 1 atm using steam as an activating reagent. X-ray photoelectron spectroscopy (XPS) was adopted to measure the surface composition and chemical structure of carbon surface. Various elemental spectra (C, O, and S) of each carbon sample were further deconvoluted by peak synthesis. Results showed that the surfaces of PCB and PCB-PAC consisted mainly of C-C and C-O. The PCB-PAC surface had a higher percentage of oxygenated functional groups (C=O and O-C=O) than PCB. The O1s spectra show that the oxygen detected on the PCB surface was mainly bonded to carbon (C-O), whereas the oxygen on the PCB-PAC surface could be bonded to hydrogen (O-H) and carbon (C-O). Sulfur on the surface of PCB consisted of 58.9 wt% zinc sulfide (ZnS) and 41.1 wt% S=C=S, whereas that on the surfaces of PCB-PAC consisted mainly of S=C=S. Furthermore, the increase of oxygen content from 9.6% (PCB) to 11.9% (PCB-PAC) resulted in the increase of the pH values of PCB-PAC after steam activation.     

土壤柴油污染修复的抽气提取去除实验研究

为得到土壤气相抽提(SVE)去除柴油的优化条件,进行了一维土柱抽气提取去除柴油污染物的实验研究,研究不同初始含水率、不同抽气量对污染土壤中柴油去除率的影响及不同深度残留柴油的变化规律。结果表明：在本实验模拟的范围内,抽气量越大,SVE处理效果越好;初始含水率越低,处理效果越好;此外,不同深度去除率变化的规律基本上是随深度的增大而减小。实验结果可为土壤轻油污染实际治理提供实验数据基础。     

PAC-chitosan复合絮凝剂中铝形态

以不同碱化度(B)的聚合氯化铝(PAC)和不同粘度的壳聚糖为原料制备出一系列PAC-chitosan复合絮凝剂。采用Al-Ferron逐时络合比色法研究了PAC-chitosan复合絮凝剂中铝的形态分布,探讨了PAC的B值、壳聚糖的含量（C）和粘度（η）对复合絮凝剂中铝的形态分布的影响。结果表明：壳聚糖与PAC之间发生了一定的相互作用,通过试验结果推断出当B=1.5,壳聚糖粘度η=800 Pa·s,C=0.6 mg/mL絮凝效果最佳。并用某造纸废水进行了烧杯絮凝试验。絮凝试验结果与推断结果相一致。     

劳动力外出务工对承灾体恢复力的影响——以河北省邢台县旱灾调查为例

农村劳动力资源是构成农户承灾体恢复力的重要因素.一般认为农村劳动力外出务工,可以提高农户家庭的经济水平,进而提升农户的旱灾恢复力.通过对河北省邢台县的实地调查研究发现,劳动力外出务工与农户承灾体恢复力间存在着微妙的关系.研究表明,户主外出务工模式不仅在农业生产的灾后恢复上,而且在农户家庭经济的恢复上均有积极的意义.对于子女外出务工家庭而言,子女不愿意再从事农业生产,并且子女的务工收入对家庭的贡献十分有限,即子女外出务工对家庭旱灾恢复力影响较小.     

四川汶川8．0级地震典型遗址遗迹综合评估

简要介绍了四川汶川8.0级地震现场考察的有关情况,然后重点对地震典型遗址、遗迹的综合评估原则进行了详细研究,并在此基础上设计出综合评估量表.最后,对北川、映秀等典型地震遗址、遗迹进行了综合评估,并提出了保护建议.     

滚石灾害研究现状及发展趋势

滚石是我国西部山区常见的一种地质灾害,它分布范围极广,发生突然,频率高,严重威胁其周围的人类以及各种构筑物.目前,国内外有关滚石的理论研究比较薄弱,以致滚石灾害的防治工作受到严重的影响.基于对国内外大量滚石灾害研究资料的分析,将其研究现状概化为滚石风险分析、滚石运动轨迹、滚石冲击力以及滚石防护等4个方面.据此对滚石研究的发展趋势进行了探讨,以便为滚石灾害的机理研究和治理提供参考依据.