A landcover change study of takyr surfaces in Turkmenistan     

S. Maman  L. OrlovskyD.G. Blumberg  P. BerlinerB. Mamedov 《Journal of Arid Environments》2011,75(9):842-850

The shortage of fresh water in Turkmenistan may be partially alleviated by runoff water from takyrs. However, anthropogenic degradation of takyrs over the past few decades has reduced their efficacy as catchment areas. The main goal of this study was to map the spatial extent of takyrs and their change over time. Digital image processing of Landsat MSS and Landsat 7 ETM+ images were used to identify, map and classify the takyrs and estimate their overall area and degradation rates. Thereafter, a change detection procedure was applied. Results retrieved from Landsat MSS images of southern Turkmenistan (1972-1975) showed a total area of non-degraded takyr surfaces of ∼20,000 km², whereas those from Landsat 7 ETM+ images (2002-2003) showed a total non-degraded takyr area of ∼16,000 km². These include ∼8000 km² which were degraded and ∼4000 km² that were only detected by the ETM+ due to its improved spectral resolution. Accuracy was assessed by comparing the Landsat results with higher spatial resolution images of QuickBird. Additional ground points located with GPS measurements validated the classification results. We were thus able to assess the takyr areas degraded over the past decades, and find ∼16,000 km² of non-degraded takyrs suitable for water harvesting.  相似文献   

Fe-TiO2的制备及在可见光下催化降解对硝基苯胺          下载免费PDF全文

张一兵  杨燕平 《盐湖研究》2013,(4):37-41

采用水热法自制了铁掺杂的锐钛矿型铁二氧化钛光催化剂Fe-TiO2。通过分析对硝基苯胺溶液的初始浓度、二氧化钛掺铁量、TiO2用量和溶液的pH值对光催化速率的影响,研究了Fe-TiO2光催化对硝基苯胺动力学行为。结果表明,在对硝基苯胺的初始浓度为25mg／L,Fe-TiO2掺铁量为0．2％（摩尔分数）,TiO2用量为0．1g／L,溶液pH=6,室温下可见光照反应10h,对硝基苯胺的降解率D和表观反应速率常数k达到最大。光催化反应符合L-H动力学规律,对硝基苯胺的降解过程为拟一级反应,k为0．0314h^-1。  相似文献   

Macroalgae in the coral reefs of Eilat (Gulf of Aqaba, Red Sea) as a possible indicator of reef degradation     

Karnit Bahartan  Mohammad Zibdah  Alvaro Israel  Avigdor Abelson 《Marine pollution bulletin》2010,60(5):759-764

The current state of health of the coral reefs in the northern Gulf of Aqaba (Red Sea), notably the Eilat reefs, is under debate regarding both their exact condition and the causes of degradation. A dearth of earlier data and unequivocal reliable indices are the major problems hinder a clear understanding of the reef state. Our research objective was to examine coral-algal dynamics as a potential cause and an indication of reef degradation. The community structure of stony corals and algae along the northern Gulf of Aqaba reveal non-seasonal turf algae dominancy in the shallow Eilat reefs (up to 72%), while the proximate Aqaba reefs present negligible turf cover (<6%). We believe that turf dominancy can indicate degradation in these reefs, based on the reduction in essential reef components followed by proliferation of perennial turf algae. Our findings provide further evidence for the severe state of the Eilat coral reefs.  相似文献   

不同河岸植物带对非点源污染河水污染物降解试验研究     

徐成斌  于宁  马溪平  艾娇  张营  张利红 《辽宁气象》2008,(6):63-66

利用2种植物带（芦苇、香蒲与芦苇）对受非点源污染河水进行植物带处理污染物的降解效果模拟试验研究。结果表明：植物带处理污染物的降解效果明显优于无植物带,且以混合植物带效果最好。香蒲与芦苇植物带对COD、TN、TP和NH3-N去除率的周平均值分别为31．62％、37.84％、30．65％和34．31％。植物带能够截留地表径流中的颗粒物,提高水域中的溶解氧含量,对防止水土流失与改善流域水质均有显著作用。  相似文献   

东北亚区域国际合作中跨境交通走廊的发展及其对环境退化的影响   总被引：1，自引：1，他引：1  

赵伟  王荣成  丁四保 《世界地理研究》2002,11(1):33-39

东北亚区域跨境交通走廊由于图们江地区国际合作开发的深入而得到迅速发展，其对区域环境退化已经形成和将要形成重大的影响。本文在对东北亚区域国际合作中跨境交通走廊的运行及其发展进行深入研究的基础上，对跨境交通走廊的发展对区域环境退化的影响作了战略性的评价与分析，并对其未来发展提出若干建议。  相似文献   

Removal of tributyltin (TBT) by live and dead microalgal cells   总被引：3，自引：0，他引：3  

Tam NF  Chong AM  Wong YS 《Marine pollution bulletin》2002,45(1-12):362-371

The removal of tributyltin (TBT) from artificial wastewater by dead and live cells of four microalgal species, Chlorella miniata, C. sorokiniana, Scenedesmus dimorphus and S. platydiscus was investigated. Dead cells were generally more efficient in removing TBT during three days exposure. More than 90% and 85% TBT were removed by dead cells of Scenedesmus and Chlorella, respectively. Although the removal percentages of live microalgae were smaller, TBT was continuously absorbed and degraded, and TBT removal percentages similar to respective dead cells were achieved at the end of 14 days treatment. Degradation products, DBT and MBT, were recorded mainly inside the cells, and intracellular MBT concentrations were significantly higher than DBT. In terms of TBT removal, Scenedesmus cells were more effective than Chlorella, probably due to larger cell sizes and biomass. However, TBT specific uptake and degradation by Chlorella was higher than in Scenedesmus. The highest specific TBT uptake values, as well as the highest degradation, were recorded in C. miniata, a Hong Kong isolate.  相似文献   

Biologischer Abbau von 2,4-Dinitrotoluol in einer kontinuierlich betriebenen Versuchsanlage und kinetische Untersuchungen     

L. Heinze  M. Brosius  U. Wiesmann 《洁净——土壤、空气、水》1995,23(6):254-263

Biological Degradation of 2,4-Dinitrotoluene in a Continuous Bioreactor and Kinetic Studies Experimental results on the aerobic biological degradation with complete mineralization of 2,4-dinitrotoluene (2,4-DNT) are presented. A culture of Pseudomonas sp. DNT from Spain and Nishino was used. The degradation was examined with batch cultures for the determination of kinetic and stoichiometric coefficients. Further experiments were carried out with a continuous culture in a fixed-bed reactor with recirculation in order to obtain high degradation rates. The reactor was packed with ceramic Raschig rings (55 mL) and had a liquid reaction volume of 160 mL. The minimal salt media from Spanggord et al. with and without (NH₄)₂S)₄ as nitrogen source was used as substrate. 2,4-DNT was the sole source of carbon and energy. From batch experiments a yield coefficient Y_B/S = (0.30 ± 0.05) g g^?1 was calculated from a mass balance of the elements. This result was confirmed by calculations using literature data. Fitting the experimental data to the Monod equation, μ_max = 0.1 h^?1 and K_S = 0.01…0.03 mmol L^?1 were obtained. It was demonstrated by batch experiments that 2,4-DNT is not only used as the source of carbon and energy but also as the nitrogen source. In the fixed-bed reactor, a degradation of 92…97% was reached with a maximal 2,4-DNT load of 95 mg L^?1 h^?1. The rate of continuous degradation could be described by a pseudo-first-order reaction (k = 9.73 h^?1). The complete mineralization of 2,4-DNT was verified by the measurement of DOC and the formed nitrite and nitrate. The formed nitrite was nitrified simultaneously. It was demonstrated by these experiments that large scale biological treatment of industrial effluent containing 2,4-DNT may be successful.  相似文献   

A model of channel response in disturbed alluvial channels   总被引：2，自引：0，他引：2  

Andrew Simon 《地球表面变化过程与地形》1989,14(1):11-26

Dredging and straightening of alluvial channels between 1959 and 1978 in West Tennessee caused a series of morphologic changes along modified reaches and tributary streams. Degradation occurred for 10 to 15 years at sites upstream of the area of maximum disturbance and lowered bed-levels by as much as 6·1 m. Following degradation, reaches upstream of the area of maximum disturbance experienced a secondary aggradation phase in response to excessive incision and gradient reduction. Aggradation downstream of the area of maximum disturbance reached 0·12 m per year with the greatest rates occurring near the stream mouths. The adjustment of channel geometry and phases of channel evolution are characterized by six process-oriented stages of morphologic development—premodified, constructed, degradation, threshold, aggradation, and restabilization. Down-cutting and toe removal during the degradation stage causes bank failure by mass wasting when the critical height and angle of the bank material is exceeded (threshold stage). Channel widening continues through the aggradation stage as the ‘slough line’ develops as an initial site of lower-bank stability. The bank profile develops three dynamic elements (1) vertical face (70° to 90°), (2) upper bank (25° to 50°), and (3) slough line (20° to 25°). Alternate channel bars form during the restabilization stage and represent incipient meandering of the channel.  相似文献   

Use of Chrysotile Fibres in the Degradation of Cationic and Nonionic Surfactants in Aqueous Solutions     

Adriano Fachini  Inés Joekes 《洁净——土壤、空气、水》2007,35(1):100-103

It was previously observed that sodium dodecylbenzenesulfonate (SDBS) is degraded in the presence of chrysotile fibres. A higher catalytic efficiency was obtained than the reported values for TiO₂ under the same conditions. Chrysotile, a clay mineral fibre of low cost and relatively abundant, probably acts as a catalyst through an Advanced Oxidative Process (AOP) involving free radical formation. In this work, experiments with non‐ionic – Triton X‐45 (octil‐phenoxy polyethoxy ethanol) – and cationic – Herquat 3500 (alkyl dimethyl benzyl ammonium chloride) – surfactants were carried out. Diluted aqueous solutions (50 ppm) of these surfactants were kept in contact with chrysotile (4.0 g) in the dark at room temperature. The aromatic ring disappearance was followed through the absorbance peaks at 224 nm (Triton X‐45) and 208 nm (Herquat 3500) in the UV spectra. After 4 h, reductions in the surfactant solution concentration of 65.0% and 35.0% were observed for the Triton X‐45 and the Herquat 3500 surfactants, respectively. In both cases, reactions carried out without aeration showed a lower reduction of the aromatic ring concentration (30.0% less) when compared to the values obtained for the systems with airflow. The system containing the non‐ionic surfactant seems to achieve equilibrium after 2 h, what is not observed for the cationic surfactant system.  相似文献   

Laboratory Testing of Sulfamethoxazole and its Metabolite Acetyl‐Sulfamethoxazole in Soil     

Sibylla Höltge  Robert Kreuzig 《洁净——土壤、空气、水》2007,35(1):104-110

The fate of ¹⁴C‐labeled sulfamethoxazole and acetyl‐sulfamethoxazole in soil has been investigated with special respect to possible entry routes of human and veterinary pharmaceuticals into soil environments. Therefore, the stability of the test substances was monitored first in sewage sludge and bovine manure. Within the incubation period of 72 d, 1% at maximum of the initially applied radiotracers was released as ¹⁴C‐carbon dioxide while ?75% was transferred to non‐extractable residues that were operationally defined by the ethyl acetate extraction. Test‐sludge and test‐manure samples with defined aged residues were prepared and, supplementary to standard solutions, applied to silty‐clay soil samples. After standard and test‐sludge application, soil/water distribution coefficients of K_d < 5 L kg^–1 were determined revealing both test substances as potential leachers. In contrast, the sorption of sulfamethoxazole increased after test‐manure application (K_d > 10 L kg^–1). In the long‐term degradability tests, the metabolic fate of both test substances was characterized by the continuous decrease of extractable residues, resulting in disappearance times of DT₉₀ ? 33 d, and the increase of non‐extractable residues. Mineralization reached 11% at maximum. Thereby, the dynamics of these processes differed whether the test substances were applied via standard, test‐sludge or test‐manure application. This fact emphasized the relevance of entry route specific matrix effects on the fate of both test substances in soil.  相似文献