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991.
The aim of this paper was to investigate the effects of nitrogen (N) deposition on tree N cycling and identify potential biomarkers forNdeposition. Between April and October 2002 extensive fieldwork was undertaken at Mardley Heath in Hertfordshire. This woodland, located adjacent to the A1(M) motorway, is exposed to high levels of atmospheric nitrogen oxides from the traffic. Measurements of 15N, in vivo nitrate reductase (NR) activity, tissue, xylem and surface nitrate concentrations as well as N concentration and growth were made along a 700-m transect at 90° to the motorway. The 15N data show that oxidised N from the road traffic is taken up by nearby trees and is incorporated into plant tissues. Our measurements of NR activities suggest elevated rates close to the motorway. However, xylem sap, leaf tissue and leaf surface nitrate concentrations showed no differences between the roadside location and the most distant sampling point from the motorway. Taken together the 15N and nitrate reductase data suggest uptake and assimilation of N through the foliage.We conclude that for this lowland deciduouswoodland, tissue, xylem and surface measurements of nitrate are unreliable biomarkers for N deposition whereas 15N, growth measurements and integrated seasonal NR might be useful. The results also point to the benefit of roadside tree planting to screen pollution from motor vehicles. 相似文献
992.
The treatment of chromium-containing leather waste (CCLW), the major solid waste generated at the post-tanning operations of leather processing, has the potential to generate value-added leather chemicals. Various alkali and enzymatic hydrolysis were compared, and calcium oxide was found to be important for effective (but still incomplete) hydrolysis. Three possible reasons are given for the incomplete hydrolysis under alkaline conditions. Data for 19 amino acids are presented for four different treatment products. On the basis of the results, a novel three-step CCLW treatment process is proposed. The gelatin extracted in the first step is chemically modified to produce leather finishing agents. The collagen hydrolysates isolated in the second step are used as proteinic retanning agents by chemical modification. The remaining chrome cake is further hydrolyzed with acids in the third step, and the obtained chromium-containing protein hydrolysates could be used for the preparation of chromium-containing retanning agents for leather industry. The proposed three-step process provides a feasible zero discharge process for the treatment of CCLW. 相似文献
993.
Cao Junji Lee Shungcheng Zheng Xiangdong Ho Kinfai Zhang Xiaoye Guo Hai Chow Judith C. Wang Hongbin 《Water, Air, & Soil Pollution: Focus》2003,3(2):213-229
In April 1998, two intense dust storms were generated in CentralAsia and transported eastward across East Asia (15 and 19 April). This article presents the chemical characterization ofHong Kong (HK) aerosols during the dust storms. During the 15 Aprildust storm, hourly respiratory suspended particles (RSP)(particle diameter smaller than 10 m) concentrationsmonitored at 7 sites in Hong Kong reached the peak valuessynchronously between 9 and 11 a.m. on 17 April, in which thehighest concentration was 267 g m-3. Analysis ofthe RSP samples showed that concentrations of crustalelements (Ba, Ca, Cd, Cr, Fe, Mg, K+) and anthropogenicspecies (As, Ni, Pb, Zn, NH4
+, NO3
-,SO4
2- and total carbon) were substantiallyenhanced. Enhancement of these species was more than afactor of 2 to 14 relative to the non dust period. The totalcarbon content was high, at 59 g m-3 (notincluding carbonate), and the enrichment factors of Asand Pb on 17 April were 122 and 117, respectively. Thisimplied that anthropogenic materials together with mineraldust were transported to HK from Mainland China. Based onmaterial balance calculations, mineral dust contributed41% to the observed RSP mass on 17 April, which was 2 times thatof the nondust sample (22%). From the 5-day backwardtrajectory analysis, this storm was transported directlyfrom Northwest China to HK. However, there was nocorresponding observation for the 19 April dust stormaerosol. Consequently, 15 April storm had stronger impact onHK's atmosphere than 19 April storm. Compared to the HK AirQuality Objective, 15 April dust storm did not cause seriousair pollution in HK. 相似文献
994.
Removal of selenium (Se) from agricultural drainage water is important in protecting wetland wildlife. Three flow-through bioreactor channel systems (BCSs), each with three channels filled with rice (Oryza sativa L.) straw, were set in the laboratory to determine removal of selenate [Se(VI)] (1020 microg L(-1)) from drainage water with a salinity of 10.4 dS m(-1), a pH of 8.1, and a nitrate (NO3-) range of 0 to 100 mg L(-1). Results showed that the rice straw effectively reduced Se(VI) during 122 to 165 d of the experiments. Calculation of Se mass in the three BCSs showed that 89.5 to 91.9% of the input Se(VI) was reduced to red elemental Se [Se(0)], where 96.6 to 98.2% was trapped in the BCSs. Losses of each gram of rice straw were almost equal to the removal of 1.66 mg of Se from the drainage water as a form of red Se(0), indicating that rice straw is a very effective organic source for removing Se(VI) from drainage water. 相似文献
995.
Surface runoff losses of copper and zinc in sandy soils 总被引:1,自引:0,他引:1
Increased anthropogenic inputs of Cu and Zn in soils have caused considerable concern relative to their effect on water contamination. Copper and Zn contents in surface soil directly influence the movement of Cu and Zn. However, minimal information is available on runoff losses of Cu and Zn in agricultural soils, and soil-extractable Cu and Zn in relation to runoff water quality. Field experiments were conducted in 2001 to study dissolved Cu and Zn losses in runoff in Florida sandy soils under commercial citrus and vegetable production and the relationship between soil-extractable Cu and Zn forms and dissolved Cu and Zn concentrations in runoff water. Five extraction methods were compared for extracting soil available Cu and Zn. Concentrations of dissolved Cu and Zn in runoff were measured and runoff discharge was monitored. Mean dissolved Cu in field runoff water was significantly correlated with the extractable Cu obtained only by 0.01 mol L(-1) CaCl2, Mehlich 1, or DTPA-TEA methods. Dissolved Zn in runoff water was only significantly correlated with extractable Zn by 0.01 mol L(-1) CaCl2. The highest correlations to dissolved Cu in runoff were obtained when soil-available Cu was extracted by 0.01 mol L(-1) CaCl2. The results indicate that 0.01 mol L(-1) CaCl2-extractable Cu and Zn are the best soil indexes for predicting readily released Cu and Zn in the sandy soils. Both runoff discharge and 0.01 mol L(-1) CaCl2-extractable Cu and Zn levels had significant influences on Cu and Zn loads in surface runoff. 相似文献
996.
21世纪中国西部矿产资源开发的战略思考 总被引:11,自引:0,他引:11
作为全国资源的富集区,西部矿业开发要在21世纪地区经济发展中作出应有的贡献,不仅需要一个长期的开发过程,而且更需要一个明智而有效的发展战略,从西部地区资源、环境、区位条件及长期实践出发,认真把握未来市场变化、积极推动精品为先发展,努力调整地区产品结构和合理组织空间生产应成为21世纪西部矿产资源开发战略的四项基本内容,上述战略的实施不仅有束于资源的保障、中央政府的认呆和资金与技术的支持,而且有赖于整个社会环保意识的加强。 相似文献
997.
998.
可拓法评估煤矿瓦斯爆炸易发性 总被引:3,自引:0,他引:3
为了量化煤矿瓦斯爆炸的可能性,并为防治瓦斯爆炸提供量化指标,借鉴可拓学原理,对煤矿瓦斯爆炸易发性进行预评估。首先,详细阐述可拓学评估原理;接着,为了验证煤矿瓦斯爆炸易发性可拓评估的可行性,结合某一煤矿实例,比选煤矿瓦斯爆炸易发性的评价指标,并确定煤矿瓦斯爆炸易发性的分类标准,构建煤矿瓦斯爆炸易发性评估的经典域、节域和物元;然后,为了避免确定指标权重的人为主观因素的影响,提出用简单关联函数确定指标权重;最后,计算煤矿瓦斯爆炸易发性的关联函数值和关联度,确定瓦斯爆炸易发性的等级及其变量特征值。经计算,煤矿爆炸易发性的可拓评估结果为"很小"等级。同时,为了验证可拓评估结果的合理性,将其与模糊评估进行比较,两者所得评估结果相一致。从而表明:将可拓学应用于煤矿瓦斯爆炸易发性评估是合理可行的。 相似文献
999.
采用固定床动态吸附实验,用改性活性碳纤维(ACF)吸附去除CO2原料气中的H2S。通过改变改性剂种类、反应温度和原料气中CO2浓度,找出用改性ACF去除CO2原料气中H2S的规律。实验结果表明:常温下,可用NaON改性的ACF来消除CO2的酸性对去除H2S的不利影响;随着反应温度的升高,CO2与ACF形成的C(O*)中间产物增多,CO2的存在有利于改性ACF去除H2S;而当反应温度过高时,CO2与ACF形成的C(O*)中间产物发生分解,导致ACF碳化,不利于H2S的吸附去除。 相似文献
1000.
催化湿式氧化法处理吡虫啉农药废水 总被引:2,自引:0,他引:2
自制了Cu/Mn,Cu/Ce,Cu/Ni,Ce/Mn,Ce/Ag等催化剂,经过性能比较,选择催化活性较高且金属溶出量较小的Cu/Ni作催化剂。用催化湿式氧化法处理吡虫啉农药废水,考察了各种因素对处理效果的影响。实验结果表明:在进水pH为6.93、Cu/Ni加入量为4.0g、反应温度为190oC、氧分压为1.6MPa、反应时间为120min的条件下,COD去除率为95%;处理后废水的BOD5/COD从0.093增至0.590,可生化性明显改善。 相似文献