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331.
332.
Occurrence and assessment of polycyclic aromatic hydrocarbons in soils from vegetable fields of the Pearl River Delta, South China 总被引:16,自引:0,他引:16
Surface soil (0-20 cm) samples from nine representative vegetable fields located in Guangzhou, Shenzhen, Zengcheng and Huadu within the Pearl River Delta, South China were collected and analyzed for 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs) using gas chromatography coupled to mass spectrometry (GC-MS). Total concentrations of 16 PAHs (Sigma(PAHs)) ranged from 160 to 3700 microg kg(-1). Large variations were observed also between concentrations of individual PAHs from different vegetable fields and within the site as well. Acenapthylene, benzo[b]fluoranthene, fluoranthene, benzo[a]pyrene and benzo[k]fluoranthene were consistently the most prevalent individual PAHs. The values of PAH isomer ratios [anthracene/(anthracene+phenanthrene) and fluoranthene/(fluoranthene+pyrene)] indicate that combustion processes are the major sources of PAHs. Concentrations of PAHs were poorly correlated with organic carbon concentrations of soils, suggesting different sources and also indicating that the PAH pollution of this area is recent. The same outcome is confirmed by the predominance of PAHs with fewer rings (相似文献
333.
Effects of experimental nitrogen additions on plant diversity in tropical forests of contrasting disturbance regimes in southern China 总被引:1,自引:0,他引:1
Lu X Mo J Gilliam FS Yu G Zhang W Fang Y Huang J 《Environmental pollution (Barking, Essex : 1987)》2011,159(10):2228-2235
Responses of understory plant diversity to nitrogen (N) additions were investigated in reforested forests of contrasting disturbance regimes in southern China from 2003 to 2008: disturbed forest (with harvesting of understory vegetation and litter) and rehabilitated forest (without harvesting). Experimental additions of N were administered as the following treatments: Control, 50 kg N ha−1 yr−1, and 100 kg N ha−1 yr−1. Nitrogen additions did not significantly affect understory plant richness, density, and cover in the disturbed forest. Similarly, no significant response was found for canopy closure in this forest. In the rehabilitated forest, species richness and density showed no significant response to N additions; however, understory cover decreased significantly in the N-treated plots, largely a function of a significant increase in canopy closure. Our results suggest that responses of plant diversity to N deposition may vary with different land-use history, and rehabilitated forests may be more sensitive to N deposition. 相似文献
334.
乌鲁木齐市大气污染时空分布规律研究 总被引:3,自引:1,他引:3
为掌握乌鲁木齐市大气污染时空分布规律,利用近年乌鲁木齐市大气污染物的浓度最新资料,详尽分析了其空气质量的年际变化和空间分布特征。统计了2008年各污染物日、月变化规律。结果表明,近年乌鲁木齐市城区大气污染物质量浓度具有明显时空分布规律,即大气污染物质量浓度冬春季大于夏秋季,PM10和SO2浓度夜间大于白天。在空间分布上,PM10和SO2南部区域最高,中部次之,市区北部最轻,NO2则呈现出由北向南逐渐升高的分布特征。 相似文献
335.
在富营养化淡水湖泊中,微生物对水生植物的厌氧分解会导致局部水域泛黑发臭,产生草源性"湖泛"现象,但是当前对上覆水中硫酸盐还原细菌(SRB)在水生植物残体分解中的作用还不甚了解.本研究通过室内模拟实验,分别向湖水(本底硫酸根浓度为40 mg·L~(-1))中添加不同浓度的硫酸根,研究了硫酸根浓度升高对上覆水中SRB参与水生植物菹草(P.crispus)残体分解的影响.结果表明,硫酸根浓度升高显著促进了上覆水中硫酸盐还原作用,实验第50 d时,添加了40 mg·L~(-1)硫酸根实验组(40S)中可溶性硫化物(∑H_2S)为(100.11±5.08) mg·L~(-1),远高于未添加硫酸根对照组(CK)的(46.83±3.79) mg·L~(-1).硫还原细菌如脱硫化弧菌属(Desulfovibrio)、脱硫肠状菌属(Desulfotomaculum)和脱硫微菌属(Desulfomicrobium)在40S中的相对丰度显著高于CK(p0.05),而脱硫化孢弯菌属(Desulfosporosinus)则在CK中的相对丰度更高,这说明硫酸根浓度升高促进了菹草残体厌氧分解过程中某些特定种属SRB的生长繁殖.此外,硫酸根浓度升高也影响了菹草厌氧分解过程中有色溶解有机物(CDOM)组分含量的变化,类腐殖质组分在第63 d的荧光强度显著高于第10 d(p0.05),这说明硫酸根浓度升高促进了菹草厌氧分解过程中类腐殖质的产生.本研究对于进一步认识淡水水体中硫酸盐还原的环境效应及生物学机制具有重要意义,也为富营养化水体生态系统修复提供理论依据. 相似文献
336.
具有难降解、高残留特征的DDT至今在土壤中仍有残留,对农产品安全和人体健康有严重影响.本文采用批实验的方法研究了3种不同类型土壤和3个污染水平对漆酶修复DDT污染土壤的影响.研究结果表明,不同类型土壤中DDT各组分及总量(DDTs)的降解率存在显著差异,总体上为水稻土>菜园土>赤红壤,对照处理土壤中DDTs的降解率仅为20%左右,加酶处理土壤中则高达50%~65%.对于不同污染水平的DDT污染土壤,土壤中DDT各组分及DDTs的降解率均随着污染水平的提高而增大,多数在不同污染水平之间差异显著.对照处理对不同污染水平土壤中DDTs的降解率仅为15%左右,而加酶处理则高达43.60%~50.53%. 相似文献
337.
Asymmetric behaviors of capacitance and charging dynamics in the cathode and anode are general for nanoporous supercapacitors. Understanding this behavior is essential for the optimal design of supercapacitors. Herein, we perform constant-potential molecular dynamics simulations to reveal asymmetric features of porous supercapacitors and their effects on capacitance and charging dynamics. Our simulations show that, counterintuitively, charging dynamics can be fast in pores providing slow ion dif... 相似文献
338.
利用城市污泥防治水土流失 总被引:1,自引:0,他引:1
根据城市污泥的特点,分析了城市污泥在改良土壤和防治水土流失上应用的必要性和可能性,指出了存在的问题和对策。 相似文献
339.
Yu Z Liao R Li H Mo L Zeng X Sheng G Fu J 《Environmental pollution (Barking, Essex : 1987)》2011,159(10):2982-2988
In present study, atmospheric particles from Shanghai, the biggest city and the most important industrial base in China, were analyzed for polybrominated diphenyl ethers (PBDEs) and Dechlorane Plus (DP). Concentrations of ∑(20)PBDEs and DP both exhibited the changing trend of industrial area > urban areas. Jiading District had the highest levels of particulate PBDEs and DP with values of 744 ± 152 pg/m(3) and 5.48 ± 1.28 pg/m(3), respectively. Compared with similar data in other areas of the world, PBDEs in Shanghai were at medium pollution level, while DP was at lower level, which reflected their different production and use in Shanghai. The results from multiple linear regression analysis suggested that deca-BDE mixture was the most important contributor of particulate PBDEs in Shanghai. The fractions of anti-DP showed no significant differences to those of the technical mixtures (p > 0.05), which suggested that no obviously stereoselective process occurred in ambient air around Shanghai. 相似文献
340.
Wang Z Nie E Li J Yang M Zhao Y Luo X Zheng Z 《Environmental science and pollution research international》2011,19(7):2908-2917