Distribution and fractionation of phosphorus, cadmium, nickel, and lead in calcareous soils amended with composts

Composts improve organic carbon content and nutrients of calcareous soils but the accumulation and distribution of phosphorus and heavy metals among various fractions in soil may vary under the south Florida conditions. The accumulation of P, Cd, Ni, and Pb with depth and the distribution of water soluble, exchangeable, carbonate, Fe-Mn oxides, organic and residual forms of each element were investigated in soils amended with municipal solid waste (MSW) compost, co-compost and biosolids compost and inorganic fertilizer (as control). Total concentrations of P, Cd, Ni, and Pb were higher in the 0-22 cm soil layers and decreased considerably in the rock layers. These elements were in the decreasing order of P > Pb > Ni > Cd. Amounts of water soluble and exchangeable forms of P, Cd, Ni and Pb were negligible at 0-22 cm soil depths except for Cd in the 10-22 cm depth. Amending calcareous soil with either organic or inorganic amendments rendered phosphorus, nickle and lead in the residual form followed by Fe-Mn oxides form in the 0-10 and 10-22 cm soil layers. Cadmium was predominantly in the Fe-Mn oxides fraction followed by the residual and carbonate forms in both soil layers. A significant positive correlation was found between various organic carbon fractions and organic forms of P, Cd and Pb in the surface soil layer. Soil amended with MSW compost had higher concentration of Cd in the organic fraction whereas, co-compost and MSW compost amended soil had higher concentrations of organic Ni fraction in the 0-10 cm soil layer.     

Ocean pollution from land-based sources: East China Sea, China

The environment of East China Sea (ECS) has been faced by huge stresses from anthropogenic activities and population growth in the Yangtze River drainage basin and the areas along the coasts. Improper use of natural resources and short-term economic objectives have resulted in severe environmental degradation in a fairly short time frame and the degradation has now reached a level where the health and well being of the coastal populations are threatened. The main pollutants are inorganic nitrogen, phosphate, oil hydrocarbons, organic matters and heavy metals. Nutrients cause eutrophication of the coastal waters and the estuarine area and very often stimulate the occurrence of red tides. The environmental pollution of Yangtze River basin directly impact on the state of the marine environment in the ECS. The ecosystem stability is maintained by a steady water discharge from the river, that mixes with the marine salty water in the estuary, and the sediment loads from the river that balance ocean erosion in the delta and its adjacent coastal area. The large-scale water transfer and dam constructions in the Yangtze River basin will change this basis. For the ECS the challenge is to reverse the negative processes taking place and to restore ecosystem balance. The main challenge is to integrate socioeconomic and environmental decision making in order to promote sustainable development. A better understanding of the driving forces in society that cause these environmental pressures is required in order to overcome these obstacles. International cooperation may be an important contributor to the progress and in particular provide access to financial, technological, scientific and human resource assistance.     

Leaching and uptake of heavy metals by ten different species of plants during an EDTA-assisted phytoextraction process

In a pot experiment, the potential use of 10 plant species, including six dicotyledon species and four monocotyledon species, was investigated for the EDTA-enhanced phytoextraction of Pb from contaminated soil. Mung bean and buckwheat had a higher sensitivity to the EDTA treatment in soils. In the 2.5 and 5.0 mmol kg(-1) EDTA treatments, the Pb concentrations in the shoots of the six dicotyledon species ranged from 1,000 to 3,000 mg kg(-1) of dry matter, which were higher than those of the monocotyledon species. The highest amount of phytoextracted Pb (2.9 mg Pb pot(-1)) was achieved in sunflowers, due to the high concentration of Pb in their shoots and large biomass, followed by corns (1.8 mg Pb pot(-1)) and peas (1.1 mg Pb pot(-1)). The leaching behavior of heavy metals as a result of applying EDTA to the surface of the soil was also investigated using short soil-leaching columns (9.0-cm diameter, 20-cm height) by the percolation of artificial rainfall. About 3.5%, 15.8%, 13.7% and 20.6% of soil Pb, Cu, Zn and Cd, respectively, were leached from the soil columns after the application of 5.0 mmol kg(-1) of EDTA. The growth of sunflowers in the soil columns had little effect on the amount of metals that were leached out. This was probably due to the shallowness of the layer of soil, the short time-span of the uptake of metals by the plant and the plant's simple root systems.     

Acute toxicity and genotoxicity of two novel pesticides on amphibian, Rana N. Hallowell

Imidacloprid [1-(6-chloro-3-pyridylmethyl)-N-nitro-imidazolidin-2-ylideneamine] and RH-5849 [2'-benzoyl-l'-tert-butylbenzoylhydrazinel] are two pesticides used in China since 1992. In the present study we conducted acute toxicity test, micronucleus (MN) test and comet assay of the two pesticides on amphibian, Rana N. Hallowell, a sensitive organism suitable for acting as the bio-indicator of aquatic and agricultural ecosystems. The values of LC50-48 h of imidacloprid were found to be 165 mg l(-1) for tadpoles of Rana limnocharis and 219 mg l(-1) for tadpoles of Rana N. Hallowell. On the other hand, RH-5849 showed no acute toxicity to tadpoles during the 96 h exposure even it was saturated in the test solutions. There were significant differences in the MN frequencies between the negative controls and the treated groups at the dose of 8 mg l(-1) for imidacloprid (p < 0.05) and 40 mg l(-1) for RH-5849 (p < 0.01). Comet assay found significant differences (p < 0.01) in the distributions of DNA damage grades between the negative controls and groups treated in vitro with 0.05, 0.1, 0.2 and 0.5 mg l(-1) of imidacloprid and 5, 25, 50 and 100 mg l(-1) of RH-5849, respectively. DNA damage scores increased with the exposure levels of the two pesticides and dose-effect relationships were observed for both imidacloprid (r2 = 0.92) and RH-5849 (r2 = 0.98). The MN test and comet assay revealed potential adverse effects of the two pesticides on DNA in the erythrocytes of amphibians in aquatic and agricultural ecosystems.     

Effects of four chlorobenzenes on serum sex steroids and hepatic microsome enzyme activities in crucian carp, Carassius auratus

Four chlorobenzenes (chlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, p-chloro-methylbenzene) were administrated to the crucian carps (Carassius auratus) by peritoneal injections in the laboratory for 30 days. Serum testosterone and 17 beta-estradiol concentrations were detected using radioimmunology assay (RIA), and the activities of two hepatic microsome enzymes, glutathione s-transferase (GST) and UDP-glucuronosyltransferase (UDPGT), were measured using the modified methods as described by Habig and Owens. Results showed that the four chlorobenzenes caused significant increases in serum testosterone concentration in the crucian carps (P < 0.05) compared to the controls, but they caused no significant effect on 17 beta-estradiol level. All test chemicals caused a change in hepatic GST activity in crucian carps, with significant increases in enzyme activity (P < 0.05). Chlorobenzene, 1,3-dichlorobenzene and p-chloro-methylbenzene resulted in a marked inhibition to UDPGT activity in crucian carp (P < 0.05) except 1,4-dichlorobenzene. The changes in hepatic microsome enzyme activities may have resulted in the alterations of serum sex steroids levels in the crucian carps. The results indicated that these four chlorobenzenes may result in the changes of endocrine functions and may affect the reproductive success of this and other species.     

人工神经网络和专家系统在污水生物处理系统中的应用

对近年来国内外污水生物处理系统中人工神经网络和专家系统的应用进行了简要的回顾。分析了废水生物处理工艺难于控制的原因及人工神经网络和专家系统的结构和特点。结果表明．国外智能控制发展迅速,并且应用领域遍及污水生物处理的各个方面,国内尚处于起步阶段。简要探讨了废水生物处理智能控制今后应深入研究的问题及方向。     

低浓度Pb2+、Cd2+对鲫鱼肝脏组织中 HSP70诱导的影响

以鲫鱼(Carassius auratus)作为实验对象,经过40 d Pb2+、Cd2+不同浓度的暴露后,运用SDS-PAGE和Western Blotting方法检测鱼肝脏组织内应激蛋白HSP70的诱导表达情况.结果表明,在实验浓度下,与对照组相比,Pb2+、Cd2+对鱼肝脏内HSP70有显著的诱导(P＜0.05),但在Cd2+浓度为0.2 mg/L有停止表达HSP70的现象,可能是由于浓度过高造成了组织病理损伤而破坏了诱导表达机制.实验还发现,在实验浓度低于国家渔业用水标准时,HSP70仍然表现为明显诱导(P＜0.05),充分说明运用分子生物学指标要比传统的环境检测指标敏感,具有对污染物早期预警的作用.     

污染底泥及其间隙水分层特性的模拟实验研究

底泥冲刷沉降、再悬浮是作用于水环境内源污染的主要因素,而底泥间隙水的污染释放则是主要途径。通过底泥培养实验,研究了污染底泥及其间隙水的分层特性。结果表明,底泥及其污染物具有显著的分层特性。底泥间隙水中CODMn随深度的增加略有下降的趋势;底泥湿容重和干容重呈增大的趋势;含水率随底泥深度的增加而减小。底泥深度对底泥泥沙颗粒的级配有很大影响,在表层以细颗粒为主,随着深度的增加．底泥粒径增加,但趋势衰减较快。这对底泥冲刷作用下的再悬浮有很大影响。     

不同共代谢基质下四氯乙烯厌氧生物降解研究

分别用葡萄糖、乳酸盐和醋酸盐作为驯化好的厌氧污泥的共代谢基质 ,对四氯乙烯 ( PCE)的降解进行研究。结果表明 ,PCE是通过还原脱氯发生生物降解的。实验的回归结果表明 ,反应均符合一级动力学方程 ;反应速率常数的大小依次为 k乳酸盐 >k葡萄糖 >k醋酸盐 ;以乳酸盐作为共代谢基质时 ,PCE的降解速率较快 ,在实验条件下乳酸盐是最合适的共代谢基质     

絮凝剂对高速厌氧反应器污泥颗粒化的强化作用

以考察絮凝剂对厌氧反应器中活性污泥性能的影响为目的,将聚合氯化铝(PAC)、聚丙稀酰胺(PAM)、聚季铵盐3种不同类型絮凝剂以不同投加量添加到反应器中,采用生物化学甲烷势(BMP)和厌氧毒性测定(ATA)分析方法,评价了3种絮凝剂的厌氧生物可降解性以及3种絮凝剂对厌氧污泥产甲烷活性、沉降性能等方面的促进或抑制作用。确定以聚季铵盐作为厌氧污泥颗粒化促进剂,建议采用多次投加方式,反应器中聚季铵盐质量浓度以10-50mg／L为宜。