纳米二氧化钛对污泥厌氧发酵产甲烷的影响

以污水处理厂初沉污泥和剩余污泥的混合物为发酵基质,建立连续流污泥厌氧反应器并评估了纳米二氧化钛对污泥厌氧消化产甲烷的慢性毒性影响。长期实验结果表明高浓度的纳米二氧化钛能够抑制甲烷的产生,且当二氧化钛的质量浓度为300 mg/L时,甲烷的最大产量(以VSS计)为132 m L/g,是空白组的81%。而低浓度的纳米二氧化钛对污泥产甲烷影响不明显。荧光原位杂交技术显示高浓度纳米二氧化钛作用下产甲烷古菌的数量小于低浓度作用下。此外高浓度纳米二氧化钛作用下与产甲烷相关酶的活性及乙酸钠的降解量均低于低浓度纳米二氧化钛作用下,然而活性氧和乳酸脱氢酶的释放量却高于低浓度作用下。     

Humanitarian information systems and emergencies in the Greater Horn of Africa: logical components and logical linkages

Natural and man-made emergencies are regular occurrences in the Greater Horn of Africa region. The underlying impoverishment of whole populations is increasing, making it more difficult to distinguish between humanitarian crises triggered by shocks and those resulting from chronic poverty. Shocks and hazards can no longer be seen as one-off events that trigger a one-time response. In countries that are both poor and exposed to frequent episodes of debilitating drought or chronic conflict, information needs tend to be different from the straightforward early warning/commodity accounting models of information systems that have proven reliable in past emergencies. This paper describes the interdependent components of a humanitarian information system appropriate for this kind of complex environment, noting the analytical links between the components and operational links to programme and policy. By examining a series of case studies from the Greater Horn region, the paper demonstrates that systems lacking one or more of these components will fail to provide adequate information--and thus incur humanitarian costs. While information always comes with a cost, the price of poor information--or none--is higher. And in situations of chronic vulnerability, in which development interventions are likely to be interspersed with both safety nets and emergency interventions on a recurrent basis, investment in improved information is a good investment from both a humanitarian and a financial viewpoint.     

Effects of sub‐chronic low‐level dietary intake of chlordane on rats with cirrhosis of the liver.

Abstract

Male rats, 60 days old, were treated with chlordane during or after induction of liver cirrhosis with carbon tetrachloride to determine the effect of treatment with chlordane on the response of the rats to the disease. When liver cirrhosis was induced simultaneously with chlordane treatment the disease symptoms were aggravated; the lipid content of the tissue was lowered significantly, growth rate was significantly lower than controls and there was no apparent replacement of damaged liver tissue by liver growth. The cytochrome P₄₅₀ content of the liver was similar after both treatments. Continuation of the chlordane treatment after termination of the carbon tetrachloride treatment brought about a more rapid recovery from the induced cirrhotic condition. All these responses were to a dose range one tenth the recommended “no effect”; level for healthy animals.     

鱼类和两栖类胚胎幼体慢性毒性短期试验

采用鲤鱼和黑斑蛙进行了丙烯腈、乙腈、硫氰酸钠和二甲基甲酰胺等４种污染物的鱼类和两栖类胚胎幼体毒性试验．结果表明，４种污染物对鲤鱼的慢性毒性值分别为２．２６、５５６、２８．３和１１３１ｍｇ／Ｌ，已腈、硫氰酸钠和二甲基甲酰胺对黑斑蛙的慢性毒性值分别为２８２８、５６．５和４５２５ｍｇ／Ｌ，说明采用胚胎幼体试验能够有效地预测污染物的慢性毒性效应．     

CHARACTERIZATION OF TOXIC CONDITIONS ABOVE WILSON'S CREEK NATIONAL BATTLEFIELD PARK,MISSOUR1

ABSTRACT: Wilson's Creek has an extensive history of toxicity from both point and nonpoint sources. Seven-day chronic daphnid (Ceriodaphnia dubia) bioassays identified one toxic site in the Wilson's Creek watershed. Procedures for the characterization phase of a Toxicity Identification Evaluation (TIE) were modified for chronic assessment and performed on four water samples from the toxic site. The characterization involved chemical/physical alterations of samples, combined with bioassays, to help in identification of the class(es) of toxicants; followed by chemical analyses. To help understand the additivity of mixtures, toxic units were derived. Successive samples contained concentrations of copper, cadmium, nickel and zinc that literature values describe as being chronically toxic to daphnids. Summed chronic toxic units for these values greatly exceeded ambient toxic units, and more than accounted for observed toxicity. Substantial fluctuations in water quality occurred over the five sampling periods of the characterization studies and a Test of Methods, June through August, 1991. This variability illustrates the difficulty in detecting and documenting nonpoint sources of pollution. Tests using living organisms, in conjunction with toxicity identification methods, on samples taken over time appear to be appropriate for detecting acute and chronic toxicity in areas impacted by intermittent point and nonpoint-source toxicity.     

沉积物中六氯苯对摇蚊幼虫的慢性毒性效应

以淡水底栖动物花翅羽摇蚊(Chironomus kiiensis)幼虫为受试生物,研究了沉积物中六氯苯(HCB)对其28 d的慢性毒性效应,观察摇蚊幼虫的存活情况和活动行为,以死亡率、羽化率和羽化时间为受试终点,计算28 d试验后沉积物中HCB对摇蚊的半数致死浓度(lethal concentration 50,LC50)以及50%羽化时间(50%emergence time,EmT50)。结果表明,HCB对摇蚊28 d的LC50为59.8 mg·kg-1,对摇蚊羽化率的半数效应浓度(half maximal effective concentration,EC50)为59.8 mg·kg-1。与大多数污染物不同,HCB有促进摇蚊幼虫筑巢行为和羽化的作用,随着HCB染毒浓度升高,摇蚊幼虫筑巢行为加强,EmT50缩短。暴露于高浓度HCB(21.6 mg·kg-1)时,摇蚊的EmT50与对照相比明显缩短,尤其对雄性摇蚊影响更大。但与对照相比,HCB对羽化摇蚊的性别比没有很大影响。     

城镇污水处理厂进出水对日本青鱂早期阶段亚慢性毒性效应

采用日本青鳉胚胎及幼鱼暴露评估污水处理厂进出水的综合毒性效应。水样采自广州市3个污水处理厂的进水口和出水口。96 h青鳉幼鱼急性毒性试验表明:6个水样均没有对青鳉幼鱼产生急性毒性效应。14 d胚胎暴露试验结果:3个污水处理厂的进水及1号和3号污水处理厂的出水均引起胚胎死亡,胚胎孵化率均低于70%且均与对照组产生了显著性差异(p0.05)。3个厂的进水和1号、2号厂出水的鱼苗畸形率与对照组也有显著差异(p0.05),其中3号厂进水鱼苗畸形率高达(33.73±8.94)%。而6个水样的胚胎孵化时间均与对照组无显著差异(p0.05),均在9 d左右。7 d鱼苗暴露试验结果:1、2、3号3个水厂进水的鱼苗死亡率分别是(30.16±2.75)%,(24.07±1.60)%,(37.90±4.77)%,与对照组产生明显差异(p0.05)。出水对鱼苗的致死效应明显低于进水,但出水对鱼苗的致死效应相对于对照组仍有显著差异(p0.05)。