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1.
造纸漂白废水中多氯联苯的测定   总被引:6,自引:1,他引:5  
杨春  姚渭溪 《环境科学》1994,15(6):63-65
介绍了造纸氯化漂白废水中痕量多氯联苯的测定方法,采用国产GDX-501树脂进行富集,经素氏提取,浓硫酸洗涤和去活化的氧化铝-硝酸银硅胶层析柱净化后,用毛细管气相色谱法测定,实验结果表明,造纸氯化漂白废水中产生的PCBs为10^-9级,且以低氯取代产物为主,方法回收率在60%以上。  相似文献   

2.
We report a case of a female fetus born to an unrelated couple with a complex fetal phenotype of a pleural effusion, a cardiac malformation, and syndactyly of the toes. Prenatal exome sequencing identified a variant of uncertain significance in the PORCN gene that was upgraded to likely pathogenic following postnatal clinical examination. The phenotype described in cases with variants in the PORCN gene is often associated with findings that cannot be prospectively diagnosed by ultrasonography. This is the first report of a prenatal phenotype involving a fetal effusion associated with variants in the PORCN gene, with skeletal findings identified later in gestation on ultrasonography. The diagnosis was confirmed on neonatal examination.  相似文献   

3.
用生物水净化剂对投加无机肥和有机肥的养殖水体进行试验研究。结果表明,无论是投加无机肥或有机肥的养殖水体,生物水净化剂对其水质都有较强的净化作用。与对照组相比较,处理组NH3-N、叶绿素均有不同程度的降低,NH3-N最高降幅达到89.4%,COD得到有效控制,透明度显著增加。在有机肥实验中,生物水净化剂对藻类有明显的抑制作用,浓度越高,对藻类的抑制作用越明显。饵料生物方面,尽管生物水净化剂对大型浮游动物(轮虫和浮游甲壳动物)的直接影响不明显,但它对原生动物有明显的促进作用。因此,生物水净化剂在改善养殖水体水质方面有较高的应用价值。  相似文献   

4.
The aim of this study was to determine how the potential to rely on arbuscular mycorrhiza (AM) for plant nutrition differs between a conventional and a low-input cropping system in the long term. The roles of fertilisation rate, composting of recycled plant residues and stage of the rotations in the overall impact of the cropping systems on soil quality and AM were also identified. The conventional cropping system with a non-leguminous crop rotation (barley–barley–rye–oat–potato–oat) was fertilised at either full or half the recommended rate. In the low-input cropping system, one year with barley was replaced by clover, and oat was cultivated mixed with pea. Straw and clover were returned to the soil either with or without composting. In the low-input system, biotite and rock phosphate were used to compensate for K and P in the harvested yield, while animal manure was applied at the start only. After 15 years, crop growth and nutrition, AMF colonisation and soil quality were assessed in the field, while the AM contribution to growth and nutrient uptake were determined in a bioassay in a growth chamber. AM functioning made a higher contribution to soil quality in terms of crop performance and environmental benefits in the low-input cropping system than at either fertilisation rate in the conventional system. Halving fertilisation in the conventional system prevented some costs and enhanced some of the benefits of AM in comparison with full fertilisation. However, only the low-input system with composting conclusively favoured AM in comparison with the conventional system. It resulted in the highest percentage colonisation and, in a bioassay with flax and clover, gave a relative average contribution to growth of 27% and to P uptake of 68% in comparison with 4 and 36%, respectively, for the conventional cropping system with full fertilisation. Rye yield was in the low-input system without composting similar to that in the conventional system with full fertilisation, and with composting 87% of the latter one. Incorporation of clover green manure without composting inhibited AM functioning, leading to a temporary loss of AM contribution to crop performance. This effect draws attention to the impact of the form of recycled organic matter on supporting ecosystem services such as nutrient cycling.  相似文献   

5.

Objectives

To determine the proportion of children that require surgery in the first year of life and thereafter in order to improve the counseling of parents with a fetus with a right aortic arch (RAA).

Methods

Fetuses diagnosed with isolated RAA, defined as the absence of intra- or extracardiac anomalies, between 2007 and 2021 were extracted from the prospective registry PRECOR.

Results

In total, 110 fetuses were included, 92 with a prenatal diagnosis of RAA and 18 with double aortic arch (DAA). The prevalence of 22q11 deletion syndrome was 5.5%. Six pregnancies were terminated and five cases were false-positive; therefore, the follow-up consisted of 99 neonates. Surgery was performed in 10 infants (10%) in the first year of life. In total, 25 (25%) children had surgery at a mean age of 17 months. Eight of these 25 (32%) had a DAA. Only one child, with a DAA, required surgery in the first week of life due to obstructive stridor.

Conclusions

Children with a prenatally diagnosed RAA are at a low risk of acute respiratory postnatal problems. Delivery in a hospital with neonatal intensive care and pediatric cardiothoracic facilities seems only indicated in cases with suspected DAA. Expectant parents should be informed that presently 25% of the children need elective surgery and only incidentally due to acute respiratory distress.  相似文献   

6.
兰州市西固区蔬菜重金属污染现状及健康风险评价研究   总被引:1,自引:0,他引:1  
针对西北地区典型的工业区-兰州市西固工业区内种植的蔬菜进行重金属含量状况调查分析,对购自当地市场的8种蔬菜中Cu、Cd、Pb、Zn 4种重金属元素的含量进行分析,通过污染指数法和经蔬菜途径重金属暴露接触对人体的健康风险进行了系统评价.结果表明,蔬菜中均不含有Pb元素或Pb元素在蔬菜中的含量比较少,低于分析方法检测限;Cu元素含量最高的是茄子为0.067 mg/kg,含量最低的是菜花为0.015 mg/kg;Cd元素含量最高的是芹菜为0.067 mg/kg,含量最低的是白菜为0.023 mg/kg;Zn元素含量最高的是菠菜为1.001 mg/kg,含量最低的是辣椒为0.274 mg/kg.美国环境健康风险评估方法评价所得THQ值均小于1,表明实验所采集的大多数蔬菜样品的重金属含量符合农产品安全质量要求.  相似文献   

7.
Two chromium removal experiments were performed in bioreactors with and without a magnetic field under the same conditions.The release of the chromium present in the biomass was tested in two experiments one with the initial pH of the medium and one with pH 4.0.The objective was to remove Cr(Ⅵ) and total Cr from the effluent,this was carried out by placing biological treatments of synthetic effluent contaminated with 100 mg/L of Cr(Ⅵ) in a bioreactor with neodymium magnets that applied a magnetic field(intensity85.4 mT) to the mixed culture.The removal of Cr(Ⅵ) was approximately 100.0% for the bioreactor with a magnetic field and 93,3% for the bioreactor without a magnetic field for9 hr of recirculation of the synthetic effluent by the bioreactor.The removal of total Cr was61.6% and 48.4%,with and without a magnetic field,respectively;for 24 hr.The desorption of Cr(VI) in the synthetic effluent was 0.05 mg/L,which is below the limit established by Brazilian legislation(0.1 mg/L) for the discharge of effluent containing Cr(Ⅵ) into bodies of water.The results obtained for the removal of chromium in synthetic effluent suggested that there was no significant influence on the viable cell count of the mixed culture.The desorption of Cr(Ⅵ) in synthetic effluent after bioadsorption of chromium by the mixed culture in the process of removal of chromium in bioreactors with and without a magnetic field was not significant in either of the experiments with different initial pHs.  相似文献   

8.
呼和浩特市大气气相和颗粒物中有机污染物的定性分析   总被引:5,自引:0,他引:5  
选用聚氨基甲酸酯泡沫塑料吸附块和玻璃纤维滤膜构成的大气全态采样头,以内蒙古四子王旗摹为对照点,于冬夏两季捕集呼和浩特市(呼市)大气气相和颗粒物中的有机污染物,样品经提取分离后用色质联机,气相色谱仪,液相色谱仪鉴定出3类(烃类、芳在,酞酸酯类)近80种有机污染物,对其中45种进行定量分析,结果表明呼市地区属于大气有机污染物高浓度地区。  相似文献   

9.
Production of upland rice under shifting cultivation system is an important economic activity in the mountainous areas of northern Vietnam. A comparative study of two districts with differential market access and population pressure was conducted to highlight the effect of these variables on upland rice systems in northern Vietnam. Farmers in the district with a greater population pressure have a shorter cropping and a shorter fallowing cycle than in the district with lower population pressure. Farmers reported a high incidence of food shortage in both districts. Income from livestock and wages are important for food purchases, especially in the district with a better access to market. Even in these upland districts, access to lowland fields is a critical determinant of food security.  相似文献   

10.
垃圾渗滤液水溶性有机物对土壤Pb溶出的影响   总被引:8,自引:3,他引:5  
付美云  周立祥 《环境科学》2007,28(2):243-248
研究了不同填埋年限(0 a、4~5 a、12 a)的垃圾渗滤液水溶性有机物(DOM)对2种污染土壤重金属Pb溶出的影响.结果表明,垃圾渗滤液DOM具有促进土壤Pb溶出的作用.填埋年限不同的垃圾渗滤液DOM对土壤Pb溶出的影响不同,填埋年限短的垃圾渗滤液DOM对土壤Pb溶出率最高.因为填埋年限越长,垃圾渗滤液DOM中高分子组分(相对分子质量>25?000)所占比例越高,而高分子组分相对于低分子组分(相对分子质量<1?000)对土壤Pb溶出能力较弱.红壤中,渗滤液DOM的低分子组分对Pb的平均溶出率高出高分子组分123.8%;潮土中也表现出类似的结果.与无渗滤液DOM的对照相比,垃圾渗滤液DOM的加入明显提高污染土壤Pb的平均溶出率,并且随体系pH的升高,DOM这种促进作用表现得更为明显.  相似文献   

11.
The geometric framework model predicts that animal foraging decisions are influenced by their dietary history, with animals targeting a combination of essential nutrients through compensatory foraging. We provide experimental confirmation of nutrient-specific compensatory foraging in a natural, free-living population of social insects by supplementing their diet with sources of protein- or carbohydrate-rich food. Colonies of the ant Iridomyrmex suchieri were provided with feeders containing food rich in either carbohydrate or protein for 6 days, and were then provided with a feeder containing the same or different diet. The patterns of recruitment were consistent with the geometric framework: while feeders with a carbohydrate diet typically attracted more workers than did feeders with protein diet, the difference in recruitment between the two nutrients was smaller if the colonies had had prior access to carbohydrate than protein. Further, fewer ants visited feeders if the colony had had prior access to protein than to carbohydrates, suggesting that the larvae play a role in worker foraging behaviour.  相似文献   

12.
CA-125, alpha-fetoprotein (AFP), and human chorionic gonadotropin (HCG) were determined in maternal serum in the first trimester from 14 women with a Down's syndrome fetus and 61 women with a healthy fetus. In the second trimester, 15 and 60 serum samples were determined from women with a Down's syndrome and a healthy fetus respectively. In both trimesters, maternal serum CA-125 was found to be elevated in Down's syndrome pregnancies compared with controls. Using discrimination functions, our preliminary results indicate that CA-125 is a better marker than AFP and HCG respectively for a Down's syndrome fetus in the first trimester and improves the detection rate in the second trimester.  相似文献   

13.
Here we describe a foetus with intrauterine growth retardation (IUGR), cerebral malformations and a 46,XY,der(1),t(1;6)(p36.3;q25.2) karyotype owing to a familial cryptic translocation segregating in three generations. A balanced translocation was present in the mother, the maternal uncle, the aunt and the grandmother. A female first cousin with dysmorphisms, hydrocephalus and mental retardation was a carrier of a partial trisomy 1p and a partial monosomy 6q. Multiple miscarriages were present in the family pedigree. Parents of the foetus had three other pregnancies: a male with a balanced translocation, and two foetuses with 1p36.3–pter monosomy and 6q25.2–qter trisomy. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

14.
提出用浓H2SO4从大气飘尘样品的环己烧提取液中一次萃取后,用同步荧光光谱测定苯并(a)芘的方法。选用△λ为20nm时可获最佳效果,用浓硫酸萃取的时间仅1min,苯并(a)芘在浓硫酸相中1h内稳定,样品加标的回收率为85%,其它多环芳烃化合物在530—600nm的测定波长范围不干扰苯并(a)芘的测定。用乙酰化滤纸层析-荧光分光光度的统一方法作为对比对实际样品进行了测定,结果与后者的偏差在±15%以内,分析周期可缩短24h。  相似文献   

15.
目的制定安装于带温控装置吊舱内的机载外挂电子设备挂飞可靠性试验剖面,并提出一种安装于带温控装置吊舱内的机载外挂电子设备挂飞可靠性试验方法。方法结合机载外挂电子设备的典型任务剖面及其复杂多样的环境条件,以某机载侦察相机为例,给出带温控装置吊舱内的机载外挂电子设备可靠性鉴定试验中试验方案的选择依据,然后根据GJB 899A—2009中的温度应力、振动应力简化处理原则和典型任务剖面的持续时间及其占比,得到温度、振动应力条件,并合成挂飞可靠性试验剖面。结果使用该方法对某机载侦察相机的温度、振动应力进行处理,得到了带温控装置的吊舱内的机载外挂电子设备挂飞可靠性试验剖面。结论提出的带温控装置吊舱内的机载外挂电子设备挂飞可靠性试验剖面设计方法,为安装于带温控装置的吊舱内的机载外挂电子设备开展可靠性鉴定试验提供了指导。  相似文献   

16.
Bilateral renal agenesis is a lethal congenital anomaly. It appears to be transmitted in a polygenic pattern. The prenatal ultrasound findings consist of severe oligohydramnios, absence of the fetal bladder, and failure to identify fetal kidneys. Twin gestations with renal agenesis have been described in the paediatric literature. We detail a case of a patient with two prior affected pregnancies with bilateral renal agenesis. Her latest pregnancy was diagnosed prenatally, with one fetus with bilateral and the other fetus with unilateral renal agenesis. The ultrasound findings should be differentiated from the stuck twin phenomenon.  相似文献   

17.
The ant genus Cardiocondyla is characterized by a bizarre male polymorphism with wingless fighter males and winged disperser males. Winged males have been lost convergently in several clades, and in at least one of them, wingless males have evolved mutual tolerance. To better understand the evolutionary pathways of reproductive tactics, we investigated Cardiocondyla venustula, a species, which in a phylogenetic analysis clusters with species with fighting and species with mutually tolerant, wingless males. Wingless males of C. venustula use their strong mandibles to kill freshly eclosed rival males and also engage in short fights with other adult males, but in addition show a novel behavior hitherto not reported from social insect males: they spread out in the natal nest and defend “territories” against other males. Ant males therefore show a much larger variety of reproductive tactics than previously assumed.  相似文献   

18.
The sinusoidal fetal heart rate pattern has been described in association with severe fetal anaemia, with fetal hypoxaemia, and with the administration of parenteral narcotics. Here, we report a case of decreased fetal movement in which a sinusoidal tracing was recorded. The sonographic diagnosis of a massive fetal intracranial haemorrhage was made. A non-interventive approach was taken and the fetus died soon after in utero. We review 28 previous cases in which the prenatal sonographic diagnosis of fetal intracranial haemorrhage was made, including the underlying maternal and fetal factors and neonatal outcomes. We propose that the sinusoidal tracing in this case was due to the intracranial bleed and suggest that fetal intracranial haemorrhage be considered in the sonographic evaluation of the fetus with a sinusoidal pattern.  相似文献   

19.
梯形渠道岸边排污浓度分布的理论分析   总被引:1,自引:0,他引:1  
从无限区域圆形瞬时源扩散的浓度分布公式人手,推导出梯形区域内瞬时线源扩散的近似浓度计算公式,进而得到了梯形渠道岸边排污的浓度分布公式计算公式表明,边坡倾角对污染物的浓度分布影响较大,浓度值随边坡倾角的增加而减小,近似遵循双曲线的递减规律.浓度分布解析解得到了扩散方程数值解的良好验证,两者在污染源附近有所差异,但随着距污染源距离的增加,计算结果愈加吻合,该解析公式可为天然河流岸边污染混合区的污染物浓度估算提供有力的工具.  相似文献   

20.
于2016年8月在鸭绿江口邻近海域采集水样,讨论了鸭绿江口邻近海域夏季粒级Chl a含量的空间分布规律及环境影响因素。结果表明,调查海域总Chl a含量介于2.91~17.46 μg/L之间,平均含量为6.54±3.56 μg/L,表层Chl a含量高于底层。小型级(Micro)Chl a含量表、底层分布规律相近,高值区均位于河流入海口处;表层和底层微微型级(Pico)Chl a分布规律相近,含量值在河流入海口处由东北向西南逐渐降低。微型级(Nano)Chl a含量在表层高值区位于河流入海口处偏西方向,底层则呈现北低南高的分布趋势。Micro级Chl a为夏季鸭绿江口邻近海域总Chl a的主要贡献者,平均贡献率为55.10%;Pico级和Nano级Chl a平均贡献率为27.61%和17.29%。Chl a主成分分析结果表明:底层各粒级Chl a含量与各环境因子均呈显著正相关(p < 0.05);表层各粒级Chl a含量与盐度、透明度呈显著负相关,与硝酸盐(NO3-N)、亚硝酸盐(NO2-N)、磷酸盐(PO4-P)、DIN、氮磷比、悬浮物浓度等呈显著正相关(p < 0.05);Micro级Chl a含量与营养盐因子相关性更显著。  相似文献   

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