不同取样尺度下华北落叶松人工林土壤呼吸的空间变异性

基于在3个取样尺度(4、2、1 m)对庞泉沟自然保护区的落叶松人工林(L_arix principis-rupprechtii)土壤呼吸速率(Rs)以及生物和非生物因子的观测数据,对不同取样尺度Rs的空间变异性进行了研究,分析了不同取样尺度下5、10和15 cm深度的土壤温度(T_5、T_(10)、T_(15))、10 cm深度的土壤水分(Ws)、土壤全氮(N)、全碳(C)、碳氮比(C/N)、全硫(S)、凋落物量(L_w)和凋落物含水量(L_m)对Rs空间变异的影响,并计算了3种尺度各变量在不同置信水平与估计精度下的最佳采样数量.结果表明,1除4 m取样尺度的C/N比、2 m的Ws和1 m的T_10、T_15的空间变异属于弱变异外,Rs及其它相关因子的空间变异均属于中等变异;Rs、C/N比和S的变异系数随着取样尺度的增大而减小,N、C、Ws、T_5、T__(10)、T__(15)、L_w和L_m则相反.2随着取样尺度的减小,Rs、Ws、T_5、T_(10)、T_(15)、L_w和L_m的空间自相关性减弱,而C、N和C/N比的空间自相关性增强,S则随着取样间距的减小空间自相关性先减弱后增强.3不同取样尺度下影响Rs空间变异的关键因子不同,在较大的尺度上土壤温度是影响Rs空间变异性的主要因素,而在较小的尺度上则受C、L_m和L_w的共同影响.4随着置信水平和估计精度的减低,R_s及其影响因子的合理取样数目逐渐减少;Rs、C/N比和S的取样数目随着取样间距的减小而增加,而N、C、Ws、T_5、T_(10)、T_(15)、L_w和L_m的取样数量则减少.     

基于贝叶斯公式的地下水污染源识别

将贝叶斯公式与地下水二维水质对流-扩散方程相耦合,建立依靠监测井监测值的地下水污染源参数（污染源强度M、排放位置（X₀,Y₀）和排放时刻T₀）反演模型.针对监测井监测值信息量不充分或者监测值与模型参数关联性较弱的问题,提出了一种基于贝叶斯公式与信息熵的监测井优化设计方法.构建一个污染物在承压含水层中瞬时排放的算例,在确定单井监测及监测次数条件下,以监测井位置D及监测频率Dt的优化为目标,分别进行模型参数后验分布信息熵最小的单目标监测方案优化,以及信息熵最小且监测耗时最短的多目标监测方案优化.依据优化后的监测方案采用延迟拒绝自适应Metropolis算法进行污染源参数反演识别.算例研究表明：在预设定单井监测,且监测次数为5次条件下,单目标优化后的监测方案为D=（830.2,199.8）,△t=2.7,在此监测方案下,4个污染源参数M,X₀,Y₀,T₀的反演均值误差分别为19.5%、13.2%、3.4%、1.3%;多目标优化后的监测方案为D=（807.9,199.4）,△t=1.2,在此监测方案下,4个污染源参数M,X₀,Y₀,T₀的反演均值误差分别为19.9%、13.4%、3.7%、4.2%.与基于单目标优化的监测方案的反演结果相比,基于多目标优化的监测方案条件下,污染源参数的反演均值误差虽分别增加了0.4%、0.2%、0.3%、2.9%,但监测时间却显著缩短了55.6%.     

污染场地土壤气中VOCs定量被动采样技术研究及应用

污染场地中土壤气样品的采集是蒸气入侵风险评估的关键,目前最常用的主动土壤气采集技术包括真空苏玛罐和泵吸附管,其操作繁琐、成本高、易受多种因素影响、只能采集短时间的浓度.土壤气定量被动采样技术是一种新兴的采样技术,很好地克服了主动式采样存在的不足,是目前污染场地中土壤气调查的研究热点.通过总结现有研究,就定量被动采样技术的理论、被动采样器吸附剂和外壳材料的选择、被动采样器吸附速率的研究及定量被动采样在污染场地中的应用进行论述.综合研究发现,只要严格控制吸附速率,被动采样能够提供准确的定量土壤气浓度测量;采样器结构的设计、外壳材料的选择能够有效控制吸附速率;吸附速率受环境因素和土壤性质的影响,场地校正是获得准确结果的有效途径.我国在土壤气采样领域的研究刚刚起步,建议:加大高效、广谱型或混合型吸附材料及相应测试方法和设备的研发;加强吸附速率的影响因子及场地校准方法的研究;加强土壤钻孔内土壤气的补给速率的模型和场地实测研究;增加不同种采样器的现场应用比较研究;进行适合我国国情的技术标准的研究与制订.      

First-trimester prenatal diagnosis in twin pregnancies

Two twin pregnancies at risk for a sex-linked disorder are described. Both pregnancies were dichorionic. Transabdominal sampling was chosen for prenatal diagnosis. Molecular genetic techniques raised suspicion with regard to the accuracy of the samples in one case. Second-trimester amniocentesis confirmed the error. Selective feticide of the affected fetus was performed. When first-trimester prenatal diagnosis is offered in dichorionic twin pregnancies, confirmation through molecular genetic testing can confirm that villi have been obtained from different fetuses. All parties must be aware that additional invasive diagnostic procedures in the second trimester may be required in cases of doubt.     

Postnatal placental confirmation of trisomy 2 and trisomy 16 detected at chorionic villus sampling: A possible association with intrauterine growth retardation and elevated maternal serum alpha-fetoprotein

Detection of trisomy 2 and trisomy 16 mosaicism through chorionic villus sampling (CVS) is not an infrequent finding. We describe here two cases, one of non-mosaic trisomy 2 and the other of high level mosaicism for trisorny 16. Amniocentesis in both cases demonstrated non-mosaic 46,XY karyotypes. Each pregnancy continued to delivery of liveborn, normal-appearing boys; both pregnancies were complicated by severe intrauterine growth retardation (IUGR). Postnatal studies of placental biopsies in both cases confirmed the original CVS findings, whereas cord blood karyotypes were normal in both boys. Both children have demonstrated adequate catch-up growth.     

Extra embryonic/fetal karyotypic discordance during diagnostic chorionic villus sampling

From a total of 1312 diagnostic chorionic villus samplings (CVS) there were 22 which showed discordance between the karyotype of the chorionic villi and that of the fetus. This frequency was some 20-fold higher than that reported at amniocentesis. In the majority of discordant cases, the fetal karyotype was normal while the placenta! karyotype was mosaic. In four cases, the placenta! karyotype was non-mosaic (a trisomy 16, a monosomy X, and two tetraploids) while the fetal karyotype was normal. In one case, the placenta was trisomy 18 while the fetus was mosaic. There were two ‘false-negative’ results where short-term methods showed only normal cells while both long-term cultures of chorionic villi and fetal cells were mosaic, in one 46,XY/47.XXY and in the other 46,X Y/47.X Y, + 21.     

Short communication the natural history of fetal cytomegalovirus infection as assessed by serial ultrasound and fetal blood sampling: A case report

A patient in whom intrauterine fetal cytomegalovirus (CMV) infection was diagnosed at approximately 25 weeks' gestation is presented. The fetus was evaluated by serial fetal blood samplings and ultrasound examinations. The fetus manifested evidence of severe thrombocytopenia and hepatic inflammation, with recovery over a period of approximately 8 weeks. The initial sonographic findings of marked fetal ascites and cardiomegaly gradually resolved; ventriculomegaly developed during the third trimester. At delivery, the baby was morphologically normal with the exception of mild ventriculomegaly. Cord blood was negative for CMV IgM but urine was culture-positive for CMV. At age 3, the child has a severe but stable unilateral hearing deficit and is otherwise developmentally normal. This case demonstrates the utility of serial ultrasound and fetal blood sampling in the prenatal diagnosis and management of fetal CMV infection.     

Pregnancy outcome after transcervical cvs with a flexible biopsy forceps: Evaluation of risk factors

The pregnancy outcome of 1936 women who had transcervical chorionic villus sampling (CVS) with a flexible biopsy forceps was evaluated. Follow-up until 4 weeks after delivery was 99.4 per cent. Various patient- and procedure-related risk factors for spontaneous loss (fetal or neonatal death) were analysed using stepwise logistic regression analysis. The overall spontaneous loss rate was 4.5 per cent. Factors found to be significantly associated with spontaneous loss were quantity of villi ≤ 15 mg (relative risk (RR) 2.13), a history of first-trimester miscarriage (RR 1.87) or delivery between 16 and 27 weeks (RR 3.87), cervical culture positive for anaerobes (RR 4.52) or group B streptococcus (RR 3.62), post-procedural bleeding >3 days (RR 1.99), and multiple insertions (RR 2.64). Significant differences in loss rates between individual operators were found. A learning effect was not present. There were no infants born with terminal transversal limb anomalies in our series.     

石油类废水采样器分析

讨论了现有的石油类废水的采样器。用分液漏斗和普通玻璃漏斗组装成石油类污水采样器，用CY-2000多功能红外测油仪对模拟水样进行分析。结果表明水样中石油类平均值为11．00mg／L，显著性检验t值为1．476〈t0.05（6）=2．45，无显著性差别。说明设计的采样器更符合实际要求。     

悬浮液进样FAAS法测定黄棕壤中的微量铜

本文采用悬浮进样火焰原子吸收光谱法测定黄棕壤中微量铜 ,并对样品的研磨时间、悬浮液浓度、酸度选择及校正方法等进行了探讨。实验表明 :该法的检出限 (K =3)为 0 .12μg· g-1,精密度 (RSD)为4.6 % ,加标回收率为 98～ 10 6 % ,对水系沉积物 GSD5、GSD6标准样品测定结果与推荐值吻合。