Concentrations of perfluoroalkyl compounds in maternal and umbilical cord sera and birth outcomes in Korea

This study analyzed the concentrations of perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA) and perfluorohexane sulfonate (PFHxS) in maternal and umbilical cord sera at delivery from the general population in Korea. Seventy samples were analyzed with ion-pairing and LC/MS/MS. PFOS, PFOA and PFHxS were detected in both maternal and umbilical cord sera. There was a high correlation of PFC concentrations between maternal and cord serum samples, implying transplacental transport. Ranking of transplacental transfer efficiency was PFOA > PFHxS > PFOS. Student’s t-tests revealed that concentrations of maternal PFOA were related with decreases in birth weight, birth length and ponderal index, suggesting a possible impact on fetal growth. With multiple logistic regression models, maternal PFOS concentration showed a significant inverse association with ponderal index (OR = 0.22; 95% CI, 0.05–0.90). Umbilical cord PFHxS concentration showed a significant inverse association with birth weight (OR = 0.26; 95% CI, 0.08–0.85) or a marginally significant inverse association with birth length (OR = 0.33; 95% CI, 0.09–1.17). This is the first report demonstrating an inverse association of birth outcomes with PFHxS exposure. Concentrations of maternal PFOA were decreased with parity, implying that delivery is one of the major routes for PFOA elimination in women. This study demonstrated prenatal exposure of PFCs through placental transfer which could result in possible developmental effects in the population sampled. Our results may provide data basis to conduct a larger scale investigation into developmental effects of PFCs in the future and contribute to understanding levels of PFC contaminations from a variety of populations in the globe.     

Enhancement of aerobic biodegradation in an oxygen-limiting environment using a saponin-based microbubble suspension

This study investigated the ability of a saponin-based microbubble suspension to enhance aerobic biodegradation of phenanthrene by subsurface delivery. As the microbubble suspension flowed through a sand column pressure buildup and release was repeatedly observed, which delivered oxygen to the less permeable regions. Burkholderia cepacia RPH1, a phenanthrene-degrading bacterium, was mainly transported in a suspended form in the microbubble suspension. When three pore volumes of the microbubble suspension containing B. cepacia RPH1 was introduced into a column contaminated with phenanthrene (100 mg/kg), the oxygen content declined to 5% from an initial value of 20% within 5 days and correspondingly, 34.4% of initial phenanthrene was removed in 8 days. The addition of two further three pore volumes enhanced the biodegradation efficiency by a factor of 2.2. Our data suggest that a saponin-based microbubble suspension could be a potential carrier for enhancing the aerobic biodegradation under an oxygen-limiting environment.     

汶川地震灾区小流域洪水计算方法初探

汶川地震灾区小流域山洪不仅造成巨大损失,同时也是泥石流等灾害的激发因素,探寻一种准确且可操作的洪水峰值流量计算方法对防灾减灾具有重要意义。本文选择不同产流和汇流计算方法,组合成不同水文模型,进行小流域洪水过程计算,对模拟结果和参数选择进行对比,旨在探究最适合该地区的小流域水文计算方法。分别选择SCS曲线法、Green-Ampt入渗法、初损稳渗法进行坡面产流计算,应用SCS单位线法、Snyder单位线法和运动波方程进行坡面和沟道汇流计算,组合成5种小流域产汇流计算模型,利用6场洪水进行参数率定和结果验证。模拟结果对比分析,得出SCS曲线法是最适宜的产流模型,其与SCS单位线、运动波汇流计算方法组合而成的SCS和SKK模型,峰现时间的模拟误差最小,在0~25 min之间;洪峰流量模拟的相对误差较小,平均误差不超过4%;洪水总量模拟误差在10%左右。另外,这两种模型参数设置及确定较简单,更适合在数据稀缺的小流域中进行洪水模拟应用。研究可为汶川地震灾区小流域山洪和泥石流等灾害的流量估算提供方法和参数借鉴。     

Effects of fluoride on the removal of cadmium and phosphate by aluminum coagulation

This study focuses on the effects of pH and fluoride at different molar ratios of fluoride to Al (R_F:Al) on the removal of cadmium (Cd²⁺) and phosphate by Al coagulation. Fluoride at R_F:Al ≥ 3:1 inhibits the removal of Cd over wide Al dose ranges from 5 to 10 mg/L as Al. The removal of phosphate decreases significantly at high R_F:Al of 10:1 whereas at lowered R_F:Al (i.e., ≤ 6:1), an adverse effect is observed only at insufficient Al doses below 2 mg/L. Fluoride shows inhibitive effects towards the removal of Cd at pH 7 and 8 and that of phosphate at pH 6. Fluoride decreases the ζ-potential in both systems, and the decreasing extent is positively correlated to the elevated R_F:Al. The Al fluoride interactions include the formation of Al–F complexes and the adsorption of fluoride onto Al(OH)₃ precipitates, i.e., the formation of Al(OH)_nF_m. Al–F complex formation inhibits Al hydrolysis and increases residual Al levels, and a more significant increase was observed at lower pH. Al–F complexes at high R_F:Al complicate the coagulation behavior of Al towards both negative and positive ionic species. Moreover, fluoride at low R_F:Al shows little effect on Al coagulation behavior towards Cd^2 + and phosphate, and the spent defluoridation adsorbent, i.e., aluminum (Al) hydro(oxide) with adsorbed fluoride at R_F:Al of below 0.1:1, may be reclaimed as a coagulant after being dissolved.     

Soil organic carbon decomposition and carbon pools in temperate and sub-tropical forests in China

Decomposition of soil organic carbon (SOC) is a critical component of the global carbon cycle, and accurate estimates of SOC decomposition are important for forest carbon modeling and ultimately for decision making relative to carbon sequestration and mitigation of global climate change. We determined the major pools of SOC in four sites representing major forest types in China: temperate forests at Changbai Mountain (CBM) and Qilian Mountain (QLM), and sub-tropical forests at Yujiang (YJ) and Liping (LP) counties. A 90-day laboratory incubation was conducted to measure CO(2) evolution from forest soils from each site, and data from the incubation study were fitted to a three-pool first-order model that separated mineralizable soil organic carbon into active (C(a)), slow (C(s)) and resistant (C(r)) carbon pools. Results indicate that: (1) the rate of SOC decomposition in the sub-tropical zone was faster than that in the temperature zone, (2) The C(a) pool comprised approximately 1-3% of SOC with an average mean residence time (MRT) of 219 days. The C(s) pool comprised approximately 25-65% with an average MRT of 78 yr. The C(r) pool accounted for approximately 35-80% of SOC, (3) The YJ site in the sub-tropical zone had the greatest C(a) pool and the lowest MRT, while the QLM in the temperature zone had the greatest MRT for both the C(a) and C(s) pools. The results suggest a higher capacity for long-term C sequestration as SOC in temperature forests than in sub-tropical forests.     

Tests of soil organic carbon density modeled by InTEC in China's forest ecosystems

The integrated terrestrial ecosystem C-budget model (InTEC) developed by Chen and co-workers has been used successfully to predict carbon dynamics of forests in Canada. It was tested here for forest soil organic carbon (SOC) density of China's northern temperate zone and southern subtropical zone. The results show that the simulated SOC density is highly correlated and in broad agreement with observations in Liping and in Changbaishan, representing the southern subtropical zone and the northern temperate zone in China, respectively. SOC density ranged from 2.2 to 11.2 kg/m(2) in Liping and from 3.4 to 14.8 kg/m(2) in Changbaishan. The correlation coefficients (r(2)) are 0.63 (N=16) and 0.76 (N=14) between the simulated and measured data in Liping and Changbaishan, respectively. The SOC densities under different vegetation types in Liping decrease in the order of mixed forest, broadleaf forest, Chinese fir, couch grass, and Chinese redpine, and in Changbaishan in the order of mixed forest, silver fir, larch forest, and birch forest.     

水平循环荷载下大直径单桩承载变形特性有限元分析∗

大直径单桩基础是近海风电产业常用的基础型式,研究大直径单桩在风、浪、流等水平循环荷载作用下的承载变形特性意义重大.基于ABAQUS软件平台,通过建立桩土相互作用的三维有限元模型,对已有的大直径单桩离心模型试验开展数值模拟.数值计算时采用一个循环弹塑性本构模型描述桩侧土体的循环应力应变响应,通过.调用该模型的UMAT子程序,设置适当的桩土接触条件、分析步及计算参数,建立了能够追踪水平循环荷载下砂土中大直径单桩位移时程的有限元分析方法.通过与已有离心模型试验结果的对比发现,建立的有限元方法可以描述砂土中大直径单桩在水平单调及循环荷载下的变形过程,反映循环荷载位移曲线的非线性、滞回性及位移累积特性,预测随循环荷载次数增加,桩身弯矩、位移等的分布特征及演化规律.