On the Relationship Between Mean and Variance of Soil Moisture Fields1

Abstract: The objective of this work was to explain an apparent contradiction in the literature related to the relationship between mean and variance (or standard deviation) of soil moisture fields. Some studies found an increase in soil moisture variance with decreasing mean soil moisture, while others showed a decrease. The evidence of maximum variance in the mid‐range of mean soil moisture was also reported in the literature. In this paper, we focus on the effects of spatial variability of soil texture on the relationship between variance and mean of soil moisture during soil dry‐down processes. Soil texture influences soil moisture mean and variance through its direct effects on evaporation and drainage, which are two main factors controlling soil drying. A differential equation describing soil moisture dry down is proposed and studied. Our study shows that as mean soil moisture is greater than a threshold, variance increases with decreasing mean soil moisture. If mean soil moisture is less than the threshold, variance decreases with decreasing mean soil moisture. The threshold depends on soil texture and is between the field capacity and the wilting point. The soil moisture dry‐down equation is also applied to explain the apparent contradiction with regard to the relationship between mean and variance of soil moisture fields reported in the literature.     

基于读者反应的红色旅游英译文本可读性研究

随着我国红色旅游业的快速发展,以翻译为主要途径的外宣工作的重要性日益彰显,如何评价外宣文本的可读性逐渐成为学界关注的热点问题。文中以井冈山景区的英译文本为例,通过问卷调查和访谈的方式收集了十五位目标语读者关于外宣文本的反馈意见。结果显示:译文的可读性受文本质量、文本长度和读者背景等诸多因素的影响。由于译者对英译文本的目标语读者和文本功能认识不足,译文在词汇、语句和语篇等层面均存在不同程度的问题。     

Hydroxyl radical (OH) yields from the ozonolysis of both double bonds for five monoterpenes

A new method has been applied to determine OH-radical yields from the ozonolysis of both double bonds from five selected, atmospherically relevant monoterpenes, namely terpinolene, α-phellandrene, limonene, α-terpinene and γ-terpinene. While OH-yields for the faster reacting double bond agreed with previous literature values, the yields from the second double bond were determined for the first time and are as follows: limonene 7–10%, terpinolene 39–48%, α-phellandrene 8–11% and α-terpinene 12–14%. Only for γ-terpinene the rate coefficient for the reaction of ozone with the two double bonds was too similar in order to distinguish the OH-yield with this method. In all cases the yield from the second double bond was significantly lower than the first. The reasons for this difference are discussed in terms of the Criegee-intermediate reactions, in particular the number of abstractable H-atoms and the number of possible hydroperoxide products.     

Improvements in anisotropic models of single tree effects in Cartesian coordinates

For anisotropic density functions of e.g. fruit or leaf dispersal, most mathematical research is only done in polar coordinates. However, in software solutions aiming to derive inverse models for real world dispersal data, Cartesian coordinates may be preferred for several reasons. Thus, we introduce an anisotropic model in Cartesian coordinates following the approach in Wälder et al. (2009) with the von Mises approach. By introducing a correction factor, we thereby consider the fundamental attribute, that the integral over a density function with respect to the Cartesian coordinates has to be equal 1. It may have been overlooked so far that guaranteeing for this attribute needs different approaches whether working in polar or Cartesian coordinates. One result is that our approach can be used also for other anisotropic models rather than models from the von Mises approach.     

Biomonitoring of persistent organochlorine pesticides, PCDD/PCDFs and dioxin-like PCBs in blood of children from South West Germany (Baden-Wuerttemberg) from 1993 to 2003

In the context of a monitoring program, persistent organic pollutants (POPs) were quantified in the blood of 10 year old children at four different demographic regions in Baden-Wuerttemberg, a highly industrialised federal state in South West Germany. DDE, HCB, PCB 138, PCB 153 and PCB 180 were measured in 1996/1997, 1998/1999, 2000/2001 and 2002/2003 in individual samples of about 400 children per year. PCDD/PCDFs and some relevant coplanar PCBs were determined in pooled samples from children in seven cycles from 1993 to 2003. Blood concentrations of the investigated compounds decreased in that time period by a factor of 2-4 with the exception of most PCDFs. The concentrations of POPs in the blood of the children were distinctly lower than the concentrations reported for adults. Breast feeding was associated with about 30% higher median concentrations of DDE, HCB, PCBs and a 30% increase for mean PCDD/PCDF concentrations. Concerning demographic differences, significant lower concentrations of HCB, PCBs and PCDD/PCDFs could be seen in children from Mannheim compared to the region of Aulendorf. About 10-20% higher concentrations were found in boys compared to girls for HCB, indicator PCBs and PCDD/PCDFs. The pattern of non-ortho and mono-ortho PCBs in the blood of children was similar to the pattern reported for mother's milk, and PCB 126 and PCB 156 contributed about 70% to the toxicity of dioxin-like PCBs and about one-third to total TEQ including PCDD/PCDFs.