Mobility of Zn, Cd and Pb in soils as affected by poultry litter extract--I. Leaching in soil columns

Application of poultry litter to cropland may increase metal mobility, because the soluble organic ligands in poultry litter can form water-soluble complexes with metals. In this study, one uncontaminated soil and two metal-contaminated soils were sampled. A portion of the uncontaminated soil was amended with Zn, Pb, and Cd at rates of 400, 200, and 8 mg kg(-1), respectively. Packed soil columns were leached with H2O, EDTA, CaCl2, and poultry litter extract (PLE) solutions separately. No leaching of Zn, Cd, and Pb with the PLE was found in the uncontaminated soil. The retention of PLE-borne Zn indicated the potential for Zn accumulation in the soil. A large portion of the metals was leached from the metal-amended soil, and EDTA solubilized more Zn, Cd, and Pb than CaCl2 and PLE. In the metal-contaminated soils, the leaching of Zn and Cd with PLE was consistently larger than that for CaCl2, indicating that these metals were mobilized by organic ligands. The PLE did not mobilize Pb in these soils. The utilization of poultry litter in metal-contaminated soils might accelerate the movement of Zn and Cd in soil profiles.     

含制药残液废水的处理工艺研究

探讨了含制药残液废水的预曝-生物接触氧化-混凝沉降处理工艺。研究结果表明,经石灰乳调pH8.0曝气48h的废水,COD_(Cr)去除率可达47.5％;采用出水回流,进水COD_(Cr)1500～4000mg/L时,负荷为1.00～2.67kg/m~3·d,COD_(Cr)去除率超过86％;生化出水经投加PAC52.8mg/L,COD_(Cr)去除率为64.8％,达到国家工业废水排放标准。     

‘False-negative’ and ‘false-positive’ prenatal cytogenetic results due to ‘true’ mosaicism

A 37-year-old gravida was referred for CVS because of advanced maternal age. A trisomy 21 was present in all cells after short-term incubation (direct processing (DP)) and long-term culture. According to our policy, a retap was offered for confirmation of the result during the legally required 3-day waiting period between communication of the result and termination of pregnancy. Unexpectedly all cells after DP showed a normal male chromosome complement. Further investigations revealed mosaicism in trophoblast tissue and a normal karyotype in amniotic fluid cells and fetal blood (50 mitoses each). The parents elected to continue the pregnancy after extensive ultrasound examinations did not show suspicious findings. After the birth of a healthy child, cell cultures from ten different placental sites confirmed mosaicism. Four out of 100 mitoses from a lymphocyte culture showed an additional chromosome 21. The child had no dysmorphic features and the development was normal at the age of 10 weeks. This case demonstrates the restricted validity of prenatal cytogenetic analysis in the presence of true fetal mosaicism. It also stresses the benefit of our policy to offer a retap in cases with abnormal cytogenetic results prior to termination of pregnancy which is considered unnecessary by many cytogeneticists.     

Occurrence and behaviour of organophosphorus insecticides in the River Wuchuan,southeast China

Organophosphorus (OP) insecticides are used worldwide, yet their persistence in the environment is not well understood. This paper summarises recent research on 17 OP insecticides in the River Wuchuan, an important catchment in China, by determining their concentrations in water, soil, sediment and plants by gas chromatography with flame photometric detection (GC-FPD). The concentrations of the total OP insecticides ranged from 92.77 to 229 ng l-1 in river water, 1.61 to 9.93 ng g-1 dry weight in soil, 1.24 to 7.56 ng g-1 dry weight in sediment and 75.28 to 326 ng g-1 dry weight in plants. There was a relatively high abundance of methamidophos, dichlorvos, malathion, omethoate and dimethoate in all water, soil, sediment and plant samples. On average, these five compounds collectively accounted for 64%, 71%, 71% and 54% of the total OP insecticide concentration in water, soil, sediment and plants, respectively, which was similar to the composition of OP insecticides in application formulations used in our study area and in China as a whole. The results therefore reflect the application pattern to some extent, and suggest that the sources of the OP insecticides are mainly from current usage. When compared with other areas, the levels of OP insecticides in the River Wuchuan were moderate. The animal and human risks from exposure to OP insecticides in water and plants were evaluated against relevant threshold values. The results therefore provide important information on the current contamination status of a key agricultural watershed in China, and point to the need for urgent action to control the use of some excessively applied and potentially persistent agrochemicals, such as methamidophos, omethoate and dimethoate.     

UV/NO3-光化学降解水中的磺胺甲恶唑

本文研究了UV/NO₃^-体系对水中磺胺甲恶唑（SMX）的降解;考察了NO₃^-用量、pH值、SMX初始浓度、水体成分中常见的无机阴离子（Cl^-、SO₄^2-和HCO₃^-）和天然有机物（NOM）对SMX去除的影响;最后探讨了SMX在该体系中的降解产物和转化机理.结果表明：相比于单独UV,UV/NO₃^-对SMX的去除效果更优,这可能归因于UV激发NO₃^-产生的羟基自由基（HO^·）,通过加入HO^·淬灭剂甲醇,有力地证明了体系中HO^·的存在及其对SMX的降解作用.SMX在UV/NO₃^-体系中的降解符合准一级反应动力学.SMX的去除效率随着NO₃^-浓度的增加而逐渐提高,随着其初始浓度的增大而减小.溶液pH值对UV/NO₃^-降解SMX的影响显著,SMX去除效率表现为酸性>中性>碱性.向UV/NO₃^-体系中加入不同浓度的Cl^-和SO₄^2-对SMX的降解基本没有影响;HCO₃^-对SMX的去除有显著的促进作用,这可能归因于HO^·同HCO₃^-反应产生的碳酸根自由基（CO₃^·-）;NOM的存在会抑制SMX的降解,且NOM浓度越高,抑制越明显.在UV/NO₃^-降解SMX的反应中,根据检出的5种产物,提出SMX可能的转化机理包括4种不同的反应路径,分别为断键反应、脱氨羟基化、羟基化和亚硝化.     

Bayesian estimation of age-specific bird nest survival rates with categorical covariates

The populations of many North American landbirds are showing signs of declining. Gathering information on breeding productivity allows critical assessment of population performance and helps identify good habitat-management practices. He (Biometrics (2003) 59 962–973) proposed a Bayesian model to estimate the age-specific nest survival rates. The model allows irregular visiting schedule under the assumption that the observed nests have homogeneous nest survival. Because nest survival studies are often conducted in different sites and time periods, it is not realistic to assume homogeneous nest survival. In this paper, we extend He’s model by incorporating these factors as categorical covariates. The simulation results show that the Bayesian hierarchical model can produce satisfactory estimates on nest survival and capture different factor effects. Finally the model is applied to a Missouri red-winged blackbird data set.