“The Kesterson effect”

Hypothesized to be derived from Cretaceous marine sedimentary rocks, selenium contamination of the Kesterson National Wildlife Refuge is traced through irrigation drainage to the source bedrock of the California Coast Ranges. This biogeochemical pathway of selenium is defined here as the “Kesterson effect.” At the refuge ponds, this effect culminated in 1983 in a 64% rate of deformity and death of embryos and hatchlings of wild aquatic birds. From the previous companion paper on irrigation drainage, the Kesterson effect has been implicated in nine of 11 reconnaissance areas studied in the western United States. Deformities have resulted in at least five of these sites. Climatic, geologic, hydrologic, and soil conditions in these reconnaissance areas are similar to those in the area surrounding Kesterson National Wildlife Refuge in the west-central San Joaquin Valley of California. In California, selenium, as selenate, was ultimately found weathered with sulfur from marine sources in soluble sodium and magnesium sulfate salts, which are concentrated by evaporation on farmland soils. The Se, mobilized by irrigation drainage, is bioaccumulated to toxic levels in refuge wetland ponds that are located mainly in hydrologically closed basins and thus act as concentrating disposal points. The depositional environment of the ponds may be similar to that of the nutrient-rich continental shelf edge and slope in which Cretaceous, Eocene, and Miocene sediments found to be seleniferous in the California Coast Ranges were deposited. Bioaccumulation may be therefore a primary mechanism of selenium enrichment in ancient sediments in addition to that of the formerly suggested Cretaceous volcanic pathway.     

Application of recombinant gene technology for production of polyhydroxyalkanoic acids: Biosynthesis of poly(4-hydroxybutyric acid) homopolyester

Screening of a large number of bacteria revealed several strains, which utilize 1,4-butanediol and/or 4-hydroxybutyric acid (4HB) as a carbon source for growth and for synthesis of polyhydroxyalkanoic acids (PHA) containing 4HB as one constituent among others (mostly 3-hydroxybutyric acid). However, none of the wild-type strains investigated in this study was able to produce a homopolyester consisting solely of 4HB. Only several poly(3-hydroxybutyric acid)-leaky mutants ofAlcaligenes eutrophus strain JMP222 synthesized poly(4HB) homopolyester, which amounted to approximately 10% (w/w) of the cellular dry matter. If the PHA synthase structural gene ofA. eutrophus strain H16 was expressed in these mutants, the amount of poly(4HB) was increased to approximately 30% (w/w). The occurrence of poly(4HB) was demonstrated by gas chromatographic as well as¹H and¹³C nuclear magnetic resonance spectroscopic analysis.Paper presented at the Bio/Environmentally Degradable Polymer Society—Second National Meeting, August 19–21, 1993, Chicago, Illinois.     

Laboratory-scale chlorination to estimate the levels of halogenated DBPs in full-scale distribution systems

Occurrence of halogenated disinfection by-products (DBPs) (trihalomethanes –THMs– and haloacetic acids –HAAs–) in the waters of two utilities in Quebec City (Canada) was investigated using two approaches: experimental chlorination studies and full-scale sampling within distribution systems. Experimental studies were designed to reproduce treatment plant and distribution system conditions (chlorine dose, water temperature, pH and water residence time). Differences in halogenated DBPs in the two distribution systems under study were significant and comparable to those observed in experimental laboratory studies. For the waters of both utilities, chlorination studies better reproduced the occurrence of halogenated DBPs in points of the distribution system located near the treatment plant (low residence time of water) than in other points. Multivariate regression models for THMs, HAAs and their species were developed using the data from experimental studies in order to predict halogenated DBP levels measured in the distribution system. Models were all statistically significant, but showed low ability to predict full-scale halogenated DBPs, particularly in points located at distribution system extremities. Specifically, experimental chlorination-based models are not able to simulate the decrease of HAA levels. Results of this research suggest that the use of experimental data to predict halogenated DBP levels in full-scale distribution systems – for operational, regulatory and epidemiological purposes – must be done with caution.     

郑州市PM2.5中有机酸的污染特征、来源解析及二次生成

大气颗粒物中的有机酸广泛参与大气中的各种物理化学反应,对二次有机气溶胶和霾的形成贡献极大,因此分析颗粒物中有机酸的浓度分布特征、评估其污染来源、探究其二次生成,对深入研究有机气溶胶及其二次转化具有重要意义.在郑州市不同季节采集大气细颗粒物（PM_2.5）样品,识别并定量二元酸类、脂肪酸类和树脂酸类有机酸共30种,探究其浓度分布特征、季节变化、来源贡献及二次生成.定量的二元酸类以丙二酸（di-C₃）和琥珀酸（di-C₄）含量最为丰富,并且表现出明显的季节变化特征：夏季 > 秋季 > 冬季 > 春季;脂肪酸类表现出明显的双峰优势,以棕榈酸和硬脂酸（C₁₈）最为丰富,季节变化特征为冬季最高,春季最低.利用主成分分析结合多元线性回归（MLR）方法对郑州市PM_2.5中的有机酸进行来源解析,结果表明,35%的有机酸来自于燃烧源和交通源,24%来自于烹饪源、23%来自于二次生成以及17%来自于天然源.利用标记物种的比值（如di-C₃ /di-C₄、F/M和C_18：1 /C₁₈）探究有机气溶胶二次形成及其老化过程.结果表明,夏季光化学反应剧烈,有机气溶胶老化或二次生产比例较高,冬季光化学反应较弱,有机气溶胶老化程度较低.采用相关性分析与MLR相结合的方法,量化了气相氧化和液相氧化对二元酸形成的相对贡献,气相氧化在采样过程中起主导作用,占比为58%,特别是夏季,占总二次转化的61%.     

高铁酸钾预处理强化污泥破解及厌氧产酸

在序批式污泥厌氧反应器中探究了高铁酸钾对污泥破解及厌氧产酸的影响。实验结果表明高铁酸钾对污泥具有较强的破解性,当高铁酸钾的质量浓度由0 mg/L增加至16 mg/L时,溶解性COD与总COD的比值由6.2%升至35.6%。同时污泥液相中溶解性蛋白质的质量浓度由561 mg/L增加至1 365 mg/L。高铁酸钾的浓度与挥发性悬浮固体(VSS)的减量具有一定的线性关系。当高铁酸钾的质量浓度为8 mg/L时,污泥厌氧产挥发性脂肪酸最大,并且最大值为895 mg/L,其浓度是空白组2.56倍。     

Degradation of acetic acid with sulfate radical generated by persulfate ions photolysis

The photolysis of was studied for the removal of acetic acid in aqueous solution and compared with the H₂O₂/UV system. The radicals generated from the UV irradiation of ions yield a greater mineralization of acetic acid than the OH radicals. Acetic acid is oxidized by radicals without significant formation of intermediate by-products. Increasing system pH results in the formation of OH radicals from radicals. Maximum acetic acid degradation occurred at pH 5. The results suggest that above this pH, competitive reactions with the carbon mineralized inhibit the reaction of the solute with and also OH radicals. Scavenging effects of two naturally occurring ions were tested; in contrast to ions, the presence of Cl⁻ ions enhances the efficiency of the /UV process towards the acetate removal. It is attributed to the formation of the Cl radical and its great reactivity towards acetate.     

Effects of long-term soil amendment with sewage sludges on soil humic acid thermal and molecular properties

Sewage sludges are frequently used as soil amendments due to their high contents of organic matter and nutrients, particularly N and P. However, their effects upon the chemistry of soil humic acids, one of the main components of the soil organic matter, need to be more deeply studied in order to understand the relation between organic matter structure and beneficial soil properties. Two sewage sludges subjected to different types of pre-treatment (composted and thermally dried) with very different chemical compositions were applied for three consecutive years to an agricultural soil under long-term field study. Thermal analysis (TG–DTG–DTA) and solid-state ¹³C NMR spectroscopy were used to compare molecular and structural properties of humic acids isolated from sewage sludges, and to determine changes in amended soils. Thermally dried sewage sludge humic acids showed an important presence of alkyl and O/N-alkyl compounds (70%) while composted sludge humic acids comprised 50% aromatic and carbonyl carbon. In spite of important differences in the initial chemical and thermal properties of the two types of sewage sludges, the chemical and thermal properties of the soil humic acids were quite similar to one another after 3 years of amendment. Long-term application of both sewage sludges resulted in 80–90% enrichment in alkyl carbon and organic nitrogen contents of the soil humic acid fraction.     

蒸发过程早期渗滤液中有机酸挥发规律研究

对早期填埋场渗滤液进行了常规和载气蒸发实验,通过定时分批截留冷凝液并测定其TOC和挥发性脂肪酸（volatile fatty acids, VFAs）浓度,研究了不同pH条件下早期渗滤液中有机污染物的挥发规律.结果表明,pH=4时蒸发冷凝液中TOC呈由高而低的变化趋势,pH=7时TOC变化趋势截然相反.冷凝液中VFAs（乙酸除外）浓度变化规律与TOC相似,并且结构越复杂相对挥发速率越大.分析表明,早期渗滤液蒸发冷凝液中有机物主要由VFAs组成.是否具有载气及载气量多少对早期渗滤液有机物蒸发的影响不明显.