Topographical Influences on the Spatial Distribution of Soil Mercury at the Catchment Scale

The catalytic effect of Cu(II) on the formation of disinfection by-products (DBPs) and chlorine degradation during chlorination of humic acid (HA) solutions was comparatively investigated under different experimental conditions. The experimental results showed that the total organic halogen (TOX) and trihalomethane (THM) formation increased with increasing Cu(II) concentration during chlorination, while haloacetic acids (HAAs) increased insignificantly. Accelerated chlorine decay and increased TOX and HAA formation were observed at high pH in the presence of 1.0 mg/L Cu(II) compared with that observed at low pH but THM formation decrease. Furthermore, the Cu(II) effect catalyzed the formation of brominated DBPs as it did for chlorine analogues in the presence of bromide ion. The microcalorimetry analysis demonstrated that more DBPs were formed in the Cu(II)-catalyzed chlorination, in which second-order rate constants obtained from reaction of HA with chlorine under given experimental conditions were 0.00256 M^?1?s^?1 (without Cu(II)) and 0.00865 M^?1?s^?1 (with Cu(II)), respectively. To discriminately examine the role of Cu(II) in greater detail, nine model compounds, which approximately represent the chemical structural units of HA, were individually oxidized by chlorine. It was demonstrated that carboxylic acids significantly enhanced the formation of TOX, THMs, and HAAs in the presence of Cu(II). Based on the previously published information and our experimental results, the possible pathway for Cu(II)-catalyzed TOX, THM, and HAA formation from chlorination of carboxylic acids were tentatively proposed.     

Temporal trends in bromide release following rewetting of a naturally drained gully mire

Abstract. Recently, there has been interest in the occurrence of bromide (Br^-) in natural waters since it has been demonstrated that Br^-, in association with humic substances in raw waters, is readily incorporated into haloacetic acids in the form of organically bound bromine (Br) during water chlorination. We report results of the effects of experimentally rewetting a naturally drained gully mire on the hydrochemistry of Br^-, iron (Fe) and dissolved organic carbon (DOC) in the peat water. Results obtained over a three year period showed that rewetting substantially increased the concentrations of these solutes in the pore water, with peak values of 1 mg dm^-3 (Br^-), > 60 mg dm^-3 (Fe) and > 300 mg dm^-3 (DOC) detected in some samples after rewetting, compared with typical values < 0.05 mg dm^-3 (Br^-), < 1 mg dm^-3 (Fe) and < 15 mg dm^-3 (DOC) under the drained conditions. Bromide, Fe and DOC release were highly seasonal, with the largest concentrations observed in late-summer to autumn. However, whereas seasonal peak concentrations of Fe and DOC have since remained at these higher levels, seasonal peak concentrations of Br^- were progressively attenuated over time, suggesting the latter phenomenon is a flush effect, with no longer-term consequences for water quality.     

Bromide Ion Incorporation Into Brominated Disinfection By-Products

During chlorination and ozonation, a key concern is the conversion of bromide ions (Br^?) to disinfection by-products (DBPs) such as trihalomethanes (THMs), haloacetic acids (HAAs), and bromate (BrO₃ ^?). The objective of this study was to investigate the effects of water quality parameters (dissolved organic carbon (DOC), Br^?, pH, and temperature) on the percent conversion of Br^? to the known DBPs. Ten to twelve surface and ground waters having different DOC (1.2–10.6 mg/L) and Br^? (7–312 μg/L) were subjected to bench scale chlorination and ozonation experiments at various pH (6.5–8.5) and temperature (15,^°C–25,^°C) conditions. The results show that the average percent of bromide incorporation was 24.5% for THMs and 9.5% for HAAs, and 12% for BrO₃ ^? for the waters, respectively. In addition, the percent of bromide incorporation depends on source water pH. The percent of bromide incorporation increased with increasing pH (6.5 to 8.5) for THMs (18% to 28%) and BrO₃ ^? (6.9% to 19%) and was insignificantly influenced by pH for HAAs. Coagulation using alum was effective in removing DBP reactive precursors such as DOC, which resulted in the smaller percentage of bromide incorporation for coagulated waters. The calculated average health risk factor for bromate was 4.3× 10^?4 for the ten source waters, which is approximately 10 times higher than that for the average THMs (4.4× 10^?5), respectively.     

加氯及毛管冲洗控制再生水滴灌系统灌水器堵塞

再生水滴灌系统中灌水器生物堵塞与其内部堵塞物质-附生生物膜的形成、生长有着密切关系,加氯配合毛管冲洗既可以借助加氯杀菌抑制微生物生长,又可以利用毛管冲洗的剪切力作用而促进毛管内部堵塞物质的脱落而冲出系统外部,有望成为一种控制灌水器内部生物膜形成与堵塞的有效措施。为此,借助周期循环式活性污泥法(cyclic activated sludge system,CASS)工艺污水处理厂现场再生水滴灌系统灌水器堵塞试验,研究毛管冲洗、加氯、加氯配合毛管冲洗3种模式对再生水滴灌系统灌水器堵塞控制效果。研究发现加氯配合毛管冲洗可有效降低灌水器内附生生物膜中微生物的数量,较单独的毛管冲洗、加氯以及未进行任何处理条件下微生物磷脂脂肪酸(phospholipid fatty acids,PLFAs)含量分别降低了52.2%、44.2%、73.2%,微生物分泌的黏性胞外聚合物(extracellular polymeric substances,EPS)含量也分别降低了约28.0%、22.9%、63.9%,在微生物及其分泌的黏性多聚物的共同作用下,使得灌水器内部堵塞物质总量分别降低了47.4%、43.1%、69.1%,进而使得灌水器相对平均流量和灌水均匀度最高分别提升了40.0%、53.0%,灌水均匀度(coefficient of uniformity,CU)达到了70%以上。同时表明在推迟加氯起始时间后(即灌水器相对平均流量(discharge ratio variation,Dra)降至80%开始加氯),加氯仍可以达到满意的堵塞控制效果。但加氯配合毛管冲洗也会显著增加微生物活性,分别提升了36.5%、29.0%、15.7%,这也使得对灌水器堵塞的恢复效果逐渐降低。     

Dietary toxicity of decomposed arborescent leaf litter against larval mosquito: involvement of a lignin-polypeptidic complex

To characterize the toxic compounds involved in the dietary toxicity of decomposed arborescent leaf litter against larval mosquito, a toxic fraction was extracted from crude leaf litter by using hot water. Preliminary characterization of this fraction, called the insoluble fraction (IF) because it progressively precipitates after extraction, has suggested the involvement of lignin-like compounds in the toxicity. Further analyzes are currently being performed by using additional phytotoxicity-based methods. The involvement of lignin-like compounds in the toxicity was indicated by both the comparative effects of different enzymatic oxidative treatments and reversed-phase high-performance liquid chromatography analysis of the phenolic aldehydes and acids obtained after alkaline nitrobenzene oxidation. However, these lignin-like compounds may not be involved alone in the toxicity, as no specific feature of those components was associated with the toxicity. Among the possible compounds associated with lignin-like compounds in the toxicity, peptidic compounds were suggested by comparative determination of the C/N ratio and then revealed by denaturation experiments, use of specific binding protein molecules, and thin-layer chromatography analysis. A possible role of these peptidic compounds associated with lignin-like compounds in the dietary toxicity of the leaf litter against the larval mosquito midgut is discussed.     

METAL-COMPLEX FORMATION BY LICHEN COMPOUNDS

The formation of soluble complexes, frequently coloured, when solid lichen compounds were shaken with water suspensions of biotite, granite, and basalt indicated that chemical weathering had occurred. The formation of colourless complexes and the adsorption of the dissolved lichen compound or complex by the silicate phase complicate the interpretation of the spectrophotometric analysis data. Lichen compounds invariably released greater amounts of Ca than of Mg, Fe, and Al from the silicates and, for each lichen compound, the release of Ca was usually greater from biotite than from granite or basalt. Release of cations from the silicate materials resulted largely from metal-complex formation rather than from reactions directly involving hydrogen ions. Citric, salicylic, and phydroxy-benzoic acids and EDTA, used as control organic acids, usually released considerably greater amounts of cations from the silicates than did the lichen compounds, consistent with the higher water solubility of the control organic acids. Similar amounts of Fe, Al, Ca, and Mg were released from the silicates by solutions of the lichen compounds and by solid lichen compounds. Lichen compounds are sufficiently soluble in water to form soluble metal complexes and to effect chemical weathering of minerals and rocks.     

Influence and Interactions of Processing Conditions and Starter Culture on Formation of Acids,Volatile Compounds,and Amino Acids in Wheat Sourdoughs

The aim of this work was to study the influence of process parameters and the starter culture on the characteristics of wheat sourdough by using response surface methodology. Influence of fermentation temperature (16–32°C), ash content of flour (0.6–1.8%), and fermentation time (6–20 hr) were considered as independent factors and their effects were studied in sourdough fermented with Lactobacillus plantarum, L. brevis, Saccharomyces cerevisiae, or with a combination of yeast and lactic acid bacteria. Formation of acidity, free amino acids, and volatile compounds were considered the main responses. A possibility to enhance formation of potential flavor compounds and precursors without excessive acidity formation in wheat sourdoughs was established. The total amount of amino acids increased by 25–50%, depending on the strain and fermentation conditions. The total amount of volatile compounds increased seven‐ to 100‐fold, depending on the strain and fermentation conditions. Sourdough started with S. cerevisiae was an effective way to optimize the amount of volatile compounds without excessive acidity formation in appropriate processing conditions. Ash content of flour and fermentation time were the most significant factors to modify metabolic activity of wheat sourdoughs. Frequent interactions between the studied factors were observed on the formation of acidity, amino acids, and volatile compounds with most of the strains studied. Possibility to improve current industrial fermentation processes and control flavor attributes of breads by using optimized sourdough was established.     

再生水地下回灌过程中溶解性有机物的去除研究

在实验室通过模拟方法研究了城市再生水地下回灌后的水质变化,重点分析了土壤含水层处理（SAT）对再生水中溶解性有机物（DOM）及消毒副产物的前体物去除效果。结果表明,在系统稳定时期,SAT对溶解性有机碳（DOC）平均去除率为37.2%。利用XAD树脂分离出再生水中占最主要DOM的3个部分：疏水性有机酸（HPOA）、过渡亲水性有机酸（TPIA）和亲水性有机物（HPI）。HPOA、TPIA和HPI在SAT中去除率分别为33.9%、21.5%和44.1%。再生水有较高的消毒副产物生成势（BPDFP）,经过SAT后三卤甲烷生成势THMFP和卤乙酸生成势HAAFP分别降低了11.0%和21.5%,但单位质量DOC的BPDFP却升高了,Specific THMFP和Specific HAAFP分别增大了42.4%和25.7%。即经过SAT处理后再生水中的消毒副产物的前体物浓度会减少,但是剩下的难降解的DOM有更高的氯化活性。     

Effect of the chlorinated washing of minimally processed vegetables on the generation of haloacetic acids

Chlorine solutions are usually used to sanitize fruit and vegetables in the fresh-cut industry due to their efficacy, low cost, and simple use. However, disinfection byproducts such as haloacetic acids (HAAs) can be formed during this process, which can remain on minimally processed vegetables (MPVs). These compounds are toxic and/or carcinogenic and have been associated with human health risks; therefore, the U.S. Environmental Protection Agency has set a maximum contaminant level for five HAAs at 60 μg/L in drinking water. This paper describes the first method to determine the nine HAAs that can be present in MPV samples, with static headspace coupled with gas chromatography-mass spectrometry where the leaching and derivatization of the HAAs are carried out in a single step. The proposed method is sensitive, with limits of detection between 0.1 and 2.4 μg/kg and an average relative standard deviation of ～8%. From the samples analyzed, we can conclude that about 23% of them contain at least two HAAs (<0.4-24 μg/kg), which showed that these compounds are formed during washing and then remain on the final product.     

Formation by mechanical stimulus of the flavor compounds in young leaves of Japanese pepper (Xanthoxylum piperitum DC.)

The volatile compounds formed in slapped and crushed young leaves of Japanese pepper (Xanthoxylum piperitum DC.) were compared with those of intact leaves by using a dynamic headspace gas analysis combined with GC-MS in an on-line system, together with the results of a sensory evaluation. The results indicated that the factors influencing the aroma note were mainly the constituent oxygenated monoterpenes and C(6) compounds and the quantity of terpene hydrocarbons. To clarify the formation mechanism for the aroma, the activities of lipoxygenase and beta-D-glucosidase were investigated. The results revealed that the hydrolysis of glycosides and the degradation of unsaturated fatty acids both played an important role in the formation of the major aroma compounds in young leaves of Japanese pepper.     

Individual organic compounds in water extracts from podzolic soils of the Komi Republic

The contents of organic compounds in water extracts from organic horizons of loamy soils with different water contents from the medium taiga zone of the Komi Republic were determined by gas-liquid chromatography and chromatography-mass spectrometry. The mass concentration of organic carbon in the extracts was in the range of 290?C330 mg/dm³; the mass fraction of the carbon from the identified compounds was 0.5?C1.9%. Hydrocarbons made up about 60% of the total identified compounds; acids and their derivatives composed less than 40%. Most of the acids (40?C70%) were aliphatic hydroxy acids. The tendencies in the formation of different classes of organic compounds were revealed depending on the degree of the soil hydromorphism. The acid properties of the water-soluble compounds were studied by pK spectroscopy. Five groups of compounds containing acid groups with similar pK_a values were revealed. The compounds containing groups with pK_a < 4.0 were predominant. The increase in the surface wetting favored the formation of compounds with pK_a 3.2?C4.0 and 7.4?C8.4.     

Microwave-Enhanced Advanced Oxidation Treatment of Lipids and Food Wastes

Fats, oils, and grease (FOG) and source separated organics (SSO) were treated with the microwave-enhanced advanced oxidation process (MW-AOP) at 90 and 110 °C, with varying amounts of hydrogen peroxide dosages. The treatment efficiency, in terms of soluble substrates and volatile fatty acids (VFA), increased with an increase in both temperature hydrogen peroxide dosages. Fatty acids and compounds with carbonyl group and/or hydroxyl group in both initial and treated FOG samples were identified by gas chromatography-mass spectrometry. MW-AOP treatment temperatures and hydrogen peroxide dosages dictated the formation of degradation products. The degradation followed peroxidation mechanism to produce lower molecular weight substrates such as short chain fatty acids which would be less inhibitory to microbes. After the MW-AOP treatment, both SSO and FOG comprised of more soluble and low molecular weight compounds. These compounds included VFA and nutrients that would be readily available for bacterial or plant uptake.     

Application of RVA and Time‐Lapse Photography to Explore Effects of Extent of Chlorination,Milling Extraction Rate,and Particle‐Size Reduction of Flour on Cake‐Baking Functionality

Three factors (extent of chlorination, milling extraction rate, and particle‐size reduction) in cake‐baking functionality of Croplan 594W flour were explored using a Rapid Visco‐Analyser (RVA) and time‐lapse photography. The extent of chlorination and milling extraction rate showed dramatic effects, but postmilling to reduce flour particle size was a less significant factor. RVA results showed that starch pasting was accelerated, and both peak and set‐back viscosities were enhanced, with increasing extent of chlorination. These effects were exaggerated by the high sugar concentration relevant to cake baking, compared to the same effects in water. Cake baking with chlorinated flours, in a formulation with 50% sugar (%S) and 275 parts total solvent (TS), showed that, as the extent of chlorination increased, cake moisture content and edge height decreased. Cake center height and shape factor were curvilinear, with maxima near flour with pH 4.6. Dramatic collapse occurred for cakes baked with unchlorinated flour samples, due to delayed starch pasting, as documented by time‐lapse photography and comparison to the geometry of the final cooled cakes. Starch pasting and egg white setting occurred too early for the cakes baked with excessively chlorinated flour (pH ≤4.0), but too late for the cakes baked with unchlorinated or insufficiently chlorinated flours (pH ≥4.9), compared to the ideal starch pasting and egg white setting behavior with appropriately chlorinated flours (pH >4.0 and <4.9). Informal sensory texture evaluation showed that cake mouthfeel was related to both moisture content per se and the relationship between moisture content and cake relative humidity (%RH). Excessive flour chlorination resulted in unacceptably dry cake mouthfeel.     

加氯处理对再生水滴灌系统灌水器堵塞及性能的影响

选取有压力补偿功能和无压力补偿功能,标称流量1.0～2.6 L/h的6种灌水器,研究了加氯间隔1～4周、系统余氯质量浓度2.5～10 mg/L对二级处理再生水滴灌系统灌水器堵塞和系统均匀性的影响,以便确定加氯处理最优运行方式。系统采用每天灌溉12 h的运行方式,累计运行84 d（1 008 h）。结果表明,加氯处理可有效地减轻灌水器堵塞,使滴灌系统保持均匀系数大于90%的良好性能,流量小于1.38 L/h的灌水器效果更为明显。尽管控制系统余氯浓度2.5、5.0和10.0 mg/L均可以杀死再生水中99.9%的细菌,但加氯间隔1周和2周处理减轻堵塞使系统保持良好性能的效果优于加氯间隔4周的处理。从保持滴灌系统性能良好的角度出发,建议采用低浓度高频率的加氯处理运行方式。     

胡麻产量形成模拟模型研究

胡麻产量形成模型是胡麻生长模型中的重要子模型,其准确性关系到整个模型的模拟性能。本研究拟构建能较准确预测不同生产情况下胡麻的产量形成模型,为胡麻实际生产提供科学指导。模型利用2012—2013年胡麻西北主产区定西和榆中试验站不同肥料、不同播种方式、不同种植密度和不同氮磷水平的试验结果,以胡麻生理生态过程为主线,分别构建了产量构成因素法(基于品种遗传参数:单位面积蒴果数、每果粒数、粒重与水肥胁迫因子、累积光合速率)的产量形成模型和基于粒壳比法(基于粒壳比和蒴果干物质总量)的产量形成模型;利用2014—2015年试验区实测数据对模型进行较广泛验证。验证结果表明,产量构成因素法对定西地区不同肥料、不同播种方式、不同种植密度产量模拟值的RMSE平均为133.47 kg×hm~(-2),粒壳比法的RMSE平均为195.51 kg×hm~(-2);利用最小二乘法计算的决定系数R2产量构成因素法与粒壳比法分别为0.819 8和0.743 9。榆中地区12个氮磷处理水平产量构成因素法平均RMSE值为140.70 kg×hm~(-2),粒壳比法的RMSE平均为193.22 kg×hm~(-2);产量构成因素法与粒壳比法预测的产量值与观测值R2分别为0.832 9和0.805 8。结果表明,产量构成因素法对产量的模拟效果优于粒壳比法,针对不同品种不同栽培方式,把单位面积蒴果数、每果粒数与粒重作为品种遗传参数的产量构成因素法能更精确模拟胡麻的产量,具有较高的预测性和通用性。     

Iron Mobilization and Mineralogical Alterations Induced by Iron-Deficient Cucumber Plants (Cucumis sativus L.) in a Calcareous Soil

Dicotyledons cope with ion (Fe) shortage by releasing low-molecular-weight organic compounds into the rhizosphere to mobilize Fe through reduction and complexation mechanisms. The effects induced by these root exudates on soil mineralogy and the connections between Fe mobilization and mineral weathering processes have not been completely clarified. In a batch experiment, we tested two different kinds of organic compounds commonly exuded by Fe-deficient plants, i.e., three organic acids (citrate, malate, and oxalate) and three flavonoids (rutin, quercetin, and genistein), alone or in combination, for their ability to mobilize Fe from a calcareous soil and modify its mineralogy. The effect of root exudates on soil mineralogy was assessed in vivo by cultivating Fe-deficient and Fe-sufficient cucumber plants (Cucumis sativus L.) in a RHIZOtest device. Mineralogical analyses were performed by X-ray powder diffraction. The batch experiment showed that citrate and, particularly, rutin (alone or combined with organic acids or genistein) promoted Fe mobilization from the soil. The combinations of rutin and organic acids modified the soil mineralogy by dissolving the amorphous fractions and promoting the formation of illite. These mineralogical alterations were significantly correlated with the amount of Fe mobilized from the soil. The RHIZOtest experiment revealed a drastic dissolution of amorphous components in the rhizosphere soil of Fe-deficient plants, possibly caused by the intense release of phenolics, amino acids, and organic acids, but without any formation of illite. Both batch and RHIZOtest experiments proved that exudates released by cucumber under Fe deficiency concurred to the rapid modification (on a day-scale) of the mineralogy of a calcareous soil.     

Physiological and Growth Responses of Transplants of the Moss Pseudoscleropodium purum to Atmospheric Pollutants

Chlorine is the most commonly used chemical for water and wastewater disinfection worldwide, and it reacts with both ammonia and dissolved organic nitrogen. Using the salicylate spectrophotometric method, effects of glycine on the classic breakpoint chlorination are studied using glycine as a surrogate for dissolved organic nitrogen. The results show that the shape of the breakpoint chlorination curve with glycine was analogous to that of water without glycine. Increasing the glycine concentration moves the chlorination breakpoint curve to the right, demonstrating that more chlorine must be added to replace the chlorine consumed by glycine and yield the desired residual active chlorine concentration. At the peak of the chlorination breakpoint curve, both NH₂Cl and mono-chlorinated organic chloramine reach their maximum. The Cl₂/N ratio of the peak is linearly related to the glycine concentration, and our calculations indicate that the maximum of mono-chlorinated organic chloramine formation by glycine chlorination occurs at a stoichiometric ratio of 1:1; the same as that for chlorinating ammonia to NH₂Cl. The distribution of NH₂Cl and organic chloramines is controlled by [Gly]/[NH₃-N]. At the breakpoint, ammonia and glycine are completely oxidized by chlorine, which leads to chlorine depletion. The stoichiometric ratio for the complete oxidation of glycine was 3:1, larger than that for complete oxidation of ammonia (2:1). For the different stoichiometric ratio in reaction of oxidation of ammonia and glycine, the sum of ammonia and glycine cannot be used as a chlorine dosage control parameter. The chlorine control method involving ammonia and glycine for chlorine and chloramination process is established.     

Comparison of solid-phase microextraction and stir bar sorptive extraction for the quantification of malodors in wastewater

Malodors in wastewater from animal-rearing facilities are due to the presence of characteristic polar compounds. The efficiency and reproducibility of three solid-phase microextraction (SPME) fibers (Carboxen-PDMS, polyacrylate, and PDMS) as well as PDMS-coated stir bars for the measurement of some of these compounds in the liquid phase were compared. In initial experiments, the SPME fibers and stir bars were exposed to a standard water solution containing a mixture of 18 compounds with a range of octanol-water partition coefficients. The polyacrylate SPME fibers and PDMS-coated stir bars, having been found to possess the best combination of extraction efficiency and reproducibility of measurement, were compared for the extraction of a high-strength swine wastewater. Ten compounds, which are known contributors to malodors in wastewater, were quantified by both methods of extraction. For most compounds, greater levels were estimated by the PDMS-coated stir bars than by SPME, and measurement reproducibility was also greater. For both methods of extraction, there was greater variation in the measurement of volatile fatty acids than there was for aromatics.     

Headspace solid-phase microextraction use for the characterization of volatile compounds in vegetable oils of different sensory quality

Headspace solid-phase microextraction (HS-SPME) was used to isolate the volatile compounds, which are formed during peroxidation of fatty acids in vegetable oils. Isolated compounds were characterized by GC-MS and quantified using GC with FID detection. Four fibers for HS-SPME method development were tested, and the divinylbenzene/carboxene/PDMS fiber was selected as providing the best detection of analyzed compounds. Extraction curves, limits of detection, repeatability, and linearity were investigated for 14 aldehydes, ketones, hydrocarbons, and alcohols being products of fatty acids autoxidation. Limits of detection for 11 of these were below 1 microg/L. For quantitative purposes, to minimize the influence of temperature on hydroperoxide formation and the changes in the volatiles profile of the extracts, sampling was performed at 20 degrees C. For compound characterization by GC-MS, sampling temperature of 50 degrees C was applied. The developed method was applied to the analysis of refined and cold-pressed rapeseed oil stored at 60 degrees C for 10 days, and for 10 different vegetable oils of various degree of peroxidation. All samples were subjected to sensory analysis. The results of PCA sensory analysis were related to the amount of volatile compounds isolated by SPME method. In cases where the amount of compounds was highest, the samples were perceived as the worst, whereas those with low levels of volatile compounds were the most desired ones according to sensory evaluation. The relation was observed for both total volatiles, quantified C5-C9 aldehydes, and 14 compounds selected in method development. SPME revealed to be a rapid and sensitive method for the extraction and quantitation of trace volatile compounds from plant oils even at ambient temperature.