Contemporary trends in the acid-base status of two acid-sensitive streams in western Maryland

Recovery of streamwater acid neutralizing capacity (ANC) resulting from declines in regional acid deposition was examined using contemporary (1990-2005) data from two long-term monitoring stations located on the Appalachian Plateau in western Maryland, U.S. Two computational methods were used to estimate daily, monthly, and annual fluxes and discharge-weighted concentrations of ANC, sulfate, nitrate, and base cations over the period of record, and two statistical methods were used to evaluate long-term trends in fluxes and concentrations. The methods used to estimate concentrations, as well as the statistical techniques, produced very similar results, underlining the robustness of the identified trends. We found clear evidence that streamwater sulfate concentrations have declined at an average rate of about 3 microeq L(-1) yr(-1) at the two sites due to a 34% reduction in wet atmospheric sulfur deposition. Trends in nitrate concentrations appear to be related to other watershed factors, especially forest disturbance. The best evidence of recovery is based on a doubling of ANC (from 21 to 42 microeq L(-1)) at the more acid-sensitive site over the 16-year period. A slowing, or possible reversal, in the sulfate, nitrate, and SBC trends is evident in our data and may portend a decline in the rate of--or end to--further recovery.     

Climate-induced episodic acidification of streams in central ontario

In this study we have analyzed the hydrochemical effect of drought conditions during 311 hydrological episodes in nine headwater streams in central Ontario over the past 20 years. Acid Neutralization Capacity (ANC) was logarithmically correlated (p<0.05) to antecedent discharge in eight of the nine streams, with the largest decline in ANC occurring after low antecedent flow. In eight of the nine streams SO4(2-) was the most important driving mechanism of ANC decline, but dilution as well as organic acidity was important in several streams. No decrease in the SO4(2-) driven ANC decline was observed over the 20 year study period despite a approximately 40% reduction in SO4(2-) deposition. The strong correlation between ANC decline and low antecedent discharge demonstrates that episodic acidification during rain events is strongly associated with preceding drought conditions, especially in wetland-dominated catchments. The results have important implications for recoveryfrom acidification, especially in northern ecosystems where climate scenarios forecast that warmer and drier conditions will be more common.     

Recovery of streams from episodic acidification in northern Sweden

Between 1990 and 1999, SO4(2-) deposition in northern Sweden decreased by over 50%. To determine if a corresponding amelioration of stream acidity has occurred, we analyzed trends in anthropogenically driven episodic acidification in five streams during the same time period, using the Boreal Dilution Model (BDM) (Bishop, K. H.; Laudon, H.; Kohler, S. Water Resour. Res. 2000, 36, 1873-1884). Although there was no significant change in the annual average streamwater chemistry, the anthropogenically driven episodic acidification associated with spring flood runoff decreased by between 40% and 80%. A strong correlation between winter SO4(2-) deposition and the anthropogenic component of episodic acidification in these five streams suggests that future reductions of acid deposition will further improve the spring flood acidification situation in northern Sweden. These results argue that reduced emissions of acid precursors have generated significant improvements in the surface water chemistry during episodes associated with spring runoff in northern Sweden.     

Mercury concentration in fish from streams and rivers throughout the western United States

We collected and analyzed 2,707 large fish from 626 stream/river sites in 12 western U.S. states using a probability design to assess the regional distribution of whole fish mercury (Hg) concentrations. Large (>120 mm total length) fish Hg levels were strongly related to both fish length and trophic guild. All large fish that we sampled exceeded the wet weight detection limit of 0.0024 microgxg(-1), and the mean Hg concentration in piscivores (0.260 /microgxg(-1)) was nearly three times that of nonpiscivores (0.090 microgxg(-1)). Fish tissue Hg levels were not related to local site disturbance class. After partialing out the effects of fish length, correlations between Hg and environmental variables were low (r < 0.3) for the most common genera (trout and suckers). Stronger partial correlations with Hg (r > 0.5) were observed in other genera for pH, stream size, and human population density but patterns were not consistent across genera. Salmonids, the most common family, were observed in an estimated 125,000 km of stream length, exceeded 0.1 microg Hg x g(-1) (deemed protective for fish-eating mammals) in 11% of the assessed stream length, and exceeded the filet equivalent of 0.3 microg Hgxg (-1) (USEPA tissue-based water quality criterion) in 2.3% of that length. Piscivores were less widespread (31,400 km), but they exceeded the 0.1 and 0.3 microg Hgxg(-1) criteria in 93% and 57% of their assessed stream length, respectively. Our findings suggest that atmospheric transport is a key factor relative to Hg in fish across the western United States.     

Influence of partial acidification of skim milk on ultrafiltration performance and physicochemical properties of the produced streams

The influence of partial acidification of skim milk (SM) using glucono-δ-lactone (GDL), citric acid (CA) or lactic acid (LA), on physicochemical properties (e.g. viscosity and calcium balance) of ultrafiltration (UF) retentates produced at 10 and 55°C was investigated. Ultrafiltration retentates produced using CA showed a significantly lower amount (P < 0.05) of ionic calcium and higher apparent viscosity than GDL and LA. Regardless of the acid used, total calcium concentration and apparent viscosity of streams were modified compared with SM, which impaired UF overall performance. Specifically, CA at 10°C and GDL at 55°C, both reduced the permeate flux when compared to the other acids.     

2009年食品饮料市场十大趋势分析

在刚刚结束的第十三届中国国际食品添加剂和配料展览会(FIC2009)上,同期举办了新产品技术发布会,嘉吉增稠稳定方案商务单位做了题为《2009年食品饮料市场十大趋势分析》的精彩演讲。为处于经济危机压力下的众多食品制造商指明了未来的发展之路。     

马里兰烟品种比较试验

为筛选出优质的马里兰烟品种在生产上推广应用,解决品种单一的问题,对6个引进品种和5个新选育的F1品种进行了田间比较试验。结果表明:新选育的F1品种MH5,田间长势好,黑胫病和叶部病害发病轻,产量较高,产值最高,原烟外观质量和评吸质量好,化学成分协调。引进品种Md872,田间长势好,抗病性强,产量最高,产值较高,原烟外观质量和化验、评吸结果较好。以上2个品种均优于对照品种Md609。引进品种Md10的产量、产值较高,抗叶部病害,成熟早,原烟外观质量和化验、评吸结果也较好,与对照品种M609相当。     

西式肉糜火腿气孔成因分析

西式肉糜火腿成品切面和表面普遍存在一些大大小小不同的气孔或气泡,影响了产品的感官质量和保质期。采用正交试验对影响气孔形成的要素进行全面分析,确定出气孔形成的关键因素,并提出相应的控制措施。     

马里兰烟叶提取物的制备与应用

用乙醇、环己烷作主溶剂 ,对马里兰烟叶进行提取 ,经过滤、浓缩制得马里兰烟叶提取物。将该提取物加入卷烟中进行评吸 ,结果表明 ,马里兰烟叶提取物具有提高卷烟香气、增大烟味浓度 ,掩盖杂气 ,使吸味醇和 ,余味干净舒适的作用     

马里兰烟系列雄性不育系转育研究

为选育马里兰烟雄性不育系,以马里兰烟优良品系 Md609-1、Md609-2、Md609-3为轮回亲本,以马里兰烟胞质不育系Msmd609为不育源,进行连续回交转育。经过 5个连续世代单株选择和回交转育,选育出了 3份稳定性状的不育系,具备各对应品系典型特征特性,已转育成各对应品系的雄性不育同型系。其中,不育材料 Msmd609-3经济性状好、品质较优,具有一定的推广应用价值。      

全球造纸工业发展趋势分析

近年来,全球浆纸行业发展迅速,特别是近10年来,全行业的发展突飞猛进。本文通过汇集造纸业内多位权威专家和机构公布的数年数据以及国际权威数据,通过剖析行业整体的发展特点的同时，预测未来全球造纸产业的发展趋势。     

Episodes of elevated methylmercury concentrations in prairie streams

Methylmercury (MeHg) and total mercury (THg) concentrations were determined weekly from late March through mid-December 2000 in unfiltered water samples from two prairie streams in south-central Minnesota. The Little Cobb River and County Ditch 86 drain predominantly agricultural watersheds, but riparian areas along much of the Little Cobb River are forested, whereas County Ditch 86 is a utilitarian drainage waterway with grassed riparian areas. Episodes of elevated MeHg concentration (1.3 ng/L) were observed in both streams in early May during a period of algal bloom. Between late May and late September, MeHg concentrations varied between 0.05 and 0.39 ng/L in the Little Cobb River and between 0.03 and 0.29 ng/L in County Ditch 86. Precipitation was well below average in August and September, and discharge in both streams ceased by late September. MeHg concentrations in the Little Cobb River increased dramatically in early October after autumnal leaf fall, increasing from 0.44 to 4.90 ng/L over a 5-week period. In contrast, MeHg concentrations in County Ditch 86 varied between 0.22 and 0.48 ng/L over the same time frame. The observed differences are thoughtto reflect differences in the amounts of litterfall entering the two streams. These results show that algal bloom and leaf fall events can result in elevated MeHg concentrations in surface waters, potentially leading to increased MeHg accumulation in fish.     

The effect of acidification on myofibrillar proteins

Isolated myofibrillar proteins of mutton, beef and chicken were treated with an acidulent to give various pH values and stored at 5°C for 20 h before analysing the proteins using sodium dodecylsulphate polyacrylamide gel electrophoresis. It was found that protein degradation occurred below pH 4·5, with a decrease in band intensity of all major myofibrillar proteins, particularly myosin heavy chain, and the appearance of new bands at approximately 140 and 70 kd. The degradation had an optimum around pH 3·0 and was inhibited by a high temperature pre-treatment or the presence of the endopeptidase inhibitors pepstatin A and leupeptin. Results are discussed in terms of the action of acid proteinase enzymes.     

Determinants of fetal exposure to polyfluoroalkyl compounds in Baltimore, Maryland

Polyfluoroalkyl compounds (PFCs), such as perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA), are ubiquitous, man-made chemicals. Human data suggest that in utero exposures to these chemicals occur and some evidence of developmental toxicity in animals exists. To assess the distribution and determinants of fetal exposure to PFCs, we analyzed cord serum samples from 299 singleton newborns delivered between 2004 and 2005 in Baltimore, MD for 10 PFCs by employing on-line solid-phase extraction coupled with reversed-phase high-performance liquid chromatography-tandem mass spectrometry. PFOS and PFOA were detected in 99 and 100% of umbilical cord sera, with geometric mean concentrations of 4.9 and 1.6 ng/mL, respectively. PFOS and PFOA concentrations were highly correlated (Pearson's r = 0.64 after natural log transformation, p < 0.01). Eight other PFCs were detected less frequently and at lower concentrations than PFOS and PFOA. Geometric mean concentrations of PFOS for Asians (6.0 ng/mL) and Blacks (5.1 ng/mL) were higher than those for Whites (4.2 ng/mL), while PFOA levels were more evenly distributed by race. Other maternal demographic and socioeconomic characteristics, including age, education, marital status, and living in the city limits were not significantly associated with cord concentrations. Our findings suggest that in utero exposure to PFOS and PFOA is ubiquitous in a population of babies born in Baltimore, MD.     

马里兰烟施氮量研究初报

试验设计施氮量60、90、120、150、180、210kg/hm^2共6个处理。结果表明，前两个处理施氮太少，田间长势较弱，烟株发育不良，叶少、片小、均价、上等烟比例、产量、产值较低，收益少。后两个处理，施氮量太多，田间长势过旺，叶多、片大、病害较重，特别是210kg/hm^2处理，尽管获得较高产量，但均价和上等烟比例低，产值不高，加上成本增加，收益减少，烟叶评吸质量较差。施氮量120－150kg/hm^2，田间长势正常，烟株个体生长发育良好，群体结构合理，均价和上等烟比例较高，产量和产值最高，收益最大，烟碱含量适中，评吸质量较好。可初步认定，在当地条件下，施氮量120－150kg/hm^2为最佳处理。     

Microstructural changes in casein supramolecules during acidification of skim milk

Pasteurized skim milk was acidified using different levels of glucono-δ-lactone at 10, 20, 30, and 40°C to give slow, medium, and fast rates of acidification. Milk coagulation was monitored by measuring turbidity and curd firmness, and microstructural changes during acidification were observed on glutaraldehyde-fixed, agar-solidified milk samples using transmission electron microscopy. Rate of acidification had little influence on changes observed during acidification, except at 10°C. At 40°C, the casein supramolecules were spherical throughout acidification, whereas at lower temperatures they became progressively more ragged in appearance. All of the milks gelled at the same pH (pH 4.8), as measured by curd firmness, whereas increases in turbidity, assumed to be brought about by an increase in number of light-scattering particles, were observed to start at about pH 5.2 to 5.4. As the milk was acidified, aggregates of loosely entangled proteins were observed, presumably originating from proteins that had dissociated from the casein supramolecules. These aggregates were often as large as the casein supramolecules, particularly as the pH of the milk approached the isoelectric point of the caseins. Larger aggregates were observed at 40°C than at the lower temperatures, suggesting the involvement of hydrophobic interactions between the proteins. A 3-phase model for acid-induced gelation of milk is proposed in which the first phase involves temperature-dependent dissociation of proteins from the casein supramolecules, with more dissociation occurring as temperature is decreased. Dissociation continues as milk pH is lowered, with the released proteins forming into loosely entangled aggregates, some as large as the casein supramolecules. The second phase of acid gelation of milk occurs between pH 5.3 and pH 4.9 and involves a reassociation of proteins with loosely entangled protein aggregates forming into more-compact colloidal particles or combining with any remaining casein supramolecules. The third and final phase involves rapid aggregation of the colloidal casein supramolecules into a gel network at about pH 4.8. Different gel structures were formed based on temperature of acidification, with a coarse-stranded gel network formed at 40°C and a fine-stranded gel network at 10°C.     

Lagrangian mass-flow investigations of inorganic contaminants in wastewater-impacted streams

Understanding the potential effects of increased reliance on wastewater treatment plant (WWTP) effluents to meet municipal, agricultural, and environmental flow requires an understanding of the complex chemical loading characteristics of the WWTPs and the assimilative capacity of receiving waters. Stream ecosystem effects are linked to proportions of WWTP effluent under low-flow conditions as well as the nature of the effluent chemical mixtures. This study quantifies the loading of 58 inorganic constituents (nutrients to rare earth elements) from WWTP discharges relative to upstream landscape-based sources. Stream assimilation capacity was evaluated by Lagrangian sampling, using flow velocities determined from tracer experiments to track the same parcel of water as it moved downstream. Boulder Creek, Colorado and Fourmile Creek, Iowa, representing two different geologic and hydrologic landscapes, were sampled under low-flow conditions in the summer and spring. One-half of the constituents had greater loads from the WWTP effluents than the upstream drainages, and once introduced into the streams, dilution was the predominant assimilation mechanism. Only ammonium and bismuth had significant decreases in mass load downstream from the WWTPs during all samplings. The link between hydrology and water chemistry inherent in Lagrangian sampling allows quantitative assessment of chemical fate across different landscapes.     

Hydrothermal carbonization of municipal waste streams

Hydrothermal carbonization (HTC) is a novel thermal conversion process that can be used to convert municipal waste streams into sterilized, value-added hydrochar. HTC has been mostly applied and studied on a limited number of feedstocks, ranging from pure substances to slightly more complex biomass such as wood, with an emphasis on nanostructure generation. There has been little work exploring the carbonization of complex waste streams or of utilizing HTC as a sustainable waste management technique. The objectives of this study were to evaluate the environmental implications associated with the carbonization of representative municipal waste streams (including gas and liquid products), to evaluate the physical, chemical, and thermal properties of the produced hydrochar, and to determine carbonization energetics associated with each waste stream. Results from batch carbonization experiments indicate 49-75% of the initially present carbon is retained within the char, while 20-37% and 2-11% of the carbon is transferred to the liquid- and gas-phases, respectively. The composition of the produced hydrochar suggests both dehydration and decarboxylation occur during carbonization, resulting in structures with high aromaticities. Process energetics suggest feedstock carbonization is exothermic.     

川西高原牧区传统发酵牦牛酸奶挥发性风味成分的分析

采用顶空固相微萃取-气相色谱/质谱联用技术,以普通酸奶为对照,检测并分析了川西高原牧区传统发酵牦牛酸奶的挥发性风味成分。研究结果显示,川西高原牧区传统发酵牦牛酸奶的主体挥发性风味物质为乙醇（13%³4%）、3-甲基-1-丁醇（4%¹5%）、2-甲基-1-丁醇（1%⁸%）和乙酸乙酯（1%¹0%）,与普通酸奶存在明显差异,丰富的醇类物质是牦牛酸奶呈现醇香的直接原因。传统牦牛酸奶中乙醛、双乙酰和乙偶姻的相对百分含量低于普通酸奶,且短链及中链脂肪酸(C₂^C₁₀)的总百分含量低于普通酸奶。总体而言,川西高原牧区传统发酵牦牛酸奶的风味物质组成复杂,分布较为分散,不同风味化合物之间相互平衡的结果使得乳香与醇香适度搭配、香味丰满。