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711.
712.
Contribution of additives Cu to its accumulation in pig feces: study in Beijing and Fuxin of China 总被引:13,自引:1,他引:12
Massive amounts of pig manure are produced by intensive pig farm in China, and the composition of pig manure has changed much due to the use of feed additives. However, little is known about the exact Cu (copper) feed as additives or present as contaminants in pig feed and the residues in feces. One hundred and thirty-seven feeds and one hundred and forty-two fecal samples from 48 pig farms were collected in Beijing and Fuxin cities in 1999 and 2005, respectively. The concentrations of Cu were in the range of 6.86-395.19 mg/kg in the feed samples, and the mean values were in the order of weaner〉 grower-finisher〉 sow's feeds. The high concentrations over EU recommendations implied that excessive levels of Cu are fed on many pig farms in Beijing and Fuxin. Cu was also present in high concentrations in feces, and concentrations were highly variable. Cu concentrations in the feces from grower-finisher and weaner pigs were significantly greater than feces of sows. The super-intensive and small-scale farms had higher levels of Cu in feces than the middle farms. Cu concentrations in pig feces were approximately 5-times greater than in pig feeds. Feed management in grower-finisher pigs on super-intensive and small-scale pig farms is needed to reduce high Cu concentrations in feces and risks to soil contamination while feces are land-applied. 相似文献
713.
714.
715.
Hybrid constructed wetlands for highly polluted river water treatment and comparison of surface- and subsurface-flow cells 总被引:1,自引:0,他引:1
A series of large pilot constructed wetland (CW) systems were constructed near the confluence of an urban stream to a larger fiver in Xi'an, a northwestern megacity in China, for treating polluted stream water before it entered the receiving water body. Each CW system is a combination of surface- and subsurface-flow cells with local gravel, sand or slag as substrates and Phragmites australis and Typha orientalis as plants. During a one-year operation with an average surface loading of 0.053 m3/(m2.day), the overall COD, BOD, NH3-N, total nitrogen (TN) and total phosphorus (TP) removals were 72.7% ~ 4.5%, 93.4% + 2.1%, 54.0% + 6.3%, 53.9% ~ 6.0% and 69.4% :t: 4.6%, respectively, which brought about an effective improvement of the fiver water quality. Surface-flow cells showed better NH3-N removal than their TN removal while subsurface-flow cells showed better TN removal than their NH3-N removal. Using local slag as the substrate, the organic and phosphorus removal could be much improved. Seasonal variation was also found in the removal of all the pollutants and autumn seemed to be the best season for pollutant removal due to the moderate water temperature and well grown plants in the CWs. 相似文献
716.
利用2015—2016年西南涡个例数据与同期的细颗粒物(PM2.5)浓度数据进行时空匹配,对比分析西南涡过境前后四川盆地PM2.5浓度变化,并结合温度、湿度、风等气象要素及逆温特征,深入研究西南涡对PM2.5污染的影响机理.结果表明:①2015—2016年四川盆地共182个西南涡,其中,干涡72个(多集中在春季),弱降水涡75个(多集中在春季和冬季),强降水涡35个(多集中在夏季).②总体而言,干涡过境使四川盆地PM2.5浓度增加,降水涡使PM2.5浓度减小,强降水涡的削减作用强于弱降水涡.全年来看,干涡过境使四川盆地PM2.5浓度增加10.52%,强、弱降水涡过境分别使PM2.5浓度减小29.72%、9.71%.③除降水外,3类西南涡对PM2.5影响的主导气象要素和逆温条件为相对湿度、风速和逆温层底高.而主导季节差异的气象要素和逆温条件各异:干涡的主导因素是温度垂直变化和逆温强度,在温度随高度递减和逆温强度较小的春季和夏季,对PM2.5浓度的增幅减小(甚至有削减作用);弱降水涡的主导因素是湿度和风速、逆温强度和逆温层厚度,春季其过境时湿度和风速最小,逆温强度和逆温厚度仅次于冬季,甚至使PM2.5浓度增加;强降水涡的主导因素是风速、湿度和逆温层底高,夏季其过境时风速和低层湿度最小,逆温层底高最低,对PM2.5的削减作用远弱于其他季节. 相似文献
717.
采油井场土壤微生物群落结构分布 总被引:6,自引:1,他引:6
为了评价采油井场石油污染的微生物修复潜力,选取油井旁持续污染区(W)、井场曾经污染区(S)、原泥浆池区(M)和周边农田区(F)这4个不同位置,对0~400 cm不同深度土壤进行调查取样.利用高通量测序技术,对样品16S rRNA基因V4区序列进行测定,结合石油含量、三氮等物化性质,分析了微生物的生物多样性、群落组成及其和环境因子的关系.结果表明,石油污染减少了土壤的生物多样性,石油含量、盐度是造成微生物群落结构差异的最主要环境因子.通过组间差异分析发现,W和M土壤不仅存在着大量的石油降解细菌,其中的高盐样品中还含有嗜盐石油降解古菌.S与F具有相似的群落结构,表明石油烃的自然衰减.因此,该井场具有丰富的石油修复菌种资源,具有很好的微生物修复潜力. 相似文献
718.
通过室内模拟实验研究了3种不同粒径TiO_2添加量、溶液pH、吸附时间及初始Hg~(2+)浓度等因素对模拟废水中Hg(Ⅱ)吸附效果的影响.由单因素研究可知最优条件为:5 nm TiO_2和100 nm TiO_2添加量分别为7.5 g·L~(-1)和2.0 g·L~(-1),其它条件相同,溶液pH为8.0,初始Hg~(2+)浓度均为15 mg·L~(-1),吸附5 min,汞的去除率分别为99.5%和99.3%;25 nm TiO_2添加量为10 g·L~(-1),溶液pH为8.0,初始Hg~(2+)浓度为15 mg·L~(-1),吸附60 min时,汞的去除率为62.8%.3种粒径TiO_2吸附Hg(Ⅱ)强弱顺序为:100 nm TiO_25 nm TiO_225 nm TiO_2.分两次量吸附结果表明,5nm TiO_2分量吸附效果明显优于单独吸附效果;100 nm TiO_2的分量吸附与单独吸附差异不大.正交试验结果表明,影响Hg(Ⅱ)去除率的因素排序为:溶液pH初始Hg~(2+)浓度吸附时间TiO_2添加量.最优实验方案为:溶液pH=8.0,100 nm TiO_2添加量为2.0 g·L~(-1),初始Hg~(2+)浓度为25 mg·L~(-1),吸附10 min.在此实验条件下,Hg(Ⅱ)去除率为99.9%,吸附后溶液中Hg(Ⅱ)平衡浓度为0.033 mg·L~(-1)0.05mg·L~(-1),低于目前企业规定的水污染物中汞的排放限值,Hg(Ⅱ)的最大吸附量为26.95 mg·g~(-1).吸附等温线符合Langmuir等温方程,说明100 nm TiO_2对Hg(Ⅱ)的吸附是典型的单分子层吸附. 相似文献
719.
YOU Ke-wei GE Yun-shan HU Bin NING Zhan-wu ZHAO Shou-tang ZHANG Yan-ni XIE Peng 《环境科学学报(英文版)》2007,19(10):1208-1213
The types and quantities of volatile organic compounds (VOCs) inside vehicles have been determined in one new vehicle and two old vehicles under static conditions using the Thermodesorber-Gas Chromatograph/Mass Spectrometer (TD-GC/MS).Air sampling and analysis was conducted under the requirement of USEPA Method TO-17.A room-size,environment test chamber was utilized to provide stable and accurate control of the required environmental conditions (temperature,humidity,horizontal and vertical airflow velocity,and background VOCs concentration).Static vehicle testing demonstrated that although the amount of total volatile organic compounds (TVOC) detected within each vehicle was relatively distinct (4940μg/m~3 in the new vehicle A,1240μg/m~3 in used vehicle B,and 132μg/m~3 in used vehicle C),toluene,xylene,some aromatic compounds,and various C_7-C_(12) alkanes were among the predominant VOC species in all three vehicles tested.In addition,tetramethyl succinonitrile,possibly derived from foam cushions was detected in vehicle B.The types and quantities of VOCs varied considerably according to various kinds of factors,such as,vehicle age, vehicle model,temperature,air exchange rate,and environment airflow velocity.For example,if the airflow velocity increases from 0.1 m/s to 0.7 m/s,the vehicle's air exchange rate increases from 0.15 h~(-1) to 0.67 h~(-1),and in-vehicle TVOC concentration decreases from 1780 to 1201μg/m~3. 相似文献
720.
毛乌素沙地农业生态系统SEREn协调发展的时序测度 总被引:2,自引:0,他引:2
基于协调发展理论,构建农业生态系统社会、经济、资源和环境(简称SEREn)的发展度、承载力、协调发展度动态模型及其综合判定法则,通过在毛乌素沙地偏农区的榆阳区与偏牧区的乌审旗运用该模型,得到:①近27a两地发展度、承载力及协调发展度基本上均沿时间序列增加;②SE与REn协调发展的类型也均逐渐趋于更高水平;③农牧业产业结构逐渐由以资源环境消耗为主的资源密集型向以资金、科技利用为主的技术密集型转变;④受人类活动强度与农业生态系统开放性的影响,榆阳区与乌审旗SEREn的承载力和发展度产生了相应时序演变特征,使得SE与REn协调发展状况也发生相应变化。通过对SE与REn协调发展状况的综合判定,能够探查同时满足一定时段内社会经济发展要求和资源环境状况的关键因子,使资源环境的开发利用能够促进社会经济的发展,而社会经济的发展又为资源环境的保护与恢复提供更多的支撑。为构建资源节约型、环境友好型农业社会经济体系,促使SE与REn趋于高水平协调发展提供方法与理论借鉴。 相似文献