离子色谱法同时测定水中总氮和总磷

采用碱性过硫酸钾消解—离子色谱法同时测定水中总氮和总磷的含量。该方法避免了国标法中过硫酸钾和氢氧化钠对吸光度的干扰,对总氮和总磷测定的精密度有很大的提高。该方法在实验测定的浓度范围内总氮和总磷的相对标准偏差分别为3.84%和4.24%;总氮和总磷的最低检出限分别为0.007 mg/L和0.009 mg/L,比国标法更低;对实际试样总氮和总磷的加标回收率分别为92.6%～105.3%和94.7%～100.2%。     

SOIL SOLUTION CONCENTRATIONS: EFFECT OF EXTRACTION TIME USING POROUS CERAMIC CUPS UNDER CONSTANT TENSION1

ABSTRACT: Porous ceramic cups under constant tension (0.45 bar) were used to extract solutions from undisturbed soil columns. Solution concentration changed with length of extraction time. Significant relationships were found between extraction time and concentrations of P, Ca, and K in soil solution for two sample depths in an Omega loamy sand soil column. At two extraction time classes and at two sample depths, combined data from 12 soil columns representing two soil series reinforce the relationship. As time to extract a sample increases, the sample probably represents solution held by soil at tensions approaching those applied to the ceramic cup. We recommend that the choice of an extraction tension be given consideration in studies using porous ceramic cups under constant tension for monitoring constituents of soil solution. In addition, care must be taken to attain good physical contact between the cups and the soil material.     

Alkaline phosphatase activity in amniotic fluid in pregnancies with fetal disorders

Alkaline phosphatase (ALP) activity was determined in 255 amniotic fluid samples collected by amniocentesis between 15 and 39 weeks of gestation. The samples were originally used for chromosomal analysis and/or alpha-fetoprotein measurements. The mean ALP activity in early amniotic fluid from pregnancies with fetal trisomy 18 and 21 syndromes was half of that found in the controls. Highly elevated ALP activity (over 10 times the median level) was found in 14 samples. Two of these pregnancies had normal outcome. Three samples were from pregnancies with intrauterine fetal death. Fetal disorders, including abdominal wall defect (four cases), Meckel's syndrome (two), hydrops fetalis syndrome (two) and genital anomaly (one), were observed in nine cases. Moderately elevated ALP activity (over three times the median) was found in 10 cases, including five pregnancies with a preterm labour shortly after the sample collection. The results indicate that elevated ALP activity in the third trimester amniotic fluid is often associated with fetal disorders.     

Stem Growth of Picea Abies in South Western Sweden in the 10 Years Following Liming and Addition of PK and N

Liming and/or application of specific nutrients have been proposed as countermeasures to the acidification of forest soils in southern Sweden. In this study the stem growth of Picea abies (L.) Karst. growing on acidic mineral soils in SW Sweden was investigated 10 years after additions of lime (Ca; 3000 kg lime ha⁻¹), lime plus P (25 kg ha⁻¹) and K (80 kg ha⁻¹), or N in low doses (2 × 10 kg ha⁻¹ yr⁻¹) (treatments: CaPK, Ca, N, CaPKN, and 2Ca2P2K, respectively). Compared with the control, stem growth was increased following all treatments involving lime additions, including liming alone. The PK addition did not seem to affect growth. The most plausible cause of the observed growth increases was that the lime additions indirectly increased the supply of plant-available N. The annual low-dose N addition did not significantly affect growth. This suggests that air-borne deposition of N, which supplies very small doses of N throughout the year, has a minor or even negligible influence on P. abies growth.     

Impact of Harvest Intensity on Long-Term Base Cation Budgets in Swedish Forest Soils

The effects of harvesting on the long-term mass balances of calcium (Ca), magnesium (Mg) and potassium (K) were evaluated on a regional level in Sweden. A new high-resolution weathering database was used together with estimates of total deposition, losses through harvest and leaching. Estimates were made for pine and spruce separately and for two harvesting intensity scenarios: stem harvesting and whole-tree harvesting. The mass balance calculations showed net losses of Ca and Mg in almost the whole country for both scenarios. The losses were smaller for pine than for spruce. The K balances were mainly positive for pine but negative for spruce. Leaching was a main factor in the mass balances, especially for Ca and Mg. Whole-tree harvesting in spruce forests led to substantially higher net losses of K and Ca than stem harvesting, according to the calculations. In the whole-tree harvesting scenario in spruce forests the estimated yearly net losses of Ca, Mg and K corresponded to at least 5%, 8% and 3% of the pools of exchangeable base cations, respectively, at 25% of the analysed sites. If losses of this magnitude continue the depletion of the pools of Ca, Mg and K may lead to very low base saturation of the soils, possibly accompanied by negative effects on soil fertility, runoff water quality, tree vitality and tree growth within a forest rotation in parts of Sweden. Avoiding whole-tree harvesting can improve the situation substantially for K, but the losses of Ca and Mg will still be significant.     

两种大气汞排放监测方法的比较研究

对吸附管离线采样法及高锰酸钾溶液吸收法两种固定源大气汞排放监测方法进行了比较研究。结果表明:由于有更严谨周密的采样过程及质量保证/质量控制过程,吸附管离线采样法监测精度高于高锰酸钾溶液吸收法。吸附管离线采样法在含汞废气低浓度情况下其相对标准偏差为7.88%,而高浓度条件下监测精度明显下降。高锰酸钾溶液吸收法在采样方法上存在一些缺陷,未来该国标方法应重点在采样环节进行修订完善,并亟待建立适合于高浓度固定源含汞废气监测的高锰酸钾溶液吸收法。     

Fe_3O_4/石墨烯活化过硫酸盐降解罗丹明B废水的研究

利用水热法合成石墨烯负载Fe3O4催化剂,利用X-射线衍射、红外光谱、比表面积等对其进行表征。以Fe3O4/石墨烯为催化剂,活化过硫酸钾降解罗丹明B,考察了石墨烯与Fe3O4配比、催化剂用量、氧化剂浓度、pH值和温度等因素对其降解性能的影响。石墨烯的加入可以显著提高罗丹明B的降解率,氧化剂用量的增加有利于降解反应,弱酸性条件有利于降解;温度升高对罗丹明B降解有利。在该反应体系中存在的自由基以SO-4为主,·OH和O-2为辅。     

密云水库水源地保护区水体叶绿素a含量与营养物质浓度关系

在密云水库水源地保护区内选择3个典型水库,分析水体营养物质浓度对叶绿素a(Chl-a)含量的影响,并利用水体营养物质浓度计算叶绿素a含量。结果表明:总磷浓度(C_(TP))与叶绿素a浓度之间呈极显著正相关;高锰酸钾盐指数(C_(COD))和总氮浓度均与Chl-a之间呈正相关,但相关程度有所降低。在此基础上,提出了利用C_(TP)计算Chl-a的单变量方程和利用C_(TP)和C_(COD)计算Chl-a的双变量方程,其中双变量方程计算效果略优。对于水深较浅的草型水库,可利用C_(TP)和C_(COD)计算Chl-a。     

Comparative cytotoxicity of nanoparticles and ions to Escherichia coli in binary mixtures

The objective of this study was to understand toxicity of mixture of nanoparticles (NPs) (ZnO and TiO₂) and their ions to Escherichia coli. Results indicated the decrease in percentage growth of E. coli with the increase in concentration of NPs both in single and mixture setups. Even a small concentration of 1 mg/L was observed to be significantly toxic to E. coli in binary mixture setup (exposure concentration: 1 mg/L ZnO and 1 mg/L TiO₂; 21.15% decrease in plate count concentration with respect to control). Exposure of E. coli to mixture of NPs at 1000 mg/L (i.e., 1000 mg/L ZnO and 1000 mg/L TiO₂) resulted in 99.63% decrease in plate count concentration with respect to control. Toxic effects of ions to E. coli were found to be lesser than their corresponding NPs. The percentage growth reduction was found to be 36% for binary mixture of zinc and titanium ions at the highest concentration (i.e., 803.0 mg/L Zn and 593.3 mg/L Ti where ion concentrations are equal to the Zn ions present in 1000 mg/L ZnO NP solution and Ti^+ 4 ions present in 1000 mg/L TiO₂ NP solution). Nature of mixture toxicity of the two NPs to E. coli was found to be antagonistic. The alkaline phosphatase (Alp) assay indicated that the maximum damage was observed when E. coli was exposed to 1000 mg/L of mixture of NPs. This study tries to fill the knowledge gap on information of toxicity of mixture of NPs to bacteria which has not been reported earlier.     

K+强化高盐环境下厌氧氨氧化脱氮效能

针对含盐废水生物脱氮效能较低的问题,采用厌氧序批式反应器研究了K~+浓度变化对厌氧氨氧化污泥脱氮效能的影响.结果表明,适量的K~+可有效的提升反应器脱氮效能,K~+对厌氧氨氧化污泥脱氮效能的影响主要分为4个阶段:适应阶段,K~+浓度为(0~2 mmol·L~(-1)),K~+的突然添加破坏了原有反应平衡,但最终厌氧氨氧化菌适应了K~+的存在,由于K~+还未对厌氧氨氧化菌产生明显效果,NH_4~+-N和NO_2~--N去除率略有上升;活性提升阶段(2~8 mmol·L~(-1)),K~+对厌氧氨氧化生物系统有促进作用,随着K~+浓度的提升,NH_4~+-N和NO_2~--N去除率显著提升;活性稳定阶段(8~20 mmol·L~(-1)),厌氧氨氧化菌脱氮效能处于稳定状态,NH_4~+-N和NO_2~--N去除率虽有下降,但还是高于未添加K~+时;抑制阶段(大于20 mmol·L~(-1)),此时厌氧氨氧化菌活性降低,K~+对厌氧氨氧化产生较大抑制,脱氮效能已低于0 mmol·L~(-1).在整个周期内K~+浓度8 mmol·L~(-1)时达到最佳去除效果,NH_4~+-N与NO_2~--N的平均去除率为89.24%和84.87%,NRR为1.113 kg·(m~3·d)~(-1).