Simultaneous determination of dissolved organic nitrogen, nitrite, nitrate and ammonia using size exclusion chromatography coupled with nitrogen detector

Accurate quantification of dissolved organic nitrogen (DON) has been a challenge due to the cumulative analytical errors in the conventional method via subtracting dissolved inorganic nitrogen species (DIN) from total dissolved nitrogen (TDN). Size exclusion chromatography coupled with an organic nitrogen detector (SEC-OND) has been developed as a direct method for quantification and characterization of DON. However, the applications of SEC-OND method still subject to poor separations between DON and DIN species and unsatisfied N recoveries of macromolecules. In this study, we packed a series of SEC columns with different lengths and resin materials for separation of different N species and designed an independent vacuum ultraviolet (VUV) oxidation device for complete oxidation converting N species to nitrate. To guarantee sufficient N recoveries, the operation conditions were optimized as oxidation time ≥ 30 min, injection mass (sample concentration × injection volume) < 1000 µL × mg-N/L for macromolecular proteins, and neutral pH mobile eluent. The dissolved O₂ concentration in SEC mobile phase determined the upper limit of VUV oxidation at a specific oxidation time. Compared to conventional HW50S column (20 × 250 mm), HW40S column (20 × 350 mm) with mobile phase comprising of 1.5 g/L Na₂HPO₄·2H₂O + 2.5 g/L KH₂PO₄ (pH = 6.85) could achieve a better separation of DON, nitrite, nitrate, and ammonia. When applied to river water, lake water, wastewater effluent, groundwater, and landfill leachate, the SEC-OND method could quantify DON as well as DIN species accurately and conveniently even the DIN/TDN ratio reached 0.98.     

竞争吸附方程的修正和应用

以竞争吸附的一般模式为基础,修正了竞争吸附方程。研究了不同实验条件下修正竞争吸附方程的变化形式,为改进实验设计提供了理论依据。修正竞争吸附方程应用于描述pH对土壤吸附钴的影响,取得了满意的结果。     

关于秦皇岛市竞争力的初步分析及对策研究

我国城市竞争力研究成果表明秦皇岛市综合竞争力在全国排序第39位,基础设施、环境、区位等硬竞争力较强,而企业管理、制度、文化等软竞争力较弱,因此虽然在河北省名列前茅,但在沿海城市中比较落后,为了增强城市竞争力,必须正确定位、协调发展;发挥优势、加快发展;加快招商引资;进一步开放;加快科技进步,加强精神文明建设;强化城市营销和品牌建设;强化城市和企业管理。     

Normative Framing and Public Attitudes toward Biofuels Policies

Although the power of elite issue frames to shape public attitudes toward different policies is well established, the relative influence of different types of frames in competitive framing environments remains uncertain. For example, we do not fully understand the relative influence of economic versus normative frames on the public's policy attitudes, despite the common use of both types of frames to promote the same policy in many settings. Using data from a 2010 national Internet survey, this paper investigates the relative influence of economic versus normative frames on public attitudes toward the contentious policy issue of biofuels. The results indicate the importance of normative frames in shaping public attitudes on this issue, suggesting the relevance of normative frames more generally in shaping public opinion beyond the narrow confines of typical “morality” policies such as abortion or gambling.     

Competitive sorption between 17α-ethinyl estradiol and bisphenol A/4-n-nonylphenol by soils

The sorption of 17α-ethinyl estradiol(EE2),bisphenol A(BPA),and 4-n-nonylphenol(NP) in single systems and the sorption of EE2 with different initial aqueous concentrations of BPA or NP were examined using three soils.Results showed that all sorption isotherms were nonlinear and fit the Freundlich model.The degree of nonlinearity was in the order BPA(0.537-0.686) > EE2(0.705-0.858) > NP(0.875-0.0.951) in single systems.The isotherm linearity index of EE2 sorption calculated by the Freundlich model for Loam,Silt Loam and Silt increased from 0.758,0.705 and 0.858,to 0.889,0.910 and 0.969,respectively,when BPA concentration increased from 0 to 1000 μg/L,but the effect of NP was comparably minimal.Additionally,EE2 significantly suppressed the sorption of BPA,but insignificantly suppressed that of NP.These findings can be attributed to the difference of sorption affinity of EE2,NP and BPA on the hard carbon(e.g.,black carbon) of soil organic matter that dominated the sorption in the low equilibrium aqueous concentration range of endocrine-disrupting chemicals(EDCs).Competitive sorption among EDCs presents new challenges for predicting the transport and fate of EDCs under the influence of co-solutes.     

“竞争申请制”:可持续发展政策试点与央地关系重构

可持续发展目标(SDGs)的提出,开启了人类可持续发展领域最宏大的政策实验,也为开展国际视野的比较公共政策研究提供了难得机遇。执行SDGs及国家可持续发展政策需要处理好中央政府与地方政府间关系,而政策试点是协调这一关系的重要政策工具。已有文献对经济政策试点做了较充分的研究,然而对旨在实现经济、社会与环境协调的可持续发展政策试点,现有研究尚缺乏成型理论。在复杂央地关系格局下,对于需持续投入成本且成果难以界定的可持续发展政策试点,其具有怎样的不同于经济政策试点的机制?此外,众多西方学者将美国作为政策试点研究的制度基础并视其为“民主实验室”。然而,政策试点在以中国为代表的不同体制国家中同样存在,并以多样的机制发挥作用。那么,不同国家体制内的可持续发展政策试点又有哪些异同?政策试点影响下中国既有的央地关系发生了怎样的重构?对此,本文基于最典型案例原则,选取中国与美国响应SDGs分别开展的政策试点进行比较研究。笔者识别了不同体制下试点机制的异同,指出中国基于“竞争申请制”开展的可持续发展政策试点强化了中央部委与地方政府间关系,形成了地方官员的可持续发展激励,保障了政策试点的实施。     

土壤-植物系统中磷和砷相互作用关系的研究进展

砷元素导致的环境污染问题日益突出,施磷已成为植物修复砷污染土壤过程中必要强化措施之一。土壤-植物系统中磷和砷的相互作用关系是非常复杂的,研究表明：磷和砷在土壤中往往是共生的,但又存在竞争吸附关系;磷和砷在不同植物中的相互作用关系主要有拮抗效应和协同效应;有必要通过分子生物学手段对磷和砷表达基理进行深入研究,获得对砷具有超积累能力的植株。     

Development of IC-ELISA for detection of organophosphorus pesticides in water

Diethyl (carboxymethyl) phosphonate (DECP) was used as the hapten to develop an indirect competitive enzyme-linked immunosorbent assay (IC-ELISA) for detecting organophosphorus pesticides (OPs). Conjugator of DECP with bovin serum albumin (BSA) was used as the immunogen for producing the polyclonal antibodies (PcAbs). Three antisera were obtained after the immune procedure. Characterization studies of the PcAbs indicated that the titer of antiserum-1 was highest in 3 antisera, and antiserum-1 had high affinity and specificity to the parathion, dichlorvos and pirimiphos. The IC-ELISA showed an IC₅₀ of 0.428 μ g/mL with a detection limit of 0.0125 μ g/mL to parathion. The assay also indicated that the IC₅₀ values of pirimiphos and dichlorvos were 0.331 μ g/mL and 1.25 μ g/mL respectively, and the detection limits of pirimiphos and dichlorvos were 0.0116 μ g/mL and 0.048 μ g/mL respectively. Recoveries of parathion, pirimiphos and dichlorvos spiked into water samples ranged from 90% to 160%. The results indicated that the ELISA could be a convenient and supplemental analytical tool for monitoring OPs residues in environmental water samples.     

Effects of economic growth on biodiversity in the United States

For many citizens and policymakers, the empirical relationship between economic growth and biodiversity conservation has not been sufficiently established for purposes of identifying the types of economic policies amenable to biodiversity conservation. Some think economic growth conflicts with biodiversity conservation; others think economic growth conduces biodiversity conservation. With panel data from 1997‐2011, encompassing US continental states, we developed a series of statistical models to investigate the relationships among species endangerment, human population, and economic growth as indicated by GDP and per capita GDP. Species endangerment is highly correlated with population and GDP, and per capita GDP is a significant regressor of species endangerment. Across US continental states, competitive exclusion of non‐human species occurs via human economic growth and population growth.     

Determination of 10 particle-associated multiclass polar and semi-polar pesticides from small streams using accelerated solvent extraction

A new analytical method using accelerated solvent extraction was developed for the determination of 10 particle-associated polar and semipolar pesticides. In addition, six deuterated analogues of the target compounds were evaluated as internal standards. The method yielded acceptable accuracy (73–103% recovery) and precision (<25% relative standard deviation) for eight compounds. Using size exclusion chromatography (SEC) as cleanup step resulted in higher recoveries compared to solid phase extraction (SPE) cleanup.

Deuterated standards with 10 or more deuterium atoms performed well as internal standards concerning similar recovery and correlation with the target analytes.

The method was employed to extract particle-associated pesticides from 16 streams located in an area with intense agriculture in France. Acetochlor, pirimicarb, tebuconazole, fenpropidin, -endosulfan and chlorfenvinphos were detected at concentrations up to 1 mg kg⁻¹ dry weight. A comparison with aquatic toxicity data indicated potential risk to the benthic fauna exposed to these concentrations of pirimicarb, -endosulfan and chlorfenvinphos.

We suggest that the method presented here be used for the extraction and quantitation of particle-associated polar pesticides.