Derivation of predicted no effect concentrations (PNEC) for 2,4,6-trichlorophenol based on Chinese resident species

2,4,6-Trichlorophenol (2,4,6-TCP) is a common chemical intermediate and a by-product of water chlorination and combustion processes, and is a priority pollutant of the aquatic environment in many countries. Although information on the toxicity of 2,4,6-TCP is available, there is a lack of information on the predicted no-effect concentration (PNEC) of 2,4,6-TCP, mainly due to the shortage of chronic and site-specific toxicity data. In the present study, acute and sub-chronic toxicity of 2,4,6-TCP on six different resident Chinese aquatic species were determined. PNEC values were calculated and compared by use of two approaches: assessment factor (AF) and species sensitivity distribution (SSD). Values for acute toxicity ranged from 1.1 mg L⁻¹ (Plagiognathops microlepis) to 42 mg L⁻¹ (Corbicula fluminea) and the sub-chronic no observed effect concentrations (NOECs) ranged from 0.05 mg L⁻¹ (Mylopharyngodon piceus) to 2.0 mg L⁻¹ (C. fluminea). PNECs obtained by the assessment factor approach with acute (AF = 1000, 0.001 mg L⁻¹) or chronic (AF = 10, 0.005 mg L⁻¹) toxicity data were one order of magnitude less than those from SSD methods (0.057 mg L⁻¹). PNEC values calculated using SSD methods with a 50% certainty for 2,4,6-TCP was less than those obtained by use of the USEPA recommend final chronic value (FCV) method (0.097 mg L⁻¹) and the one obtained by use of the USEPA recommend acute-to-chronic (ACR) methods (0.073 mg L⁻¹). PNECs derived using AF methods were more protective and conservative than that derived using SSD methods.     

Copper oxide nanoparticles can induce toxicity to the freshwater shredder Allogamus ligonifer

Increased commercialisation of nanometal-based products augments the possibility of their deposition into aquatic ecosystems; this, in turn, may pose risks to aquatic biota and associated ecological functions. Freshwater invertebrate shredders mostly use microbially-colonized plant litter as food resource and play an important role in aquatic detritus food webs. We assessed lethal effects of nanoCuO on the shredder Allogamus ligonifer (Trichoptera, Limnephilidae) by determining the concentration that induced 50% of death (LC₅₀), and sublethal effects of nanoCuO on the feeding behaviour and growth of the shredder by exposing the animals to: (i) stream water supplemented with nanoCuO and microbially-colonized leaves, and (ii) stream water (without nanoCuO) and microbially-colonized leaves pre-exposed to nanoCuO. Results from acute lethal tests showed that the 96 h LC₅₀ of nanoCuO was very high (569 mg L⁻¹). In the absence of nanoparticles, leaf consumption rate was 0.27 mg leaf DM mg⁻¹ animal DM d⁻¹ and the shredder growth rate was 56 μg animal DM mg⁻¹ animal DM d⁻¹. A significant inhibition in leaf consumption rate (up to 47%) and invertebrate growth rate (up to 46%) was observed when shredders were exposed to the higher tested sublethal concentration of nanoCuO (75 mg L⁻¹) through either contaminated stream water or pre-contaminated food. The exposure to increased nanoCuO concentration via water or pre-contaminated food led to higher accumulation of copper in the larval body. Leached water-soluble ionic copper from the nanoCuO adsorbed or accumulated in the shredder (up to 10.2% of total Cu) seemed to influence the feeding behaviour and growth of the shredder.     

农业生态环境污染监测技术探讨

农业生态环境污染监测是以农产品污染监测为中心的各环境要素的污染监测。依据农业区域中污染源排放危害农产品的特征污染物选择大气环境污染物、水环境污染物、土壤环境污染物、农产品污染物作为监测指标;依据农业区域中各类污染源的特点布设大气环境污染、水环境污染、土壤环境污染、农产品污染监测点位;在农产品生长期或生产期,大气环境污染及水环境污染同步监测一次,农产品污染在收获时监测一次,依据污染源污染物排放强度确定土壤环境污染监测频次。     

基于耦合关系的中国区域土地利用效益水平测度

新时期,土地利用的属性决定了土地利用能同时产生社会经济效益与生态环境效益,而这两种效益的交互耦合进一步决定了土地利用的整体效益。本研究建立了土地利用的社会经济效益与生态环境效益的耦合模型,设计了分别测度这两种效益的指标体系,用熵值赋权法计算了各指标的权重,进而计算了中国31个省(市、自治区)土地利用中这两种效益的系数及其耦合协调发展系数。结果显示:第一类地区是我国社会经济与生态环境均较好的上海市;第二类地区主要是社会经济发展较好但生态环境建设相对滞后的地区;第三类是生态环境较好但社会经济发展相对滞后的地区;第四类是社会经济发展相对滞后但生态环境建设更为落后的地区;第五类是生态环境建设滞后但社会经济发展更为落后的地区。最后,对每一个类型的成因和未来发展思路作了说明,在此基础上,又说明了中国土地利用的整体效益仍较为有限、整体效益表现出较为明显的区域分布特征、社会经济与生态环境的协调发展已成为提高我国土地利用效益的现实选择等基本政策含义。     

入世前后中国农业贸易引致的就业“创造与替代”

我国加入世贸组织后,除了粮食安全、比较优势、竞争力等方面的影响研究外,农产品贸易开放对我国农业生产部门就业的影响一直令人关注,是具有比较优势的劳动密集型农产品出口带来更多就业创造,还是土地密集型农产品进口引致更多就业替代?本文运用1994-2009年数据,对入世前后农产品贸易开放引致的农业就业效应进行全面系统的实证分析,并对在不同情形下我国未来贸易引致的农业就业替代效应的程度和方式进行了模拟分析。研究结果表明:入世后我国农产品贸易引致的农业就业效应呈现出更明显的就业净替代变化;同时,在技术水平不变的情况下,我国未来劳动密集型农产品的实际出口增速与平抑就业替代压力的"理想增速"相距甚远,未来土地密集型净进口所产生的农业就业替代量将在较大程度上超过劳动密集型净出口创造的就业机会,我国农业就业整体"净替代"的趋势可能将长期持续。     

Influence of ionic strength and pH on the limitation of latex microsphere deposition sites on iron-oxide coated sand by humic acid

This study, for the first time, investigates and quantifies the influence of slight changes in solution pH and ionic strength (IS) on colloidal microsphere deposition site coverage by Suwannee River Humic Acid (SRHA) in a column matrix packed with saturated iron-oxide coated sand.Triple pulse experimental (TPE) results show adsorbed SRHA enhances microsphere mobility more at higher pH and lower IS and covers more sites than at higher IS and lower pH. Random sequential adsorption (RSA) modelling of experimental data suggests 1 μg of adsorbed SRHA occupied 9.28 ± 0.03 × 10⁹ sites at pH7.6 and IS of 1.6 mMol but covered 2.75 ± 0.2 × 10⁹ sites at pH6.3 and IS of 20 mMol. Experimental responses are suspected to arise from molecular conformation changes whereby SRHA extends more at higher pH and lower ionic strength but is more compact at lower pH and higher IS. Results suggest effects of pH and IS on regulating SRHA conformation were additive.     

Comparison of competitive and synergetic adsorption of three phenolic compounds on river sediment

Knowledge of toxic chemical sorption by soil/sediment is critical for environmental risk assessment of toxic chemicals, especially for the multi-sorbate system in river ecosystem. Sorption characteristics of 2, 4-Dichlorophenol, 2, 4-Dinitrophenol and 2, 4-Dimethyphenol on sediment were investigated. Adsorption isotherms in single- and multi-sorbate systems fitted well the Freundlich model. The adsorption effects were different among three selected phenolic compounds in single- and multi-sorbate systems. The synergetic affect that 2, 4-Dinitrophenol and 2, 4-Dimethyphenol bring to 2, 4-Dichlorophenol can be explained by the compression of double electronic layer and the charge neutrality. Adsorption kinetic results showed that pseudo-second-order model can be used to describe the experimental data and the adsorption affinity of phenolic compounds influenced greatly by the adsorption velocity. The present study suggests that the fate and transport of emerging pollutants such as phenolic compounds could be affected in the presence of different hydrophobic pollutants in aquatic systems.     

Adsorption of sulfamethoxazole on functionalized carbon nanotubes as affected by cations and anions

The environmental risks of antibiotics have attracted lots of research attention, but their environmental behavior is not clear yet. Functionalized carbon nanotubes (CNTs) were used as model adsorbents and sulfamethoxazole (SMX) was used as a model antibiotic to investigate the effect of both cations (Ca²⁺, Cs⁺) and anions (phosphate) on antibiotics adsorption. Various mechanisms (such as electrostatic interaction, hydrophobic interaction, π-π and hydrogen bonds) play roles in SMX adsorption. Cations and anions could “wedge into” these mechanisms and thus alter SMX adsorption. This study emphasized that both increased and decreased SMX adsorption could be observed with the addition of cations/anions, depending on environmental conditions (such as pH in this current study). The net effect is the balance between the increased and decreased effects. The contribution of different mechanisms to the overall antibiotic adsorption on solid particles should be identified to accurately predict the apparent effect by cations and anions.     

古黄河泗阳段流域生态环境保护工程

通过采取治、退、拆、清、修、整、建、养、植等生态修复综合措施、建立古黄河生态保护圈,加强古黄河泗阳段周边环境的生态保护,进一步净化水体环境,增加古黄河泗阳段蓄水量,提高水质的稳定性,使得社会效益、环境效益和经济效益达到最佳统一,实现水资源的持续利用。同时改善古黄河地区的空气环境,实现古黄河泗阳地区的蓝天碧水。     

Effect of aging on catalytic properties in mechanochemical degradation of pentachlorophenol by birnessite

Mechanochemistry, a technique concerning with milling contaminated samples for prolonged times, induces massive degradation of pollutants by grinding them in ball mills with different soil components or additives. In the present study, laboratory experiments were conducted to evaluate the effect of aging on the mechanochemical efficiency of the Mn-oxide birnessite in degrading pentachlorophenol (PCP). A comparative study on an aged birnessite (KBiA), used after 3 years from synthesis, and a fresh birnessite (KBiF), employed immediately after synthesis, was carried out. The differences between the two birnessites, evidenced by spectroscopic and diffractometric techniques, are mainly relative to reduction of the Mn(IV) centered at the MnO₆ octahedra layers from the birnessite structure, which represent the most reactive sites for PCP degradation. The long term air drying at room temperature, by favouring reduction of Mn(IV) to Mn(III), produces an inorganic substrate that offers paucity of the less reactive sites for PCP degradation, thus reducing the oxidative potential of the KBiA. Accordingly, the more reactive fresh birnessite was employed in the experiment with a polluted soil. Adding a small amount of KBiF to soil only induces a light increase in PCP removal, probably due to the mechanically induced PCP adsorption and transformation onto clay minerals present in the soil. Besides, adding a higher dose of birnessite causes a stronger degradation of PCP.