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981.
982.
The different toxicity characteristics of arsenic species result in discrepant ecological risk. The predicted no-effect concentrations (PNECs) 43.65, 250.18, and 2.00 × 103 μg/L were calculated for As(III), As(V), and dimethylarsinic acid in aqueous phase, respectively. With these PNECs, the ecological risk from arsenic species in Pearl River Delta in China and Kwabrafo stream in Ghana was evaluated. It was found that the risk from As(III) and As(V) in the samples from Pearl River Delta was low, while much high in Kwabrafo stream. This study implies that ecological risk of arsenic should be evaluated basing on its species. 相似文献
983.
Effects of water regime, crop residues, and application rates on control of Fusarium oxysporum f. sp. cubense 总被引:1,自引:0,他引:1
Biological soil disinfestation is an effective method to control soil-borne disease by flooding and incorporating with organic amendments, but field conditions and resources sometimes limited its practical application. A laboratory experiment was conducted to develop practice guidelines on controlling Fusarium wilt, a widespread banana disease caused by Fusarium oxysporum f. sp. cubense(FOC). FOC infested soil incorporated with rice or maize straw at rates of 1.5 tons/ha and 3.0 tons/ha was incubated under flooded or water-saturated(100% water holding capacity) conditions at 30℃ for 30 days. Results showed that FOC populations in the soils incorporated with either rice or maize straw rapidly reduced more than 90% in the first 15 days and then fluctuated till the end of incubation, while flooding alone without organic amendment reduced FOC populations slightly. The rapid and dramatic decrease of redox potential(down to- 350 m V) in straw-amended treatments implied that both anaerobic condition and strongly reductive soil condition would contribute to pathogen inactivation. Water-saturation combined with straw amendments had the comparable effects on reduction of FOC, indicating that flooding was not indispensable for inactivating FOC. There was no significant difference in the reduction of FOC observed in the straw amendments at between 1.5 and 3 tons/ha. Therefore,incorporating soil with straw(rice or maize straw) at a rate of 3.0 tons/ha under 100%water holding capacity or 1.5 tons/ha under flooding, would effectively alleviate banana Fusarium wilt caused by FOC after 15-day treating under 30℃. 相似文献
984.
Arsenic is one of the most common inorganic contaminants in groundwater worldwide, mainly due to the release of naturally occurring arsenic from aquifer sediments (Amini et al., 2008, Li and Cai, 2015 and Rahman et al., 2015). Naturally occurring arsenic exists predominantly in arsenate and arsenite species in groundwater. 相似文献
985.
文章以腐殖酸和纳米Fe2O3为对象,着重研究了腐殖酸分子在纳米Fe2O3表面的吸附过程中的疏水效应,借助红外光谱和热重等分析方法研究了腐殖酸吸附前后的疏水性随溶液环境变化的规律。结果表明,当离子强度为0、0.005、0.01和0.05 mol/kg,pH值从7变到12时,纳米Fe2O3吸附溶解性腐殖酸分子后形成的复合体的热失重量随着pH值的升高先减小后增大。当pH值从7升高到10时,亲水性降低,疏水性增强;当pH值从10升高到12时,亲水性增强,疏水性降低。当离子强度为0.001 mol/kg,pH值从7变到12时,复合体的热失重量随着pH值的升高而减小,亲水性降低,疏水性增强。当pH值为定值,离子强度变化时,纳米Fe2O3吸附溶解性腐殖酸分子后形成的复合体的热失重量随着离子强度的增加不断变化,曲线呈现出波动趋势,亲、疏水性在交替变化。红外光谱分析结果说明,对纳米Fe2O3吸附溶解性腐殖酸分子后形成的复合体的亲疏水性起主要影响的官能团可能是亲水性的羟基-OH、羰基C=O和疏水性的CH2烷烃。 相似文献
986.
Contamination by persistent toxic substances in surface sediment of urban rivers in Chaohu City, China 总被引:3,自引:0,他引:3
The concentration and spatial distribution of persistent toxic substances (PTS) in the river sediment in Chaohu City, China were investigated. A total of nine surface sediments were collected and the selected PTS pollutants including six heavy metals and nineteen polybrominated diphenyl ethers (PBDEs) were analyzed. The mean heavy metal concentrations (in mg/kg, dry weight) ranged within 0.18-1.53 (Hg), 50.08-200.18 (Cu), 118.70-313.65 (Zn), 50.77-310.85 (Cr), 37.12-92.72 (Pb) and 13.29-197.24 (As), and Cu, Zn and As have been regarded as the main metal pollutants. The levels of PBDEs (1.2-12.1 ng/g) and BDE-209 (2.4-30.5 ng/g) were at the middle level of the global range. BDE-209 was the predominant congener (67.0%-85.7%), which agrees with the fact that technical deca-BDE mixtures are the dominant PBDE formulation in China. The relative high level of PTS pollutants in the western part of the city is probably owing to the intensive agricultural activities and lack of sewerage system there. The ecological risk assessment with the sediment quality guidelines (SOGs) indicates that the urban river sediments in the city have been heavily contaminated by heavy metals with probable ecotoxicological impacts on freshwater organisms and the main toxic pollutants are Hg and As. The results of current study imply that the city, and perhaps many other small cities in China as well, requires immediate pollution control measures with emphasis on not only conventional organic pollutants but also on PTS such as heavy metals and PBDEs. 相似文献
987.
988.
化工产业是天津滨海新区重要的支柱产业,该行业废水因污染种类复杂,具有高盐、高毒、难降解等特点,是滨海新区污染物控制的主要威胁。通过对滨海某化工区实际废水进行几种主流预处理技术及其组合工艺的研究,明晰了其在实验条件下各自的特点,验证了其实际处理效果,进一步掌握了其反应过程中的特性,为研究后续的示范工程应用及大规模推广打下基础。实验表明,制药废水经内电解处理后毒性削减率最高可达到46%,对化学合成废水有较好的去毒效果,该技术可有效地提高制药废水的可生化性;光催化氧化对苯胺和氯苯的最佳降解条件分别是15 g/L TiO(23 h)及17.5 g/L TiO2;负载型纳米铁和纳米四氧化三铁催化剂分别适合极酸和中性、偏碱性条件,催化效率高,COD去除效果好。 相似文献
989.
990.
于2021年4月对鸭绿江干流及其主要支流水体中14种目标有机磷酸酯(OPEs)的浓度水平及污染特征进行了调查研究。结果表明,鸭绿江中∑OPEs的浓度从上游到下游逐渐升高,质量浓度为11.6~557.0 ng/L,平均质量浓度为202.5 ng/L,处于世界偏低,全国中下水平。鸭绿江水体中ρ(氯代OPEs)>ρ(烷基代OPEs)>ρ(芳基代OPEs)。14种OPEs中,磷酸三(1氯2丙基)酯(TCPP)质量浓度最高,其次是磷酸三(2氯乙基)酯(TCEP),平均占比分别为31.8%和20.9%。鸭绿江上游水体中OPEs的质量浓度为11.6~135.5 ng/L,平均值为52.8 ng/L,质量浓度最高的是烷基代OPEs;下游水体中OPEs的质量浓度为179.1~557.0 ng/L,平均值为382.3 ng/L,质量浓度最高的是氯代OPEs。上游水体中OPEs主要来源于大气沉降、径流携带等环境迁移,下游水体则主要受到丹东市区生活污水和沿江工业园区废水排放的影响。研究可为今后科学评估此类物质的环境风险并采取精准管控措施,提供数据支持和科学依据。 相似文献