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771.
Abstract: A study was conducted to determine the effects of three land covers (sunn hemp –Crotalaria juncea, sudex, a sorghum‐sudangrass hybrid –Sorghum bicolor x S. bicolor var. sudanese, and common oats –Avena sativa) planted as vegetative filter strips on the reduction of sediment and nutrient loading of surface runoff within the Kaika‐Waialua watershed on the island of Oahu, Hawaii. Runoff samples were collected and analyzed for total suspended solids (TSS), total dissolved solids (TDS), phosphorous, and three forms of nitrogen (nitrate, ammonium, total nitrogen). Study results show that during seven out of 10 runoff events, the three cover crop treatments significantly reduced TSS as compared to the fallow treatment. Average removal efficiencies were 85, 77, and 73% for oats, sunn hemp, and sudex, respectively, as compared to the fallow treatment. Nutrient concentrations were low with phosphorous concentrations, lower than 1 (μg/ml) for all treatments, and total nitrogen (TN) concentrations below 7 (μg/ml) except in the sunn hemp treatment, where TN concentrations were less than 10 (μg/ml). Results of analysis of TDS showed that the cover crop treatments did not decrease dissolved solids concentrations in comparison with the fallow treatment. Analysis of nutrient concentrations in runoff samples did not detect any significant decreases in phosphorous, nitrogen, ammonium, or TN concentrations in comparison to the fallow treatment. However, a significant increase in TN concentrations in the sunn hemp treatment was detected and showed the nitrogen fixing capacity of sunn hemp. No treatment effects on runoff volume were detected, and runoff volumes were directly correlated with rainfall amounts showing no crops significantly impacted soil infiltration rates. These results were attributed to extremely low soil hydraulic conductivities (0.0001‐7 cm/day at the soil surface, 15 and 30 cm below the soil surface). This study showed that cover crops planted as vegetative filters can effectively reduce sediment loads coming from idle and fallow fields on moderately steep volcanically derived highly weathered soils. 相似文献
772.
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774.
依据2000—2012年每月1次的调查资料,简要描述和讨论了深圳湾及邻近沿岸水域中溶解无机磷(DIP)质量浓度的时空分布,并结合盐度(S)和溶解无机氮实测数据探讨DIP的来源和氮:磷(N∶P)原子比.结果表明,深圳湾和珠江口东南沿岸中DIP质量浓度分别为(0.184±0.167)mg·L-1和(0.025±0.013)mg·L-1.在深圳湾,由于受到周边陆源排放的影响,DIP质量浓度在丰水期较低,枯水期较高.在珠江口东南沿岸,由于受到多个环境因子的制约,DIP质量浓度在夏秋季较高,冬春季较低.2000—2012年珠江口东南沿岸DIP质量浓度的年际变化趋势基本上保持平稳;深圳湾DIP质量浓度在2000—2004年呈上升趋势,从0.173 mg·L-1上升至0.236 mg·L-1,2005—2012年则呈下降趋势,从0.221mg·L-1下降至0.120 mg·L-1;2000—2012年深圳湾和珠江口东南沿岸N∶P原子比的年际变化均呈上升趋势,分别从31.8和41.5上升至44.9和60.1.研究海区中的DIP具有"保守性",主要来自陆源排放.依二元混合质量平衡模式估算的珠江口东南沿岸DIP的陆源质量分数约为63.0%,而深圳湾的都87%.研究海区中N∶P原子比高达48.3±36.9,暗示磷是初级生产的潜在限制因子. 相似文献
775.
Hemraj Bhattarai Lekhendra Tripathee Shichang Kang Chhatra Mani Sharm Pengfei Chen Junming Guo Prakriti Sharma Ghimire 《环境科学学报(英文版)》2021,33(4):37-52
Precipitation represents an important phenomenon for carbon and nitrogen deposition. Here, the concentrations and fluxes of dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) with their potential sources were analyzed in wet precipitation during summer monsoon from the Northern Indo-Gangetic Plain (IGP), important but neglected area. The volume-weighted mean (VWM) concentration of DOC and TDN were 687.04 and 1210.23 µg/L, respectively. Similarly, the VWM concentration of major ions were in a sequence of NH4+ > Ca2+ > SO42- > Na+ > K+ > NO3? > Cl? > Mg2+ > F? > NO2?, suggesting NH4+ and Ca2+ from agricultural activities and crustal dust played a vital role in precipitation chemistry. Moreover, the wet deposition flux of DOC and TDN were 9.95 and 17.06 kg/(ha?year), respectively. The wet deposition flux of inorganic nitrogen species such as NH4+-N and NO3?-N were 14.31 and 0.47 kg/(ha?year), respectively, demonstrating the strong influence of emission sources and precipitation volume. Source attribution from different analysis suggested the influence of biomass burning on DOC and anthropogenic activities (agriculture, animal husbandry) on nitrogenous species. The air-mass back trajectory analysis indicated the influence of air masses originating from the Bay of Bengal, which possibly carried marine and anthropogenic pollutants along with the biomass burning emissions to the sampling site. This study bridges the data gap in the less studied part of the northern IGP region and provides new information for policy makers to deal with pollution control. 相似文献
776.
人工湿地脱氮途径及其影响因素分析 总被引:26,自引:0,他引:26
简述了人工湿地脱氮模型。各种形态的氮在人工湿地系统中可以通过氨的挥发、植物吸收、介质沉淀吸附以及微生物硝化/反硝化作用等过程被去除。讨论了各脱氮途径对人工湿地脱氮的贡献,在大多数人工湿地的pH条件下,湿地地面氨挥发可以忽略,湿地植物叶片氨挥发量尚不清楚。湿地介质的直接吸附是短期的。植物在湿地脱氮过程中起了重要作用,但一般认为植物直接吸收和存储只占湿地脱氮的一小部分,一般低于30%。微生物的硝化/反硝化作用,是人工湿地脱氮的最主要的形式。讨论了影响人工湿地硝化作用的主要因素:溶解氧,pH和温度。大多数人工湿地的pH适合硝化作用,溶解氧和温度对湿地硝化作用的影响最大。温度不仅影响微生物的硝化作用,而且可以间接地影响植物的生长从而影响人工湿地的脱氮性能。 相似文献
777.
珠江水质和含氮消毒副产物的时空变化 总被引:2,自引:0,他引:2
研究区域是珠江广东省段的3条干流(西江、北江、东江)及交汇处(广州),目标是研究分析2年内29个采样点的常规水质指标的时空变化及溶解性有机氮(dissolved organic nitrogen,DON)对于消毒副产物生成势(specific disinfection byproduct formation potential,SDBPFP)的影响.结果表明,对于常规水质指标浓度而言,在时间上,西江、北江、东江三者基本无变化,但交汇处有稍微的变化,一般在7、10月份浓度偏高;在空间上,各干流及交汇处沿径流方向浓度呈逐渐增大趋势,且交汇处水质指标的浓度普遍高于干流.水体的PO34-浓度、总氮(total nitrogen,TN)浓度最高分别超出《国家地表水环境质量》Ⅴ类水质标准10倍、4倍.溶解性有机碳(dissolved organic carbon,DOC)浓度与UV254呈良好的线性关系,R2=0.901;但DON与卤乙腈(halogenacetonitrile,HANs)浓度的线性关系较差,R2为0.440.卤乙腈生成势(specific halogen acetonitrile formationpotential,SHANFP)与DOC/DON比值基本无线性关系. 相似文献
778.
Chemical identification and genotoxicity analysis of petrochemical industrial wastewater 总被引:2,自引:0,他引:2
Jing ZHANG Shigong WANG Can WANG Hongying HU 《Frontiers of Environmental Science & Engineering》2012,6(3):350-359
The actual harmful effects of industrial wastewater can not be reflected by the conventional water quality index. Therefore, the change in dissolved organic matter and the genetic toxicity of petrochemical wastewater were observed in the current study by examining the wastewater treatment plant of a large petrochemical enterprise in Northwest China. Using XAD-8, MSC, and DA-7 resins, the wastewater was separated into six fractions, namely, hydrophobic acid (HOA), hydrophobic neutral (HOB), hydrophobic alkaline, hydrophilic acid, hydrophilic alkaline, and hydrophilic neutral. Umu-test was used to detect the genetic toxicity of the wastewater samples, and fluorescence spectra were also obtained to examine genetic toxic substances. The results show that wastewater treatment facilities can effectively reduce the concentration of organic matter in petrochemical wastewater (p<0.05). However, the mixing of aniline wastewater can increase the amount of organic carbon (p<0.05) and can overload facilities. This finding shows that the mixed collection and joint treatment of different types of petrochemical wastewater can affect the water quality of the effluent. Particularly, hydrophobic substances can be difficult to remove and account for a relatively large proportion of the effluent. The mixture of aniline wastewater can increase the genetic toxicity of the effluent (p<0.05), and biologic treatment can not effectively decrease the toxicity. Most of the genetic toxicology may exist in the HOA and HOB fractions. Fluorescence spectroscopy also confirms this result, and tryptophan-like substances may play an important role in genetic toxicity. 相似文献
779.
780.
水溶性有机质对土壤硝化作用过程的影响 总被引:3,自引:0,他引:3
以江苏省宿迁市潮土为供试土壤,设置DOC220、DOC440和DOC880 3个添加水溶性有机质(DOM)处理,分别含有机碳(DOC)220、440和880 mg.L-1。试验结果表明,DOM对硝化过程有一定的抑制作用,在培养第16天时,未添加DOM的对照中NH4 -N几乎100%已经转化为NO3--N,而添加DOM的3个处理硝化率分别比对照降低7.83%、13.60%和19.12%;与对照相比,添加DOM的处理中NH4 -N含量降低缓慢,但培养过程中亚硝酸盐的积累显著增加,对照在第12天时NO2--N达到最大积累量67.83 mg.L-1,而DOC220、DOC440和DOC880处理土壤中NO2--N积累量分别在第12、14和16天达到最大值,与对照相比积累量分别增加21.17%、33.91%和59.90%。此外,DOM的添加也降低了NO3--N的生成速率,到第16天时,对照已经达到最大积累量143.61 mg.L-1NO3--N,但此时DOC220、DOC440和DOC880处理中NO3--N含量比对照分别低41.97、78.09和91.30 mg.L-1。为排除因添加DOM带来外源氮所引起的影响,同时进行了相同初始氮量下添加DOM与单施(NH4)2SO4对硝化作用影响的比较试验,结果同样表现出亚硝酸盐积累量的增加和NO3--N生成速率的降低,表明DOM中所含的有机碳及小分子化合物影响了硝化作用。高有机质环境下存在潜在的亚硝酸盐积累风险,对土壤和水体生态系统健康可能有一定影响。 相似文献