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71.
72.
The benefits of adding composted organic materials to soils to enhance carbon storage could be countered by the mobilisation of some harmful pollutants commonly found in frequently degraded urban soils. Therefore non-composted materials could be a safer option. In the present study, carbon and trace element fluxes in soil pore water were studied in response to the surface mulch addition and the incorporation into an urban soil of greenwaste compost versus two non-composted amendments; a woody oversize material and biochar following inoculation with the vertical burrowing earthworm Lumbricus terrestris. The aim was to establish (i) to what extent the non-composted amendments impacted on mobility of soluble trace elements in the soil, compared to the composted amendment, and (ii) if/how this was regulated by earthworm activity.Both composted and non-composted amendments enhanced dissolved organic carbon (DOC) in soil pore water to ∼100-300 mg l−1 in the upper depth of the soil profile above which they were applied as a mulch and similarly within the mesocosms in which they were mixed. Dissolved organic carbon, dissolved nitrogen (DTN) and trace metals, especially Cu and Pb, where enhanced to the greatest extent by greenwaste compost, because of strong co-mobilisation of metals by DOC. Biochar enhanced As and Cu mobility in the field profile and, additionally Pb in the mesocosms, with no effect on Cd. The woody, oversize amendment neither greatly increased DOC nor As, Cu, Pb or Zn mobility although, unlike the other amendments, earthworms increased DOC and Cd mobility when soils were amended with this material.This study concludes that non-composted amendments had a lower impact on DOC and thus trace element co-mobility than the composted greenwaste in this urban soil, whilst the general influence of earthworms was to reduce DOC and hence associated trace element mobility. In wider environmental terms the addition of non-composted materials to some urban soils, versus composted greenwaste could reduce the risk of mobilising potentially harmful elements, whilst usefully improving soil quality. 相似文献
73.
潮间带沉积物中重金属污染评价及生物有效性研究进展 总被引:1,自引:0,他引:1
潮间带是一个典型的环境脆弱带和敏感带,极易受到人类活动的破坏.潮间带重金属除了直接对潮间带生物有影响外,还可以通过过食物链的富集和放大作用影响人类健康,同时由于潮间带水动力和生物活动的影响,造成重金属的重新分布和释放,产生重金属的"二次污染",直接危害近岸环境.开展重金属元素在潮间带沉积物中含量、赋存形态、污染评价及其生物有效性已成为目前环境科学领域中十分重要的研究内容和任务,国内外学者均对河流沉积物重金属污染开展了大量的研究.文章从这4个方面阐述了潮间带沉积物重金属研究进展,以期为潮间带沉积物重金属研究提供一定的参考. 相似文献
74.
Agroforestry systems have the potential to increase sequestration of atmospheric carbon dioxide (CO2) as soil organic carbon (SOC) because of the increased rates of organic matter addition and retention. However, few studies have characterized the relative stability of sequestered SOC in soil. We characterized SOC storage in aggregate size and chemical stability classes to estimate the relative stability of SOC pools after the addition of Leucaena-KX2 pruning residues (mulch) from 2006 to 2008 in a shaded coffee agroforestry system in Hawaii. Soil samples were separated by microaggregate isolation, density flotation and dispersion, and acid hydrolysis, resulting in five distinct fractions that differed in relative stability: coarse particulate organic matter (POM), fine POM, microaggregate-protected POM, silt + clay hydrolyzable soil organic matter (SOM), and silt + clay non-hydrolyzable SOM. With mulch addition, the fine POM fraction increased. There was also a shift in the proportion of SOC to more stable silt + clay fractions. In the absence of mulch there was no significant change in SOC fractions. Given that the turnover time of SOC in silt + clay fractions is on the order of decades to centuries, the potential benefits of active shade management and mulching compensate for the loss of C sequestration in tree biomass from pollarding. 相似文献
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78.
Surface water quality of factory-based and vegetable-based peri-urban areas in the Yangtze River Delta region,China 总被引:1,自引:0,他引:1
QingLi Zhang XueZheng Shi Biao Huang DongSheng Yu I. Öborn K. Blombäck HongJie Wang T.F. Pagella F.L. Sinclair 《CATENA》2007
Detailed surveys of surface water in two contrasting peri-urban areas in the Yangtze River Delta region of China were conducted to determine the distribution of heavy metals, nitrogen (N) and phosphorus (P) as well as the speciation of N and P. A factory-based (FB) area was compared with a vegetable-based (VB) area during the dry season. The concentrations of heavy metals in the surface water in the FB area were higher than those in the VB area, suggesting modest contamination of surface water with Zn, Cu, Cr and Pb but not Cd, from discharge of factory effluent in the FB area but not the VB area. Although total N (TN) and total P (TP) levels in the surface water were high in both areas, the surface water in the VB area had significantly higher levels of nitrate N (NO3–N), organic N (ON) and TN than those in the FB area. In both areas, the levels of water-soluble P (WP), organic P (OP) and TP were high in the river water that received municipal wastewater. The distribution of N and P species throughout the surface water system indicated that the NO3–N and ON mainly came from vegetable fields, while ammonium N (NH4–N), WP and OP were mainly from municipal wastewater. Treatment of municipal wastewater prior to discharge to reduce N and P by purification is recommended together with research and extension to develop more efficient use of N and P fertilizer by vegetable farmers. 相似文献
79.
S. M. Contreras-Ramos E. M. Escamilla-Silva L. Dendooven 《Biology and Fertility of Soils》2005,41(3):190-198
Biosolids, mainly from textile industries and the rest from households, were vermicomposted with Eisenia fetida, cow manure and oat straw for 2 months at three different moisture contents (60%, 70% and 80% dry weight base) in triplicate to reduce pathogens and toxic organic compounds, and to find the best medium for growth of E. fetida. The vermicompost with the best stability and maturity and a weight loss of 18% was obtained with 1,800 g biosolid, no straw and 800 g manure at 70% water content. This vermicompost had the following properties: pH 7.9; organic C content of 163 g kg–1; an electrolytic conductivity of 11 mS cm–1; a humic-to-fulvic acid ratio of 0.5 (HA/FA); total N content of 9 g kg–1; water soluble C (Cw) less than 0.5%; cation exchange capacity of 41 cmolc kg–1; a respiration rate of 188 mg CO2-C kg–1 compost-C day–1; a NO3–/CO2 ratio greater than 8; and a NH4+/NO3– ratio lower than 0.16. The vermicompost gave a germination index for cress (Lepidium sativum) of 80% after 2 months while the earthworm production increased 1.2-fold and volatile solids decreased five times. In addition, the vermicompost contained less than 3 CFU g–1Salmonella spp., no fecal coliforms and Shigella spp. and no eggs of helminths. Concentration of sodium was 152 mg kg–1 dry compost, while concentrations of chromium, copper, zinc and lead were below the limits established by the USEPA. 相似文献
80.
重庆市蔬菜地土壤重金属特征研究 总被引:8,自引:1,他引:8
研究结果表明重庆市蔬菜地0~20cm和20~40cm土层土壤重金属Cr、Ni、Cu、Zn、As、Pb含量无显著差异,Cd、Hg含量差异显著。不同土壤类型平均重金属含量和变异系数差异均较小。城郊区、工矿区和一般农区重金属Ni、Cu、Zn、As、Pb含量及阳离子代换量无显著差异。不同土壤类型和不同区域重金属间均具较强相关性,重金属Cu、Ni、Cr间具有较强伴生关系。重庆市蔬菜地土壤重金属Cd污染较重。 相似文献