臭氧法对酸性嫩黄G溶液的脱色效率和残留物的分析

实验考察了臭氧对酸性嫩黄G色度脱除和其溶液pH值的变化情况,并对降解溶液中的残留物进行定量分析。结果发现,20min时,脱色率达到97.5%;有酸性物质生成并使得溶液的pH值随反应时间的推移下降,pH与脱色率总体变化趋势一致。经反应,分子中的—SO3Na基团大部分生成了SO42-;N并没有氧化成NO2-、NO3-,而是生成其它含N化合物。     

骆驼刺叶绿素荧光特性对不同程度干旱处理的响应

干旱是影响荒漠生态系统植物生长主要因素之一,研究其对干旱区植物叶绿素荧光特性影响有助于为干旱程度变化对干旱区植物生理生态影响的研究提供一定的理论依据.本文选择准噶尔盆地南缘荒漠区典型植物骆驼刺(Alhagi sparsifolia),设置0(对照)、轻度、中度和重度3种干旱程度的处理,研究干旱程度变化对骆驼刺叶绿素荧光...     

Evaluation of aerated biofilter systems for microbial methane oxidation of poor landfill gas

In the long-term, landfills are producing landfill gas (LFG) with low calorific values. Therefore, the utilization of LFG in combined heat and power plants (CHP) is limited to a certain period of time. A feasible method for LFG treatment is microbial CH(4) oxidation. Different materials were tested in actively aerated lab-scale bio-filter systems with a volume of 0.167 m(3). The required oxygen for the microbial CH(4) oxidation was provided through perforated probes, which distributed ambient air into the filter material. Three air input levels were installed along the height of the filter, each of them adjusted to a particular flow rate. During the tests, stable degradation rates of around 28 g/(m(3) h) in a fine-grained compost material were observed at a CH(4) inlet concentration of 30% over a period of 148 days. Compared with passive (not aerated) tests, the CH(4) oxidation rate increased by a factor of 5.5. Therefore, the enhancement of active aeration on the microbial CH(4) oxidation was confirmed. At a O(2)/CH(4) ratio of 2.5, nearly 100% of the CH(4) load was decomposed. By lowering the ratio from 2.5 to 2, the efficiency fell to values from 88% to 92%. By varying the distribution to the three air input levels, the CH(4) oxidation process was spread more evenly over the filter volume.     

Nitrogen and phosphorus status of soils and trophic state of lakes associated with forage-based beef cattle operations in Florida

Forage-based livestock systems have been implicated as major contributors to deteriorating water quality, particularly for phosphorus (P) from commercial fertilizers and manures affecting surface and ground water quality. Little information exists regarding possible magnitudes of nutrient losses from pastures that are managed for both grazing and hay production and how these might impact adjacent bodies of water. We examined the changes that have occurred in soil fertility levels of rhizoma peanut (Arachis glabrata Benth.)-based beef cattle pastures (n = 4) in Florida from 1988 to 2002. These pastures were managed for grazing in spring followed by haying in late summer and were fertilized annually with P (39 kg P2O5 ha(-1)) and K (68 kg K2O ha(-1)). Additionally, we investigated trends in water quality parameters and trophic state index (TSI) of lakes (n = 3) associated with beef cattle operations from 1993 to 2002. Overall, there was no spatial or temporal buildup of soil P and other crop nutrients despite the annual application of fertilizers and daily in-field loading of animal waste. In fact, soil fertility levels showed a declining trend for crop nutrient levels, especially soil P (y = 146.57 - 8.14 x year; r2= 0.75), even though the fields had a history of P fertilization and the cattle were rotated into the legume fields. Our results indicate that when nutrients are not applied in excess, cow-calf systems are slight exporters of P, K, Ca, and Mg through removal of cut hay. Water quality in lakes associated with cattle production was "good" (30-46 TSI) based on the Florida Water Quality Standard. These findings indicate that properly managed livestock operations may not be major contributors to excess loads of nutrients (especially P) in surface water.     

Forest carbon management in the United States: 1600-2100

This paper reviews the effects of past forest management on carbon stocks in the United States, and the challenges for managing forest carbon resources in the 21st century. Forests in the United States were in approximate carbon balance with the atmosphere from 1600-1800. Utilization and land clearing caused a large pulse of forest carbon emissions during the 19th century, followed by regrowth and net forest carbon sequestration in the 20th century. Recent data and knowledge of the general behavior of forests after disturbance suggest that the rate of forest carbon sequestration is declining. A goal of an additional 100 to 200 Tg C/yr of forest carbon sequestration is achievable, but would require investment in inventory and monitoring, development of technology and practices, and assistance for land managers.     

Experimental oxidative dissolution of sphalerite in the Aznalcollar sludge and other pyritic matrices

After the collapse on 25 Apr. 1998 of the Aznalcóllar mine tailings dike in southwestern Spain, 45 km2 of the Guadiamar valley were covered by a pyritic sludge containing up to 2% sphalerite (ZnS). Later, the sludge was mechanically removed and calcium carbonate was plowed into the soil to immobilize heavy metals. By June 2001 more than 60% of the sulfides in the residual sludge had oxidized and soil Zn contents reached locally phytotoxic levels. Therefore, the oxidative dissolution of sphalerite in the sludge and other pyritic samples was examined. Flow-through oxidation experiments showed that: (i) about 5 and 17% of the sludge Fe and Zn were in soluble form, respectively, because the sludge sample had been partly oxidized in the field; (ii) the oxidation rates of the residual pyrite and sphalerite were similar; (iii) the overall sulfide oxidation rate was relatively unaffected by the addition of calcite; and (iv) poorly crystalline Fe (hydr)oxides containing Zn in occluded form and Zn (hydroxi)carbonates were formed in the presence of calcite. The rate of oxidation of reference sphalerite greatly increased when it was incorporated in the sludge or in a reference pyrite matrix. This enhancement was due to galvanic interaction because pyrite oxidation was depressed in the presence of sphalerite. Oxidation by Fe3+ ions was less important because the oxidation rates of native sphalerite were not greater at low than at high pH. The fast oxidation rate of sphalerite in the Aznalcóllar sludge indicates a need for quick adoption of remediation measures in similar accidents elsewhere. The use of calcite amendments has little influence on the oxidation rate but does result in the accumulation of Zn in relatively insoluble forms.     

Behavior of an aerated submerged fixed-film reactor (ASFFR) under simultaneous organic and ammonium loading

The performance of an aerated submerged fixed-film reactor (ASFFR) under simultaneous organic and ammonium loading and its effect on nitrification was studied. Organic loadings varied in the range of 1.93 to 5.29 g chemical oxygen demand (COD) m-2 d-1 and NH4-N loadings were in the range of 116 to 318 mg NH4-N m-2 d-1. Increments of loading rates were obtained both by increasing the flow rate and increasing the influent substrate in individual pilot runs. Results showed that with organic loading rates up to 3.97 g COD m-2 d-1, complete nitrification was achievable. Although high organic loading such as 5.29 g COD m-2 d-1 could cause nitrification to stop, shifting to lower organic loadings made nitrification start and set rapidly to its previous steady-state concentrations. Comparison of results showed that in the ASFFR, nitrification would be severely affected by an organic loading rate of 5.29 g COD m-2 d-1 by increasing either the flow or the influent substrate. It should be noted that the average value of dissolved oxygen was 3.4 mg L-1 with an air supply of 15 L min-1, and there was no indication of oxygen limitation. The results of this study show the flexibility of ASFFRs under changing organic loads. Furthermore, for achieving complete nitrification and optimum application of these reactors for protecting receiving water from the environmental hazards of ammonium, the maximum organic loading that would present complete nitrification should be considered.     

Spatiotemporal evolution of soil pH and zinc after the Aznalcollar mine spill

The residual pollution after the Aznalcóllar (southwestern Spain) pyrite mine spill is still a threat due to the continuing oxidation of sulfuric minerals. The objective of this paper was to analyze the combined effect of pyrite oxidation, sugar beet foam applications, and meteorological conditions on the spatiotemporal evolution of the pH and EDTA-extractable Zn concentration, using non co-located data from 11 sampling dates between June 1999 and March 2002. Median pH values ranged from 4.4 at the beginning of the monitoring period to 7.6 at the end, although values near 2.5 were observed throughout the entire period, despite of two sugar beet foam (SBF) applications. Zinc distributions were positively skewed and median concentrations ranged from 17 to 94 mg kg(-1). The inverse relationship between pH and Zn became weaker toward the end of the monitoring period as a consequence of the precipitation and posterior dissolution of newly formed minerals from the reaction products of the pyrite oxidation. Normal score maps showed that after the SBF applications only 0.5% of the monitored area was below the pH = 4 threshold, while on other dates up to one-third of the area remained below this value. The better performance of the second SBF application could be explained in terms of pyrite oxidation pathways and environmental conditions. From this analysis, with data obtained under uncontrolled field conditions, it is concluded that SBF should be applied before or during the wet and cold season to alleviate acidification, caused by the oxidation of pyrite or other sulfuric minerals.     

Decommissioning of offshore oil and gas facilities: a comparative assessment of different scenarios

A material and energy flow analysis, with corresponding financial flows, was carried out for different decommissioning scenarios for the different elements of an offshore oil and gas structure. A comparative assessment was made of the non-financial (especially environmental) outcomes of the different scenarios, with the reference scenario being to leave all structures in situ, while other scenarios envisaged leaving them on the seabed or removing them to shore for recycling and disposal. The costs of each scenario, when compared with the reference scenario, give an implicit valuation of the non-financial outcomes (e.g. environmental improvements), should that scenario be adopted by society. The paper concludes that it is not clear that the removal of the topsides and jackets of large steel structures to shore, as currently required by regulations, is environmentally justified; that concrete structures should certainly be left in place; and that leaving footings, cuttings and pipelines in place, with subsequent monitoring, would also be justified unless very large values were placed by society on a clear seabed and trawling access.