Exposure of Gas Station Attendants to Methylcyclopentadienyl Manganese Tricarbonyl (MMT) Used in Gasoline

Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organic derivative of manganese (Mn) used in Canada as an antiknock agent and octane enhancer in gasoline. In a recent study, we measured the atmospheric concentrations of MMT at selected outdoor sites in Montreal. Results ranged from 0.18 to 25 ng m^-3 (expressed as Mn) and do not reflect personal exposure levels. The highest values were obtained at a gas station (mean of 12 ng m^-3). By extension, evaluation of the personal exposure of gas station attendants constitutes a promising area of research. In an earlier study, the sampling method used allowed the possibility that the samples could have included ultra-fine particles, which may have passed through the filters used, and the chemical analysis used (neutron activation) did not discriminate between MMT and other Mn compounds. The present study aims to validate an improved sampling method and to assess personal exposure of gas station attendants to MMT. The MMT recovery of the new sampling method was found to be 91.6%. The exposure of 13 gas station attendants was measured on 1 to 6 occasions each (n = 32). They were working in two busy gas stations located in Montreal and they were asked to wear a portable pump for 2 hr. The air was pumped through two tubes in series filled with the adsorbent Tenax TA?, with glass wool plugs at both ends. The tubes were wrapped in aluminum foil and samples were analyzed for MMT by gas chromatograph-atomic emission detector (GC-AED). Results vary between 0.3 and 11.4 ng m^-3, with a mean of 3.9 ng m^-3. The highest values obtained in the first study may be due to the analytical techniques used previously, where detection of different Mn compounds other than MMT was possible. Since GC-AED is specific to MMT in the samples, the MMT found in air raises doubt as to the time required for the photodegradation of MMT.

     

Manganese contamination in Montreal in relation with traffic density

Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organic derivative of manganese used as an additive in unleaded gasoline in Canada since 1977. Moreover, Canada is the only country in the world to have authorized the replacement of lead alkyls by MMT in gasoline. The purpose of the present study is to assess the importance of air contamination by Mn in relation to other air pollutants (gaseous and particulates), meteorological variables and traffic density. The concentration of both the gaseous (O₃, CO, NO, NO₂, SO₂) and the particulate pollutants (Mn, Pb, NO^? ₃, SO^?? ₄, TSP) had been measured by the Montreal Urban Community in 1990 at seven sampling stations located in high traffic and low traffic density areas. Data on the meteorological conditions during that same period were also used. Non-parametric correlation, ANOVA and discriminant analyses were used to compare gaseous and particulate pollutants found between both levels of traffic density. In almost 50% of the daily air samples measured in 1990, the Mn concentrations are higher than the urban background level estimated at 0.04 μg m^?3 and the variations of Mn concentrations are significantly correlated in time with traffic density. Moreover, Mn and TSP discriminate the best high and low traffic density areas. No significant differences have been observed between Pb, O₃ and SO₂ concentrations in both areas. These results should not be interpreted in terms of potential health effects since it is presently impossible to determine the fate of the Mn in the environment and its importance in terms of human exposure.     

Manganese Biogeochemistry in a Central Czech Republic Catchment

Mn biogeochemistry was studied from 1994 to 2003 in a small forested catchment in the central Czech Republic using the watershed mass balance approach together with measurements of internal stores and fluxes. Mn inputs in bulk deposition were relatively constant during a period of sharply decreasing acidic deposition, suggesting that the Mn source was terrestrial, and not from fossil fuel combustion. Mn inputs in bulk deposition and Mn supplied by weathering each averaged 13 mg m^?2 year^?1 (26 mg m^?2 year^?1 total input), whereas Mn export in streamwater and groundwater averaged 43 mg m^?2 year^?1. Thus an additional Mn source is needed to account for 17 mg m^?2 year^?1. Internal fluxes and pools of Mn were significantly greater than annual inputs and outputs. Throughfall Mn flux was 70 mg m^?2 year^?1, litterfall Mn flux was 103 mg m^?2 year^?1, and Mn net uptake by vegetation was 62 mg m^?2 year^?1. Large pools of labile or potentially labile Mn were present in biomass and surficial soil horizons. Small leakages from these large pools likely supply the additional Mn needed to close the watershed mass balance. This leakage may reflect an adjustment of the ecosystem to recent changes in atmospheric acidity.     

Response of blue spruce (Picea pungens) to manganese pollution from MMT

The use of methylcyclopentadienyl manganese tricarbonyl (MMT) in unleaded gasoline has become a source of manganese (Mn) contamination to which urban ecosystems are exposed. The potential of coniferous trees as spatial and chronological indicators of Mn pollutation was investigated. Manganese concentrations in xylem from blue spruce (Picea pungens) growing near (high-exposure site) and far (low-exposure site) from a road were measured as a function of the year of wood formation. Exchangeable Mn content, which is the soil fraction most readily available for uptake by trees, was also measured in the soils of both sectors. The results of the soil analysis show that exchangeable Mn concentrations are about 10 times higher in soils exposed to contamination (p<0.0005), in=" comparison=" with=" the=" concentrations=" found=" in=" soils=" weakly=" exposed.=" however,=" the=" mn=" concentrations=" in=" the=" trees=" near=" the=" road=" were=" not=" significantly=" different=" from=" those=" in=" the=" reference=" trees=" (p=">0.05). Therefore, it appears that blue spruce is not sensitive to soil Mn contamination arising from the use of MMT in gasoline.     

Emission rates and physico-chemical characteristics of Mn particles emitted by vehicles using Methylcyclopentadienyl Manganese Tricarbonyl (MMT) as an octane improver

Since 1990, methylcyclopentadienyl manganese tricarbonyl (MMT) has been added to all gasoline in Canada as an antiknock agent. The objective of this study is to determine the percentage of manganese emitted by different types of automobiles and to evaluate the size and chemical characteristics of the Mn-containing particles. Nine vehicles with different mileage and engine capacity were tested using standard procedures for urban and highway driving cycles. One ran on gasoline without MMT and served as a control. The particles were collected using two separate systems: a trapping device consisting of a water tank connected to the tailpipe and a pumping device linked to a cassette containing Teflon filters. Water samples were analyzed by neutron activation to determine the amount of Mn emitted at the tailpipe for each test. Teflon filters were analyzed by electron microscopy to determine the size and the chemical characteristics of the particles. The amount of manganese emitted from the tailpipe varied from 4 to 41% of the manganese consumed, depending on the driving cycle and the vehicle. For the urban cycle, the emission rate was positively correlated with previous mileage. Almost all particles found on teflon filters had a size less than 5 μm. They appeared to be mainly Mn oxides but other elements could be masked by the gold and paladium peaks.     

Evaluation of Pollutant Emissions Related to the Use of MMT in Gasoline

Since 1976, methylcyclopentadienyl manganese tricarbonyl (MMT), an organic derivative of Mn, has been used in Canada as an anti-knock agent in unleaded gasoline. In a preliminary evaluation of the contribution of MMT to urban air pollution, the CO and NO_x emissions of 10 vehicles each having traveled less than 17 000 miles were sampled. Five of these vehicles were filled with MMT-free gasoline and the remaining five with MMT-added gasoline. The emissions were evaluated according to the Federal Test Procedure which simulates urban and highway driving cycles. As for the NO_x and CO analysis, it was carried out by means of infrared spectrometry, while the concentration of Mn in the gasoline was determined through neutron activation. Overall, the amount of CO emitted by the vehicles using MMT-added gasoline was 1.48 g mile^-1 ± 1.77. The amount emitted by the vehicles using clear (MMT-free) gasoline was 0.74 g mile^-1 ± 0.88. As for the NO_x emission level, it was 0.20 g mile^-1 ± 0.15 for the vehicles using MMT-added gasoline vs 0.17 g mile^-1 ± 0.18 for the vehicles using clear gasoline. However, probably due to the small sample size and the very high level of emission of one of the vehicles using MMT-added gasoline, these differences are not statistically significant. Further studies should take into account variables such as the driving history and the representativity of the fleet of vehicles tested.     

基于MODIS和AERONET的气溶胶地表直接辐射效应评价

气候变化背景下进一步开展高污染地区气溶胶直接辐射效应的研究,对于该地区的大气环境监测、气候变化评估以及农业生产布局等具有重要意义。利用全球气溶胶监测网（AERONET）多年观测资料以及MODIS地表反照率数据,借助6S（Second Simulation of a Satellite Signal in the Solar Spectrum）辐射传输模式,定量评估2001年1月−2016年12月中国AERONET北京、香河和太湖3个典型高污染站点多年晴空条件下的气溶胶直接辐射效应。结果表明：（1）各个高污染站点气溶胶PM2.5质量浓度季节变化特征差异明显,秋冬污染较为严重,其中高值主要集中在1月、2月、11月和12月;（2）与无气溶胶影响相比,气溶胶致使各站点地表直接辐射年际变化较明显。在气溶胶影响下,北京、香河和太湖3个站点2001−2016年地表日平均直接辐射年际变化较明显,均呈波动增加趋势,且香河站日平均直接辐射增加最大（621.14W·m⁻²）,太湖站次之（743.29W·m⁻²）,北京站最小（488.14W·m⁻²）。（3）气溶胶影响下各站点地表直接辐射明显降低,且气溶胶对各站点影响差异较大。2001−2016年,北京、太湖和香河站年平均地表直接辐射分别降低32.29%、24.01%和15.07%。其中,气溶胶对北京站的地表直接辐射影响最大,香河站最小。（4）近15a来,北京、香河和太湖3个站点气溶胶地表辐射效应均呈现增加趋势。     

Natural and Anthropogenic Contributions to PM10 and PM2.5 in an Urban Area in the Western Mediterranean Coast

Source apportionment analysis was used to identify the factors contributing to atmospheric pollution at a monitoring location in the Southeast of Spain, a well documented area with an arid climate and high insolation favouring two sources of particulate matter: secondary transformation in the atmosphere and resuspension of crustal dry soils to the air. These conditions are further complicated by numerous industrial facilities in the area of the historical city of Cartagena. This paper describes the air quality of an area which includes a zinc metallurgical industry, a petrochemical factory, an oil power station, a shipyard and natural phenomena including African dust transport and resuspension of regional and/or local crustal materials. Major and trace element concentrations in PM10 and PM2.5 were determined at two monitoring stations in Cartagena (one PM10 sampler located at a traffic hotspot and the PM2.5 sampler at a suburban station), during 2004 and 2005. Results showed that in the PM10 fraction, the zinc metallurgical activity was linked to high levels of Cd, Zn and Pb; shipyard emission was associated with high levels of Cr and Ni; and high Ni and V levels were associated with the secondary aerosol indicating the contribution from oil combustion (oil-fired power station or petrochemical facilities). In the PM2.5 size fraction, the zinc source is defined by Zn and Pb; V, Ni and As appear with the oil combustion emissions. In contrast to PM10, shipyard activity is not consistently defined. Consistent sources found in both size fractions include crustal materials and traffic emissions.     

Evolution, Sources and Distribution of Mineral Particles and Amorphous Phase of Atmospheric Aerosol in An Industrial and Mediterranean Coastal Area

The aim of this work is to propose a methodology that helps to learn about the distribution of different types of solid compounds in atmospheric aerosol, collected in an industrial area located in a Mediterranean basin that produces mineral raw materials. The work is developed from TSP samples collected daily in an open area near a ceramic production facility with a High Volume TSP sampler. The sampler permits the collection of sufficient daily quantities of particulate sample for subsequent X-ray diffraction characterisation and quantification. The results have shown that atmospheric aerosol in the area are dominated by particles coming from combustion processes, mainly vehicular traffic, and dust emissions originating when raw materials are transferred and treated. Combustion particles present a seasonal evolution. Mineral particles are mainly dependent upon weekly industrial activity and their contents suffer high increases during periods of atmospheric particle accumulation which are produced when certain meteorological conditions exist. Data have also shown an approximation of the particle distribution in aerosol from different source origins (vehicular traffic, dust emissions, secondary formation, marine aerosols). During days with intermediate pollution levels (which suppose 60% of the total) combustion particles compromise around 55 to 60% of the TSP while mineral particles coming from industrial dust emissions make up 20% of the TSP. In time intervals of atmospheric particulate accumulation these particle levels in the air can reach the legislated guideline values. During these episodes, mineral contents coming mainly from dust emissions compromise more than the 50% of the aerosol.     

2000年以来长江流域水沙情势变化及成因分析

基于长江干流屏山、朱沱、寸滩、宜昌、汉口、大通6个水文站的实测水沙资料,采用线性回归、Mann-Kendall趋势分析和突变检验、Sen’s估计以及累积距平法,分析长江干流2001—2018年径流输沙年际、年内变化趋势及其成因。结果表明:2000年以来长江干流各水文站年输沙量较2000年前显著降低,降幅高于56%;年径流量下降不明显,降幅低于8%;输沙量变异程度高于径流量变异程度。2001—2018年,长江流域平均月径流量为718108 m^3,平均月输沙量为1247104 t,且主要分布在6—9月。趋势分析显示,年降雨量和径流量变化趋势不明显,年输沙量呈极显著减小趋势,其中屏山、朱沱、寸滩站分别在2010年和2012年左右发生突变,宜昌、汉口、大通站在2005年发生突变;屏山站月径流量无明显变化趋势,大通站1月径流量显著增加,其他4个水文站均在1—4月呈显著增加趋势;各水文站月输沙量主要在6—10月呈显著减少趋势。水利工程和水土保持生态环境建设等人类活动是长江流域输沙减少的主要原因。     

Particle-associated Polycyclic Aromatic Hydrocarbons in the Atmosphere of Hong Kong

Polycyclic aromatic hydrocarbons (PAHs) in total suspended particulates (TSP) collected at six rural and urban stations in Hong Kong from 1993–1995 using high volume air samplers were identified using GC-MS (gas chromatography-mass spectrometry). The results showed that the PAHs exhibited distinct spatial and seasonal variability. The total PAH content (ΣPAH) in the samples ranged from 0.41 to 48 ng m^-3. The unsubstituted analogs are the characteristic products of high temperature combustion processes. The highest average ΣPAH was measured at the street-level station in Mong Kok indicating that vehicles were high PAHs contributors. The rural station at Hok Tsui exhibited the lowest PAH level, however; influences of city plumes could be seen when northerly or northeasterly winds prevailed in the winter. All stations experienced the highest loading of PAHs in autumn and the lowest in summer; the former was 2.8 times greater than the latter. This seasonal variability is due to the Asian monsoon system, precipitation, micrometeorology, and the rate of photodegradation. In summer, Hong Kong experiences relatively clean oceanic air and high rates of precipitation and photodegradation, while upon the onset of the winter monsoon, local air mass is replaced by polluted air streams from the Asian continent. Benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(e)pyrene, indeno(1,2,3-cd)pyrene and benzo(ghi)perylene were the dominant species in the samples. The PAH distribution patterns at different stations were similar within each season. However, seasonal variations existed. For example, phenanthrene contributed up to 14% of the total PAH in summer, while the dominance of benzo(b)fluoranthene, benzo(k)fluoranthene was more significant in autumn and winter.     

Atmospheric Emission Inventory for Natural and Anthropogenic Sources and Spatial Emission Mapping for the Greater Athens Area

A spatially, temporally and chemically resolved emission inventory for particulate matter and gaseous species from anthropogenic and natural sources was created for the Greater Athens Area (GAA; base year, 2007). Anthropogenic sources considered in this study include combustion (industrial, non-industrial, commercial and residential), industrial production, transportation, agriculture, waste treatment and solvent use. The annual gaseous pollutants (????x, SOx, non-methane volatile organic compounds (NMVOCs), CO and ????₃) and particulate matter (PM_2.5 and PM_2.5?C10) emissions were derived from the UNECE/EMEP database for most source sectors (SNAP 1?C9; 50?×?50 km²) and their spatial resolution was increased using surrogate spatial datasets (land cover, population density, location and emissions of large point sources, emission weighting factors for the GAA; 1?×?1 km²). The emissions were then temporally disaggregated in order to provide hourly emissions for atmospheric pollution modelling using monthly, daily and hourly disintegration coefficients, and additionally the chemical speciation of size-segregated particles and NMVOCs emissions was performed. Emissions from agriculture (SNAP 10) and natural emissions of particulate matter from the soil (by wind erosion) and the sea surface and of biogenic gaseous pollutants from vegetation were also estimated. During 2007 the anthropogenic emissions of CO, SOx, NOx, NMVOCs, NH₃, PM_2.5 and PM_2.5?C10 from the GAA were 151,150, 57,086, 68,008, 38,270, 2,219, 9,026 and 3,896 Mg, respectively. It was found that road transport was the major source for CO (73.3%), NMVOCs (31.6%) and NOx (35.3%) emissions in the area. Another important source for NOx emissions was other mobile sources and machinery (23.1%). Combustion for energy production and transformation industries was the major source for SOx (38.5%), industrial combustion for anthropogenic PM_2.5?C10 emissions (59.5%), whereas non-industrial combustion was the major source of PM_2.5 emissions (49.6%). Agriculture was the primary NH₃ source in the area (72.1%). Natural vegetation was found to be an important source of VOCs in the area which accounted for approximately the 5% of total VOCs emitted from GAA on a typical winter day. The contribution of sea-salt particles to the emissions of PM_2.5 was rather small, whereas the emissions of resuspended dust particles exceeded by far the emissions of PM_2.5 and PM_2.5?C10 from all anthropogenic sources.     

Atmospheric bulk deposition of trace metals to the Seine river Basin, France: concentrations, sources and evolution from 1988 to 2001 in Paris

Concentrations of Cd, Cu, Ni, Pb and Zn were determined in bulk atmospheric deposition collected at five stations in the Seine River basin (France), to evaluate sources and fluxes of atmospheric trace metals. Bulk deposition (wet + dry) was sampled weekly from March 2001 to February 2002 for 4 sites and from March to December 2001 for the last one. The concentrations of the elements in bulk deposition (dissolved + particulate form) followed the order: Zn > Pb > Cu > Ni > Cd. Concentrations of Zn, Pb and Ni were highly correlated with one another, suggesting a common source, related to the combustion of coal and heavy fuel. Metal concentrations in bulk deposition did not exhibit a high degree of temporal variability over the annual cycle and were not obviously related to meteorological parameters (rainfall, wind). Estimates of the total annual direct atmospheric deposition of metals to the Seine Estuary ranged from 16 kg yr^{? 1} for Cd to 5600 kg yr^{? 1} for Zn. Loadings of Cd, Cu and Ni from direct atmospheric inputs were less than 1% of those contributed by the Seine River and loadings of Pb and Zn represented 1.27% and 1.56% of the Seine contribution. Direct atmospheric inputs are negligible compared to fluvial inputs, but the indirect atmospheric deposition to the estuary was not estimated. Based on these results, trace metal concentrations in Paris have decreased by a factor of 4.6 for Zn and by a factor of 50 for Ni from 1988 to 2001. Of particular interest is the continued decrease in bulk deposition of Pb during this period, underlining the impact of policy initiatives concerning the reduction of lead on emissions in France.     

The Morphophysiological Responses of Free-Floating Aquatic Macrophytes to a Supra-optimal Supply of Manganese

Among the many anthropogenic abiotic stresses, manganese (Mn) toxicity has been recognized for its impact on aquatic ecosystems as well as on the biological components of these ecosystems, including aquatic plants. The objective of this study was to determine the Mn accumulation ability of aquatic macrophytes (Azolla caroliniana, Salvinia minima and Spirodela polyrhiza) and evaluate the morphophysiological responses of the species that gather the highest amount of Mn when exposed to a supra-optimal supply of manganese. The experiments were conducted in the laboratory, and the effects of Mn were evaluated based on plant growth; the concentration of total chlorophyll, carotenoids, and anthocyanins; the enzymatic activity of catalase and peroxidase; and leaf anatomy. All of the studied species accumulated Mn in their tissues. Moreover, it was observed that this accumulation was dependent on the concentration of the metal in solution. S. polyrhiza showed higher concentrations of Mn in its tissues (17.062?mg?g^?1 dry weight (DW)), followed by S. minima (4.283?mg?g^?1 DW) and A. caroliniana (1.341?mg?g^?1 DW). Despite the Mn accumulation in all species, S. polyrhiza was the only one selected for further analyses because of its greater ability to accumulate Mn. The high Mn concentration found in tissues of S. polyrhiza suggests that this species has the potential to sequester and accumulate this metal. However, a sensitive response in the plants exposed to higher Mn concentrations (0.4?mM) was observed. The phytotoxicity effects of this accumulation were responsible for a decrease in the plant growth, a reduction in the pigment content (total chlorophyll, carotenoids, and anthocyanins), a low activity of catalase, and the disarrangement of the leaf aerenchyma.     

SWAT模型在粤北连江流域的应用研究

选择粤北连江流域为研究区域,以分布式水文模型SWAT作为模拟工具,对流域内的水文过程进行模拟。利用流域内高道、凤凰山和黄麖塘3个水文站2001—2010年的实测月平均径流量进行敏感性分析和参数率定。以2001—2005年作为校准期,2006—2010年作为验证期,以相对误差（Re）、决定系数（R²）以及Nash-Suttcliffe效率系数（Ens）作为模型适用性的评价指标。校准期3个水文站的月径流量模拟值的相对误差分别是2.72%,5.91%,1.63%,决定系数均大于0.9,Nash-Suttcliffe系数分别为0.97,0.89,0.70,而验证期相对误差分别是2.62%,5.36%,9.32%,决定系数均大于0.9,Nash-Suttcliffe系数分别为0.90,0.69,0.69。各项评价指标均符合精度要求,说明SWAT模型可以用于连江流域的径流模拟。     

Manganese foliar supplementation impacts rice yield in tropical lowlands

Abstract

The aim of this work was to evaluate manganese (Mn) sources and levels effects in irrigated rice production in central Brasil (tropical lowlands of Tocantins state). The experiment was conducted in a 5x5?+?1 factorial scheme, five Mn sources and five levels (0.5; 1.0; 1.5; 2.0; and 2.5?kg ha^?1), applied in induction of tillering of rice plants, plus a control without treatment, and Mn content in leaves (mg kg^?1), number of panicles per area (m²), hundred grains weight (g), intact grains (%), and grain yield (kg ha^?1) were analyzed. Treatments with Mn-carbonate source got the best results and this source at the level of 1.5?kg ha^?1 provided the highest yield: 7,375?kg ha^?1. Higher values were obtained with the application of 1.0 to 1.5?kg ha^?1 of Mn, except for the intact grains where the best means were obtained at 2.5?kg ha^?1.     

Manganese toxicity alleviated by mycorrhizae in soybean

Abstract

Soybean (Glycine max (L.) Merr.) plants nodulated with Bradyrhizobium japonicum. Nitragin strain 61A118, were grown with or without the vesicular‐arbuscular mycorrhizal (VAM) fungus Glomus mosseae (Nicol. Gerd.) Gerd. and Trappe in pot cultures in soil high (40.4 μg/g) in available Mn. Leaves of the nonVAM plants showed severe symptoms of Mn toxicity and had toxic (314 μg/g) concentrations of Mn in the foliage. NonVAM plants had significantly lower dry weights and nodule mass than VAM plants. Concentrations of Mn in the VAM plants were significantly (P<0.05) lower than in the nonVAM plants, and there were no symptoms of Mn toxicity. Both VAM and nonVAM plants had a significant negative correlation between shoot dry mass and leaf Mn concentration. Since levels of Mn increased with increasing VAM‐fungal colonization, we conclude that it was not the VAM condition per se which alleviated Mn toxicity. We suggest that the significantly higher levels of Mn in the leaves (P<0.05) and the roots (P<0.001) of nonVAM plants was due to increased uptake of Mn by the nonVAM plants. This exudation, which are generally observed in nonVAM plants, and to the role of such exudates in solubilizing MnO₂ and chelating the resulting Mn²? for facilitated absorption.     

Compost and phosphorus amendments for stimulating microorganisms and growth of ryegrass in a Ferralsol and a Luvisol

A greenhouse pot experiment was carried out to investigate the effects of different P‐fertilizer application forms (triple superphosphate [TSP], compost + TSP, TSP‐enriched compost) on the growth of ryegrass and the soil microbial biomass. The fertilizers were applied at equivalent doses for all nutrients to a neutral Luvisol in comparison with an acidic Ferralsol. Fertilizer application led to significantly increased contents of microbial biomass C, N, and P. Furthermore, yields of shoot C and root C, and concentrations of P, Ca, Mg, K, Fe, and Mn in shoots and roots were significantly increased. These increases always followed the order TSP < compost + TSP < TSP‐enriched compost. Sole TSP application led only to maximum concentrations of N and S. In the Ferralsol, TSP had only minimal positive effect on the P concentration of the grass shoots. The positive effect of TSP‐enriched compost, i.e., incubating TSP together with compost for 24 h, did not differ between the neutral Luvisol and the acidic Ferralsol, i.e., the effect is independent of the soil type. Consequently, soluble inorganic P fertilizer should generally be mixed into an organic fertilizer before application to soil.     

Manganese reduction and denitrifying enzyme activity in soil microcosms

Abstract

A series of laboratory experiments was conducted to determine if denitrifying enzyme activity (DEA) was related to manganese (Mn) reduction. Reduction of Mn occurred after nitrate (NO₃‐) or nitrous oxide (N₂O) reduction was near completion. Denitrifying enzyme activity was not directly related to Mn reduction. Rather, both DEA and Mn reduction were related to carbon (C) supply. The presence of acetylene tended to decrease the rate of Mn reduction.     

甘肃省古浪县土地利用与社会经济协调度评价

土地利用与社会经济协调度评价对指导区域土地利用和社会经济发展具有重要意义。参照协调度与协调发展度的相关概念,从土地利用与社会经济两个方面建立综合评价指标体系,并构建评价模型,对甘肃省古浪县2000—2008年土地利用与社会经济的相对和绝对协调度及协调发展度进行了定量测算。研究结果表明,古浪县的相对协调度等级变化较大,2001,2002和2006年属于社会经济快速发展型,2003年属于土地利用倒退型,2004—2005,2007—2008年属于土地利用快速发展型;绝对协调度等级较高,2000年属于中级协调,其余年份协调度等级属于优质协调;协调发展度呈现逐年上升趋势,由轻度失调社会经济滞后型上升到了良好协调土地利用滞后型。