Long-term impact of chronosequential land use change on soil carbon stocks on a Swedish farm

Agricultural practices and land use significantly influence soil carbon storage. The processes that are affected by land use and management are generally understood, but uncertainties in projections are high. In this paper, we investigate the long-term effects of chronosequential land use change from grassland to cropland and vice versa on soil carbon stock dynamics in four fields on a Swedish farm. Between 1850 and 1920, three of the fields were converted from grassland into cropland, and one was converted back to grassland in 1971. The fourth (control) field is a grassland that has never been ploughed. In 1937, the four fields were sampled at 111 points in a regular grid (25 or 50 m) and the dried soil samples were stored at our Department. In 1971 and 2002, the original grid points were revisited and re-sampled. Land use changes affected the soil C stock significantly. In 1937, carbon stocks were significantly smaller in the arable fields than in the grassland soil. In the field that was converted from arable back to grassland, soil C increased significantly at an average rate of about 0.4 Mg ha⁻¹ year⁻¹. A soil C balance model (ICBM) driven by standard meteorological data and soil carbon input estimated from yield records described soil carbon dynamics reasonably well, although the range of simulated relative changes in C stocks between 1937 and 2002 in the four fields (from −7.4 to +8.8%) was narrower than those measured (from −19.5 to +16.5%). There are only few long-term studies in Northern Europe available for quantifying the effect of land use change on soil carbon stocks and the results presented here are therefore useful for improving predictions of changes in soil carbon driven by land use change.     

Dynamics in input and output coefficients for land use studies: a case study for nitrogen in crop rotations

Increasingly, model-based approaches play a role in the design and development of new land use systems. Simulation modeling may play a role in the generation of land use systems for land units, and optimization modeling (e.g. linear programming – LP) may be used in the upscaling to farm and region. In the quantification of new land use systems for land units, often equilibrium conditions with respect to soil resources are assumed, following a so-called target-oriented approach. This facilitates ex ante computation of inputs and emissions of nutrients and allows their use in static optimization models based on LP. The condition of equilibrium in soil resources is often not met, nor is it the ultimate aim. Hence, the dynamics in new systems are insufficiently dealt with. This paper presents an approach for the design of land use systems (crop rotations) and their quantification in terms of input and output coefficients, using particular yields and dynamics in soil resources as targets. Interactions between N input and output of succeeding crops are explicitly taken into account. A simple N-balance model is used describing major processes affecting soil N-dynamics. For the Koutiala region in Mali five crop rotations are evaluated that differ in target crop yield, crop choice, crop residue management and external N source. Modeled crop rotations aiming at high yields, in combination with incorporation of crop residues and legumes, result in depletion of soil N stock. Only in crop rotations aiming at high yields and with incorporation of crop residues combined with a supply of large quantities of animal manure, soil N depletion can be prevented. Four approaches are presented of how to use the dynamic input–output coefficients of these systems in land use studies using LP: (i) use of average coefficients, (ii) use of discounted coefficients, (iii) use of pessimistic estimates of coefficients in an optimization of the land use allocation followed by a recalculation of the objective values for the optimized land use with optimistic coefficients, and (iv) a combined use of systems characteristics, i.e. cumulative N-inputs of land use systems over the time horizon and the magnitude of the soil N pool at the end of the time horizon, which can be used as filters for land use systems. Though none of the approaches completely captures the dynamics in input–output coefficients, they enable a well-founded consideration of the consequences of dynamics in, for instance, soil N stocks in static optimization approaches for farm and regional studies.     

Soil organic carbon stocks in soil aggregates under different land use systems in Nepal

We investigated the soil organic carbon (SOC) associated with various aggregate size fractions in soil profiles under different land uses. Bulk soil samples were collected from incremental soil depths (0–10, 10–20, 20–40, 40–60, 60–80 and 80–100 cm) from sites with the four dominant land use types [forest, grazing land, irrigated rice in level terraces (Khet) and upland maize-millet in sloping terraces (Bari)] of the Mardi watershed (area 144 km²), Nepal. The bulk soil was separated into five aggregate size fractions and the associated SOC contents were determined. Soil physical parameters necessary for estimating the soil SOC stock such as bulk density, stone and gravel content, and SOC content, were also measured for each soil depth. The SOC stock (mean ± SE, kg C m^–2) in the topsoil (0–10 cm) was higher in grazing land soil (3.4 ± 0.1) compared to forest soil (1.4 ± 0.2) and cultivated soil [Bari (2.0 ± 0.2) and Khet (1.2 ± 0.2)]. Forest and grazing lands had similar SOC contents, but the higher content of gravel and stone in forest soil resulted in a lower estimate of the SOC stock per unit area. The total SOC stock in the soil profile (to 1 m depth) over the entire watershed was estimated to be 721470 TC (tonnes of carbon). Its distribution was 52, 30, 11 and 7% in forestland, Bari, grazing land and Khet, respectively. The estimated depth wise distribution of SOC stock for 1 m soil depth in the entire watershed was 28, 22, 28 and 22% in the 0–10, 10–20, 20–40, and > 40 cm soil depths, respectively. There was a net loss of SOC stock (0–40 cm soil depth) of 29%, due to internal trading of land uses in the period from 1978 to 1996. Macro aggregates (> 1 mm) were found to be the dominant size in Bari and grazing land, whereas in forest and Khet soil micro aggregates (< 1 mm) dominated. Micro aggregates of size < 0.25 mm had a higher SOC concentration than aggregates of 0.25–0.5 mm, regardless of the depth or land uses and they may therefore contribute to soil C sequestration.     

Energetic and exergetic analysis of a triple-effect distiller driven by solar energy

This paper relates to the energetic and exergetic analysis of single-, double- and triple-effect distiller driven by solar energy. Energetic analysis makes it possible to define an applicable zone of operation according to the following criteria: water rejection limit to 50%, maximum salinity limit to 5.5%, and minimum energy consumption. This analysis also makes it possible to quantify energies: energy necessary for the vapour condensation and the power consumption per unit mass of pure water. Exergetic analysis makes it possible to show that the most significant exergy losses are condenser losses and water alimentation losses and that the condenser losses decrease with the number of effects. The exergetic efficiencies have also been found. They are located between 19 and 26% for a triple-effect system, between 17 and 20% for a double-effect system, and less than 4% for the single-effect system. Consequently, it seems interesting to implement a double- or triple-effect system.     

能源化工产业节能减排新模式

简述了陕北地区能源化工产业的现状,详细介绍了延长石油实施多种资源综合利用及二氧化碳的捕获、利用与封存(CCUS)产业的发展情况,重点介绍了靖边项目在提高资源利用率和节能减排方面的优势。对能源化工产业节能减排新模式进行了探索,走经济建设和环境保护协调发展的产业道路。     

不对称催化及其在精细化工中的应用

综述了不对称催化的进展及其在精细化工中的应用情况。     

Land use impact on nitrogen discharge by stream: a case study in subtropical hilly region of China

As a crucial factor of water eutrophication, nitrogen (N) discharge by agricultural non-point sources (NPS) has become a worldwide concern, and so has its relationship to land use. This study was aimed at the quantitative relationships between N discharge by stream and land use. It was conducted in the Meicun watershed of Xuancheng County, Anhui Province, in the subtropical low hilly area of China. The study integrated dynamic monitoring of nutrient discharge by stream water and Geographic Information Systems (GIS) analysis of land use of the watershed. Results showed that NO₃⁻-N discharge ranged between 50 and 60% of the total nitrogen (T-N) and was 2.5–3.0 times as much as NH₄⁺-N. There was a significant difference between forested and mixed sub-watersheds for NH₄⁺-N, NO₃⁻-N and T-N concentrations. Significant correlations existed between NH₄⁺-N, NO₃⁻-N and T-N concentrations in stream water and the area percentages of forest and paddy fields. The study found that the discharges of NH₄⁺-N, NO₃⁻-N and T-N decreased exponentially with forest area increase, but a steep decline for NO₃⁻-N and T-N seemed to occur when the forest percentage surpassed 70% and then there was almost no change. Similarly, the discharges of NH₄⁺-N, NO₃⁻-N and T-N increased exponentially with the paddy fields increase, but a steep augmentation occurred for NO₃⁻-N and T-N when the paddy percentage surpassed 20% and then it remained at a plateau. The study showed that in the subtropical hilly region, paddy fields could increase N discharge due to farming management practices. Thus, primary measures to reduce N in the receiving water body would include a change in farming management and building an ecological interception system for paddy fields.     

Land use change and soil organic carbon dynamics

Historically, soils have lost 40–90 Pg carbon (C) globally through cultivation and disturbance with current rates of C loss due to land use change of about 1.6 ± 0.8 Pg C y⁻¹, mainly in the tropics. Since soils contain more than twice the C found in the atmosphere, loss of C from soils can have a significant effect of atmospheric CO₂ concentration, and thereby on climate. Halting land-use conversion would be an effective mechanism to reduce soil C losses, but with a growing population and changing dietary preferences in the developing world, more land is likely to be required for agriculture. Maximizing the productivity of existing agricultural land and applying best management practices to that land would slow the loss of, or is some cases restore, soil C. There are, however, many barriers to implementing best management practices, the most significant of which in developing countries are driven by poverty. Management practices that also improve food security and profitability are most likely to be adopted. Soil C management needs to considered within a broader framework of sustainable development. Policies to encourage fair trade, reduced subsidies for agriculture in developed countries and less onerous interest on loans and foreign debt would encourage sustainable development, which in turn would encourage the adoption of successful soil C management in developing countries. If soil management is to be used to help address the problem of global warming, priority needs to be given to implementing such policies.     

后石油经济时代中国能源化工的选择

中国面临总能耗和总碳排放的巨大压力,但人均能耗和人均碳排放增长是中国发展的合理诉求.现代社会的交通燃料和多种重要基础化工材料均以石油为主要原料,而石油资源短缺和可持续发展理念要求寻找石油经济的替代模式.本丈对后石油时代能源化工的主要问题,即交通燃料和重要基础化工原料的生产工艺替代,从技术层面探讨了中国能源化工的发展如何面对资源与碳排放的双重挑战.     

空分装置在煤化工生产中的节能降耗和安全运行

从运用行业成熟技术和确保空分设备安全运行2个方面分析了空分装置在煤化工生产中的节能降耗和安全运行,提出了安全运行的方法。     

Methane oxidation in soils with different textures and land use

Intact core samples from soils with different textures and land use were tested for their capacity to oxidise methane. The soil cores were taken from arable land, grassland and forest. It was found that coarse textured soils (6.74–16.38 μg CH₄ m^-2 h^-1) showed a higher methane uptake rate than fine textured soils (4.66–5.34 μg CH₄ m^-2 h^-1). Increasing soil tortuosity was thought to reduce the methane oxidation rate in fine textured soils. The oxidation rate of forest soils (16.32–16.38 μg CH₄ m^-2 h^-1), even with a pH below 4.5, was very pronounced and higher than arable land (11.40–14.47 μg CH₄ m^-2 h^-1) and grassland (6.74–9.30 μg CH₄ m^-2 h^-1). Within the same textural class arable land showed a faster methane uptake rate than grassland. In grassland with a fine texture, even methane production was observed. Nitrogen availability and turnover in these land use systems were thought to cause the different oxidation rates. Decreasing the moisture content slowed down the oxidation rate in all soils. This could be caused by an increased N turnover and a starvation of the methanotrophic bacteria. This revised version was published online in August 2006 with corrections to the Cover Date.     

柠檬酸酯的合成及其在日化工业中的应用

重点综述了柠檬酸酯表面活性剂作为洗涤助剂、化妆品添加剂和食品添加剂等工业中的应用;讨论了柠檬酸酯合成中温度、时问、原料配比（物质的量比）、催化剂种类及用量等因素对产率的影响;特别指出了柠檬酸酯合成中生成的水去除的重要性以及产品的分离和纯化的复杂性;最后提出了柠檬酸酯的合成目前存在的问题、发展方向和应用前景等。     

化学工业中反应器以及容器清洗的最佳用水方案

概述了清洗生产纺织行业辅助产品的反应器和容器中用水的最佳方案。先用空气(约2．2t／a)作第一次清洗,既回收了产品又减少了废水污染负荷;再利用水处理工厂可处理清洗水并重新回用。在清洗反应器时减少了60％的用水量,清洗容器时减少了90％,这些都归因于：1)采用新的生产方案,减少工艺中的清洗环节;2)引入下一步生产中反应器所需的清洁度的概念;3)使用新的容器清洗程序。由于被处理的水量减少,污染负荷降低,意味着只需一个更小的废水处理工厂同时消耗更少的化学产品、减少了以后要处理的污泥量,最终达到合理用水的目的。     

Soil phosphorus stocks and distribution in chemical fractions for long-term sugarcane,pasture, turfgrass,and forest systems in Florida

Phosphorus distribution and stability in soils of the Everglades Agricultural Area (EAA) of south Florida is important because of changing land uses. We investigated the effects of land use on P distribution in the soil profile and between chemical fractions for a histosol of the Florida Everglades. Labile, Fe–Al bound, Ca-bound, humic–fulvic acid, and residual P pools in 0–15, 15–30, and 30–45 cm depths were determined for drained soils planted to sugarcane (Saccharum sp.) for 50 yr, pasture for 100 yr, turfgrass for 60 yr, and forest for 20 yr. The P concentrations of all chemical fractions decreased with depth in the profile, indicating accumulation in surface soil resulting from oxidation and fertilization. Trends in P distribution between chemical fractions were similar between land uses. Labile P comprised less than 1% of total P. Fe–Al bound P averaged 2.9% of the total P for turfgrass and forest, but 11.4 and 9.6% for sugarcane and pasture. Increasing soil disturbance and long-term fertilization increased P allocation to inorganic fractions, as Ca-bound P contained 49% of total P for sugarcane but 28% for other land uses. Total P stocks in the soil profile (0–45 cm) averaged 1,323, 2,005, 2,294, and 2,317 kg P ha⁻¹ for pasture, sugarcane, turfgrass, and forest, respectively. Under current land uses P in organic fractions represents an unstable pool since the soil is prone to oxidation under drained conditions. In contrast, P sequestered in inorganic fractions is more stable under current land uses, thus sugarcane cultivation and incorporation of bedrock CaCO₃ into surface soil by tillage will enhance long-term P sequestration.     

在陕北能源重化工基地发展氯碱工业的分析

分析在陕北能源重化工基地发展氯碱工业在盐、煤炭、电力等方面具有的优势和应着力解决的几个问题,探讨氯碱产业链的发展方向。     

化工节能思索与“九五”目标

指出节约能源是化学工业实现可持续发展的重要条件，评述了“九五”期间化学工业在重点耗能行业合成氨、烧碱、电石等生产过程采取的节能措施及应达到的能耗目标。     

The impact of grassland ploughing on CO2 and N2O emissions in the Netherlands

The contribution of ploughing permanent grassland and leys to emissions of N₂O and CO₂ is not yet well known. In this paper, the contribution of ploughing permanent grassland and leys, including grassland renovation, to CO₂ and N₂O emissions and mitigation options are explored. Land use changes in the Netherlands during 1970–2020 are used as a case study. Three grassland management operations are defined: (i) conversion of permanent grassland to arable land and leys; (ii) rotations of leys with arable crops or bulbs; and (iii) grassland renovation. The Introductory Carbon Balance Model (ICBM) is modified to calculate C and N accumulation and release. Model calibration is based on ICBM parameters, soil organic N data and C to N ratios. IPCC emission factors are used to estimate N₂O-emissions. The model is validated with data from the Rothamsted Park Grass experiments. Conversion of permanent grassland to arable land, a ley arable rotation of 3 years ley and 3 years arable crops, and a ley bulb rotation of 6 years ley and one year bulbs, result in calculated N₂O and CO₂ emissions totalling 250, 150 and 30 ton CO₂-equivalents ha^–1, respectively. Most of this comes from CO₂. Emissions are very high directly after ploughing and decrease slowly over a period of more than 50 years. N₂O emissions in 3/3 ley arable rotation and 6/1 ley bulb rotation are 2.1 and 11.0 ton CO₂-equivalents ha^–1 year^–1, respectively. From each grassland renovation, N₂O emissions amount to 1.8 to 5.5 ton CO₂-equivalents ha^–1. The calculated total annual emissions caused by ploughing in the Netherlands range from 0.5 to 0.65 Mton CO₂-equivalents year^–1. Grassland renovation in spring offers realistic opportunities to lower the N₂O emissions. Developing appropriate combinations of ley, arable crops and bulbs, will reduce the need for conversion of permanent pasture. It will also decrease the rotational losses, due to a decreased proportion of leys in rotations. Also spatial policies are effective in reducing emissions of CO₂ and N₂O. Grassland ploughing contributes significantly to N₂O and CO₂ emissions. The conclusion can be drawn that total N₂O emissions are underestimated, because emissions from grassland ploughing are not taken into account. Specific emission factors and the development of mitigation options are required to account for the emissions and to realise a reduction of emissions due to the changes in grassland ploughing.     

(火积)理论及其在化工过程节能中的应用进展

(火积)和(火积)耗散极值原理的提出,为化工过程系统节能开辟了新的方向。阐述了(火积)的物理意义、(火积)是过程量等(火积)理论的最新研究成果,从(火积)在换热器设计、热力学过程中的不可逆性、换热网络综合等方面的应用情况综述了(火积)理论在化工过程系统节能中的最新应用进展。重点围绕(火积)耗散率与熵产率的异同点比较分析、(火积)耗散极值原理与换热网络综合结合等方面,阐述了(火积)理论的科学性。     

发展低碳经济用新能源引领产业绿色可持续发展

习近平主席提出新的碳减排目标,不仅体现出中国主动为应对全球气候变化多做贡献的大国担当,也充分展示了我们作为全球能源革命前沿国家的底气和实力.作为全球新能源发展速度最快的国家,目前,我国新能源装机规模位居全球第一,站在全球科技和产业革命的制高点,新能源可能是中国继5G之后又一个领先全球的行业.未来十年,太阳能将成为全球最...     

聚合物相变储能材料的合成及应用研究进展

相变储能技术在节能、环保方面有着巨大的市场潜力和广阔的应用前景,因此越来越受到人们的重视。本文着重介绍了聚合物相变储能材料的合成方法,并综述了聚合物相变储能材料在建筑、电力、太阳能利用等方面的应用研究进展。