Increase In Total Organic Carbon Research Articles

Transformation of physicochemical soil properties along a mountain slope due to land management and climate changes — A case study from the Karkonosze Mountains, SW Poland

The gradients of soil physicochemical properties along mountain slopes and across climate-elevation gradients were studied in the Karkonosze Mountains, focusing on the human-impacted zonality of the vegetation cover. The main focus of the study was the environmental consequences, both human-induced and spontaneous, of vegetation changes in the mountains which may occur due to climate change. In soils developed from granite, a clear altitude-related differentiation of soil properties was manifested by: (i) an increase in total organic carbon (TOC) with elevation; (ii) an increase in exchangeable acidity and aluminum (Alex); (iii) a decrease in pH, (iv) a decrease in base saturation; and (v) finer soil texture and higher content of base cations in the foothills and lower slopes. These altitude-dependent trends have a threshold-type distribution, i.e. the values stabilize at 750–1000ma.s.l. or are reversed in the subalpine zone. Grass vegetation decreased TOC and Alex, but increased soil pH and base saturation compared with forest vegetation at the same altitude zone. Soils under spruce had higher TOC but lower pH compared with beech stands.Present-day changes of mountain area management in Central Europe, i.e. the replacement of spruce monocultures with beech or mixed stands in the lower forest zone and reforestation (mainly with spruce or mountain pine) of abandoned meadows and pastures at and above the timberline significantly influence topsoil properties, but there is a contrasting direction of changes in the lower and upper altitude zones. Expected climate changes may shift the upper limits of the individual forest zones and reinforce the ongoing changes in forest management. The final regional result of changes is difficult to calculate and strongly dependent on the degree of anthropogenic transformation of vegetation cover. However, both the current changes in management practices and possible climate changes will reinforce the existing vertical gradients of mountain soil properties, including the elevation-related increase in TOC, exchangeable acidity and Alex, as well as the decrease in soil pH and base saturation.

Effects of copper particles on a model septic system's function and microbial community

There is concern surrounding the addition of nanoparticles into consumer products due to toxicity potential and the increased risk of human and environmental exposures to these particles. Copper nanoparticles are found in many common consumer goods; therefore, the disposal and subsequent interactions between potentially toxic Cu-based nanoparticles and microbial communities may have detrimental impacts on wastewater treatment processes. This study investigates the effects of three copper particles (micron- and nano-scale Cu particles, and a nano-scale Cu(OH)2-based fungicide) on the function and operation of a model septic tank. Septic system analyses included water quality evaluations and microbial community characterizations to detect changes in and relationships between the septic tank function and microbial community phenotype/genotype. As would be expected for optimal wastewater treatment, biological oxygen demand (BOD5) was reduced by at least 63% during nano-scale Cu exposure, indicating normal function. pH was reduced to below the optimum anaerobic fermentation range during the micro Cu exposure, suggesting incomplete degradation of organic waste may have occurred. The copper fungicide, Cu(OH)2, caused a 57% increase in total organic carbon (TOC), which is well above the typical range for septic systems and also corresponded to increased BOD5 during the majority of the Cu(OH)2 exposure. The changes in TOC and BOD5 demonstrate that the system was improperly treating waste. Overall, results imply individual exposures to the three Cu particles caused distinct disruptions in septic tank function. However, it was observed that the system was able to recover to typical operating conditions after three weeks post-exposure. These results imply that during periods of Cu introduction, there are likely pulses of improper removal of total organic carbon and significant changes in pH not in the optimal range for the system.

Kvantita a kvalita p�dnej organickej hmoty p�dy zmenenej z ornej na lesn�

Comparative studies on quantitative and qualitative characteristics of soil organic matter were studied in arable and afforested in 1964 Stagni-Haplic Luvisol in Arboretum Mlyňany (Slovakia). The studies were conducted at three stands – arable soil located next to Arboretum (control), under thuja trees (Thuja orientalis L.) and under junipers (Juniperus Chinensis L.). Results of the studies showed, that in A horizons, 50 years of thuja and juniper trees growing on formerly arable land, had resulted to the significant (by 69% under thuja and by 126% under juniper) increase of total organic carbon (Cox) compared to control arable land. KMnO4 oxidisable carbon (CL) and mainly hot water-soluble carbon (Chwd) had higher contents in soil under studied trees than on arable land. The conversion of cropland to forest led to lowering of soil organic matter quality, assessed as the ratio of total carbon and nitrogen (Cox/NT), which was in arable soil 10.2, under thuja trees 13.9 and under junipers 12.0. Surprisingly, the quality of humus between examined sites differed only minimally, since the change of humus quality is a long term process.

Lipid biomarkers in Lake Enol (Asturias, Northern Spain): Coupled natural and human induced environmental history

The lipid content of three cores from Lake Enol (Picos de Europa National Park, Asturias, Northern Spain) was studied. The n-alkane profiles indicated a major input from terrigenous plants [predominance of high molecular weight (HMW) alkanes] since ca. 1695 AD to the water body, although the uppermost cm revealed a predominance of organic matter (OM) derived from algae, as the most abundant alkane was C17. Three units revealing different environmental conditions were defined. Unit A (ca. 1695–1860 AD) in the lowermost parts of ENO13-10 (<12cm) and ENO13-15 (<28cm) was identified and was characterized by higher OM input and evidence of minimal degradation (high CPI values, predominance of HMW n-alkanoic acids and good correspondence between the predominant n-alkane and n-alkanoic acid chains). These findings could be linked to the Little Ice Age, when cold and humid conditions may have favored an increase in total organic carbon (TOC) and n-alkane and n-alkanoic acid content (greater terrigenous OM in-wash), and may have also reduced bacterial activity. In Unit B (ca. 1860–1980 AD) the lack of correspondence between the n-alkane and n-alkanoic acid profiles of ENO13-10 (12–4cm) and ENO13-15 (28–8cm) suggested a certain preferential microbial synthesis of long chain saturated fatty acids from primary OM and/or bacterial activity, coinciding with a decrease in OM input, which could be linked to the global warming that started in the second half of the 19th century. In ENO13-7 the low OM input (low TOC) was accompanied by some bacterial degradation (predominance of HMW n-alkanoic acids but with a bimodal distribution) in the lowermost 16–5cm. Evidence of considerable phytoplankton productivity and microbial activity was especially significant in Unit C (ca. 1980–2013 AD) identified in the uppermost part of all three cores (5cm in ENO13-7, 4cm in ENO13-10 and 8cm in ENO13-15), coinciding with higher concentrations of n-alkanes and n-alkanoic acids, which were considered to be linked to warmer and drier conditions, as well as to greater anthropogenic influence in modern times.Plant sterols, such as β-sitosterol, campesterol and stigmasterol, were significantly present in the cores. In addition, fecal stanols, such as 24-ethylcoprostanol from herbivores, were present, thereby indicating a continuous and significant pollution input derived from these animals since the 17th century, being more important in the last 20years.

Evolution of the South Asian monsoon wind system since the late Middle Miocene

Abstract The evolution and timing of the inception of the South Asian monsoon (SAM) has been one of the most debated climatic mysteries amongst climate workers. The Himalaya–Tibetan plateau (HTP) complex has been implicated as the main driver for SAM circulation. However, there are intense debates as to whether there was a critical elevation of the HTP complex that drove the SAM and at what time such a critical elevation was attained. Also, the role of the HTP complex in driving the SAM has been questioned in recent climate model studies. The model simulation suggests a major intensification of the SAM as early as ~ 30 Ma, whereas marine records from the Arabian Sea indicate a major strengthening of the South Asian summer or southwest monsoon winds between 10 and 8 Ma. The continental vegetation, on the other hand, captured a major transition from C 3 to C 4 type during 8–7 Ma but whether this change was local or global and whether this transition was driven by monsoonal precipitation is not unanimously accepted. Our new record from Ocean Drilling Program holes located off the Oman margin and on the Owen Ridge, western Arabian Sea shows appearance of monsoon wind proxy planktic foraminifer Globigerina bulloides , a significant increase in total organic carbon, and a negative shift in stable carbon isotope record of benthic foraminifera at ~ 12.9 Ma. These proxies indicate that present day South Asian monsoon wind system began to develop during the late Middle Miocene (~ 12.9 Ma) and summer monsoon was in its full strength in the late Miocene (~ 7 Ma). From 11 to 7 Ma, the summer monsoon was weaker when winter monsoon was stronger.

Low temperature magnetic properties of the Late Archean Boolgeeda iron formation (Hamersley Group, Western Australia): environmental implications

The origin of the iron oxides in Archean and Paleoproterozoic Banded Iron Formations is still a debated question. We report low and high temperature magnetic properties, susceptibility and saturation magnetization results joined with scanning microscope observations within a 35 meters section of the Late Archean Boolgeeda Iron Formation of the Hamersley Group, Western Australia. With the exception of two volcanoclastic intervals characterized by low susceptibility and magnetization, nearly pure magnetite is identified as the main magnetic carrier in all iron-rich layers including hematite-rich jasper beds. Two populations of magnetically distinct magnetites are reported from a 2 meter-thick interval within the section. Each population shows a specific Verwey transition temperature: one around 120-124 K and the other in the range of 105-110 K. This temperature difference is interpreted to reflect two distinct stoichiometry and likely two episodes of crystallization. The 120-124K transition is attributed to nearly pure stoichiometric magnetite, SEM and microprobe observations suggest that the lower temperature transition is related to chemically impure silician magnetite. Microbial-induced partial substitution of iron by silicon is suggested here. This is supported by an increase in Total Organic Carbon (TOC) in the same interval.

Comparative Study of Different Soil Amendments and Microbes for Integrated Nutrient Management and Growth Promotion of Jatropha Curcas

Increased alkalinity caused reduction in growth of Jatropha curcas plant. This experiment was designed to test the efficacy of beneficial microbes and vermicompost individually and in combinations to alleviate the stressful effect of alkaline stress on growth of Jatropha. Plants inoculated with bacterial consortia had significantly increase in vegetative growth parameters. Soil analysis showed increase in total organic carbon (TOC) by 68% compared to soil before plantation treated with Bacterial consortia + vermicompost. Nitrogen (N) and phosphorus (P) content in the soil was increased by 25% and 84% before plantation treated with Bacterial consortia. Maximum uptake of potassium (K) and sodium (Na) content was observed in consortia. Plant analysis showed that consortia could increase uptake of micronutrients compared to control and other treatments. It can be concluded that multispecies bacterial consortia alone or in combination with mycorrhiza and vermicompost can reduce alkaline stress and enhances the seed germination potential, vegetative growth, and nutrient status of soil.

Lake-dredged material (LDM) in pedotechnique for the restoration of Mediterranean soils affected by erosion/entisolization processes

Anthropic-accelerated erosion processes have led to an increase in reported loss of soil surface horizons worldwide. Lake-dredged materials (LDMs) have often been considered suitable for upland disposal. This study aimed to assess the potential beneficial use of LDMs in soil rebuilding strategies for Mediterranean soils affected by the loss of surface horizons with consequent erosion/entisolization processes. Different model proto-horizons (MPHs) were assembled by means of the co-utilization of LDMs, other mineral matrices, organic amendment, and mineral fertilizer for the growth of a pasture grass under controlled (pot) conditions. The evolution of nine different MPHs was monitored by means of an evaluation/comparison of several physical–chemical parameters (texture, pH, electrical conductivity, N, P, K, and cation-exchange capacity) and the stability-modification of organic matter (OM) quality in relation to plant development (dry matter production, agronomic efficiency, and plant cover). The addition of LDM resulted in statistically significant (p < 0.05) improvement to both plant performance and several soil physical–chemical properties. Compared with the reference soil (degraded soil without any additional treatment), the model proto-horizons treated with the highest LDM content (50 % w LDM without any additional treatment) showed the largest total dry matter production, the highest agronomic efficiency, and a quali-quantitative increase in plant cover. A more balanced texture (loamy) and a generalized increase in total organic carbon, cation-exchange capacity, N, and K were also detected with particular reference to models treated with the higher LDM content. Humic substances greatly increased in the treatment with the higher LDM amounts showing a generalized soil organic matter equilibrium, i.e., no mineralization or humification process prevalence. This study showed that there is indeed the possibility of turning what is currently an awkward refuse material into a commodity that can be properly and advantageously used in pedotechniques for soil rebuilding and land recovery and protection. From this standpoint, LDM would appear to be apt for inclusion on a possible list of useful pedotechnomaterials.

Pliocene to Pleistocene climate and environmental history of Lake El'gygytgyn, Far East Russian Arctic, based on high-resolution inorganic geochemistry data

Abstract. The 3.6 Ma sediment record of Lake El'gygytgyn/NE Russia, Far East Russian Arctic, represents the longest continuous climate archive of the terrestrial Arctic. Its elemental composition as determined by X-ray fluorescence scanning exhibits significant changes since the mid-Pliocene caused by climate-driven variations in primary production, postdepositional diagenetic processes, and lake circulation as well as weathering processes in its catchment. During the mid- to late Pliocene, warmer and wetter climatic conditions are reflected by elevated Si / Ti ratios, indicating enhanced diatom production in the lake. Prior to 3.3 Ma, this signal is overprinted by intensified detrital input from the catchment, visible in maxima of clastic-related proxies, such as K. In addition, calcite formation in the early lake history points to enhanced Ca flux into the lake caused by intensified weathering in the catchment. A lack of calcite deposition after ca. 3.3 Ma is linked to the development of permafrost in the region triggered by cooling in the mid-Pliocene. After ca. 3.0 Ma the elemental data suggest a gradual transition to Pleistocene-style glacial–interglacial cyclicity. In the early Pleistocene, the cyclicity was first dominated by variations on the 41 kyr obliquity band but experienced a change to a 100 kyr eccentricity dominance during the middle Pleistocene transition (MPT) at ca. 1.2–0.6 Ma. This clearly demonstrates the sensitivity of the Lake El'gygytgyn record to orbital forcing. A successive decrease of the baseline levels of the redox-sensitive Mn / Fe ratio and magnetic susceptibility between 2.3 and 1.8 Ma reflects an overall change in the bottom-water oxygenation due to an intensified occurrence of pervasive glacial episodes in the early Pleistocene. The coincidence with major changes in the North Pacific and Bering Sea paleoceanography at ca. 1.8 Ma implies that the change in lake hydrology was caused by a regional cooling in the North Pacific and the western Beringian landmass and/or changes in the continentality. Further increases in total organic carbon and total nitrogen content after ca. 1.6 Ma are attributed to reduced organic matter decay in the sediment during prolonged anoxic periods. This points to more extensive periods of perennial ice coverage, and thus, to a progressive shifts towards more intense peak glacial periods. In the course of the Pleistocene glacial–interglacial sequence eight so-called "super-interglacials" occur. Their exceptionally warm conditions are reflected by extreme Si / Ti peaks accompanied by lows in Ti, K, and Fe, thus indicating extraordinary high lake productivity.

Organic matter pools and nutrient cycling in different coffee production systems in the Brazilian Cerrado

Agroforestry and organic systems have been used to reduce the negative effects that conventional coffee cultivation has on soils. In this work, 13C-CPMAS-NMR, Fourier transform infrared spectroscopy, elemental composition, classical humus fractionation and the soil fertility status were used to evaluate the impact of these three systems on a Latosol from the Brazilian Cerrado. Continuous input of tree residues promoted changes to the soil organic matter with increase in total organic carbon, humic acids (HA) and light organic matter, mainly in the topsoil. Available P and cation exchange capacity were also increased and the acidity status decreased in the agroforestry system. Moreover, HA from the agroforestry were enriched in O-alkyl C, O-di-alkyl C and alkyl C groups and the organic system resulted in HA richer in carboxyl groups. The conventional system resulted in greater aromatic and methoxyl participation, and lower phenol groups. HA from the agroforestry system were richer in easily degradable structures and the chemical fractionation demonstrated a decrease in both recalcitrant fractions, allowing for a more conservative and sustainable management of soil fertility. The modifications were not as evident in the organic system, probably due to the low organic fertilizer input.

Óxidos de ferro e área superficial de Latossolo subtropical sob campo e floresta nativa

As condições climáticas atuais indicam avanço da vegetação de floresta sobre os campos na região dos Campos de Cima da Serra no Rio Grande do Sul. Essa mudança na vegetação altera o conteúdo de matéria orgânica e a umidade do solo. Este estudo objetivou avaliar os óxidos de ferro pedogênicos em um Latossolo sob campo e floresta nativa e relacionar os mesmos com os teores de carbono orgânico e a área superficial específica do solo. Os teores de carbono orgânico são maiores no solo sob floresta e, possivelmente, influenciaram processos dissolutivos de óxidos de ferro cristalinos e a neoformação de tipos metaestáveis de baixa cristalinidade. O incremento de C orgânico no solo sob floresta elevou expressivamente a área superficial específica do solo, mascarando o efeito geralmente positivo dos óxidos de Fe sobre essa característica física.

Hydrogenotrophic denitrification for tertiary nitrogen removal from municipal wastewater using membrane diffusion packed-bed bioreactor

A lab-scale membrane diffusion packed-bed bioreactor was used to investigate hydrogenotrophic denitrification for tertiary nitrogen removal from municipal wastewater. After start-up, the bioreactor had been operated for 165 days by stepwise increasing influent loading rates at 30 and 15°C. The results indicated that this bioreactor could achieve relatively high nitrogen removal efficiencies. The denitrification rates reached 0.250 and 0.230 kg N/(m(3)d) at 30 and 15°C respectively. The total nitrogen concentration in effluent was entirely below 2.0 mg/L at the steady operation state. The average increase of total organic carbon in effluent was approximately 0.41 mg/L, suggesting the risk of organic residue can be completely controlled. Dissolved oxygen (DO) did not show obviously negative effects on hydrogenotrophic denitrification. There was only slight decrease of DO concentration in effluent, which demonstrated almost all of the hydrogen was used for nitrate reduction.

Chironomid assemblages in cores from multiple water depths reflect oxygen-driven changes in a deep French lake over the last 150 years

We sampled modern chironomids at multiple water depths in Lake Annecy, France, before reconstructing changes in chironomid assemblages at sub-decadal resolution in sediment cores spanning the last 150 years. The lake is a large, deep (zmax = 65 m), subalpine waterbody that has recently returned to an oligotrophic state. Comparison between the water-depth distributions of living chironomid larvae and subfossil head capsules (HC) along three surface-sediment transects indicated spatial differences in the influence of external forcings on HC deposition (e.g. tributary effects). The transect with the lowest littoral influence and the best-preserved, depth-specific chironomid community characteristics was used for paleolimnological reconstructions at various water depths. At the beginning of the twentieth century, oxygen-rich conditions prevailed in the lake, as inferred from M. contracta-type and Procladius sp. at deep-water sites (i.e. cores from 56 to 65 m) and Paracladius sp. and H. grimshawi-type in the core from 30 m depth. Over time, chironomid assemblages in cores from all three water depths converged toward the dominance of S. coracina-type, indicating enhanced hypoxia. The initial change in chironomid assemblages from the deep-water cores occurred in the 1930s, at the same time that an increase in lake trophic state is inferred from an increase in total organic carbon (TOC) concentration in the sediment. In the 1950s, an assemblage change in the core from 30 m water depth reflects the rapid expansion of the hypoxic layer into the shallower region of the lake. Lake Annecy recovered its oligotrophic state in the 1990s. Chironomid assemblages, however, still indicate hypoxic conditions, suggesting that modern chironomid assemblages in Lake Annecy are decoupled from the lake trophic state. Recent increases in both TOC and the hydrogen index indicate that changes in pelagic functioning have had a strong indirect influence on the composition of the chironomid assemblage. Finally, the dramatic decrease in HC accumulation rate over time suggests that hypoxic conditions are maintained through a feedback loop, wherein the accumulation of (un-consumed) organic matter and subsequent bacterial respiration prevent chironomid re-colonization. We recommend study of sediment cores from multiple water depths, as opposed to investigation of only a single core from the deepest part of the lake, to assess the details of past ecological changes in large deep lakes.

Sediment geochemical records of environmental change in Lake Wuliangsu, Yellow River Basin, north China

We present a paleolimnological record from shallow Lake Wuliangsu in the Yellow River Basin, north China, using a short (56 cm) sediment core. Our objective was to investigate environmental changes in this semi-arid region over the past ~150 years. The sediment core was dated using 137Cs and 210Pb. We examined stratigraphic trends in core lithology, nutrients, stable isotopes (δ13C and δ15N) and trace element concentrations in the Lake Wuliangsu core to discern between natural sediments and those affected by human agency. A lithologic transition from yellow, coarse-grained sediment to grey, fined-grained sediment marked the lake’s formation about 1860. Until ~1950, sediments displayed relatively low and constant heavy metal concentrations, indicating little human influence. In the 1950s, enrichment factors (EFs) increased, reflecting greater impact of human activities. Carbon and nitrogen stable isotopes in organic matter (OM), along with heavy metal concentrations, were used to infer past shifts in trophic state and identify pollutants that came from agriculture, industry and urbanization. In the late 1950s, the first evidence for environmental change is recorded by increases in total organic carbon (TOC), total organic nitrogen (TN), TOC/TN, EFs, δ13C and a decrease in δ15N. After about year 2000, a more rapid increase in trophic status occurred, as indicated by greater total phosphorus (TP), EFs, δ15N and lower δ13C values. Changes in isotope and TOC/TN values in the lake sediments may reflect a shift in lake ecology during this period. The first increase in trophic status during the late 1950s was mainly a result of agricultural development in the catchment. In contrast, the change after ca. AD 2000 was driven largely by urban and industrial development. Agreement between paleolimnologic data from Lake Wuliangsu, and both instrumental and written records, indicates that the lake sediments provide a reliable archive for investigating the formation and environmental history of the lake.

Foraminiferal morphogroups as a tool to approach the Toarcian Anoxic Event in the Western Saharan Atlas (Algeria)

The present contribution constitutes the first morphogroup analysis of foraminiferal assemblages applied to the Toarcian Oceanic Anoxic Event (T-OAE) in the Maghreb region, which represented the northern palaeomargin of Gondwana. The ecostratigraphic and palaeoecologic analysis of the foraminiferal assemblages has allowed interpretation of the evolution of the biotic crisis associated with the T-OAE in the Saharan Atlas deposits and the recovery of foraminiferal assemblages in the sea-bottom after the event. The foraminiferal assemblages of the Uppermost Pliensbachian (Emaciatum Zone) represent optimum ecological conditions (good oxygen and nutrient availability in the infaunal microhabitats) as evidenced by the high diversity of K-strategists and the low diversity of r-strategists (representing a minor proportion in the assemblages). The beginning of the Toarcian (Polymorphum Zone) shows an initial phase of unstabilization of the benthic environment, affecting some particular species while opportunistic forms proliferate (Epistomina and Lenticulina). Variations in the oxygenation degree affecting the infaunal microhabitat favoured stress-tolerant species with extensive niche such as Lenticulina and Eoguttulina. Later, a benthic azoic interval includes the lower part of the Levisoni Zone. In this interval, a slight increase of total organic carbon (TOC) values recorded can be related to dysoxic or anoxic conditions in low-oxygen bottom-water, beyond the ecological tolerance of opportunist forms. After the benthic mass extinction interval, a slow colonisation is registered (upper part of the Levisoni Zone) with a dominance of r-type strategists (Lenticulina, Reinholdella and Eoguttulina).

Membrane contactor/separator for an advanced ozone membrane reactor for treatment of recalcitrant organic pollutants in water

An advanced ozone membrane reactor that synergistically combines membrane distributor for ozone gas, membrane contactor for pollutant adsorption and reaction, and membrane separator for clean water production is described. The membrane reactor represents an order of magnitude improvement over traditional semibatch reactor design and is capable of complete conversion of recalcitrant endocrine disrupting compounds (EDCs) in water at less than three minutes residence time. Coating the membrane contactor with alumina and hydrotalcite (Mg/Al=3) adsorbs and traps the organics in the reaction zone resulting in 30% increase of total organic carbon (TOC) removal. Large surface area coating that diffuses surface charges from adsorbed polar organic molecules is preferred as it reduces membrane polarization that is detrimental to separation.

黄土丘陵区三种典型退耕还林地土壤固碳效应差异

PDF HTML阅读 XML下载 导出引用 引用提醒 黄土丘陵区三种典型退耕还林地土壤固碳效应差异 DOI: 10.5846/stxb201201020003 作者: 作者单位: 西北农林科技大学资源与环境学院,西北农林科技大学农学院,西北农林科技大学资源与环境学院,西北农林科技大学资源与环境学院,西北农林科技大学资源与环境学院,西北农林科技大学资源与环境学院 作者简介: 通讯作者: 中图分类号: 基金项目: 陕西省自然科学基础研究计划资助项目(2010JQ5001); 教育部高等学校博士点基金(20090204120038); 国家自然基金(30971695); 西北农林科技大学基本科研业务费专项(QN2011153); 西北农林科技大学博士启动金(2010BSJJ032) Variance analysis of soil carbon sequestration under three typical forest lands converted from farmland in a Loess Hilly Area Author: Affiliation: Northwest Agricultural & Forestry University,Northwest Agricultural & Forestry University,,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:探讨了黄土丘陵区退耕种植10-40a的柠条、沙棘及刺槐林地土壤总有机碳库及其活性组分密度随退耕时间、土层分布及相对比例的变化差异。结果表明:100 cm深土壤碳库在退耕10a时仅柠条林地碳库未比坡耕地显著增加,但退耕20-40a 3种林地比退耕10a时都已有显著增加,且增幅均为刺槐＞沙棘＞柠条,其中总有机碳的最大增幅分别达到90.92、27.87、14.89 Mg/hm2,活性有机碳的分别达到30.28、10.51、9.67 Mg/hm2。各还林地碳库增加在退耕10a时主要来自0-40 cm浅层土,而40-100 cm深层土碳库到退耕20a起才开始显著增加。对比退耕10a时,到退耕40a时柠条、沙棘及刺槐林地0-20 cm表层土分别平均累积了35.4%、27.9%、27.1%的总有机碳,20.2%、45.1%、23.1%的活性有机碳,而20-100 cm各土层间对碳库累积比例大小变化无一致规律,平均每20 cm厚土层累积了17.4%的总有机碳和17.6%活性有机碳。并且相比坡耕地,各林地均使100 cm深土壤活性有机碳占总有机碳的比例提高,改良了碳库质量。综上分析,长期退耕下3种林地固碳效应有明显差异,以刺槐林地碳累积效应较强。 Abstract:Quantifying soil carbon sequestration may be an important consideration under large scale afforestation because it has been counted in global carbon budgets according to the Kyoto Protocol. The conversion of cropland to forest as part of a huge ecological afforestation engineering scheme has played a very important role in reversing ecological destruction in the Loess Plateau and strongly affects the carbon cycle. This research was conducted to determine the changes in total soil organic carbon and its labile fraction in soil to 100 cm under three typical forested lands. These typical forest lands are Caragana, Buckthorn, and Robinia, which have been converted from farmland between 10 and 40 years ago in a Loess Hilly Area. The results showed that, compared with sloped farmland, the concentration of total organic carbon and labile organic carbon in soil at 100 cm was not higher in Caragana forest land 10 years after conversion from farmland. The carbon pool was significantly increased in Buckthorn and Robinia after the same period. Compared with 10 years since farmland conversion, the total organic carbon and labile carbon was further increased in all forest lands after 20 to 40 years of conversion from farmland. This increase followed the order Robinia > Buckthorn > Caragana, and the highest increase in total organic carbon reached 90.92, 27.87, and 14.89 Mg/hm2, and for labile organic carbon was 30.28, 10.51, and 9.67 Mg/hm2 respectively. The changes in soil organic carbon in different soil layers were also significantly different with time since farmland conversion. The soil organic carbon and its labile fraction was increased mainly in the 0-40 cm soil layer 10 years after farmland conversion in all forest lands. The soil organic carbon pools in the 40-100 cm layer were increased significantly 20 years after farmland conversion. As a result, all soil layers showed a contribution to soil organic carbon increase with long term conversion of cropland to forest. Forty years after farmland conversion 35.4%, 27.9%, and 27.1% of the increased total organic carbon and 20.2%, 45.1%, and 23.1% of the increased labile organic carbon in the soil to 100 cm was sequestrated in the 0-20 cm layer under Caragana, Buckthorn, Robinia forest land respectively. By contrast, the proportion of soil organic carbon sequestration showed inconsistent changes among the forest lands in the 20-100 cm soil layer, with an average of 17.4% of the increased total organic carbon and 17.6% of the increased labile organic carbon sequestrated in each 20 cm layer. Additionally, in comparison with sloped farmland, the ratio of labile organic carbon to total organic carbon was significantly different in each soil layer of all forest lands 40 years after farmland conversion. This was especially so in the 60-100 cm soil layer where the ratio was increased by 146.7%, 76.9%, and 126.1% in Caragana, Buckthorn, and Robinia forest lands, respectively. The ratio in the 100 cm soil layer also increased by 63.7%, 34.0%, and 47.0% in Caragana, Buckthorn, and Robinia, respectively, which indicated the activation of soil carbon pools had been enhanced, and the quality of soil was improved indirectly. Consequently, conversion of cropland to forest could sequestrate carbon in soil and Robinia is the better forest land to improve the soil organic carbon pool. Soil carbon sequestration following the afforestation of former arable land would be a powerful carbon sink for anthropogenic CO2 production in the Loess Plateau in the future. 参考文献 相似文献 引证文献

Predicting the bioavailability of sediment-associated polybrominated diphenyl ethers using a 45-d sequential Tenax extraction

A 45-d Tenax extraction was used to evaluate the bioavailability of polybrominated diphenyl ethers (PBDEs) in three spiked sediments. The effect of aging on desorption kinetics of PBDEs was investigated by incubating one of the sediments for 7, 14, 30 and 60d at room temperature. Desorption kinetics were well described by a three-compartment model. The fraction of very slow desorption (Fvs) contributed the most of the desorbed PBDEs from sediments. The total desorption amount of PBDEs decreased with the increase of total organic carbon in the sediments, suggesting that organic matter is an important factor controlling the partition of PBDEs in sediments. The total desorption amount of PBDEs decreased while log [(Fslow+Fvs)/Frap] increased with logKow of PBDE congeners, indicating that the bioavailability of PBDEs in sediment decreases with logKow of the congeners. As the residential time of PBDEs in the sediment increased from 7 to 60d, Frap of individual PBDE congeners decreased gradually with simultaneous increase of Fvs. There was a good positive correlation between Frap and F6/F24, indicating that either 6h or 24h Tenax extraction could be a proxy for Frap and bioavailability. In general, the results in present study suggest that the bioavailability of nona- and deca-BDEs in sediment is very low due to their strong hydrophobicity and large molecular size.

Changes in soil organic carbon fractions in a tropical Acrisol as influenced by the addition of different residue materials

Residues of Leucaena (Leucaena leucocephala (L), Senna siamea (S) and maize stover (M) were tested to evaluate their effect on soil organic matter accumulation and composition under sub-humid tropical conditions. On an Imperata cylindrica (I) dominated grass fallow, a total amount of 30 Mg ha−1 DM were applied within 18 months. Two months after the last application, changes in the light and heavy soil organic carbon fraction (LF and HF) and in the total soil organic carbon content (LF + HF) in the topsoil were observed. All organic materials increased the proportion of the LF fraction in the soil significantly. The increase in HF was 39 to 51% of the increase in total organic carbon, depending on the source of the organic material. The potential of the tested organic materials to increase total soil organic carbon content (including all soil organic carbon fractions) was in the order L > S > M > I, whereas the order of increase of the HF fraction was L = S > I > M. Cation exchange capacity of the newly formed heavy soil organic carbon was highest with L and lowest with M. Ranking of the transformation efficiency of applied plant residues into the heavy soil organic carbon fraction was I > L = S > M. Transformation efficiency of the residues could neither be explained by lignin nor lignin/N ratio, but rather by extractable polyphenols (Folin–Denis extraction). The results show that accumulation of the HF fraction in tropical soils is feasible through the application of large quantities of plant residues, but depends strongly on the composition of the applied materials.

Systematics of pyrolytic N2 and CH4 release from peat and coals of different thermal maturity

Open system non-isothermal (programmed) pyrolysis with a constant heating rate of 0.5 °C/min up to a final temperature of 1200 °C was used to study the liberation of molecular nitrogen (N2) and methane (CH4) from organic-rich sedimentary matter of different thermal maturity. The sample set analysed comprised peats, lignites, bituminous coals and anthracites. Temperature ranges, shapes and intensities of pyrolytic peaks in the CH4 and N2 pyrograms are sensitive indicators of the chemical composition of the sedimentary organic matter and may serve as characteristic fingerprints of organofacies and depositional environment. Within the coalification sequence, an increase in total organic carbon (TOC)-normalized methane yields was observed from peat to medium volatile bituminous coal, followed by a distinct decrease for the anthracites. The onset of methane and nitrogen liberation temperatures shifted towards higher temperatures with increasing rank, reflecting the increase in thermal stability of the residual organic matter. A systematic temperature shift was also observed for the methane generation maximum (peak). The N2 pyrograms exhibit bimodal generation curves (two maxima) up to the bituminous coal rank, while essentially only one single high-temperature N2 generation maximum persists at the anthracite level. This is attributed to a predominance of nitrogen-containing moieties (e.g. pyridinic and pyrrolic) of high thermal stability. The N2 pyrograms of the lignites show a higher degree of complexity, indicating a substantial variability in nitrogen-containing compound groups. Characteristic N2 spikes were found in the Miocene lignites of the Lower Rhine Basin, similar to those observed previously in Greek lignites. The origin of these “anomalies” and their relation to depositional environment and diagenesis still remains unknown.