Dissolve Organic Carbon Research Articles

Ambivalent effects of mass cultivation of biodiesel producible green alga Tetraselmis striata on a microbial ecosystem: Evidence from mesocosm experiments

A 280-ton plant for the mass cultivation of Tetraselmis striata was operated from 2012 to 2019 to produce biodiesel fuel in western Korean coastal waters (Incheon) as a pilot project. This was the first instance globally where a microalgal mass cultivation plant for biodiesel production was implemented in coastal waters, and no prior studies had investigated the impact of microalgal mass cultivation plant on surrounding microecosystems. In this study, bioreactors (1× and 10×) mimicking a large-scale T. striata cultivation plant were installed in semi-permeable a mesocosms (5 tons) to assess their impact on the microbial ecosystem. The results showed that the release of large amounts of dissolve organic carbon (DOC) from the T. striata bioreactors. The 10× pond had a DOC concentration of 21.3 mg/L compared to the control pond of 2.1 mg/L. For the Water Quality Index (WQI), the 1× and 10× bioreactor installed mesocosms improved from Class II (Good) at the beginning of the experiment to Class I (Excellent) via decreasing nutrient levels and increasing of DO levels. However, from a biodiversity perspective, the microbial ecosystem deteriorated, with reductions in the diversity of zooplankton, ciliates, and phytoplankton. The correlation analysis and random forest variable importance measures indicated that the primary factor driving these changes was the alteration of the bacterial community due to elevated DOC levels. These findings indicate that while the mass cultivation of T. striata may improve physicochemical water quality, it has adverse effects on biological environments. Therefore, it is crucial to monitor physical, chemical, and biological factors comprehensively when cultivating microalgae on a large scale in marine environments.

Seasonal timing of extreme drought regulates N2O fluxes in a semiarid grassland

Terrestrial ecosystems are important sources of nitrous oxide (N2O), a powerful greenhouse gas which can be strongly impacted by increasing droughts in association with climate change. However, detailed information on whether and how drought timing regulates N2O fluxes is still lacking. Here, we conducted a 3-year field experiment on a semiarid grassland in which extreme drought was imposed in either early-, mid-, or late-growing seasons repeatedly from 2014 to 2016. We found that early drought affected N2O emission with high interannual variability (increased, decreased and unchanged N2O emission in 2014, 2015, and 2016, respectively), coincident with changes in inorganic nitrogen (SIN), dissolve organic carbon (DOC), microbial biomass carbon (MBC), and soil functional genes (bacterial amoA, nirK, nirS, and nosZ). However, middle drought consistently suppressed N2O emissions due to simultaneous decreases in MBC, DOC and the abundances of archaeal amoA, nirK, and narG genes, causing the largest reduction in N2O emissions across the three years. In contrast, late drought had little effect on N2O fluxes, even though DOC and SIN decreased and the abundance of nirK, nirS, and nosZ increased. As a result, soil organic C and mineral N availability and functional gene abundances were not always robust factors for predicting N2O emissions under droughts across all treatments, except for abundance of AOA and nosZ. Our results highlight the vital role of seasonal timing in regulating the response of N2O emissions to extreme droughts.

Application and evaluation of SWAT-C model to predict TOC loading in the Hwangryong River Watershed

Objectives : This study aims to assess the applicability of the SWAT-C water quality model recently developed to predict in-stream Total Organic Carbon (TOC) in a watershed within South Korea.Methods : The SWAT-C model was tested in the Hwangryong River Watershed. SWAT-C is an advanced version of Soil and Water Assessment Tool (SWAT) to simulate carbon cycling at the watershed scale. The model was simulated for 11 years (2010-2020) consisting of 2-year warm-up (2010-2011), 6-year calibration (2012-2017), and 3-year validation (2018-2020) periods. SWAT-C was calibrated and validated against monthly streamflow and TOC loads. The model performance was evaluated using NSE (Nash-Sutcliffe efficiency), KGE (Kling-Gupta efficiency), and PBIAS (percent bias) Simulated Dissolve Organic Carbon (DOC) and Particulate Organic Carbon (POC) loads were also presented to see the major caron type loaded to the downstream.Results and Discussion : The calibration results showed that SWAT-C could depict streamflow and TOC loads with acceptance model performances (NSE > 0.5, KGE > 0.5 and PBIAS =< 25%). Especially, the seasonal variations of TOC loads were well simulated by SWAT-C. The TOC load was predicted to increase in the summer season with high precipitation and slightly lower in the other seasons. This seasonal pattern is likely caused by frequent heavy rainfall events in summer.Conclusion : This study demonstrated that SWAT-C model is applicable in South Korea with sufficient prediction accuracy. Thus, SWAT-C would serve as an efficient tool to monitor TOC loads in South Korea.

Evaluation of organics reduction performance of the GAC filtration with regenerated carbons using the long-term operational data of drinking water treatment facilities

Abstract Degradation of raw water quality promoted the introduction of GAC (granular activated carbon) filtration and ozonation into Korean drinking water treatment facilities in 1994 in order to cope with organic pollutants. This study focuses on the evaluation of organics reduction performance of the GAC filtration with regenerated carbons using long-term operational data. Three drinking water treatment facilities at Busan were selected for this purpose. It was found in this study that GAC filtration and ozonation helped these facilities to reduce the treated levels of DOC (dissolve organic carbon) as well as of 1,4-dioxane. Regeneration affected organics reduction performance of GAC filtration. The GAC filtration with regenerated carbons was found more effective for DOC reduction, while the filtration with virgin carbons was more effective for THM (trihalomethane) reduction. These results were related to the pore size change that occurred after the regeneration. The regeneration increased the meso pore volume but decreased the micro pore volume. The regeneration cycle was important for the decrease in the micro pore volume. The micro pore volume remained relatively unchanged after the first regeneration but was substantially decreased after the regeneration was repeated by more than second time.

滇南喀斯特断陷盆地土地利用方式对土壤有机碳及其活性组分的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 滇南喀斯特断陷盆地土地利用方式对土壤有机碳及其活性组分的影响 DOI: 10.5846/stxb202108112216 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（42071127）；云南大学人才项目（C176220100083） Effects of land use types on soil organic carbon and soil labile organic carbon in karst faulted basin of southern Yunnan Author: Affiliation: 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:土地利用方式是影响土壤有机碳库的重要因素，为探究喀斯特断陷盆地土壤有机碳库对土地利用方式及环境因素的响应，以滇南喀斯特地区5种典型土地利用方式(耕地、草地、灌丛、人工林、天然林)为研究对象，分析不同土地利用方式土壤有机碳(SOC)及活性有机碳(LOC)组分，即可溶性有机碳(DOC)、易氧化性有机碳(EOC)及微生物量碳(MBC)的含量、储量及分配比例在土壤垂直剖面(0-60 cm)的变化特征。结果表明：5种土地利用方式的SOC含量随土层深度的增加逐渐降低，其储量依次为灌丛(191.77 t/hm2)、草地(166.86 t/hm2)、耕地(142.47 t/hm2)、人工林(134.31 t/hm2)和天然林(102.62 t/hm2)；EOC和MBC的平均含量及储量均以草地及灌丛最高、人工林及天然林次之，二者在土壤垂直剖面上与SOC含量的变化特征一致，但EOC和MBC含量在土层间的下降幅度大于SOC；土地利用方式和土层深度对DOC无显著影响(P>0.05)；活性有机碳的分配比例受土地利用方式及土层深度的显著影响(P<0.01)，其中人工林的EOC/SOC和MBC/SOC显著低于草地、灌丛及天然林。通径分析指出SOC和EOC主要受C/P比、全磷、砂粒和交换性钙的影响，砂粒和C/P比是影响MBC的主要因子。研究阐明在喀斯特断陷盆地地区EOC和MBC对土地利用方式的响应比SOC更敏感。另外，今后在土壤碳库的研究中应更多关注土壤磷和物理结构对其的影响。 Abstract:Land use types are important factor affecting soil organic carbon pool by regulating carbon fluxes between the terrestrial biosphere and atmosphere. Five typical land use types including farmland, grassland, shrubland, artificial forest and natural forest were selected to explore the responses of soil organic carbon pool to land use types and environmental factors in the karst faulted basin, China. The contents, stocks and distribution ratios of soil organic carbon (SOC) and labile organic carbon (LOC), namely dissolve organic carbon (DOC), easily oxidated carbon (EOC) and microbial biomass carbon (MBC), were analyzed along soil profiles (0-60 cm) under different land use types. The results showed that the SOC contents was 4.83-69.01 g/kg, which decreased with soil depths under the five land use types. The SOC stocks under five land use types were in descending order of shrubland (191.77 t/hm2), grassland (166.86 t/hm2), farmland (142.47 t/hm2), artificial forest (134.31 t/hm2) and natural forest (102.62 t/hm2). The contents and stocks of EOC and MBC were the highest in grassland and shrubland on average, followed by artificial forest and natural forest. The variation characteristics of EOC and MBC in the soil profile were consistent with SOC, but the decline rates of EOC and MBC contents in soil layers were obviously higher than SOC. Land use types and soil depths had no significant effects on DOC contents with a range of 0.84-1.62 g/kg under the five land use types. The ratios of labile organic carbon to soil organic carbon were affected by land use types and soil depths (P<0.01). The EOC/SOC and MBC/SOC ratios of artificial forest were lower than those of grassland, shrubland and natural forest. Pearson correlation analysis showed that SOC was positively correlated with LOC (P<0.01). In addition, SOC and LOC were positively correlated with total nitrogen, C/P ratio, C/N ratio, exchangeable calcium, soil water content, clay, sand and so on (P<0.05). Path analysis further identified that the variation in the SOC and EOC were significantly related to the changes of C/P ratio, total phosphorus, sand and exchangeable calcium and MBC was mainly influenced by sand and C/P ratio. These findings suggested that the land use types had significant effects on SOC, EOC and MBC contents and the responses of EOC and MBC to land use types were more sensitive than SOC in karst faulted basins. Moreover, more attention should be paid to soil physical structure and phosphorus availability in the future research on soil organic carbon pool. 参考文献 相似文献 引证文献

The role of photomineralization for CO2 emissions in boreal lakes along a gradient of dissolved organic matter

AbstractMany boreal lakes are experiencing an increase in concentrations of terrestrially derived dissolved organic matter (DOM)—a process commonly labeled “browning.” Browning affects microbial and photochemical mineralization of DOM, and causes increased light attenuation and hence reduced photosynthesis. Consequently, browning regulates lake heterotrophy and net CO2‐efflux to the atmosphere. Climate and environmental change makes ecological forecasting and global carbon cycle modeling increasingly important. A proper understanding of the magnitude and relative contribution from CO2‐generating processes for lakes ranging in dissolve organic carbon (DOC) concentrations is therefore crucial for constraining models and forecasts. Here, we aim to study the relative contribution of photomineralization to total CO2 production in 70 Scandinavian lakes along an ecosystem gradient of DOC concentration. We combined spectral data from the lakes with regression estimates between optical parameters and wavelength specific photochemical reactivity to estimate rates of photochemical DOC mineralization. Further, we estimated total in‐lake CO2‐production and efflux from lake chemical and physical data. Photochemical mineralization corresponded on average to 9% ± 1% of the total CO2‐evasion, with the highest contribution in clear lakes. The calculated relative contribution of photochemical mineralization to total in‐lake CO2‐production was about 3% ± 0.2% in all lakes. Although lakes differed substantially in color, depth‐integrated photomineralization estimates were similar in all lakes, regardless of DOC concentrations. DOC concentrations were positively related to CO2‐efflux and total in‐lake CO2‐production but negatively related to primary production. We conclude that enhanced rates of photochemical mineralization will be a minor contributor to increased heterotrophy under increased browning.

Response of Soil Bacterial Community Structure to Precipitation Change in Grassland of Loess Plateau

As the main participants of ecosystem functions, the response of microorganisms to variations in soil moisture caused by the changes in precipitation amounts should be quantified to evaluate the impact of climate change on semi-arid ecosystems. For this purpose, a two-year simulation of the changes in the rainfall patterns was conducted on the Loess Plateau, and five precipitation treatments (80% and 40% decrease in precipitation, D80, D40; natural precipitation, NP; 40% and 80% increase in precipitation, I40, I80) were set up. The results showed that: ① Compared with NP, the carbon-to-nitrogen ratio (C/N) was lower in DP80 or IP80, while it reached the maximum value in I40. The mean C/N value of the 0-20 cm soil layer was 10.76. The microbial biomass carbon to microbial biomass nitrogen ratio (MBC/MBN) varied significantly with the soil layer in the treatments of D80 and I80, and the maximum value was 14.15 in D80. ② In the grassland soil naturally growing on the Loess Plateau, at the phylum level, the dominant phyla were Actinobacteria, Proteobacteria, Chloroflexi, and Acidobacteria. At the class level, Actinobacteria, Acidobacteria, α-Proteobacteria, and Thermomicrobia were predominant. ③ RDA analysis showed that changes in soil dissolve organic carbon (DOC), dissolved organic nitrogen (DON), elemental carbon (EC), and pH values were the main factors affecting the distribution of soil bacteria under the five precipitation treatments in the study area. Overall, 80% increase or decrease in precipitation has a significant impact on soil active organic carbon content and bacterial abundance, especially D80. In conclusion, drought or extreme precipitation may considerably change the active organic matter content and bacterial community diversity and abundance in the soils of the Loess Plateau.

Differential Responses and Controls of Soil CO2 and N2O Fluxes to Experimental Warming and Nitrogen Fertilization in a Subalpine Coniferous Spruce (Picea asperata Mast.) Plantation Forest

Emissions of greenhouse gases (GHG) such as CO2 and N2O from soils are affected by many factors such as climate change, soil carbon content, and soil nutrient conditions. However, the response patterns and controls of soil CO2 and N2O fluxes to global warming and nitrogen (N) fertilization are still not clear in subalpine forests. To address this issue, we conducted an eight-year field experiment with warming and N fertilization treatments in a subalpine coniferous spruce (Picea asperata Mast.) plantation forest in China. Soil CO2 and N2O fluxes were measured using a static chamber method, and soils were sampled to analyze soil carbon and N contents, soil microbial substrate utilization (MSU) patterns, and microbial functional diversity. Results showed that the mean annual CO2 and N2O fluxes were 36.04 ± 3.77 mg C m−2 h−1 and 0.51 ± 0.11 µg N m−2 h−1, respectively. Soil CO2 flux was only affected by warming while soil N2O flux was significantly enhanced by N fertilization and its interaction with warming. Warming enhanced dissolve organic carbon (DOC) and MSU, reduced soil organic carbon (SOC) and microbial biomass carbon (MBC), and constrained the microbial metabolic activity and microbial functional diversity, resulting in a decrease in soil CO2 emission. The analysis of structural equation model indicated that MSU had dominant direct negative effect on soil CO2 flux but had direct positive effect on soil N2O flux. DOC and MBC had indirect positive effects on soil CO2 flux while soil NH4+-N had direct negative effect on soil CO2 and N2O fluxes. This study revealed different response patterns and controlling factors of soil CO2 and N2O fluxes in the subalpine plantation forest, and highlighted the importance of soil microbial contributions to GHG fluxes under climate warming and N deposition.

CORRELATION AMONG SOME GLOBAL PARAMETERS DESCRIBING ORGANIC POLLUTANTS IN RIVER WATER: A CASE STUDY

Organic matter in drinking water is determined by applying indirect determination methods used for quantitative measurements such as total organic carbon (TOC), chemical oxygen demand (COD), and biochemical oxygen demand (BOD). As a relatively less sophisticated and faster method ultraviolet absorption of water at 254 nm wavelength (UV254) is being now utilized in many countries to determine the organic matter in water. Because the UV254 absorbance parameter is proportional to the concentration of organics in the water in many research it is found that most natural water sources have a good correlation between, for example, TOC and UV254 absorption, and COD and UV254 absorption. Similarly, a definite correlation between the COD and BOD under certain conditions was reported in the literature. This study is aimed to establish the correlations among the parameters namely UV254, COD, BOD5, TOC, DOC (Dissolve organic carbon) for the river Sitalakhya, a specific surface water, which is the raw water source of the largest surface water treatment plant in Dhaka, Bangladesh. It is revealed that there is a very strong correlation between TOC and UV254 with R2=0.86. Similarly, between BOD5 and UV254, and between COD and UV254, a strong correlation was found with coefficient of determination, R2 value respectively 0.93 and 0.87. All other coefficients also indicate highly significant linear correlations.

A novel method for sewage sludge composting using bamboo charcoal as a separating material.

Traditional composting processes must be conducted with a bulking agent to ensure adequate air space for aeration. The bulking agent and composting materials are always completely mixed. A novel layered structure was introduced in sewage sludge composting, in which no bulking agent was used and bamboo charcoal was used as a separating material. Three lab-scale composting reactors (A: sawdust and sludge; B: bamboo charcoal and sludge; and C: sawdust, bamboo charcoal, and sludge) were continuously operated for 29days. Several physicochemical parameters were investigated to evaluate the feasibility of layered composting with bamboo charcoal. The results indicated that the maximum temperatures during the thermophilic stage in treatments A, B, and C were 51.4, 50.9, and 51°C, respectively. Layered composting with bamboo charcoal decreased the pH of the thermophilic stage from 8.98 in A to 8.75 in C, and delayed the peaks by about 120h. The degradation rates of dissolve organic carbon (DOC) and dissolved nitrogen (DN) were 75 and 71.5% in treatment B, respectively, which were significantly higher than those of control group A (60 and 59.1%, respectively). The total NH3 emissions of treatment C (2127.8mg) were significantly lower than those of A (2522.8mg). Our results suggested that layered composting using bamboo charcoal as a separating material could be an alternative strategy to the traditional composting method. Moreover, layered composting combined with sawdust could effectively reduce NH3 emissions and N loss.

Pre-chlorination contact time and the removal and control of Microcystis aeroginosa in coagulation

The use of pre-oxidation is known to improve algae removal by coagulation and control the growth of algae. The contact time between oxidants and algae in pre-oxidation stage has been found as important parameter. This study investigated the effect of pre-chlorination contact time on the control and removal of cyanobacteria Microcystis aeruginosa by coagulation. The results showed that when the alum dose was sufficient, increasing contact time showed an improvement in algae removal by coagulation in case of high chlorine dose. The algae removal ratio at high chlorine dose, 3 mg L-1 increased when contact time increased and it decreased after 30 minutes of contact time. In contrast, the result from chlorine dose, 2 mg L-1, showed an unclear trend when contact time increased. Adding 2 mg L-1 of pre-chlorination with 10 minutes of contact time was enough to control the regrowth of M. aeruginosa. In addition, dissolve organic carbon (DOC) and UV absorbance at 254 nm, which particulary indicates aromatic compounds, tended to increase when the contact time increased. The increased of DOC and UV 254 indicated the release of intracellular organic matter (IOM) from M. aeruginosa. High level of DOC, 0.68 mg L-1 in this study showed negative effect on M. aeruginosa removal by coagulation and could not be removed by coagulation process.

Long-Term Effect of Phosphate Fertilization on Cadmium Uptake by Oat and its Accumulation in Soil

Phosphate fertilizers contain varying amounts of cadmium (Cd) and other heavy metals as contaminants from phosphate rock (PR). Periodic applications of these fertilizers could result in measurable accumulations of Cd in soils and in harvested crops. A long term field study for fifteen cropping seasons (1992-2006) was conducted on an experimental plot located at the Norwegian University of Life Sciences (As, Norway) to evaluate the effect of application of cadmium enriched phosphate fertilizer on Cd uptake by Oat (Avena sativa) and its accumulation and availability in soil. Treatments consisted of three NPK fertilizer sources containing 1, 90, 381 mg Cd kg-1 P and applied at the rate of 0.03, 2.7, 11.43 g Cd ha-1yr-1, respectively. Surface soil samples (0-20 cm), collected after harvesting of oat in 1992, 1995, and 2006, and were analyzed for total and extractable Cd, pH, dissolve organic carbon (DOC) and PO4 3-. Plant samples collected in 1992, 1995, 1997, 2002 and 2006 were analyzed total Cd. Plant Cd generally decreased with increased soil pH throughout the experimental period except 1992. Increased input of Cd through fertilizers increased the Cd concentration in soil but the Cd concentration in oat grain remained unaffected. Ammonium nitrate (NH4NO3 -) extractable Cd in the soil increased with increasing rate of Cd through different sources but it decreased with increased pH throughout the experimental period with minor exceptions. Plant Cd did not show any significant correlation with extractable Cd in soil and hence the Cd input through fertilizers did not significantly affect the concentration of Cd in oat grain. Model (WHAM) prediction of Cd uptake by plants showed that crop yield, pH and DOC in combination explained about 57% of the variation in Cd uptake and DOC (r2=0.47, p<0.0001) was the most important factor. However, in individual years (e.g.2006) the combination of FA-Cd and yield did in fact explain 92% of the Cd-uptake.

Pore-water chemistry explains zinc phytotoxicity in soil

Zinc (Zn) is a widespread soil contaminant arising from a numerous anthropogenic sources. However, adequately predicting toxicity of Zn to ecological receptors remains difficult due to the complexity of soil characteristics. In this study, we examined solid–solution partitioning using pore-water data and toxicity of Zn to cucumber (Cucumis sativus L.) in spiked soils. Pore-water effective concentration (ECx, x=10%, 20% and 50% reduction) values were negatively related to pH, indicating lower Zn pore water concentration were needed to cause phytotoxicity at high pH soils. Total dissolved zinc (Znpw) and free zinc (Zn2+) in soil-pore water successfully described 78% and 80.3% of the variation in relative growth (%) in the full dataset. When the complete data set was used (10 soils), the estimated EC50pw was 450 and 79.2µM for Znpw and Zn2+, respectively. Total added Zn, soil pore water pH (pHpw) and dissolve organic carbon (DOC) were the best predictors of Znpw and Zn2+ in pore-water. The EC10 (total loading) values ranged from 179 to 5214mg/kg, depending on soil type. Only pH measurements in soil were related to ECx total Zn data. The strongest relationship to ECx overall was pHca, although pHw and pHpw were in general related to Zn ECx. Similarly, when a solution-only model was used to predict Zn in shoot, DOC was negatively related to Zn in shoot, indicating a reduction in uptake/ translocation of Zn from solution with increasing DOC.

Combining physico-chemical analysis with a Daphnia magna bioassay to evaluate a recycling technology for drinking water treatment plant waste residuals

Recycling water treatment plant (WTP) waste residuals is considered to be a feasible method to enhance the efficiency of pollutant removal. This study also evaluated the safety and water quality of a pilot-DWTP waste residuals recycling technology by combining physical-chemistry analysis with a Daphnia magna assay. The water samples taken from each treatment step were extracted and concentrated by XAD-2 resin and were then analyzed for immobilization and enzyme activity with D. magna. The measured parameters, such as the dissolve organic carbon (DOC), UV254 and THM formation potential (THMFPs) of the recycling process, did not obviously increase over 15 days of continuous operation and were even lower than typical values from a conventional process. The extract concentration ranged from 0 to 2Leq/ml as measured on the 7th and 15th days and the immobilization of D. magna exposed to water treated by the recycling process was nearly equivalent to that of the conventional process. Both the superoxide dismutase (SOD) and the catalase (CAT) activity assay indicated that a lower dose of water extract (0.5, 1, 1.5Leq/ml) could stimulate the enzyme activity of D. magna, whereas a higher dose (2Leq/ml at the sampling point C3, R3, R4 ) inhibits the activity. Moreover, the SOD and CAT activity of D. magna with DOC and UV254 showed a strong concentration–effect relationship, where the concentration range of DOC and UV254 were 4.1–16.2mg/L and 0.071–4.382cm−1, respectively. The results showed that there was no statistically significant difference (p>0.05) between the conventional and recycling treatment processes and the toxicity of water samples in the recycling process did not increase during the 15-day continuous recycling trial.

紫色土流域次降雨条件下碳、磷非点源输出过程及其流失负荷研究

通过对位于川中丘陵区的紫色土流域在次降雨过程中溶解态有机碳（DOC）和不同形态磷素的输出进行动态监测，分析降雨过程DOC和P输出负荷，并探讨降雨径流对C、P迁移和水环境的影响。研究结果表明：（1）3次降雨共产生地表径流20399.8 m³，碳、磷输出负荷为83.19 kg和5.1 kg，次降雨过程径流C、P输出动态差异较大，其中径流DOC浓度随降雨历时的延长而降低，随后迅速升高，在达峰值后逐渐降低并趋于平稳。（2）降雨径流过程中磷素迁移主要以颗粒态（PP）为主， 磷酸盐（PO₄^3--P）是径流溶解态总磷（DTP）的主要存在形式，3次降雨PP输出负荷分别为1167.491、1891.331、984.74 g；PO₄^3--P输出负荷分别为108.37、338.8、167.79 g。（3）3次降雨径流DOC输出浓度分别为3.37、4.77、6.97 mg/L，总磷（Total phosphorus，TP）输出浓度分别为0.11、0.43、0.74 mg/L；次降雨径流C/P比分别为192、48和42.1，相比于暴雨而言，大雨和中雨带来的水质问题需引起关注。;Rain has been identified as a major factor causing phosphorus (P) and dissolved organic carbon (DOC) loss, particularly in agricultural landscape. More application of chemical fertilizer and unreasonable agricultural management intensified the loss. In addition, rain also made great contribution to water pollution, such as eutrophication which degraded the surface water quality and threatened the hydrosphere ecosystem. The aim of this study was to monitor the dynamics of carbon and phosphorus losses under different rainfall events in Yanting,Sichuan Province, China (105°27' E,31°16' N) from July to August in 2012, then to better understand the processes and mechanisms of the dissolve organic carbon (DOC) and P loss, and to evaluated the effect of environment on purple soil area as well. The results showed that the total discharge of all of the rainfall events was 20399.8 m³ and the transport load of carbon and P was 83.19 kg and 5.1 kg, respectively. The higher rainfall resulted in the bigger loss load. Furthermore, the DOC and total phosphorus (TP) output dynamics were significantly different among the three types of rainfall. For example, the pattern of DOC concentration in the runoff is not consistent with the discharge of runoff, which showed that the concentration went down with the time length of rainfall first, and then sharply up, after it achieved the peak value, it decreased gradually and then tended to remain at a level. The order of peak values of total phosphorus (TP) appeared in the runoff was 20^th Jul > 20^th Aug > 30^th Aug. The particular phosphorus (PP) transported by surface flow in all kinds of rainfall types was the main form of P during runoff, while phosphate phosphorus (PO₄^3--P) occupied the main position of dissolved total phosphorus (DTP). The transport load of PP under each rainfall event was 1167.491,1891.331,984.74 g while that of PO₄^3--P was 108.37,338.8,167.79 g,respectively. The export concentration of DOC and TP in runoff under different rainfall events was 3.37,4.77,6.97 mg/L and 0.11,0.43,0.74 mg/L, respectively. One of the targets to evaluate the effectiveness of P is C/P ratio. In general the lower C/P ratio will lead to the higher effectiveness of P. In each rainfall events the ratio was 192, 48 and 42.1, respectively, which indicated that the chance of water pollution caused by big and middle rainfall types was much higher. In conclusion, the effective control measures should be taken to reduce the loss of P and carbon in this pluvial region, and more attentions should be given to big and middle rainfall types.

Characterization of Surface Runoff, Soil Erosion and Nutrient Loss on Forest-Agriculture Landscape

The study was aimed to quantify volume of surface runoff, soil erosion and nutrient loss from the forest-agriculture landscape (forest margins) in Lore Lindu National Park Central Sulawesi. Surface runoff volume and soil erosion were measured daily on erosion plots. It was installed on several land use types i.e. forest land, maize, young cocoa, medium cocoa, old cocoa, vanilla, shrub and bush and bareland, on the soil Typic Dystrudepts with slope ± 40%. The nutrient content in surface runoff and sediments were analyzed from selected surface runoff and sediment samples. Surface runoff and soil erosion from agriculture land were respectively 2.1 to 3.4 and 3.6 to 5.8 times higher than from forest lands. Meanwhile, surface runoff and soil erosion from bareland were respectively 7.0 and 23.7 times greater than forest land respectively. Sediment nutrient contents from forest land were higher than agriculture land. In the contrary, total nutrient lost from agriculture land were higher than forest land ones. Nutrient losses carried by surface runoff were larger than those losses carried by sediments. Dissolved organic carbon (DOC) loss in surface runoff was 6,1 to 8,0 times higher than total organic carbon (TOC) loss in sediments. Likewise, nitrate (NO3-) loss in surface runoff was 1.9 to 12.1 times higher than total nitrogen (TN) in sediments as well as potassium, calcium, magnesium and sodium losses. Potassium is dominant cation loss carried by the surface runoff, while calcium is mainly carried by sediment.Keywords: Dissolve organic carbon; forest-agriculture landscape; nutrient loss; soil erosion; surface runoff[How to Cite: Hidayat Y, K Murtilaksono and N Sinukaban. 2012. Characterization of Surface Runoff, Soil Erosion and Nutrient Loss on Forest-agriculture Landscape. J Trop Soils, 17 (3): 259-266. doi: 10.5400/jts.2012.17.3.259][Permalink/DOI: www.dx.doi.org/10.5400/jts.2012.17.3.259]

毛竹高速生长期土壤碳氮动态及其微生物特性

The soil carbon,nitrogen dynamics and its microbiological ecological characteristic were investigated during bamboo high-speed growth in typical bamboo(Phyllostachys Pubescens) forests.The results showed that the content of total nitrogen(TN) reduced by 13%,22% and 6% respectively in the three testing spots.TN of soil showed a significant positive correlation with alkaline hydrolysis nitrogen,ammonium nitrogen and nitrate nitrogen(R2=0.48*,0.65**,0.70** respectively) during bamboo high-speed growth indicating that the soil nitrogen was absorbed in different forms by bamboo which caused soil total nitrogen reduction.Soil total organic carbon(TOC) and dissolve organic carbon(DOC) including extraction at 20℃(20℃ DOC) and at 80℃(80℃ DOC) were significantly decreased during bamboo growth.The results showed that TOC reduced by 26%,20% and 24% respectively in three testing spots.The content of the 20℃ DOC reduced by 51%,22% and 23% in three testing spot respectively,which was considerably greater(P0.05) than the reduction of 80℃ DOC in the testing spots.The relationship between soil total nitrogen(TN) and total organic carbon(TOC) analysis showed that TN and TOC were strongly inter-correlated(R2=0.89**) indicating that the change of soil carbon was closely related with the content of soil nitrogen during bamboo high-speed growth.Soil microorganisms are important in the cycling of almost all the major plant nutrients including the turnover of organic matter.Environmental conditions and perturbation are likely to affect microbial population structures and their functions in soils which may result in a change of overall soil properties.During high-speed growth,bamboo consumed soil carbon and soil nitrogen which lead to soil nutrient deficiency,effected soil microbial biomass and excessive carbon reduction,it also changed the soil microbial community.The content of soil microbial biomass carbon decreased from 800 mg/kg at the first sampling day to 589 mg/kg at the last sampling day.Soil under different sampling date contained a variety of PLFAs composed of saturated,unsaturated,methyl-branched and cyclopropane fatty acids.Thirty-four PLFAs with chain lengths from C12 to C20 were identified.The PLFA concentration data were subjected to principal components analysis(PCA).The first two principal components(PC1 and PC2) accounted for 62.95% and 17.20% of the variation respectively,which showed soil microbial community was changed significantly during bamboo growth.Specific identified PLFAs including saturated fatty acids(14:0,16:0,18:0,20:0,i15:0,i16:0,i17:0,i18:0,a15:0,a17:0) which represented bacteria were found to be distributed on the right of the load diagram,while unsaturated fatty acids(18:2w6,9c/18:0ANTE) which represented fungi were found to be distributed on the left of the load diagram.Thus,these bacteria indicator PLFAs were more abundant in the later soil sampling,while the fungi indicator PLFAs were more abundant in the early soil sampling,indicating that with the soil nutrient consumption during bamboo high-speed growth,total PLFA and the PLFAs that represent bacteria decreased,While the PLFAs that represent fungi increased.Thus,the change of soil carbon and soil nitrogen can significantly affect soil microbial community structure in the bamboo forest soil.

2. Comparison of the disinfection by-product formation potentials between a wastewater effluent and surface waters

In this study, the chemical reactivity with chlorine as measured by disinfection by-product formation potential (DBPFP) is compared among samples of a wastewater effluent and surface waters. Water samples that had higher anthropogenic impacts were found to have higher overall DBPFP due primarily to higher dissolve organic carbon (DOC) concentrations. Effluent-derived organic matter (EfOM), however, was found to be less reactive with chlorine on a per DOC concentration basis. Yet, EfOM had higher proportions of brominated DBP, which may be associated with greater health risks. In this research, pyrolysis-GC/MS was used to establish relationship between structural features of DOC and DBPFP. We show that there is a critical set of pyrolysis fragments that separates the waters based on the degree of anthropogenic influence. Even though no single chemical marker was found to be indicative of the formation potentials of different classes of DBP, combinations of chemical fragments were found to be associated with the formation potentials of total trihalomethane (THM), brominated THM, total haloacetic acid (HAA), and brominated HAA for this set of samples. In contrast to previous work, the phenolic signature of these samples was negatively correlated to DBPFP, whereas strong relationships were found between DBPFP and the organic nitrogen and halogenated signatures.

Composition, Dynamics, and Fate of Leached Dissolved Organic Matter in Terrestrial Ecosystems: Results from a Decomposition Experiment

Fluxes of dissolved organic matter (DOM) are an important vector for the movement of carbon (C) and nutrients both within and between ecosystems. However, although DOM fluxes from throughfall and through litterfall can be large, little is known about the fate of DOM leached from plant canopies, or from the litter layer into the soil horizon. In this study, our objectives were to determine the importance of plant-litter leachate as a vehicle for DOM movement, and to track DOM decomposition [including dissolve organic carbon (DOC) and dissolved organic nitrogen (DON) fractions], as well as DOM chemical and isotopic dynamics, during a long-term laboratory incubation experiment using fresh leaves and litter from several ecosystem types. The water-extractable fraction of organic C was high for all five plant species, as was the biodegradable fraction; in most cases, more than 70% of the initial DOM was decomposed in the first 10 days of the experiment. The chemical composition of the DOM changed as decomposition proceeded, with humic (hydrophobic) fractions becoming relatively more abundant than nonhumic (hydrophilic) fractions over time. However, in spite of proportional changes in humic and nonhumic fractions over time, our data suggest that both fractions are readily decomposed in the absence of physicochemical reactions with soil surfaces. Our data also showed no changes in the 13 C signature of DOM during decomposition, suggesting that isotopic fractionation during DOM uptake is not a significant process. These results suggest that soil microorganisms preferentially decompose more labile organic molecules in the DOM pool, which also tend to be isotopically heavier than more recalcitrant DOM fractions. We believe that the interaction between DOM decomposition dynamics and soil sorption processes contribute to the 13 C enrichment of soil organic matter commonly observed with depth in soil profiles.