OC Content Research Articles

Sediment distribution and organic carbon burial in a subtropical hydroelectric reservoir

Reservoir sediment is a major player in the terrestrial carbon (C) budget, and the quantification of C burial in sediments is important in assessing the reservoir’s role in the global C budget. However, assessments of C burial in sediments of sub-tropical hydroelectric reservoirs and their potential as C sinks are thus far limited due to a lack of whole reservoir assessments of C burial. In this study, a combined seismic survey with sediment core analysis was conducted in the Xin’anjiang Reservoir, the first large hydroelectric reservoir in China. The total organic carbon (TOC), total nitrogen, isotopic C composition (δ13C), and sediment grain size were analyzed. 210Pb and 137Cs were used to obtain the sediment chronologies. The data suggest that bottom bathymetry of the pre-existing reservoir is an important factor on sediment accumulated within the reservoir. The sediment OC content and trophic state became controlling factors and accelerated the OC burial in the sediment. Based on the interpolated sediment thickness data and total reservoir area, the average TOC burial rate was estimated at 34.0 g C m−2 year−1 (ranging 0–676.7 g C m−2 year−1). This rate is within that estimated by sediment coring (mean 40.4 g C m−2 year−1, ranging 15.8–110.1 g C m−2 year−1) as a result of high heterogeneity of sediment distribution and irregular sedimentation. However, the result was close to the estimates of previous studies, demonstrating that the combined method here can also be an effective way to conduct future estimation of C burial in freshwater reservoirs.

Variations in soil properties and native woody plant species abundance under Prosopis juliflora invasion in Afar grazing lands, Ethiopia

IntroductionPastoralism and agro-pastoralism are the major modes of life in arid and semi-arid rangelands. However, rangeland quality and quantity are rapidly deteriorating due to a number of natural and human-induced factors, one of which is bush encroachment. Little is known on how bush encroachment affects the ecosystem functions and services expressed in terms of the native vegetation composition and structure, status of the soil seed bank, soil chemical and physical properties, and the abundance of mycorrhiza spores.MethodsWe assessed woody species in 64 plots distributed across four levels of Prosopis juliflora invasion (high, medium, low, and none) at two sites, Amibara and Gewane, in the Afar Region, Ethiopia. We collected composite soil samples to investigate the soil seed bank, mycorrhizal associations, and spore abundance.ResultsPlant biodiversity was generally low, with eight and four woody species in Gewane and Amibara, respectively. Prosopis juliflora was dominant in highly, moderately, and lowly invaded areas while Acacia senegal dominated the non-invaded areas. The average number of P. juliflora individuals ranged from 3/ha at non-invaded areas in Gewane to 4200/ha at highly invaded areas in Amibara while the total individual number of native woody species ranged from 0 to 88/ha at highly and lowly invaded areas, respectively. The population structure of trees/shrubs in all invasion areas showed an inverted J-shaped distribution, characterized by a high abundance of small individuals. Prosopis juliflora invasion was associated with high soil OC, Na, Ca, P, bulk density, and moisture content. Herbaceous seed numbers and species richness were highest in the moderately and highly invaded areas. All sampled tree species were associated with mycorrhiza but the percentage of root length colonization by different arbuscular mycorrhizal fungus structures varied significantly (p < 0.05) across invasion categories and sites.ConclusionsOur results revealed that although P. juliflora invasion negatively impacted the availability of native woody livestock forage species, it had a positive effect on most soil physical and chemical properties. Such variable effects call out for sustainable management practices when invaded areas are restored.

NUTRIENT POTENTIAL FROM VERMICOMPOST OF TWO CONTRASTING ORGANIC WASTES USING TROPICAL EARTHWORM AND MOSQUITO NET AS CULTURE MATERIAL

The biochemical break down of plant litters by earthworm and the associated micro-organisms are the main process of humus development. Nutrient potential from vermicompost of two contrasting organic wastes using tropical earthworm (Eudrilus eugeniae) and mosquito net as culture material was studied. The organic wastes diet are fruit wastes (FRW) and vegetable wastes (VGW). Ten earthworms were inoculated to each of the eight (8) sacks. The result of the experiment after three (3) months and three (3) weeks inoculation showed that the Eudrilus eugeniae can be cultured in sack made from old window mosquito net and the vermicompost produced in each waste are of high quality humus. The nutrient content of the vermicomposts varied among the wastes. The pH level of the wastes was found to be alkaline of which VGW recorded higher value (9.15) compared to FRW. The OC content and electrical conductivity (EC) were significantly different among the treatments. Higher values of Na, OC, K, and P were recorded in FRW, while VGW recorded higher values in Ca, Mg and EC. The highest dry matter weight of 115.75gkg -1 of vermicompost was recorded in VGW as against 109.5gkg-1 recorded in FRW. Earthworm production measured by the number survived, number of cocoon, and biomass weight at the end of the study showed VGW as best culture for earthworm production. FRW did not record any cocoon at harvest. Findings of the study confirm that tropical earthworm – Eudrilus eugeniae can be easily used for high quality vermicompost production which is socioeconomically very beneficial for soil fertility improvement and sustainable crop production. The wastes and the earthworm are in abundance in the study area and within the reach of the farmer. The farmers are therefore encouraged to harness this technology for their soil and crop production.

Sub-type source profiles of fine particles for fugitive dust and accumulative health risks of heavy metals: a case study in a fast-developing city of China.

Sub-type source profiles for atmospheric fine particle (PM2.5) were still scare in China, which limited the accurate source identification of it. Fugitive dust (including road dust, soil dust, resuspended dust, and construction dust, etc.) was one type of the most important contributors to PM2.5 and its associated toxic metals held potential threaten to human health. The chemical compositions, sources, and health risks of sub-type fugitive dust deserved an investigation for further accurate control of particles and alleviating human health risks. A total of sixty-five fugitive dust samples were collected in Suzhou, a fast-developing city in southern China, including eleven sub-types of road dust (overpass, main street, collector street, and ordinary street), soil dust (farmland and tree lawn), resuspended dust (site types were corresponding to those of road dust), and construction dust (large construction sites). Chemical analysis of water-soluble ions, elements, and carbonaceous components was carried out to establish the sub-type source profiles of PM2.5 for fugitive dust. Results showed that crustal elements were the most abundant components of fugitive dust, and soil dust was less polluted by anthropogenic activities. High contents of OC and low contents of EC were found in all the eleven types of dust. Equivalent ratios of anions and cations indicated that the fugitive dust was obviously alkaline. The contents of OC and EC in the four types of road dust were higher than those in other types of dust, while there existed differences among the sub-types of road dust. The NO3-/SO42- ratios (0.03-0.09) implied that coal-burning and motor vehicle emission co-existed in Suzhou. Coefficient divergence (CD) values of eleven sub-type source profiles showed that there were certain differences among them, which suggested the possibility of sub-type source identification. Cluster analysis indicated the heavy metals in fugitive dust were mainly from crustal materials, metallurgical manufacturing, vehicle emissions, and industrial activities. The enrichment degree of heavy metals for the four types of road dust was also inconsistent. Heavy metals in road dust and soil dust posed a non-carcinogenic risk to children through direct ingestion, and the non-carcinogenic risk of direct intake of heavy metals was much higher than that of respiratory and skin contact. It was found that the accumulative health risks of heavy metals were higher in densely populated areas, traffic intensive areas, and industrial areas through the spatial analysis. This study firstly discussed the chemical compositions of PM2.5 for eleven sub-types of fugitive dust in a Chinese city and assessed the accumulative health risks of heavy metals, which could be a demonstration for further related researches.

Coring and compaction: Best practice in blue carbon stock and burial estimations

A comparison of gouge and hammer coring techniques in intertidal wetland soils highlights a significant effect of soil compaction of up to 28% associated with the widely applied hammer coring method employed in Blue Carbon research. Hammer coring reduces the thickness of the soil profile and increases the dry bulk density, which results in an overestimation of the soil OC stock of up to 22%. In saltmarshes with multiple different soil units, we show that hammer coring is unsuitable for the calculation of OC stocks and should be avoided in favour of Russian or gouge cores. Compaction changes both soil dry bulk density and porosity and we show that resultant radiometric chronologies are compromised, almost doubling mass accumulation rates. While we show that the OC (%) content of these sediments is largely unchanged by coring method, the implication for OC burial rates are profound because of the significant effect of hammer coring on the calculation of soil mass accumlation rates.

Carbonaceous Aerosol Emitted from Biofuel Household Stove Combustion in South China

Near-source measurements of smoke emissions from household stove combustion in a rural area of South China were conducted with 7 typical biomass fuels. Particulate matter samples (both PM10 and PM2.5) were analyzed for their carbonaceous components, including organic and elemental carbon (OC, EC) as well as levoglucosan (molecular tracer of biomass burning), employing thermal-optical and GC-MS analysis. The OC and EC content in PM2.5 and PM10 smoke particles derived from the various types of vegetation showed different patterns with the smallest values observed for straw type fuels. The OC/EC ratios in PM2.5 and PM10 showed an order of straw &gt; hardwood &gt; bamboo &gt; softwood. Mass concentrations of particulate matter emitted from rice straw burning were highest with 12.23 ± 0.87 mg/m3 (PM10) and 9.31 ± 0.81 mg/m3 (PM2.5), while the mass ratios (LG/PM and OC/PM) were lowest among the 7 fuels, indicating that particle emissions from straw burning were higher than those from woody fuels, using similar burning conditions. The levoglucosan emission ratios were rather high and this single most abundant organic species was mainly present in the fine particle mode. Linear correlation analysis showed a strong relationship between levoglucosan and EC emissions.

Diuron Sorption, Desorption and Degradation in Anthropogenic Soils Compared to Sandy Soil

ABSTRACT: The aim of this study was to evaluate diuron sorption, desorption and degradation in two anthropogenic soils (Terra Preta de Índio - TPI) in contrast to a sandy soil (Quartzarenic Neosol - NQo). Sorption-desorption studies were performed by the batch equilibrium method and biodegradation in biometric bottles using radiolabeled diuron in 14C. Freundlich coefficient (Kf) values ranged from 13.50 to 50.41 µmol(1-1/n) L1/n kg-1 in TPI-2 and TPI-1, respectively, indicating very high diuron sorption in anthropogenic soils, following the order: TPI-1 ≥ TPI-2 &gt; NQo (99.10, 98.95 and 60.8%, respectively). Diuron desorption was very low in anthropogenic soils, ranging from 1.36 (TPI-1) to 1.70% (TPI-2), and 24% to NQo. Accumulated diuron mineralization to 14C-CO2 was &lt; 3% at 70 days after herbicide application, regardless of the assessed soil. Formation of 35 and 44% residue bound to TPI-2 and TPI-1 was observed, higher than to NQo (17%). In contrast, the residue extracted from NQo varied from 72 to 91%, ranging from 48 to 83% for TPI-1 and TPI-2 during the incubation period. The degradation half-life (DT50) of diuron in anthropogenic soils was of 66.65 and 68.63 days for TPI-1 and TPI-2, respectively, while a period of 88.86 days was observed for NQo. The formation of only one herbicide metabolite in all soils was evidenced. The application of diuron in arable areas in the presence of anthropogenic Amazonian soils may lead to inefficient chemical weed control, since these soils may reduce herbicide soil bioavailability due to high OC contents, where high sorption and low herbicide desorption are noted, as well as faster degradation compared to sandy soil.

Sources and radiocarbon ages of organic carbon in different grain size fractions of Yellow River-transported particles and coastal sediments

The elemental (TOC, TN and C/N) and carbon isotope (Δ14C and δ13C) compositions of organic matter were measured in different grain size fractions of particles transported by the Yellow River and surface sediments in the Bohai Sea and the Yellow Sea. In the riverine particle and sediment samples, high OC contents were associated with small grain size fractions consisting mainly of clay minerals. The δ13C and Δ14C values of the bulk riverine particulate organic carbon (POC) collected from the Lijin and Xiaolangdi sites were relatively constant but varied significantly (−21.9‰ to −26.0‰ and −325‰ to −620‰, respectively) among the different size fractions. In comparison, large spatial variations in δ13C (−20.6‰ to −24.5‰) and Δ14C (−188‰ to −646‰) values, which increased seaward due to the difference in source carbon, were found for bulk TOC Δ14C preserved in the surface sediments, but no significant differences were observed among the values in the different size fractions in most sediments. The different carbon isotopic values of the riverine POC and sedimentary TOC reflect differences in the sources, degradation and cycling time scales of the OC. The Yellow River exports very old (5220 ± 295 yrs) POC that is much older than the TOC (2457 ± 676 yrs) preserved in the surface sediments in the Bohai and Yellow seas. Calculations using a dual-isotope three end-member model indicate that pre-aged soil OC and ancient fossil OC represent major proportions (57 ± 16% and 30 ± 8%, respectively) of the riverine POC and that terrestrial biomass OC represents a minor proportion (13 ± 11%). The drainage environment of the river plays important roles in controlling the sources and ages of the riverine POC. In contrast, the TOC in the grain size fractions of the surface sediments in the Bohai and Yellow seas is dominated by marine-derived modern OC (47 ± 13%), followed by pre-aged soil OC (29 ± 9%) and ancient fossil OC (25 ± 14%). The ages of the TOC are determined mainly by the source input, rapid sedimentation, sediment minerology and decomposition of OC during early diagenesis in these large river-influenced marginal seas.

Soil Phase: Base for Deriving Land Capability Class and Crop Suitability

A detailed land resource study of Gadagi-2 micro watershed, Lingasusgur taluk, Raichur district, Karnataka state, India, was carried out during summer 2017, at the scale of 1:8000 using cadastral map overlaid on IRS Cartosat-1 merged with LISS IV satellite imagery. Initially, a detailed survey was carried out to derive soil phase units based on land surface and profile characters. Five soil series were identified and mapped into five soil phase units. It is revealed that soil were non-saline with EC &lt;4 dSm-1. The OC, available P2O5 and available K2O content of the study area were low to medium, and soil available N and S status were low in all the five soil phases. HEGiC2 soil phase was classified as class III land capability class with limitation of rooting and slope. Rest of the soil phases viz., KALhC2g1S1R1, VKRhD2g2S2R3, CHRhC2g1S1R1 and BHGhE2g2S2R2 were classified as class IV land capability with limitation of slope, texture, erosion, rooting condition and organic carbon. Suitability for horticulture and field crops were derived based on soil phase, site characteristics and climatic regimes. Proposed crop plan for field crops and horticulture crops for all five soil phase units was prepared. Suitable soil and water conservation measures such as deep and wider size pit and drip irrigation for fruit crops and forest trees, cultivation on raised beds with mulches and drip irrigation, graded bunds and strengthening of field bunds, crescent bunds were found suitable for vegetables, flowers and sole crops based on the soil phase characteristics.

Efficient sequestration of terrigenous organic carbon in the New Britain Trench

The fate of terrigenous organic carbon (OCterr) in the ocean remains an enigma for four decades. Hadal trenches, the deepest ocean realm (6–11 km deep), were recently proposed to be OC depocenters, but whether and how much OCterr was sequestrated there remain elusive. Here we conducted comprehensive analyses for four sediment cores from the New Britain Trench (NBT) close to Papua New Guinea to assess source, translocation and burial of OC. The bulk and molecular radiocarbon data suggest that the NBT landward slope and axis sediments mainly receive young and biogenic rather than petrogenic OC. The three-endmember mixing model based on Δ14C, δ13C and OC contents reveals that sediments of the NBT axis (8225 m) comprise relatively high OC contents (0.66 ± 0.08%), of which biogenic OCterr accounts for 62 ± 10%. The high proportion of biogenic OCterr was attributed to the selective translocation of OCterr-enriched coarse particles and rapid delivery of sediments supported by unique V-shape feature of the trench. In contrast, the sediment OC at the oceanward slope is primarily of a marine origin, suggesting that OCterr was efficiently trapped in the trench bottom. It is estimated that the burial rate is 2.75 ± 0.32 g C m−2 yr−1 for OC and 1.69 ± 0.41 g C m−2 yr−1 for OCterr in the NBT. Given a fact that many trenches are close to the landmasses, we propose that the hadal trenches may contribute significantly to the burial of OCterr in the ocean.

Impact of isolated atmospheric aging processes on the cloud condensation nuclei activation of soot particles

Abstract. The largest contributors to the uncertainty in assessing the anthropogenic contribution in radiative forcing are the direct and indirect effects of aerosol particles on the Earth's radiative budget. Soot particles are of special interest since their properties can change significantly due to aging processes once they are emitted into the atmosphere. Probably the largest obstacle for the investigation of these processes in the laboratory is the long atmospheric lifetime of 1 week, requiring tailored experiments that cover this time span. This work presents results on the ability of two types of soot, obtained using a miniCAST soot generator, to act as cloud condensation nuclei (CCN) after exposure to atmospherically relevant levels of ozone (O3) and humidity. Aging times of up to 12 h were achieved by successful application of the continuous-flow stirred tank reactor (CSTR) concept while allowing for size selection of particles prior to the aging step. Particles of 100 nm diameter and rich in organic carbon (OC) that were initially CCN inactive showed significant CCN activity at supersaturations (SS) down to 0.3 % after 10 h of exposure to 200 ppb of O3. While this process was not affected by different levels of relative humidity in the range of 5 %–75 %, a high sensitivity towards the ambient/reaction temperature was observed. Soot particles with a lower OC content required an approximately 4-fold longer aging duration to show CCN activity at the same SS. Prior to the slow change in the CCN activity, a rapid increase in the particle diameter was detected which occurred within several minutes. This study highlights the applicability of the CSTR approach for the simulation of atmospheric aging processes, as aging durations beyond 12 h can be achieved in comparably small aerosol chamber volumes (&lt;3 m3). Implementation of our measurement results in a global aerosol-climate model, ECHAM6.3-HAM2.3, showed a statistically significant increase in the regional and global CCN burden and cloud droplet number concentration.

Investigation of the sorption of 17α-ethynylestradiol (EE2) on soils formed under aerobic and anaerobic conditions

A study was conducted on the sorption of 17α-ethynylestradiol (EE2) on five soils formed under different redox conditions: an Arenosol (A_20) with fully aerobic conditions, two Gleysol samples (G_20 and G_40) with suboxic and anoxic conditions and two Histosols (H_20 and H_80) with mostly anoxic conditions. The soils were characterized on the basis of total organic carbon (TOC), specific surface area (SSA) and the Fourier transform infrared spectra of the humic acid and humin fractions (the soil remaining after alkali extraction) of the soil. The maximum adsorption capacity of the soils (Qmax) ranged from 10.7 to 83.6 mg/g in the order G_20 > H_20 > G_40 > A_20 > H_80, which reflected the organic matter content of the soils. The sorption isotherms were found to be nonlinear for all the soil samples, with Freundlich n values of 0.45–0.68. The strong nonlinearity found in the adsorption of the H_80 samples could be attributed to their high hard carbon content, which was confirmed by the high aromaticity of the humin fraction. The maximum sorption capacity (Qmax) of the soils did not increase indefinitely as the organic carbon content of the soils rose. There could be two reasons for this: (i) the large amount of organic matter may reduce the number of binding sites on the surface, and (ii) the decrease in SSA with increasing soil OC content may limit the ability to adsorb EE2 molecules. In anaerobic soil samples, where organic matter accumulation is pronounced, the amount of aromatic and phenolic compounds was higher than in better aerated soil profiles. Strong correlations were found between the amount of aromatic and phenolic compounds in the organic matter and the adsorption of EE2 molecules, indicating that π-π interaction and H-bonding are the dominant sorption mechanisms.

The role of laccase in stabilization of soil organic matter by iron in various plant-dominated peatlands: degradation or sequestration?

The association of organic matter with iron (Fe-OM associations) is recognized as an important stabilization mechanism for soil organic matter. Our objective was to assess the factors regulating stabilization of soil organic matter by iron in various plant-dominated peatlands, and the role of laccase in the formation of Fe-OM associations. We investigated Fe-bound OC content and related physicochemical and biochemical parameters in four plots with different successional vegetation, and a set of simulations was conducted to investigate the association of Fe and peat-derived dissolved organic carbon catalysed by laccase. Our results indicate Fe-bound OC content varies regularly with the succession gradients, and a significant positive relationship between laccase activities and Fe-bound OC content was found (R = 0.77, P < 0.05). Although laccase degradation of recalcitrant polyphenolics is related with the CO2 release from peat soils (R = 0.697; P < 0.05), the simulation results confirmed laccase can significantly promote the formation of Fe-OM association. We propose that laccase plays a unique multifunctional role in the peatland carbon cycle. That is, while laccase degrades refractory organic matter such as lignin, it may enhance carbon sequestration by promoting the formation of Fe-OM association, which is particularly effective in acidic peat environments containing abundant iron and laccase-producing fungi.

Specific surface area of combustion emitted particles: Impact of primary particle diameter and organic content

Specific surface areas of particles produced at small-scale diffusion flame burners and also in pilot and large-scale fires involving complex fuels are reported and compared. Specific surface area SBET is determined by BET (Brunauer-Emmett-Teller) analysis and also according to previously developed approach STEM relying on the primary sphere based on TEM (Tansmission Electron Microscopy) images analysis. True density is also determined and the respective influences of primary particle diameter (Dpp) and organic carbon to total carbon ratio (OC/TC) are discussed. The present study is the first to propose a careful comparison between TEM and BET specific surface areas of 20 different samples of carbonaceous particles emitted under realistic fire conditions and to bring validity range for such TEM based approach. For samples containing low and moderate OC content (less than 20%), a good agreement between STEM and SBET is reported (within ± 20% for a confidence interval of 95%), confirming the significant influence of primary particle diameter and the relevance of a purely geometrical description of the surface specific area of soot particles. For larger OC/TC, such approach fails to predict the particles specific surface area within a reasonable confidence interval.

The role of organic amendment in soils affected by residual pollution of potentially harmful elements

The addition of organic amendment in soils affected by residual pollution of potentially harmful elements (PHEs) is evaluated. The area was polluted twenty years ago and remediation actions were intensively applied, but evidence of pollution are still detected in some sectors. The amendment application produces significant changes in the main soil properties and modifies the mobility and availability of the pollutants. In general, Cu, Zn, Cd and Pb, showed a significant reduction in soluble and exchangeable forms after the vermicompost addition (percentage of reduction ranging from 59% for soluble Pb to 95% for exchangeable Zn), both in highly (UVS) as in moderately (VS1) polluted soils. This reduction is strongly related to the rise in OC content and pH. Arsenic presented no significant reduction or even an increase in soluble forms in moderately polluted soils (VS1), where the competing effects of OC and phosphorous could be responsible for this increase. Pb also showed an increase in availability after vermicompost application, probably related to the competing effect of Mg2+ coming from the organic amendment. The less mobile forms (those extracted with oxalic-oxalate, pyrophosphate and EDTA), indicate that vermicompost application reduce medium-long term mobility to similar values of those found in less polluted soils (VS2); anyway, an increase in available forms of Pb and As was detected in some cases, indicating a potential risk of toxicity that should be monitored over time.

Soil burden by persistent organochlorine compounds in the vicinity of a coal-fired power plant in Croatia: a comparison study with an urban-industrialized area.

The impact of a coal-fired Plomin Power Plant (PPP) in Croatia on PCB soil burden was examined by comparing the occurrence, levels, and profile of PCBs in soil from the PPP with the values determined in urban-industrialized soil (Varaždin, Croatia). Soil burden by organochlorine pesticides (OCPs) were also investigated at both locations. Topsoil samples were collected at five distances (100-800m) along a downwind pollution gradient from the PPP and across the city. The total content of PCBs in 100-m soil was nearly 20-fold the levels found in 800-m soil, which pointed to the PPP as a local source of soil contamination. The PPP soils were dominated by indicator PCB congeners, particularly hexa-homologs. A different profile and mass fraction range of PCBs in soils from PPP and Varaždin area indicated the different sources of contamination. Levels of total PCBs in PPP soils (0.25-19.07μgkg-1) were higher than PCB levels determined in soils from Varaždin (0.29-5.52μgkg-1), partially as a result of higher OC content in PPP soils. PPP soil burden by PCBs corresponded to a lower end of PCB level ranges reported for cities with high population and heavy industry. OCPs were detected at significantly higher levels in Varaždin soils than in PPP soils, with the highest contribution of the DDT-like compounds (DDX) detected in soils affected by river deposits. The p,p'-DDE/p,p'-DDT ratio in Varaždin soils indicated a fresh atmospheric input of p,p'-DDT. The PPP soil analysis detected a presence of only p,p'-DDE and HCB at levels corresponding to their global environmental presence.

Urban Aerosol Hygroscopicity During Haze Weather

The hygroscopicity of aerosols has an important influence on atmospheric visibility and is one of the main causes of haze pollution. Based on observations of the aerosol hygroscopic growth factor (GF), water soluble inorganic ions, and organic carbon/elemental carbon (OC/EC) data during haze weather from April 17 to May 21, in 2014, the hygroscopic properties of aerosols and corresponding effects on haze in Nanjing were analyzed. The results showed that the distribution of GF was bimodal and varied from 1.12 to 1.64. With the increase of particle size, the average hygroscopic growth factor (GFmean) changed less and the standard deviation of wettability (σ) increased gradually; meanwhile, the degree of external mixing of chemical components increased gradually. The hygroscopicity of aerosol particles in the day was better than that at night, but the mixing degree was weaker than that at night; in non-haze weather, the hygroscopicity of aerosol particles was stronger and the degree of external mixing was higher, while the hygroscopicity and mixing degree of haze particles showed opposite trends. With the increase of haze levels, the hygroscopicity of aerosol particles grew weaker and the degree of external mixing decreased further. Relative humidity can have a significant impact on the chemical components of aerosols and their hygroscopic capacity. Under a low humidity background, the main chemical components of aerosols included NH4+, NO3-, SO42-, OC, and EC, and the content of OC/EC in aerosols during haze days was more abundant; in haze weather with low relative humidity, abundant organic matter was the main reason for the decrease of the moisture absorption capacity of small-scale aerosols. The level of relative humidity in the haze weather was also an important factor affecting the hygroscopic capacity of aerosols. The contents of (NH4)2SO4, OC, and insoluble substances in aerosols were the highest, followed by NH4NO3. The contents of these chemical components showed obvious diurnal variation characteristics, which resulted in significant diurnal variation of the hygroscopicity of the aerosols. κchem calculated by the chemical composition and κmean acquired by observations using H-TDMA showed good consistency, and the correlation coefficient was 0.8903. In haze weather, the correlation between them was further enhanced. Therefore, the major chemical components of aerosols could be used to predict the hygroscopic properties of aerosols.

Reduced water motion enhances organic carbon stocks in temperate eelgrass meadows

AbstractOrganic carbon (OC) storage in coastal vegetated ecosystems is increasingly being considered in carbon financing and climate change mitigation strategies. However, spatial heterogeneity in these “blue carbon” stocks among and within habitats has only recently been examined, despite its considerable implications. Seagrass meadows have potential to store significant amounts of carbon in their sediments, yet studies comparing sediment OC content at regional and meadow scales remain sparse. Here, we collected sediment cores from six temperate eelgrass (Zostera marina) meadows on the coast of British Columbia, Canada, to quantify sediment OC stocks, accumulation rates, and sources, and to examine local and regional drivers of variability. Sediment OC content was highly variable—across all sites, stocks in the top 0–5 cm ranged from 83 to 1089 g OC m−2, while the 15–20 cm stocks exhibited a 24‐fold difference, from 59 to 1407 g OC m−2. Carbon accumulation rates ranged from 4 to 33 g OC m−2 yr−1. Isotopic mixing models revealed that sediment OC was primarily terrestrial carbon (41.3%) and canopy‐forming kelps (33.3%), with a smaller contribution of eelgrass (25.3%). Here, we show that regional variability in OC content exceeds meadow‐scale variability. This result is likely driven by landscape factors, most notably relative water motion, representing a more dominant control on seagrass OC accumulation than meadow‐scale factors such as canopy complexity. These findings elicit caution when scaling up seagrass meadow OC content and demonstrate that measures of the hydrodynamic environment could improve estimates of carbon storage in temperate soft sediment habitats.

Influence of Geographic Region on Fatty Acid and Physical Properties of Indonesian Cocoa Butter from Smallholder Estate

&#x0D; &#x0D; &#x0D; Cocoa butter is the most essensial component in chocolate formulation and represent the biggest characteristic of this product. Indonesia is the third cocoa producers with cocoa producing area spread out in different geographic region and may affect in cocoa butter profiles. The aim of this experiment was to evaluate the fatty acid characteristic and physical properties of cocoa butter from smallholder estate relate to geographic region and climate. This experiment was conducted using unfermented cocoa bean from smallholder estate in eight provinces of Indonesian most growing areas. Fatty acid composition evaluated through the different region and physical properties evaluated in melting profiles and solid fat content. The result explain the fatty acid characteristic of Indonesian cocoa butter consist of palmitic acid (C16:0) 26.28–29.20%, stearic acid (C18:0) 32,14–37.29% and oleic acid (C18:1) 32,14–37,29%. Growing temperature signifi- cantly affects the increase of palmitic acid composition contribute to cocoa butter hardness. Cocoa butter completely melt in temperature of 36.65–39.20OC and solid fat content ranged 7.288–16.82% in 33OC and ranged 0.02–0.29% in 38OC. This Indonesian cocoa butter comply to the classification of hard cocoa butter.&#x0D; &#x0D; &#x0D;

Consumption and alteration of different organic matter sources during remediation of a sandy sulfuric soil

Saturated acid sulfate soils with hypersulfidic material are productive wetland soils, but when they dry, they generate large amounts of sulfuric acid due to oxidation of pyrite to form sulfuric material (pH <4) and consequently sulfuric soils. After re-saturation of sulfuric soils and thus the re-establishment of reduced conditions, activity of sulfate reducing bacteria (SRB) can lead to a renewed formation of Fe sulfides and pH increase. Many SRB are heterotrophic and require sufficient available organic matter; however, little is known about OC consumption and changes of the composition of organic substrates during the amelioration process. To investigate remediation of a sandy, OC-poor sulfuric soil (initial pH = 2.5), short-term anoxic incubation experiments over a period of approx. 10 weeks were conducted after re-submerging under controlled laboratory conditions. We tested different organic matter quantities between 10% up to 200% of the native soil OC content. Besides wheat straw, we used lactate additions to test if this selectively promotes the activity of SRB, and thus, accelerates sulfate reduction and pH neutralization. The results showed that OC additions of ≥50% of native soil OC content and pre-adjustment of pH to values ≥5.0 were necessary to subsequently enable microbial reduction reactions to occur, which increased the pH to values ≥5.5. OC additions of ≥100% instead of 50% of native soil OC as wheat straw led to quicker changes of redox and pH values, to slightly higher microbial activity as indicated by CO2 release, and to higher proportions of newly-formed mineral-associated OC. The addition of OC as lactate solution to promote specifically SRB was only successful in combination with wheat straw addition. Here, the presence of lactate led to the quickest changes of pH and redox values and resulted in pH ≥7 and redox values ≤ −300 mV due to an active microbial population. Our results indicate that a diverse microbial community is more important for successful remediation than a selective promotion of SRB.