Contribution Of Different Sources Research Articles

Source contributions to poor atmospheric visibility in China

China suffers from serious haze pollution characterized by extremely low visibility due to intensive air pollutant emissions. Designing effective visibility impairment control strategies requires quantitative measures of the contributions of different sources. In this study, a source-oriented Community Multiscale Air Quality model was applied to quantitatively determine the source contributions to visibility impairment in China in 2013. Emissions of air pollutants from seven source categories (power plants, residential sources, industries, transportation, open burning, dust, and agriculture) were separately tracked. The industrial sector dominates the visibility impairment in Beijing, Chongqing, Guangzhou, and Shanghai, contributing to 32.6–40.7% of the overall light extinction coefficient (bext). Agriculture and power sources contribute 13.0–16.7% and 12.6–14.9% to bext, respectively. The residential sector is the largest source of visibility impairment in Xi’an (39.5%). It also contributes 12.3–25.2% in Beijing, Chongqing, Guangzhou, and Shanghai. Transportation (6.3–10.2%), open burning (1.7–8.8%), and dust emission (1.0–3.6%) have relatively smaller contributions to bext in these cities. The source contributions to bext exhibit strong spatial and seasonal variations. Contributions from industrial, power, and residential sectors are higher in the North China Plain, Northeast China, and Sichuan Basin than in other regions of China. Industrial and residential emissions become the most important sources of visibility impairment in winter. In other seasons, industrial, power, and agriculture sources are important. The large spatial and seasonal variations in the sources of bext suggest that different pollutants mitigation programs should be designed for different regions and times of the year.

Comparisons of heavy metal input inventory in agricultural soils in North and South China: A review

A national-scale inventory of heavy metal inputs is essential to understand the current situation of contribution and spatial heterogeneity of heavy metal sources in China. Published literatures from 2008 to 2018 about heavy metal inputs from various pollution sources (atmospheric deposition, livestock manures, fertilizers, and sewage irrigation) to agricultural soils were collected. In the past ten years, atmospheric deposition was the main pollution source which was responsible for 50–93% of the total As, Cd, Cr, Hg, Ni, and Pb inputs, with livestock manures contributed to approximately 76% of total Cu inputs. However, due to industrial structure, geographical condition and the characteristics of economic development, the contribution of different sources to heavy metal pollution varies in different regions. For example, atmospheric deposition was the most important contributor in North China with its highly developed heavy industry and more coal combustion, while the contribution of livestock manures was obviously higher in South China due to its flourishing agricultural production and animal husbandry. Based on the analysis for clarifying the major pollution sources of five typical heavy metals (namely Cd, As, Hg, Cu and Pb), the controlling measures are suggested to make more effective and targeted strategies to protect agricultural soils in the future.

Source partitioning of atmospheric methane using stable carbon isotope measurements in the Reuss Valley, Switzerland

ABSTRACTMeasurements of methane () mole fractions and that resolve the diel cycle in the agriculturally dominated Reuss Valley, Switzerland, were used to quantify the contributions of different sources to the atmospheric source mix. Both a nocturnal (NBL) and a diurnal convective boundary layer (CBL) approach were employed. A diel course of mole fractions was found with a daytime minimum (background around 1900 ppb) and a nocturnal maximum (up to 3500 ppb). The C value in only showed small variations during the day (9–21 hours CET, ‰ ) when the atmosphere was well mixed, but decreased by ‰ during the night. Biogenic emissions dominated in both approaches (ranging from 60 to 94%), but non-biogenic sources were rather important (42.2% and 46.0% with CBL, 5.8% and 40% with NBL approach in 2011 and 2012, respectively, of total emissions). The sink, dominated by tropospheric OH oxidation and only to a minor extend by soil surface uptake, was quantified at roughly 4% of local emissions.

Quantifying Repeatability Reproducibility Sources of Error and Capacity of a Measurement: Demonstrated Using Laboratory Soil Plasticity Tests

The repeatability, reproducibility, and sources of error inherent in a given measurement are important considerations for potential users. To quantify errors arising from a single operator or multiple laboratories, most testing standards uses a one‐way analysis of variance‐ (ANOVA‐) based method, which utilizes a simple standard deviation across all measurements. However, this method does not allow users to quantify the sources of error and capacity (i.e., the precision to tolerance ratio). In this study, an innovative two‐way ANOVA‐based analysis method is selected to quantify the relative contributions of different sources of error and determine whether a measurement can be used to check conformance of a measured characteristic to engineering specifications. In this study, the standardized Atterberg limits tests, fall‐cone device Atterberg limits tests, and bar linear shrinkage tests widely used for determining the soil plasticity were selected for evaluation and demonstration. Comparisons between results of the various testing methods are presented, and the error sources contributing to the overall variations between tests are discussed. Based on the findings of this study, the authors suggest use of two‐way ANOVA‐based R&R analysis to quantify the sources of measurement error and capacity and also recommend using the fall cone device and ASTM standardized thread rolling device for determining liquid and plastic limits of soils, respectively.

Hydrochemical Changes and Influencing Factors in the Dongkemadi Region, Tanggula Range, China

In order to detect the source and controlling factors of hydrochemical ions in glacier meltwater-recharged rivers, the chemical characteristics of the river water, precipitation, and meltwater of the Dongkemadi River Basin, China, in 2014 (from May to October) were systematically analyzed, and combined with the hydrological and meteorological data. The results show that the hydrochemical pattern of the typical river was HCO3−-Ca2+. The most cations were Ca2+ and Mg2+, and the predominant anions were HCO3− and SO42−, in the river. The concentration of major ions and total dissolved solids (TDS) in the river water were much larger than that in the precipitation and meltwater. The TDS concentration was ordered: River water > precipitation > meltwater. The water-rock interaction and the dilution effect of the precipitation and meltwater on the runoff ions resulted in a negative correlation between the ion concentration of the river water and the river flow. The chemical ions of the river runoff mainly originated from rock weathering and the erosion (abrasion) caused by glacier movement. In addition, the contributions of different sources to the dissolved components of the Dongkemadi River were ordered: Carbonate (75.8%) > silicate (15.5%) > hydatogenic rock (5.7%) > atmospheric precipitation (3%), calculated by a forward geochemical model. And the hydrochemical weathering rates of carbonate and silicate minerals were 12.30 t·km−2·a−1 and 1.98 t·km−2·a−1, respectively. The CO2 fluxes, consumed by the chemical weathering of carbonate and silicate, were 3.28 × 105 mol·km−2·a−1 and 0.91 × 105 mol·km−2·a−1, respectively.

Modeling Escherichia coli fate and transport in the Kabul River Basin using SWAT

Access to safe water is the primary goal of all development plans, yet population increase, urbanization lead to contamination of water resources. This paper focuses on microbial contamination and aims to analyze the fate and transport of Escherichia coli in the Kabul River Basin using SWAT model to evaluate the contribution of different sources. The SWAT is calibrated and validated for the monthly time step using observed E. coli concentrations for April 2013–July 2015. The model skill score; coefficients of determination (R2) equal 0.72 and 0.70, Nash–Sutcliffe efficiencies (NSE) equal 0.69 and 0.66, and percentages bias (PBIAS) equal 3.7 and 1.9 respond well for both calibration and validation, respectively. Regional measured and modeled concentrations are very high with peaks of up to 5.2 10log cfu/100 ml in the wet season. Overall, point sources that are comprised of human feces from the big cities and livestock manure from animal sheds, contribute most (44%) to the E. coli concentrations. During peak discharge the non-point sources become the most important contributors due to wash-off from the land and diluted point sources. Allthough such studies are lacking in developing countries, they can be helpful for sanitation management by developing and accessing regional sanitation scenarios.

A novel approach of combining isotopic and geochemical signatures to differentiate the sources of sediments and particulate nutrients from different land uses

Determining the source of sediments and associated nutrients from terrestrial to aquatic environments is critical for managing the detrimental impacts of soil erosion and loss of nutrients from terrestrial into aquatic environment. However, tracing the source of particulate nutrients from different land uses has not been adequately carried out due to methodological difficulties in separating sources, particularly in the Great Barrier Reef (GBR) catchment. The objective of this study was to develop a method to differentiate the sources of particulate nutrients from soils collected from different land uses (combination of beef and dairy grazing, sugarcane, forest and banana) using both geochemical and isotopic signatures. In order to select a discriminative group of signatures, all soil samples collected from each of the land use areas were fractionated to <63 μm size fraction and were analysed for both isotopic (δ13C, δ15N) and acid extractable geochemical properties (e.g. Zn, Pt and S). Considering the fact that the outcome of tracing models often depends on the type and robustness of the methods used, here we have employed a stable isotope mixing model (SIAR) to evaluate if the suite of selected elements could be used to estimate the relative contribution of different sources for a series of five virtually created sediment mixtures. For the five groups of virtual sediments, the SIAR model provided close estimates to the contribution values of sediment sources with the Mean Absolute Error (MAE) varying from 0.30 to 2.88%. Results from this study show for the first time that the combined use of isotopic and geochemical signatures enable the SIAR model to provide an accurate estimation of source apportionment where a variety of land uses needs to be investigated and shows promise as a valuable new sediment and particulate nutrient tracing tool.

Sources and Impact of Media Thermal Fluctuations in Heat-Assisted Magnetic Recording

Optical and thermal modeling is used to understand and quantify the contribution of different sources of temperature fluctuations in heat-assisted magnetic recording. The dominant sources of temperature fluctuations are spatial variations of the absorption in the recording layer and spatial variations of the underlayer effective thermal boundary resistance. They result in an increased transition jitter that is proportional to the amplitude of the source variations. Besides, the transition jitter amplitude strongly depends on the length scale of the source fluctuations: fluctuations with smaller periods lead to reduced jitter as a result of in-plane heat spreading within the medium layers. Temperature fluctuations are also proportional to the input laser power or to the average temperature gradient. Consequently, transition jitter arising from temperature fluctuations does not change with improved temperature gradients, in contrast to jitter resulting from Curie temperature distributions. Interface roughness is also investigated as it is a practical source of both optical absorption fluctuations and thermal property fluctuations. It is found to lead to sizeable jitter, whose amplitude is proportional to the roughness amplitude and reduces at small roughness wavelengths.

Probing non-Gaussian stochastic gravitational wave backgrounds with LISA

The stochastic gravitational wave background (SGWB) contains a wealth of information on astrophysical and cosmological processes. A major challenge of upcoming years will be to extract the information contained in this background and to disentangle the contributions of different sources. In this paper we provide the formalism to extract, from the correlation of three signals in the Laser Interferometer Space Antenna (LISA), information about the tensor three-point function, which characterizes the non-Gaussian properties of the SGWB . This observable can be crucial to discriminate whether a SGWB has a primordial or astrophysical origin. Compared to the two-point function, the SGWB three-point function has a richer dependence on the gravitational wave momenta and chiralities. It can be used therefore as a powerful discriminator between different models. For the first time we provide the response functions of LISA to a general SGWB three-point function. As examples, we study in full detail the cases of an equilateral and squeezed SGWB bispectra, and provide the explicit form of the response functions, ready to be convoluted with any theoretical prediction of the bispectrum to obtain the observable signal. We further derive the optimal estimator to compute the signal-to-noise ratio. Our formalism covers general shapes of non-Gaussianity, and can be extended straightaway to other detector geometries. Finally, we provide a short overview of models of the early universe that can give rise to a non-Gaussian SGWB.

Phthalate Exposure from Drinking Water in Romanian Adolescents.

Phthalates are plastic softeners that have been linked to several adverse health outcomes. The relative contributions of different sources to phthalate exposure in populations in different regions and at different life stages is unclear. We examined the relationships between water consumption, consumer product use, and phthalate exposure among 40 adolescents (20 males, 20 females) in Cluj-Napoca, Romania. Interviewers administered a questionnaire about drinking water consumption and use of phthalate-containing consumer products. Four common phthalates were measured in representative samples of participants’ municipal drinking water and consumed bottled water using gas chromatography-mass spectrometry. Urine samples were collected from participants and analyzed for the corresponding phthalate metabolites. Relationships between different exposure measures were assessed using nonparametric tests (Spearman rank correlation coefficients and the Kruskal–Wallis test). Diisobutyl phthalate, dibutyl phthalate, and bis(2-ethylhexyl) phthalate were commonly detected in bottled water, but generally not the municipal drinking water samples. Mono-n-butyl phthalate (MnBP) was the most commonly detected urinary metabolite (detected in 92.5% of participants) and had the highest maximum concentration (1139.77 µg/g creatinine). We did not identify any statistically significant associations between water consumption or consumer product use practices and urinary phthalate metabolite concentrations in our adolescent group, and directions of correlation coefficients differed by individual phthalate compound. While phthalate exposure was widespread, these results highlight the challenges in examining phthalate exposure determinants and emphasize the need for further investigation into understanding exposure sources and potential health risks from chronic low-level exposures.

Nitrous oxide variability at sub-kilometre resolution in the Atlantic sector of the Southern Ocean.

The Southern Ocean is an important region for global nitrous oxide (N2O) cycling. The contribution of different source and sink mechanisms is, however, not very well constrained due to a scarcity of seawater data from the area. Here we present high-resolution surface N2O measurements from the Atlantic sector of the Southern Ocean, taking advantage of a relatively new underway setup allowing for collection of data during transit across mesoscale features such as frontal systems and eddies. Covering a range of different environments and biogeochemical settings, N2O saturations and sea-to-air fluxes were highly variable: Saturations ranged from 96.5% at the sea ice edge in the Weddell Sea to 126.1% across the Polar Frontal Zone during transit to South Georgia. Negative sea-to-air fluxes (N2O uptake) of up to −1.3 µmol m−2 d−1 were observed in the Subantarctic Zone and highest positive fluxes (N2O emission) of 14.5 µmol m−2 d−1 in Stromness Bay, coastal South Georgia. Although N2O saturations were high in areas of high productivity, no correlation between saturations and chlorophyll a (as a proxy for productivity) was observed. Nevertheless, there is a clear effect of islands and shallow bathymetry on N2O production as inferred from supersaturations.

Carbon emissions intensity reduction target for China's power industry: An efficiency and productivity perspective

This paper proposes a scenario analysis to address whether the national and provincial CO2 emissions intensity reduction target during 2016–2020 would be achievable for China's power industry with the identification of change on carbon productivity. This productivity indicator is further decomposed to investigate contributions of different sources to productivity growth when there exists technological heterogeneity. Evaluation results show that even if all electricity-generating units in each region were able to adopt the best practice, the nationwide 18% intensity reduction target is not feasible through improving technical efficiency or upgrading technology on electricity generation and carbon abatement in a short or medium term. The existence of regional technological heterogeneity in power generation and associated CO2 emissions reduction processes implies the necessity of more differentiated regulations and policies for emission reduction across China's regions and inter-regional technology transfer. The emerging national emission trading scheme could easy some challenges in formulating emission policy for heterogeneous regions.

Quantitative human health risk assessment along the lifecycle of nano-scale copper-based wood preservatives

The use of nano-scale copper oxide (CuO) and basic copper carbonate (Cu2(OH)2CO3) in both ionic and micronized wood preservatives has raised concerns about the potential of these substances to cause adverse humans health effects. To address these concerns, we performed quantitative (probabilistic) human health risk assessment (HHRA) along the lifecycles of these formulations used in antibacterial and antifungal wood coatings and impregnations by means of the EU FP7 SUN project’s Decision Support System (SUNDS, www.sunds.gd). The results from the risk analysis revealed inhalation risks from CuO in exposure scenarios involving workers handling dry powders and performing sanding operations as well as potential ingestion risks for children exposed to nano Cu2(OH)2CO3 in a scenario involving hand-to-mouth transfer of the substance released from impregnated wood. There are, however, substantial uncertainties in these results, so some of the identified risks may stem from the safety margin of extrapolation to fill data gaps and might be resolved by additional testing. Our stochastic approach successfully communicated the contribution of different sources of uncertainty in the risk assessment. The main source of uncertainty was the extrapolation from short to long-term exposure, which was necessary due to the lack of (sub)chronic in vivo studies with CuO and Cu2(OH)2CO3. Considerable uncertainties also stemmed from the use of default inter- and intra-species extrapolation factors.

Source apportionment of fine particles based on combined numerical model and receptor model

In recent years, atmospheric particulate matter has become the primary air pollutant in most cities of China. In order to support an efficient control for particles reduction, it is of great importance to investigate the contribution of different sources to particulate matter. Source apportionment has been a conventional technique for seeking the emission sources of particulate matter. There are many ways to investigate the source of particles, such as receptor models, emission inventories, trajectory analysis, dispersion models, photochemical models and source models. Receptor models were shown to be an effective tool for source apportionment. As one of the most popular receptor models, the Positive Matrix Factorization (PMF) model estimates the sources contribution rate based on chemical characteristics of particulate samples. Traditionally, apportioning various sources of particulate matter is mainly through offline chemical composition analysis in combination with measurements in receptor regions. This method is limited by observational periods and locations and is applicable only for historical events. So researches on the source apportionment of PM2.5 with high spatial and temporal resolution in urban scale would be of great significance to control air pollution scientifically and improve urban air quality. The aim of this paper is to develop a source apportionment method of fine particulate matter based on a combination of numerical air quality model and receptor model. This method will simulate the chemical components of fine particulate matter accurately and evaluate the source contributions quantitatively at the same time. In this study, a new method is developed based on a numerical model (RegAEMS model) and a receptor model (PMF) to enhance the temporal and spatial resolutions of apportioning particulate matter sources. This method is applied to the period during the Youth Olympic Games (YOG) in Nanjing for apportioning fine particulate matter sources. With RegAEMS, the concentrations of PM2.5 and its main chemical compositions are simulated. We find that the simulations agree well with the results from the offline chemical composition analysis. Using PMF model, the components of fine particulate matter during the 2014 YOG (July to September) are identified, which include secondary organic aerosols (25.9%), combustion dust (16.5%), secondary sulfate aerosols (14.5%), secondary nitrate aerosols (12.6%), vehicle exhaust (12.0%), dusts (11.7%), and industrial activities (6.9%). Such results are in good agreement with sampling measurements. This study suggests that the contributions from combustion dust and industrial activities are lower during YOG than before and after YOG, indicating that the control measures of industrial activities during YOG are effective in reducing air pollution. This study suggests that integrated numerical modeling and receptor modeling can effectively assess contributions of different pollution sources, and thus be useful to source apportionments of heavy pollution events, providing scientific basis for emergency controls of air pollution. This finding will be useful for the local government to create efficient control strategies to reduce emissions of different sources of PM2.5.

Provenance and environmental risk of windblown materials from mine tailing ponds, Murcia, Spain

Atmospheric particulates play a vital role in the transport of potentially toxic metals, being an important exposure pathways of people to toxic elements, which is faster and can occur in a much larger scale than water, soil and biota transport. Windblown materials in abandoned tailing ponds have not been well examined. The objectives of this investigation were: to study the major physical and geochemical properties of the materials eroded by wind inside the tailing ponds, and to understand the relative contribution of different sources to its heavy metals concentration. Study area is located in Cartagena-La Union mining district (SE Spain), where metallic mining of Fe, Pb and Zn has been developed for more than 2500 years. Wind-eroded particulates were monthly collected at 3 different heights (20, 50, and 80 cm) from the ground for a period of a full year using 4 dust collectors. Four tailing samples and 4 surface soil samples from the surrounding hills were also taken. Dust, soil, and tailing samples were examined for pH, particle size distribution, electrical conductivity, calcium carbonate content, Pb, Cu, Zn, Cd, Mn, Co, Ni, Ti and Zr concentrations. The results indicated that very coarse textured, slightly saline, and almost neutral wind-eroded deposits were generated with a very high temporal variability throughout the year. They also showed that the concentration of Cd, Mn, Pb and Zn, in the dust samples is extraordinarily high (18, 1254, 1831, and 5747 mg kg−1 respectively), whereas Co, Ni, and Cu had concentrations into the range of background concentrations found in the Earth's crust (3.8, 12, and 60 mg kg−1 respectively). Besides, the concentration of both categories of heavy metals in the dust samples was higher than that in tailing and less than that of the soils. The barren surfaces of tailing ponds and also the surface soils of the surrounding area seem to be the major contributors to the dust collected. Therefore, abandoned mines as well as their tailing ponds should be rehabilitated by proper technologies and then well stabilized and/or covered by appropriate plant vegetation to control the transfer, particularly by air, of environmentally hazardous materials to other areas.

Impact on air quality of cruise ship emissions in Naples, Italy

The Municipality of Naples, with about 1 million residents and about 3 million people living in the surroundings, suffers, as for many a city, from low air quality, as demonstrated by the concentration level of pollutants measured by fixed monitoring stations of the Regional Air Quality Network. The port of Naples is among the most important ports in the Mediterranean sea with a large traffic of passengers and goods. Therefore, it contributes to atmospheric pollution of the nearby urban area with ship emissions. Public authorities need to know the contribution of different sources of atmospheric pollutants to put effective environmental policies into practice. In this article, a bottom-up methodology has been developed to assess the amount of atmospheric pollutants emitted by cruise ships traffic and its impact on the atmospheric pollution in Naples. A detailed description of in-port activities of cruise ships has been applied to calculate emission rates of NOx and SOx by using standard procedures corrected and integrated by real data to better evaluate actual engine power applied and fuel consumption. Considered activities include: navigation in port both at arrival and departure; maneuvering for berthing and unmooring and hoteling at berth. The study covers all cruise ship calls during the year 2016. The impact of cruise ship emissions on the urban area has been assessed by using the Gaussian puff model CALPUFF, thus obtaining contour maps of 1-h and year average values. Finally, in order to assess the contribution of cruise ship emissions to air quality, simulations have been compared with concentrations measured at fixed monitoring stations and during a monitoring campaign.

Critical knowledge gaps and research needs related to the environmental dimensions of antibiotic resistance

There is growing understanding that the environment plays an important role both in the transmission of antibiotic resistant pathogens and in their evolution. Accordingly, researchers and stakeholders world-wide seek to further explore the mechanisms and drivers involved, quantify risks and identify suitable interventions. There is a clear value in establishing research needs and coordinating efforts within and across nations in order to best tackle this global challenge. At an international workshop in late September 2017, scientists from 14 countries with expertise on the environmental dimensions of antibiotic resistance gathered to define critical knowledge gaps. Four key areas were identified where research is urgently needed: 1) the relative contributions of different sources of antibiotics and antibiotic resistant bacteria into the environment; 2) the role of the environment, and particularly anthropogenic inputs, in the evolution of resistance; 3) the overall human and animal health impacts caused by exposure to environmental resistant bacteria; and 4) the efficacy and feasibility of different technological, social, economic and behavioral interventions to mitigate environmental antibiotic resistance.11The recommendations from the workshop have also been communicated in a separate report published on the website of the JPIAMR (www.jpiamr.org).

Deposition of sulfur and nitrogen components in Louisiana in August, 2011

Dry and wet deposition of sulfur and nitrogen contained air pollutants lead to increase of sulfur and nitrogen to the surface, causing acidification of surface water bodies and subsequent damage to aquatic and terrestrial ecosystems. Louisiana has abundant water resources and it is important to protect water resources from excessive atmospheric deposition of sulfur and nitrogen. However, the information for understanding sulfur and nitrogen deposition and adverse effects in Louisiana is limited. In this study, a source-oriented version of the Community Multi-scale Air Quality (CMAQ) model was used to simulate emission, formation, transport, and deposition of sulfur and nitrogen species in Louisiana in August 2011 to understand the forms and quantities of sulfur and nitrogen deposition due to wet and dry processes in Louisiana, to show the spatial and temporal variations of deposition fluxes, and to quantify the contributions of different sources to sulfur and nitrogen deposition. Aerosol phase sulfate (AeroSO4) has the highest monthly total flux of 6 kg S/ha in wet deposition of sulfur. Major forms of sulfur dry depositions are AeroSO4 (~1 kg S/ha) and SO2 (~3 kg S/ha). Nitrogen deposition is mainly in forms of NO2, HNO3, NH3, and aerosol phase nitrate (AeroNO3). Electric generating utilities (EGU) are the largest contributor to sulfur depositions with monthly total flux of 1.6 kg S/ha, followed by industry (1 kg S/ha) and upwind sources. On-road vehicles and industry are important to nitrogen (except ammonia) depositions with maximum contributions of 0.6 kg N/ha and 0.8 kg N/ha, respectively. The dominate source of ammonia is “Other” implicit sector including agricultural activities.

Importance of suspended sediments and dissolved organic carbon to carbon exports in karst – The Vadu Crişului karst basin in the Pădurea Craiului Mountains, Romania

Exports of dissolved inorganic carbon (DIC) from karst aquifers are a significant contribution to the global carbon cycle. Contributions of particulate inorganic carbon (PIC) and dissolved organic carbon (DOC) in karst groundwater are often unaccounted for in carbon budgets. This investigation considers field chemistry, discrete samples, and continuous monitoring data collected between October 2016 and December 2016 to quantitatively evaluate the net export of dissolved solutes, total suspended sediments (TSS), and DOC within the Vadu Crişului karst basin in the Pădurea Craiului Mountains of northwest Romania. Measurements of carbon isotopes (δ13C) in DIC and in bedrock, specific ultraviolet absorption (SUVA), and carbon to nitrogen (C:N) ratios were used to evaluate the relative contribution of different sources of carbon to the aqueous system. δ13CDIC at the aquifer input trend toward an atmospheric signal in winter with lower DOC concentrations and SUVA values and C:N ratios corresponding to degraded carbon sources, illustrating the reduction in microbial respiration in soil with cold temperatures. At the spring, δ13CDIC values trend more toward a soil-based signal after storm events that bring increased DOC concentrations with SUVA values corresponding to significantly degraded carbon.Dissolution in this karst basin is principally driven by the carbonate equilibrium reactions, and direct meteoric recharge only accounts for 4 to 13% of observed discharge. Most recharge enters the karst basin through infiltration into dolines and epikarst on the Zece Hotare karst plateau, and this results in a broadly stable chemical signature of spring water. Storm events do have a significant impact on mechanical erosion and chemical processes operating in the karst basin; the addition of PIC and TSS flux increase landscape erosion rates by 1.1 to 1.2% and 7.9 to 8.3%, respectively, above the denudation rate computed by dissolved solutes (36.5–56.9 mm/ka). The modeled annual flux of DIC from this karst basin, 1.37 × 105 to 1.64 × 105 kg/yr, scales to a global CO2 flux of 7.08 × 1011 to 1.06 × 1012 kg/yr. Adding a modeled flux of DOC increases the estimates of CO2 flux by 12% to 22%, a significant addition to the global carbon cycle.

Oxidative potential of ambient PM2.5 in the coastal cities of the Bohai Sea, northern China: Seasonal variation and source apportionment.

Emissions of air pollutants from primary and secondary sources in China are considerably higher than those in developed countries, and exposure to air pollution is main risk of public health. Identifying specific particulate matter (PM) compositions and sources are essential for policy makers to propose effective control measures for pollutant emissions. Ambient PM2.5 samples covered a whole year were collected from three coastal cities of the Bohai Sea. Oxidative potential (OP) was selected as the indicator to characterize associated PM compositions and sources most responsible for adverse impacts on human health. Positive matrix factorization (PMF) and multiple linear regression (MLR) were employed to estimate correlations of PM2.5 sources with OP. The volume- and mass-based dithiothreitol (DTTv and DTTm) activities of PM2.5 were significantly higher in local winter or autumn (p < 0.01). Spatial and seasonal variations in DTTv and DTTm were much larger than mass concentrations of PM2.5, indicated specific chemical components are responsible for PM2.5 derived OP. Strong correlations (r > 0.700, p < 0.01) were found between DTT activity and water-soluble organic carbon (WSOC) and some transition metals. Using PMF, source fractions of PM2.5 were resolved as secondary source, traffic source, biomass burning, sea spray and urban dust, industry, coal combustion, and mineral dust. Further quantified by MLR, coal combustion, biomass burning, secondary sources, industry, and traffic source were dominant contributors to the water-soluble DTTv activity. Our results also suggested large differences in seasonal contributions of different sources to DTTv variability. A higher contribution of DTTv was derived from coal combustion during the local heating period. Secondary sources exhibited a greater fraction of DTTv in summer, when there was stronger solar radiation. Traffic sources exhibited a prevailing contribution in summer, and industry contributed larger proportions in spring and winter. Future abatement priority of air pollution should reduce the sources contributing to OP of PM2.5.