Soil quality assesment of upper Tigris basin

Economic life of the Tigris basin, part of the Mesopotamian depends heavily on agricultural production for thousands of years. Sustainability of agricultural production in this ancient region may only be possible by conserving and improving the ability of soils to function. Therefore, soil quality indexes were computed to evaluate and monitor functioning ability of pasture lands, forest lands, orchard and arable lands in the upper Tigris Basin of Mesopotamian. Soil samples were collected from (0-20 cm) at 134 locations from approximately the corners of 5km*5km size grid cells within 2.450 km 2 research site. Twelve soil properties were measured as potential indicators of soil quality. A minimum data set (MDS) for each of land use was determined by means of principal component analysis (PCA) and expert opinion (EO) techniques. The weightages of each indicator were calculated using PCA and analytical hierarchy process (AHP). Soil quality index (SQI) for every sampling locations was calculated by weighted additive method following the use of linear scoring functions to obtain unitless indicator scores. The organic matter (OM), aggregate stability (AS) and slope were considered the most powerful and common soil attributes for distinguishing land uses in regard to soil quality and they can be used to monitor and assess the soil quality in this semi-arid environment. The SQI values of four land uses were significantly different (P < 0.01) from each other. The highest SQI value was obtained for forest land with EO (SQ IEO =0.974) and the lowest SQI value was for orchards with PCA (SQI AHP =0.793). The results indicated that PCA and EO methods produced comparable results in assessment of soil quality.National Council for Scientific Research 214O374This research was funded by The Scientific and Research Council of Turkey (TUBITAK) with a grant number of TOVAG 214O374

Environmental sensitivity to desertification in northern Mesopotamia; application of modified MEDALUS by using analytical hierarchy process

Poor management, low vegetation cover, and severe erosion are undermining the stability and sustainability of lands. In this study, modified Mediterranean Desertification and Land Use (MEDALUS) method was used to identify environmentally sensitive areas (ESA) to desertification in Tigris Basin, Turkey. Soil samplings (0–20 cm) and field observations were conducted within 3.752 km2 land. Biophysical and anthropogenic parameters of sampling locations have been integrated and processed by geographic information systems obtaining soil, climate, vegetation, and management quality indexes. Additional six parameters for soil quality and one for management quality were used to adopt MEDALUS to the context of Tigris Basin. The weights for parameters and indicators were calculated using analytical hierarchy process (AHP). Tigris Basin was classified into one fragile and two critical areas using original method, whereas one fragile and three critical classes were defined with the modified method. In the original method, fragile areas represented 5.65% and low-degree critical areas 24.49% and moderate critical areas 69.86% of the study area, which are needed to be monitored for severe land degradation. Modifying MEDALUS allowed to define highly critical areas (51.41%) which have not been detected in the original method. The critical areas are primarily used for field crops with extensive tillage, medium degree of plant cover, low drought resistance, and erosion along with low management quality due to the lack of required environmental protection. The results revealed that adaptation of new parameters and weighting in MEDALUS improved the ability of classifying ESAs for a regional scale to desertification. © 2018, Saudi Society for Geosciences.National Council for Scientific Research 214O374Acknowledgements This research was funded by the Scientific and Research Council of Turkey (TUBITAK) with a grant number of TOVAG 214O374

Strategic tillage may sustain the benefits of long-term no-till in a Vertisol under Mediterranean climate

Long-term no-till or reduced tillage may decline functioning ability of soils due to surface/subsurface compaction and/or stratification of plant nutrients. A long-term (ten years) field experiment was established in 2006 in the Çukurova region of Turkey to evaluate the impact of tillage on the physical properties of a soil under a Mediterranean climate. The tillage systems investigated included two conventional (CT-1 and CT-2), three reduced (RT-1, RT-2 and RT-3) and two no-till (NT and ST), including strategic/occasional tillage. Nine-year old undisturbed no-till plots were divided into two categories and half of these plots were plowed by a moldboard plow in November 2015, and this practice was defined as strategic tillage (ST), while remaining half of the plots left undisturbed. Soil samples were collected from disturbed and undisturbed plots of NT as well as plots under other tillage systems from three soil depths (i.e., 0–10, 10–20 and 20–30 cm) in November 2016. The crop rotation at the experimental areas was winter wheat (Triticum aestivum L.), soybean (Glycine max. L.) – grain maize (Zea mays L.) – winter wheat. Soil samples were analyzed for aggregate stability (AS), mean weight diameter (MWD), bulk density (BD), water filled pore space (WFPS), water content at field capacity (FC), permanent wilting point (PWP), available water content (PAW), micropores (MiP), macropores (MaP), total porosity (TP), and penetration resistance (PR). The ST decreased MWD of surface soil compared to NT by 7.2%, while MWD under ST was higher than NT by 78.0% and 103.6% for 10–20 and 20–30 cm depths, respectively. The NT and RT resulted higher BD and PR, and lower MaP and TP than CT and ST in all three depths, though the values were generally not limiting for crop growth. The ST significantly (P < 0.01) decreased BD and PR within 30 cm of soil surface. However, water content at FC, PWP and also PAW in 0–10 and 10–20 cm depths were significantly reduced with ST compared to NT. The ST significantly (P < 0.01) increased the MaP and TP compared to NT which favors better aeration and water movement. The mean WFPS under NT, RT-2 and RT-3 systems in 0–10 cm and with all tillage systems (except ST in 10–20 cm) in subsurface layers were higher than 60%, which is considered a threshold for nitrogen losses as N2O fluxes. Implementation of ST into conservational practices under Mediterranean climate could be a viable management option to overcome some of the disadvantages of long-term conservation tillage and thereby to improve physical soil conditions for crop growth, air and water movement. © 2018 Elsevier B.V.115 O 353We acknowledge the financial contribution of the TUBITAK (Scientific and Technological Council of Turkey , Grant Number 115 O 353 ). The authors feel indebted to Dr. Shahid Farooq for his careful editing of the manuscript

Effects of NOx and SO2 on the Secondary Organic Aerosol Formation from Photooxidation of α-pinene and Limonene

Anthropogenic emissions such as NOx and SO2 influence the biogenic secondary organic aerosol (SOA) formation, but detailed mechanisms and effects are still elusive. We studied the effects of NOx and SO2 on the SOA formation from the photooxidation of α-pinene and limonene at ambient relevant NOx and SO2 concentrations (NOx: < 1to 20 ppb, SO2: < 0.05 to 15 ppb). In these experiments, monoterpene oxidation was dominated by OH oxidation. We found that SO2 induced nucleation and enhanced SOA mass formation. NOx strongly suppressed not only new particle formation but also SOA mass yield. However, in the presence of SO2 which induced a high number concentration of particles after oxidation to H2SO4, the suppression of the mass yield of SOA by NOx was completely or partly compensated for. This indicates that the suppression of SOA yield by NOx was largely due to the suppressed new particle formation, leading to a lack of particle surface for the organics to condense on and thus a significant influence of vapor wall loss on SOA mass yield. By compensating for the suppressing effect on nucleation of NOx, SO2 also compensated for the suppressing effect on SOA yield. Aerosol mass spectrometer data show that increasing NOx enhanced nitrate formation. The majority of the nitrate was organic nitrate (57–77 %), even in low-NOx conditions (<  ∼  1 ppb). Organic nitrate contributed 7–26 % of total organics assuming a molecular weight of 200 g mol−1. SOA from α-pinene photooxidation at high NOx had a generally lower hydrogen to carbon ratio (H ∕ C), compared to low NOx. The NOx dependence of the chemical composition can be attributed to the NOx dependence of the branching ratio of the RO2 loss reactions, leading to a lower fraction of organic hydroperoxides and higher fractions of organic nitrates at high NOx. While NOx suppressed new particle formation and SOA mass formation, SO2 can compensate for such effects, and the combining effect of SO2 and NOx may have an important influence on SOA formation affected by interactions of biogenic volatile organic compounds (VOCs) with anthropogenic emissions.published versionpeerReviewe

Effects of NO_<i>x</i> and SO₂ on the secondary organic aerosol formation from photooxidation of <i>α</i>-pinene and limonene

Anthropogenic emissions such as NOx and SO2 influence the biogenic secondary organic aerosol (SOA) formation, but detailed mechanisms and effects are still elusive. We studied the effects of NOx and SO2 on the SOA formation from the photooxidation of α-pinene and limonene at ambient relevant NOx and SO2 concentrations (NOx: &lt; 1to 20 ppb, SO2: &lt; 0.05 to 15 ppb). In these experiments, monoterpene oxidation was dominated by OH oxidation. We found that SO2 induced nucleation and enhanced SOA mass formation. NOx strongly suppressed not only new particle formation but also SOA mass yield. However, in the presence of SO2 which induced a high number concentration of particles after oxidation to H2SO4, the suppression of the mass yield of SOA by NOx was completely or partly compensated for. This indicates that the suppression of SOA yield by NOx was largely due to the suppressed new particle formation, leading to a lack of particle surface for the organics to condense on and thus a significant influence of vapor wall loss on SOA mass yield. By compensating for the suppressing effect on nucleation of NOx, SO2 also compensated for the suppressing effect on SOA yield. Aerosol mass spectrometer data show that increasing NOx enhanced nitrate formation. The majority of the nitrate was organic nitrate (57–77 %), even in low-NOx conditions (&lt;  ∼  1 ppb). Organic nitrate contributed 7–26 % of total organics assuming a molecular weight of 200 g mol−1. SOA from α-pinene photooxidation at high NOx had a generally lower hydrogen to carbon ratio (H ∕ C), compared to low NOx. The NOx dependence of the chemical composition can be attributed to the NOx dependence of the branching ratio of the RO2 loss reactions, leading to a lower fraction of organic hydroperoxides and higher fractions of organic nitrates at high NOx. While NOx suppressed new particle formation and SOA mass formation, SO2 can compensate for such effects, and the combining effect of SO2 and NOx may have an important influence on SOA formation affected by interactions of biogenic volatile organic compounds (VOCs) with anthropogenic emissions

OH regeneration from methacrolein oxidation investigated in the atmosphere simulation chamber SAPHIR

Hydroxyl radicals (OH) are the most important reagent for the oxidation of trace gases in the atmosphere. OH concentrations measured during recent field campaigns in isoprene-rich environments were unexpectedly large. A number of studies showed that unimolecular reactions of organic peroxy radicals (RO2) formed in the initial reaction step of isoprene with OH play an important role for the OH budget in the atmosphere at low mixing ratios of nitrogen monoxide (NO) of less than 100 pptv. It has also been suggested that similar reactions potentially play an important role for RO2 from other compounds. Here, we investigate the oxidation of methacrolein (MACR), one major oxidation product of isoprene, by OH in experiments in the simulation chamber SAPHIR under controlled atmospheric conditions. The experiments show that measured OH concentrations are approximately 50% larger than calculated by the Master Chemical Mechanism (MCM) for conditions of the experiments (NO mixing ratio of 90 pptv). The analysis of the OH budget reveals an OH source that is not accounted for in MCM, which is correlated with the production rate of RO2 radicals from MACR. In order to balance the measured OH destruction rate, 0.77 OH radicals (1σ error: ± 0.31) need to be additionally reformed from each reaction of OH with MACR. The strong correlation of the missing OH source with the production of RO2 radicals is consistent with the concept of OH formation from unimolecular isomerization and decomposition reactions of RO2. The comparison of observations with model calculations gives a lower limit of 0.03 s−1 for the reaction rate constant if the OH source is attributed to an isomerization reaction of MACR-1-OH-2-OO and MACR-2-OH-2-OO formed in the MACR + OH reaction as suggested in the literature (Crounse et al., 2012). This fast isomerization reaction would be a competitor to the reaction of this RO2 species with a minimum of 150 pptv NO. The isomerization reaction would be the dominant reaction pathway for this specific RO2 radical in forested regions, where NO mixing ratios are typically much smaller

Secondary organic aerosol formation from hydroxyl radical oxidation and ozonolysis of monoterpenes

Oxidation by hydroxyl radical (OH) and ozonolysis are the two major pathways of daytime biogenic volatile organic compound (BVOC) oxidation and secondary organic aerosol (SOA) formation. In this study, we investigated the particle formation of several common monoterpenes (α-pinene, β-pinene and limonene) by OH-dominated oxidation, which has seldom been investigated. OH oxidation experiments were carried out in the SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction) chamber in Jülich, Germany, at low NOx (0.01 ~ 1 ppbV) and low ozone (O3) concentration (< 20 ppbV). OH concentration and total OH reactivity (kOH) were measured directly, and through this the overall reaction rate of total organics with OH in each reaction system was quantified. Multi-generation reaction process, particle growth, new particle formation (NPF), particle yield and chemical composition were analyzed and compared with that of monoterpene ozonolysis. Multi-generation products were found to be important in OH-dominated SOA formation. The relative role of functionalization and fragmentation in the reaction process of OH oxidation was analyzed by examining the particle mass and the particle size as a function of OH dose. We developed a novel method which quantitatively links particle growth to the reaction rate of OH with total organics in a reaction system. This method was also used to analyze the evolution of functionalization and fragmentation of organics in the particle formation by OH oxidation. It shows that functionalization of organics was dominant in the beginning of the reaction (within two lifetimes of the monoterpene) and fragmentation started to play an important role after that. We compared particle formation from OH oxidation with that from pure ozonolysis. In individual experiments, growth rates of the particle size did not necessarily correlate with the reaction rate of monoterpene with OH and O3. Comparing the size growth rates at the similar reaction rates of monoterpene with OH or O3 indicates that, generally, OH oxidation and ozonolysis had similar efficiency in particle growth. The SOA yield of α-pinene and limonene by ozonolysis was higher than that of OH oxidation. Aerosol mass spectrometry (AMS) shows SOA elemental composition from OH oxidation follows a slope shallower than −1 in the O / C vs. H / C diagram, also known as Van Krevelen diagram, indicating that oxidation proceeds without significant loss of hydrogen. SOA from OH oxidation had higher H / C ratios than SOA from ozonolysis. In ozonolysis, a process with significant hydrogen loss seemed to play an important role in SOA formation

Investigation of the oxidation of methyl vinyl ketone (MVK) by OH radicals in the atmospheric simulation chamber SAPHIR

The photooxidation of methyl vinyl ketone (MVK) was investigated in the atmospheric simulation chamber SAPHIR for conditions at which organic peroxy radicals (RO2) mainly reacted with NO (high NO case) and for conditions at which other reaction channels could compete (low NO case). Measurements of trace gas concentrations were compared to calculated concentration time series applying the Master Chemical Mechanism (MCM version 3.3.1). Product yields of methylglyoxal and glycolaldehyde were determined from measurements. For the high NO case, the methylglyoxal yield was (19 ± 3) % and the glycolaldehyde yield was (65 ± 14) %, consistent with recent literature studies. For the low NO case, the methylglyoxal yield reduced to (5 ± 2) % because other RO2 reaction channels that do not form methylglyoxal became important. Consistent with literature data, the glycolaldehyde yield of (37 ± 9) % determined in the experiment was not reduced as much as implemented in the MCM, suggesting additional reaction channels producing glycolaldehyde. At the same time, direct quantification of OH radicals in the experiments shows the need for an enhanced OH radical production at low NO conditions similar to previous studies investigating the oxidation of the parent VOC isoprene and methacrolein, the second major oxidation product of isoprene. For MVK the model–measurement discrepancy was up to a factor of 2. Product yields and OH observations were consistent with assumptions of additional RO2 plus HO2 reaction channels as proposed in literature for the major RO2 species formed from the reaction of MVK with OH. However, this study shows that also HO2 radical concentrations are underestimated by the model, suggesting that additional OH is not directly produced from RO2 radical reactions, but indirectly via increased HO2. Quantum chemical calculations show that HO2 could be produced from a fast 1,4-H shift of the second most important MVK derived RO2 species (reaction rate constant 0.003 s−1). However, additional HO2 from this reaction was not sufficiently large to bring modelled HO2 radical concentrations into agreement with measurements due to the small yield of this RO2 species. An additional reaction channel of the major RO2 species with a reaction rate constant of (0.006 ± 0.004) s−1 would be required that produces concurrently HO2 radicals and glycolaldehyde to achieve model–measurement agreement. A unimolecular reaction similar to the 1,5-H shift reaction that was proposed in literature for RO2 radicals from MVK would not explain product yields for conditions of experiments in this study. A set of H-migration reactions for the main RO2 radicals were investigated by quantum chemical and theoretical kinetic methodologies, but did not reveal a contributing route to HO2 radicals or glycolaldehyde

Secondary Organic Aerosol (SOA) Formation from Hydroxyl RadicalOxidation and Ozonolysis of Monoterpenes

Oxidation by hydroxyl radical (OH) and ozonolysis are the two major pathways of daytime biogenic volatile organic compounds (VOCs) oxidation and secondary organic aerosol (SOA) formation. In this study, we investigated the particle formation of several common monoterpenes (α-pinene, β-pinene, and limonene) by OH dominated oxidation, which has seldom been investigated. OH oxidation experiments were carried out in the SAPHIR chamber in Jülich, Germany, at low NOx (0.01–1 ppbV) and low ozone (O3) concentration. OH concentration and OH reactivity were measured directly so that the overall reaction rates of organic compounds with OH were quantified. Multi-generation reaction process, particle growth, new particle formation, particle yield, and chemical composition were analyzed and compared with that of monoterpene ozonolysis. Multi-generation products were found to be important in OH dominated SOA formation. The relative role of functionalization and fragmentation in the reaction process of OH oxidation was analyzed by examining the particle mass and the particle size as a function of OH dose. We developed a novel method which quantitatively links particle growth to the reaction of OH with organics in a reaction system. This method was also used to analyze the evolution of functionalization and fragmentation of organics in the particle formation by OH oxidation. It shows that functionalization of organics was dominant in the beginning of the reaction (within two lifetimes of the monoterpene) and fragmentation started to be dominant after that. We compared particle formation from OH oxidation with that from pure ozonolysis. In individual experiments, growth rates of the particle size did not necessarily correlate with the reaction rate of monoterpene with OH and O3. Comparing the size growth rates at the similar reaction rates of monoterpene with OH or O3 indicates that generally, OH oxidation and ozonolysis had similar efficiency in particle growth. The SOA yield of α-pinene and limonene by ozonolysis was higher than that of OH oxidation. Aerosol mass spectrometry (AMS) shows SOA elemental composition from OH oxidation follows a slope shallower than −1 in the O / C vs. H / C diagram, indicating that oxidation proceeds without significant loss of hydrogen. SOA from OH oxidation had higher H / C ratios than SOA from ozonolysis. In ozonolysis, a process with significant hydrogen loss seemed to play an important role in SOA formation