Machine Learning Techniques to Predict the Air Quality Using Meteorological Data in Two Urban Areas in Sri Lanka

The effect of bad air quality on human health is a well-known risk. Annual health costs have significantly been increased in many countries due to adverse air quality. Therefore, forecasting air quality-measuring parameters in highly impacted areas is essential to enhance the quality of life. Though this forecasting is usual in many countries, Sri Lanka is far behind the state-of-the-art. The country has increasingly reported adverse air quality levels with ongoing industrialization in urban areas. Therefore, this research study, for the first time, mainly focuses on forecasting the PM10 values of the air quality for the two urbanized areas of Sri Lanka, Battaramulla (an urban area in Colombo), and Kandy. Twelve air quality parameters were used with five models, including extreme gradient boosting (XGBoost), CatBoost, light gradient-boosting machine (LightBGM), long short-term memory (LSTM), and gated recurrent unit (GRU) to forecast the PM10 levels. Several performance indices, including the coefficient of determination (R2), root mean squared error (RMSE), mean absolute error (MAE), mean squared error (MSE), mean absolute relative error (MARE), and the Nash–Sutcliffe efficiency (NSE), were used to test the forecasting models. It was identified that the LightBGM algorithm performed better in forecasting PM10 in Kandy (R2 = 0.99, MSE = 0.02, MAE = 0.002, RMSE = 0.1225, MARE = 1.0, and NSE = 0.99) . In contrast, the LightBGM achieved a higher performance (R2 = 0.99, MSE = 0.002, MAE = 0.012, RMSE = 1.051, MARE = 0.00, and NSE = 0.99) for the forecasting PM10 for the Battaramulla region. As per the results, it can be concluded that there is a necessity to develop forecasting models for different land areas. Moreover, it was concluded that the PM10 in Kandy and Battaramulla increased slightly with existing seasonal changes

Efficacy of a portable, moderate-resolution, fast-scanning differential mobility analyzer for ambient aerosol size distribution measurements

Ambient aerosol size distributions obtained with a compact scanning mobility analyzer, the “Spider” differential mobility analyzer (DMA), are compared to those obtained with a conventional mobility analyzer, with specific attention to the effect of mobility resolution on the measured size distribution parameters. The Spider is a 12 cm diameter radial differential mobility analyzer that spans the 10–500 nm size range with 30 s mobility scans. It achieves its compact size by operating at a nominal mobility resolution R=3 (sheath flow = 0.9 L min−1; aerosol flow = 0.3 L min−1) in place of the higher ratio of sheath flow to aerosol flow commonly used. The question addressed here is whether the lower resolution is sufficient to capture key characteristics of ambient aerosol size distributions. The Spider, operated at R=3 with 30 s up- and downscans, was co-located with a TSI 3081 long-column mobility analyzer, operated at R=10 with a 360 s sampling duty cycle. Ambient aerosol data were collected over 26 consecutive days of continuous operation, in Pasadena, CA. Over the 17–500 nm size range, the two instruments exhibit excellent correlation in the total particle number concentrations and geometric mean diameters, with regression slopes of 1.13 and 1.00, respectively. Our results suggest that particle sizing at a lower resolution than typically employed may be sufficient to obtain key properties of ambient size distributions, at least for these two moments of the size distribution. Moreover, it enables better counting statistics, as the wider transfer function for a given aerosol flow rate results in a higher counting rate.</p

Differentiating between particle formation and growth events in an urban environment

Small aerosols at a given location in the atmosphere often originate in situ from new particle formation (NPF). However, they can also be produced and then transported from a distant location to the point of observation where they may continue to grow to larger sizes. This study was carried out in the subtropical urban environment of Brisbane, Australia, in order to assess the relative occurrence frequencies of NPF events and particle growth events with no NPF. We used a neutral cluster and air ion spectrometer (NAIS) to monitor particles and ions in the size range 2–42&thinsp;nm on 485 days, and identified 236 NPF events on 213 days. The majority of these events (37&thinsp;%) occurred during the daylight hours with just 10&thinsp;% at night. However, the NAIS also showed particle growth with no NPF on many nights (28&thinsp;%). Using a scanning mobility particle sizer (SMPS), we showed that particle growth continued at larger sizes and occurred on 70&thinsp;% of nights, typically under high relative humidities. Most particles in the air, especially near coastal locations, contain hygroscopic salts such as sodium chloride that may exhibit deliquescence when the relative humidity exceeds about 75&thinsp;%. The growth rates of particles at night often exceeded the rates observed during NPF events. Although most of these night time growth events were preceded by day time NPF events, the latter was not a prerequisite for growth. We conclude that particle growth in the atmosphere can be easily misidentified as NPF, especially when they are monitored by an instrument that cannot detect them at the very small sizes.</p

Monitoring of Ultrafine Particles in the Surrounding Urban Area of In-Land Passenger Ferries

The authors would like to thank the TTSL (Transtejo e Soflusa) for giving us access to a private location for measurements in ferry terminal of Montijo.Maritime transportation, widely used both in international transport of goods and touristic purposes, has been identified as a significant source of ultrafine particles (UFP). In-land passenger ferry is a source of UFP far less addressed; however, in locations with relatively high frequency of this transportation mode, it is expected that they contribute to an increase of their concentration. Moreover, the negative effects of UFP on human health and environment are known and therefore, monitoring UFP produced by ferries is vital to assess the degree of exposure of who work or live close to ferries’ terminals or downwind to their cruising path. This work aims to study the influence of in-land ferries activities on UFP in the urban/suburban areas near ferries’ terminals and downwind across the cruising path. The UFP monitoring campaign was carried out from September to December 2018 for 19 non-consecutive periods. The sampling sites were chosen in order to maximize measurements under downwind conditions and allow the association between ferry operation and UFP concentration response. Based on data collected, correlation analysis was performed between ferry’s traffic and particle number counting (PNC) of UFP, and also with meteorological variables. Results show an increase in PNC ranging from 25 to 197% during the third minute around a ferry movement and are moderate to positive significant correlations between PNC values and the number of ferry operations (r = 0.79 to r = 0.94), showing that UFP emitted by in-land ferries contributes to PNC increase. Moreover, negative correlations (r = -0.85 to r = -0.93) between PNC and wind intensity were also found.publishersversionpublishe

Responses of gaseous sulfuric acid and particulate sulfate to reduced SO2 concentration : A perspective from long-term measurements in Beijing

SO2 concentration decreased rapidly in recent years in China due to the implementation of strict control policies by the government. Particulate sulfate (pSO(4)(2-)) and gaseous H2SO4 (SA) are two major products of SO2 and they play important roles in the haze formation and new particle formation (NPF), respectively. We examined the change in pSO(4)(2-) and SA concentrations in response to reduced SO2 concentration using long-term measurement data in Beijing. Simulations from the Community Multiscale Air Quality model with a 2-D Volatility Basis Set (CMAQ/2D-VBS) were used for comparison. From 2013 to 2018, SO2 concentration in Beijing decreased by similar to 81% (from 9.1 ppb to 1.7 ppb). pSO(4)(2-) concentration in submicrometer particles decreased by similar to 60% from 2012-2013 (monthly average of similar to 10 mu g.m(-3)) to 2018-2019 (monthly average of similar to 4 mu g.m(-3)). Accordingly, the fraction of pSO(4)(2-) in these particles decreased from20-30% to b10%. Increased sulfur oxidation ratio was observed both in the measurements and the CMAQ/2D-VBS simulations. Despite the reduction in SO2 concentration, there was no obvious decrease in SA concentration based on data from several measuring periods from 2008 to 2019. This was supported by the increased SA:SO2 ratio with reduced SO2 concentration and condensation sink. NPF frequency in Beijing between 2004 and 2019 remains relatively constant. This constant NPF frequency is consistent with the relatively stable SA concentration in Beijing, while different from some other cities where NPF frequency was reported to decrease with decreased SO2 concentrations. (C) 2020 Elsevier B.V. All rights reserved.Peer reviewe

Variation of size-segregated particle number concentrations in wintertime Beijing

The spatial and temporal variability of the number size distribution of aerosol particles is an indicator of the dynamic behavior of Beijing's atmospheric pollution cocktail. This variation reflects the strength of different primary and secondary sources, such as traffic and new particle formation, as well as the main processes affecting the particle population. In this paper, we report size-segregated particle number concentrations observed at a newly developed Beijing station during the winter of 2018. Our measurements covered particle number size distributions over the diameter range of 1.5 nm-1 mu m (cluster mode, nucleation mode, Aitken mode and accumulation mode), thus being descriptive of a major fraction of the processes taking place in the atmosphere of Beijing. Here we focus on explaining the concentration variations in the observed particle modes, by relating them to the potential aerosol sources and sinks, and on understanding the connections between these modes. We considered haze days and new particle formation event days separately. Our results show that during the new particle formation (NPF) event days increases in cluster mode particle number concentration were observed, whereas during the haze days high concentrations of accumulation mode particles were present. There was a tight connection between the cluster mode and nucleation mode on both NPF event and haze days. In addition, we correlated the particle number concentrations in different modes with concentrations of trace gases and other parameters measured at our station. Our results show that the particle number concentration in all the modes correlated with NOx, which reflects the contribution of traffic to the whole submicron size range. We also estimated the contribution of ion-induced nucleation in Beijing, and we found this contribution to be negligible.Peer reviewe

Chemistry of new particle formation and growth events during wintertime in suburban area of Beijing : Insights from highly polluted atmosphere

The high frequency of new particle formation (NPF) events observed under polluted atmospheric conditions is still poorly understood. To improve our understanding of NPF and its effects, the particle number size distribution (3-1000 nm) and submicron particle chemical composition were measured from 4 November 2017 to 17 January 2018 in suburban Beijing. During this intense campaign, 22 NPF events were identified with a frequency of 29%, including 11 cases that occurred under "clean" conditions (C-NPF) and 11 cases that occurred under "polluted" conditions (P-NPF). The observed formation rate (J(3)) and condensation sink were 4.6-148.9 cm(-3).s(-1) and 0.01-0.07 s(-1), and the majority of NPF events occurred when the condensation sink (CS) values below 0.03 s(-1), indicating that condensation vapor likely constitutes the critical limiting factor for NPF events. The correlations between log J(3) and [H2SO4] that close to previous CLOUD experimental results in the majority of NPF events (68%) suggest the high nucleation rates (up to 100 cm(-3).s(-1)) would be attributed by the amines that enhancing sulfuric acid nucleation, while the reminding cases (32%) possibly attributed to the H2SO4-NH3 clustering mechanism, which is supported by the theoretical expectations for H2SO4 nucleation with NH3 simulated by the MALTE_BOX model. The observed growth rate varied from 4.9 to 37.0 mm.h(-1), with the dominant contribution (>60%) from sulfuric acid during the early phases of growth (similar to 4 nm), which was also sufficient to explain the observed Q(GR) for 50 nm)Peer reviewe

Quantile based modelling of diurnal temperature range with the five-parameter lambda distribution

Diurnal temperature range is an important variable in climate science that can provide information regarding climate variability and climate change. Changes in diurnal temperature range can have implications for hydrology, human health and ecology, among others. Yet, the statistical literature on modelling diurnal temperature range is lacking. In this paper we propose to model the distribution of diurnal temperature range using the five-parameter lambda (FPL) distribution. Additionally, in order to model diurnal temperature range with explanatory variables, we propose a distributional quantile regression model that combines quantile regression with marginal modelling using the FPL distribution. Inference is performed using the method of quantiles. The models are fitted to 30 years of daily observations of diurnal temperature range from 112 weather stations in the southern part of Norway. The flexible FPL distribution shows great promise as a model for diurnal temperature range, and performs well against competing models. The distributional quantile regression model is fitted to diurnal temperature range data using geographic, orographic and climatological explanatory variables. It performs well and captures much of the spatial variation in the distribution of diurnal temperature range in Norway.Comment: 28 pages, 9 figures; v2: revision of the introduction, more references added and minor corrections of the tex

Interpretation of particle number size distributions measured across an urban area during the FASTER campaign

Abstract. Particle number size distributions have been measured simultaneously by scanning mobility particle sizers (SMPSs) at five sites in central London for a 1 month campaign in January–February 2017. These measurements were accompanied by condensation particle counters (CPCs) to measure total particle number count at four of the sites and Aethalometersmeasuringblackcarbon(BC)atfivesites.The spatialdistributionandinter-relationshipsoftheparticlesize distribution and SMPS total number counts with CPC total number counts and black carbon measurements have been analysed in detail as well as variations in the size distributions. One site (Marylebone Road) was in a street canyon with heavy traffic, one site (Westminster University) was on a rooftop adjacent to the Marylebone Road sampler, and a further sampler was located at Regent’s University within a major park to the north of Marylebone Road. A fourth sampler was located nearby at 160m above ground level on the BT tower and a fifth sampler was located 4km to the west of the main sampling region at North Kensington. Consistent with earlier studies it was found that the mode in the size distribution had shifted to smaller sizes at the Regent’s University (park) site, the mean particle shrinkage rate being 0.04nms−1 with slightly lower values at low wind speeds and some larger values at higher wind speeds. There was evidence of complete evaporation of the semi-volatile nucleation mode under certain conditions at the elevated BT Tower site. While the SMPS total count and black carbon showed typical traffic-dominated diurnal profiles, the CPC count data typically peaked during night-time as did CPC/SMPS and CPC/BC ratios. This is thought to be due to the presence of high concentrations of small particles (2.5–15nm diameter) probably arising from condensational growth from traffic emissions during the cooler night-time conditions. Such behaviour was most marked at the Regent’s University and Westminster University sites and less so at Marylebone Road, while at the elevated BT Tower site the ratio of particle number(CPC) to black carbon peaked during the morning rush hour and not at night-time, unlike the other sites. An elevation in nucleation mode particles associated with winds from the west and WSW sector was concluded to result from emissions from London Heathrow Airport, despite a distance of 22km from the central London sites

An estimation of virtual trades of embedded water and land through Sri Lankan seasonal crops’ trades to improve the cropping preferences

Due to the increase in population, growing urbanization, and higher demands for processed and unprocessed foods, resources related to food production have become scarce. Water and land can be considered as the primary resources to determine the crop production potential of a country. Ideally, countries that lack water and land resources can import these in virtual form. Sri Lanka is a country rich in water resources that faced bankruptcy recently. This study analyzes and explores the potential for use of land–water resources in Sri Lanka. A comprehensive framework is generated to identify the virtual land–water trade by considering ten major imports and nine major export crops in Sri Lanka. Consequently, the top ten imports/exports and top ten import/export trade partners are identified. The analysis reveals that Sri Lanka is a heavily import-dominant country, having seven times higher imports compared to exports. The country imports wheat, which is 82% of its import crops, and the same crop is the largest export (85% of crop export). Compared to its trade partners, Sri Lanka has sufficient water resources, but availability of arable land is limited. Banana is the largest export of the country, which involves higher embedded water and less land, matching the resource availability to Sri Lanka, whereas the trade partners are expected to continue importing the crop due to their water and land stress conditions. Finalization of the long-awaited agriculture policy of the country is strongly recommended