Seasonal Kendall Test Research Articles

Status and Trend of the Main Allergenic Pollen Grains and Alternaria Spores in the City of Rome (2003–2019)

Today a large part of the European population is exposed to levels of air pollution exceeding the standards recommended by the World Health Organization. Moreover, air pollution and the seasonal emission of allergenic pollen are progressively affecting human health and can cause severe allergic reactions, particularly when air pollution combines with pollen allergen peaks. Unlike atmospheric pollutants of anthropogenic origin, pollen sources have a pulsating trend that leads to high values in the flowering period and values close to, or equal to, zero in the rest of the year. This aspect makes essential the definition of data coverage standards for the main allergenic taxa. For air quality assessment detailed classification criteria for monitoring stations are defined by international standards, not the same from the European Standards for the Sampling and analysis of airborne pollen grains and fungal spores. This paper describes the status and the air concentration trends of the main allergenic pollen and the Alternaria spore measured in Rome from 2003 to 2019 by the Aerobiological Monitoring Center of Tor Vergata (Rome) and calculated by the Seasonal Kendall test with the open-source OpenAir R package. The analysis was carried out on the daily concentrations of the most widespread allergenic taxa in Italy: Asteraceae, Betulaceae, Corylaceae, Cupressaceae/Taxaceae, Poaceae, Oleaceae, Urticaceae and the Alternaria spores.

Spatiotemporal evaluation of water quality and risk assessment of heavy metals in the northern Caspian Sea bounded by Kazakhstan

The water quality of the northern Caspian Sea has not been well-known, and its contamination can adversely affect the health of swimmers and seashore residents. The study sought to determine the contamination state of the Caspian Sea in Kazakhstan and quantify human health risks coming from the existing heavy metals concentration. The Caspian Sea was found to be “fairly to marginally” contaminated (24 < CCME-WQI < 64), with Cd influencing the index significantly. Concentrations of Cd and Pb increase over time (seasonal Kendall test, p-values = 2–4 %) in sites near oil fields and ports, suggesting the significant role of anthropogenic sources in causing diverse pollution events. Pb demonstrated the highest variability and number of outliers (4.3 % of all samples with coefficients of variation reaching up to 175 %). The principal component analysis further revealed that various discharges from oilfields and upstream transport could contribute to the contamination by heavy metals and their concentrations. Contamination is associated with up to 6 % cancer risk for adults. The long exposure duration of swimmers in water increases risks by up to 18 %, indicating the local population is at a higher risk. In conclusion, statistical tests and analysis indicate the presence of anthropogenic sources, and risk assessment reveals swimming can contribute to cancer risk.

Analysis of two-decade meteorological and air quality trends in Rome (Italy)

This study presents a trend analysis of a two-decade (2000–2020) series of surface meteorological and air quality data measured in Rome (Italy). Data series are collected at three sites in Rome downtown and its coastal surroundings. This paper fills the gap due to missing or incomplete recent information about the meteorological and atmospheric composition tendencies in the Rome area. Datasets are subjected to in-depth quality control and to statistical analysis to verify the data homogeneity, whilst trend analysis is performed using the Seasonal Kendall test. The results show a statistically significant positive trend for average air temperature (0.07 °C year−1 in urban and coastal sites), whilst maximum and minimum temperatures increase more in urban (0.10 °C year−1) than in coastal (0.01 °C year−1) environment. The water vapour mixing ratio trend is higher in the city (0.10 g kg−1 year−1) than along the coast (0.03 g kg−1 year−1). The heat index tendency is more pronounced in the Rome centre (0.11 °C year−1) than in the coast (0.06 °C year−1). The monthly cumulative precipitations do not show statistically significant trends. On the other hand, air quality generally improved: surface pollutant concentrations show a significant decrease thanks to the reduction of local emissions (C6H6, − 0.12 µg m−3 year−1; SO2, − 0.09 µg m−3 year−1; CO, − 0.02 mg m−3 year−1; NOx, − 1.28 µg m−3 year−1; NO, − 0.38 µg m−3 year−1; NO2, − 0.60 µg m−3 year−1, PM10, − 0.35 µg m−3 year−1). Only O3 shows a statistically significant positive trend (0.15 µg m−3 year−1), in agreement with wider scale studies. The outcomes suggest that whilst local and national policies contribute to the improvement of air quality, the rising of temperature—as likely consequence of climate change—may be an emerging cause of concern for human thermal discomfort and potential effect on the conservation of tangible immovable heritage.

Analysing the day/night seasonal and annual changes and trends in land surface temperature and surface urban heat island intensity (SUHII) for Indian cities

• Day/night seasonal and annual changes and trends (2001- 2018) in land surface temperature and surface urban heat island intensity (SUHII) for Indian cities (Lucknow, Kolkata and Pune). • Nighttime LST is a better indicator to study the urban heating effect due to its sensitivity towards urbanization. • Positive trends in mean annual daytime (0.003 to 0.059 °C/year) and nighttime (0.030 to 0.078 °C/year) LST are observed in all cities, except in Pune where urban cooling occurs during daytime. • Nighttime SUHII is positive for all cities with mean annual SUHII ranging from 1.34 to 2.07 °C. Understanding the patterns and possible causes of urban heat islands (UHI) effect due to urbanisation-induced anthropogenic activities is an important area in urban climatic research. Few studies on long-term thermal behaviour of Indian cities are available in the literature. Towards this, the present study investigates the day/night seasonal and annual changes and trends in land surface temperature (LST) and surface urban heat island intensity (SUHII) during the last two decades for three Indian cities (Lucknow, Kolkata and Pune) with distinct urban, physiographic and climatic setting. Moderate Resolution Imaging Spectroradiometer (MODIS) LST data products acquired during daytime and nighttime from 2001 to 2018 are processed and analysed for this purpose. MODIS-based aerosol optical depth (AOD) and normalised difference vegetation index (NDVI) products are used to understand the plausible reasons of change in LST and SUHII patterns. The urban (contiguous built-up) and non-urban (surrounding rural) areas are delineated by applying city clustering algorithm on MODIS Land Cover datasets of 500 m spatial resolution. Mann-Kendall and Seasonal-Kendall tests along with Theil-Sen estimator are used for trend analysis. The findings show that the diurnal temperature range (DTR) has decreased from 2001 to 2018 due to higher increase in nighttime LST as compared to daytime. Nighttime LST is a better indicator to study the urban heating effect due to its sensitivity towards urbanisation. Positive trends in mean annual daytime (0.003 to 0.059 °C/year) and nighttime (0.030 to 0.078 °C/year) LST are observed in all cities, except in Pune where urban cooling occurs during daytime. Increase in aerosol loading (with consequent decrease in air temperature and surface insolation) and vegetative cover over time are attributed as the primary reasons of urban cooling effect in Pune during daytime. Seasonal analysis indicate high warming rates during monsoon and summer seasons, particularly during nighttime (0.062 to 0.1 °C/year). Nighttime SUHII is positive for all cities with mean annual SUHII ranging from 1.34 to 2.07 °C. Statistically significant ( p <0.01) increasing trends are observed in mean annual SUHII (0.009 °C/year to 0.022 °C/year) for Kolkata and Pune. Decreasing trend in SUHII is observed over Lucknow due to higher rate of increase in LST in non-urban area as compared to urban area. The study highlights that geographical, physiographic and climatic setting along with anthropogenic processes in urban and its surrounding non-urban areas are critical towards understanding the causative factors in exacerbating the phenomenon of urban heating.

Water quality monitoring with purpose: Using a novel framework and leveraging long-term data

Water quality monitoring programs are developed to meet goals including attaining regulatory compliance, evaluating long-term environmental changes, or quantifying the impact of an emergency event. Methods for developing these programs often fail to address multiple aspects of development (hazard identification, parameter selection, monitoring locations/frequency) simultaneously. We develop a framework for monitoring program development that is both versatile and systematic, the Hazard Based Water Quality Monitoring Planning framework, and apply it to the Quabbin watershed in Massachusetts, USA. We use a novel application of dataset deconstruction of long-term water quality datasets and the Seasonal Kendall test for trends to evaluate the effects of sampling frequency on long-term trend detection at several watershed sites. Results showed that when sampling frequency is decreased, ability to detect statistically significant trends often decreases. Absolute error in trend slopes between biweekly (twice monthly) and reduced sampling frequencies was relatively small for specific conductance and turbidity but was high for total coliform, likely due to interannual variation in rainfall and temperature We found that no one sampling reduction method resulted in a consistently lower absolute error compared to the “truth” (biweekly sampling), highlighting the importance of evaluating conditions that may affect water quality at sites in different parts of a watershed. We demonstrate the framework's usefulness, particularly for parameter and sampling frequency selection, using methods that can be readily applied to other watershed systems.

Effects of Long-Term Increases in Water Temperature and Stratification on Large Artificial Water-Source Lakes in South Korea

Long-term changes in air and water temperatures and the resulted stratification phenomena were observed for Soyang Lake (SY), Paldang Lake (PD), Chungju Lake (CJ), and Daecheong Lake (DC) in South Korea. Non-parametric seasonal Kendall and Mann-Kendall tests, Sen slope estimator, and potential energy anomaly (PEA) were applied. The lake surface water temperatures (LSWTs) of SY and DC increased at the same rate (0.125 °C/y), followed by those of CJ (0.071 °C/y) and PD (0.06 °C/y). Seasonally, the LSWT increase rates for all lakes, except PD, were 2–3 times higher than the air temperature increase rates. The lake stratification intensity order was similar to those of the LSWT increases and correlations. SY and DC displayed significant correlations between LSWT (0.99) and PEA (0.91). Thus, the LSWT significantly affected stratification when the water temperature increased. PD demonstrated the lowest correlation between LSWT and PEA. Inflow, outflow, rainfall, wind speed, and retention time were significantly correlated, which varied within and between lakes depending on lake topographical, hydraulic, and hydrological factors. Thus, hydraulic problems and nutrients should be managed to minimize their effects on lake water quality and aquatic ecosystems because lake cyanobacteria can increase as localized water temperatures increase.

Drivers of Dissolved Organic Carbon Mobilization From Forested Headwater Catchments: A Multi Scaled Approach

Understanding and predicting catchment responses to a regional disturbance is difficult because catchments are spatially heterogeneous systems that exhibit unique moderating characteristics. Changes in precipitation composition in the Northeastern U.S. is one prominent example, where reduction in wet and dry deposition is hypothesized to have caused increased dissolved organic carbon (DOC) export from many northern hemisphere forested catchments; however, findings from different locations contradict each other. Using shifts in acid deposition as a test case, we illustrate an iterative “process and pattern” approach to investigate the role of catchment characteristics in modulating the steam DOC response. We use a novel dataset that integrates regional and catchment-scale atmospheric deposition data, catchment characteristics and co-located stream Q and stream chemistry data. We use these data to investigate opportunities and limitations of a pattern-to-process approach where we explore regional patterns of reduced acid deposition, catchment characteristics and stream DOC response and specific soil processes at select locations. For pattern investigation, we quantify long-term trends of flow-adjusted DOC concentrations in stream water, along with wet deposition trends in sulfate, for USGS headwater catchments using Seasonal Kendall tests and then compare trend results to catchment attributes. Our investigation of climatic, topographic, and hydrologic catchment attributes vs. directionality of DOC trends suggests soil depth and catchment connectivity as possible modulating factors for DOC concentrations. This informed our process-to-pattern investigation, in which we experimentally simulated increased and decreased acid deposition on soil cores from catchments of contrasting long-term DOC response [Sleepers River Research Watershed (SRRW) for long-term increases in DOC and the Susquehanna Shale Hills Critical Zone Observatory (SSHCZO) for long-term decreases in DOC]. SRRW soils generally released more DOC than SSHCZO soils and losses into recovery solutions were higher. Scanning electron microscope imaging indicates a significant DOC contribution from destabilizing soil aggregates mostly from hydrologically disconnected landscape positions. Results from this work illustrate the value of an iterative process and pattern approach to understand catchment-scale response to regional disturbance and suggest opportunities for further investigations.

Air pollution trend in Chandigarh city situated in Indo-Gangetic Plains: Understanding seasonality and impact of mitigation strategies

The long-term trend of air pollutants was studied in Chandigarh, located in Indo-Gangetic Plains of India. The SPM, PM10, NOx, and SO2 depict site-specific variation having different anthropogenic activities. The results indicate that PM10 levels in Chandigarh remain higher than the prescribed annual ambient air quality standards (60 μg m−3) of India. Seasonal Kendall test indicates a declining trend of PM10 for the year 2003 to 2018 at an industrial and commercial site (1996–2016). There is a significant increase in NOx levels at all locations except at commercial sites. The results of the linear regression model and Theil–Sen slope show that SPM is declining at all locations, but results are not statistically significant. Interestingly, PM10 levels at the industrial site display a significant declining trend (1.3% year−1). Similarly, NOx levels are increasing at all sites but having a statistically significant trend at a rural location (8.9% year−1) and residential site (15.2% year−1). Air pollutants show strong seasonal variability having a higher concentration in post-monsoon and winter season, which found to be linked with regional anthropogenic activities such as crop residue burning and use of solid biomass fuel for cooking and other purposes. Lowest PM10 levels were observed during the monsoon and having a decline of 47.4–66.4% as compared to winter levels. Site-specific variations in air pollutants were found to be associated with air quality improvement policies such as shifting of an interstate bus terminal, ban on diesel autos, including strict implementation of air quality norms on industries. As the relative contribution of various pollution sources is still unknown, the seasonal pattern of pollutants will help in knowing the background concentration of pollutants and could help to formulate evidence-based policies to mitigate air pollution under National Clean Air Programme (NCAP).

Spatio-temporal variations of tropospheric nitrogen dioxide in Turkey based on satellite remote sensing

The satellite observations of NO2 acquire the total tropospheric column over an area while the current ground observations lack spatial and temporal coverage. In this study the Dutch Ozone Monitoring Instrument (OMI) NO2 (DOMINO) data product v2.0 for 2004 - 2019 period was used to analyze the spatial and temporal variations of NO2 in Turkey. Considering the seasonality characteristics of NO2, we have used pixel based Seasonal Kendall (S-K) test to investigate the trend of the change. The highest values of NO2 has been found at the metropolitan areas and perimeter of the high capacity power plants in the observed period. The monthly average concentrations of NO2 are higher in winter months due to the higher demand of heating and power usage. The S-K trend test results indicate a statistically negative trend at the largest cities such as Istanbul, Ankara and Izmir. However statistically significant positive trend has been found in some areas and Syrian border provinces in particular. Our results show that there is an abrupt change by 2011 in the tropospheric NO2 concentrations, same period when the first Syrian refugees have arrived after the political disorder. The dramatic change at the emission landscape of the NO2 in the region can be explained by changes in population concentration due to political circumstances.

A ten year record of nitrate retention and solute trends in a Wisconsin sand plains stream: temporal variation at multiple scales

Nitrate retention is an important ecosystem service provided by streams which reduces nitrogen loads to downstream ecosystems. However, most inferences about nitrate retention and uptake in streams are based on measurements at sub-annual scales. Our objective was to evaluate variation in nitration retention and solute concentrations at weekly to decadal time scales. We measured nitrate and chloride concentration, nitrate flux and nitrate retention in Emmons Creek, a groundwater-dominated, nitrate-rich stream in central Wisconsin during a 10-year period. We used a two-station mass balance approach to measure nitrate retention while accounting for groundwater inputs. Surface water nitrate concentration, nitrate yield and nitrate retention exhibited strong seasonal variation. Seasonal Kendall tests revealed positive trends for surface water discharge, nitrate and chloride concentrations and groundwater chloride concentration, but not nitrate retention. Generalized additive mixed models (GAMM), accounting for serial autocorrelations, also indicated positive trends in surface water nitrate and chloride concentrations but no trend for nitrate retention. Nitrate retention averaged 370 mg NO3-N m−2 d−1 (± 316 SD) and was highest during the spring (512 mg NO3-N m−2 d−1 ± 319), followed by summer (460 ± 322), fall (340 ± 281) and winter (165 ± 212). Nitrate retention rates in Emmons Creek were relatively high compared to most published estimates. However, our results suggest that Emmons Cr. may have saturated its capacity to retain nitrate during a period when nitrate yield from its watershed increased, which is an important finding given the increases in N availability in many regions of earth.

Water Quality of the Mun River in Thailand-Spatiotemporal Variations and Potential Causes.

The water quality of the Mun River, one of the largest tributaries of the Mekong River and an important agricultural area in Thailand, is investigated to determine its status, identify spatiotemporal variations and distinguish the potential causes. Water quality dataset based on monitoring in the last two decades (1997–2017) from 21 monitoring sites distributed across the basin were analyzed using seasonal Kendall test and water quality index (WQI) method. The Kendall test shows significant declines in fecal coliform bacteria (FCB) and ammonia (NH3) in the upper reaches and increases in nitrate (NO3) and NH3 in the lower reaches. Strong temporal and spatial fluctuations were observed in both the concentrations of individual parameters and the WQI values. Seasonal variation of water quality was observed at each monitoring site. WQI values in August (flood season) were generally among the lowest, compared to other seasons. Spatially, sites in the upper reaches generally having lower WQI values than those in the lower reaches. Excessive phosphorus is the primary cause of water quality degradation in the upper reaches, while nitrogen is the primary parameter for water quality degradation in the lower reaches. Urban built-up land is an important “source” of water pollutants in the lower basin, while agricultural land plays a dual role, affecting across the basin.

Assessing long term trends of air pollutants and associated health risks imposed on residents in Bolu (Turkey) during winter

Objective: The objective of this study was to evaluate the long term and seasonal variation of PM10 and SO2 in the the Bolu city center between 2006 and 2017 in relation to meteorological parameters and to evaluate the health risks due to metals bound to particulate matter (PM) during the winter season. Method: The Seasonal Kendall (SK) test was performed on the air quality data to find the magnitude of associated trends. In addition, seasonality of these pollutants was evaluated in conjunction with the meteorological parameters. Furthermore, daily PM samples in two different size fractions were collected between December 2014 and February 2015 and analyzed for metals by WDXRF. The generated metal concentrations were used to estimate carcinogenic and non-carcinogenic health risks imposed on the residents of the city. Results: The SK test revealed statistically significant decline in SO2 and PM10 with a rate of 1.953 and 2.932 µg/m3/year, respectively, at 5% significance level. Both of the parameters depicted very clear seasonal cycles. Performed exposure risk assessment indicated that dermal contact with PM bound metals was the main route of exposure for children, while the adults were more prone to non-carcinogenic risks from exposure through inhalation. Conclusion: Overall, children were found to be more susceptible to non-carcinogenic risks as compared to adults. The cancer risks due to As and Pb were within the acceptable limits (&amp;lt; 1×10-4).

Chloride inputs to the North Saskatchewan River watershed: the role of road salts as a potential driver of salinization downstream of North America's northern most major city (Edmonton, Canada)

Multiple anthropogenic activities are driving the salinization of freshwater environments threatening water resources worldwide. Accordingly, this research will first examine the spatial and temporal variability of major ions (i.e. Ca2+, Mg2+, Na+, K+, SO42−, CO32−, and HCO3−) upstream and downstream of the northernmost major city in North America (Edmonton, Canada). Second, this research will estimate the relative contributions of the major sources of chloride (Cl), the main constituent of road deicers, to the sub-basin around Edmonton. Monthly water quality data was for three sites on the North Saskatchewan River (NSR): Rocky Mountain House (RMH - downstream of the Rocky Mountain headwaters), Devon Bridge (upstream of Edmonton) and Pakan Bridge (downstream of Edmonton). Change ratios investigate the downstream alterations of major ions at Pakan and Devon, relative to RMH. Seasonal Kendall tests examine temporal trends (1987–2017). A mass-balance approach then quantifies the major sources of Cl in the sub-basin of the NSR between Devon and Pakan. Progressing from the Rocky Mountain headwaters (at RMH) to downstream of Edmonton (at Pakan), Cl− increased by >5.5 times, Na+ by 4.8 times and K by 2.7 times. No significant temporal trends for Cl−, Na+ and K+ were evident at Devon (upstream of Edmonton), whereas all three significantly increased at Pakan (downstream of Edmonton). Deicers (54%), agriculture (20%), along with waste water treatment plant and industrial effluent (15%) were the largest Cl sources in the NSR Devon-Pakan sub-basin. In total, 77 Gg yr−1 of Cl (or 6 t km2 yr−1) is added to the Devon-Pakan sub-basin, of which, 43 Gg yr−1 is retained. Understanding and managing the major drivers of freshwater salinization will be of increasing importance in the 21st century owing to the potential salinization of freshwater resources in the context of a changing climate.

Alpine catena response to nitrogen deposition and its effect on the aquatic system

Alpine areas are vulnerable to nitrogen (N) deposition because of low N-buffering capacity and limited ability to resist change. The objective of the study was to assess if >30 years of N deposition have resulted in a decline in exchangeable base cations (CB) coupled with an increase of exchangeable aluminum (Al). We used soil and stream data sampled between 1982 and 2015 at Green Lakes Valley, Colorado Front Range to evaluate the change in an alpine catena. The CB in the surface horizons of the summit position decreased significantly from 45 cmolc kg−1 in 1982 to 2.3 cmolc kg−1 in 2015, while the exchangeable Al increased from 0.09 cmolc kg−1 to 0.7 cmolc kg−1 in the summit and from 8.9 cmolc kg−1 to 10.5 cmolc kg−1 in the toeslope. Spatiotemporal distribution of soil moisture along the catena exhibited the lowest values during the winter months because the temperature was below freezing. The soil moisture increased in early spring as soil-temperature rose. A Seasonal Kendall test (SK) showed that the soil moisture decreased along the catena by −0.007 m3 m−3 yr−1(P < 0.001). The soil moisture trend coincided with a soil temperature increase from the summit to toeslope of 0.68° yr−1. Segmental SK analysis of acid-neutralizing capacity (ANC) measured in the outlet of the lake below the catena showed a decrease of −2.15 μeq L−1 yr−1 for the first monitoring period from 1982 to 1995, and an increase by 0.51 μeq L−1 yr−1 during the second monitoring period from 1995 to 2014. These trend analyses attest to the limited influence of the alpine soil system on the overall aquatic chemistry. Hence, a clear distinction should be made between the alpine soils and the terrestrial system (e.g., rock glacier, taluses, and screes). Most of the soils have little impact on the aquatic system, whereas other terrestrial features are more important in this regard.

ESTIMATION OF THE AIR QUALITY TRENDS IN ISTANBUL

Air pollution is a problem that accumulates with urbanization and threatens human health. The quality of the air we breathe is more important for the cities like Istanbul, having the busiest traffic flow and highest population in Turkey. In this work, in order to measure the air quality of Istanbul, the trend of air quality data will be estimated. Turkey, according to the data of Environment Performance Index 2014 prepared by Yale University, is listed low especially on air quality. In accordance with the agreements signed with the European Union the environmental indicators and thus our air quality should be improved. For this reason, in order to reduce air pollution a program is prepared and an Air Quality Index is formed Turkey-wide. Also in Istanbul, via many stations the air pollutants are being monitored. To increase the air quality, it is necessary to monitor the change within time of these pollutants and estimate their trend. However, the pollutants listed in the air quality index, as in all the environmental data, is a data that consists outliers and missing observations, asymmetrical, seasonal, serial dependent, do not fit the normal distribution. As of these properties, the trend analysis of the air pollutants are done via tests that are nonparametric In detecting the existence of a trend in the air quality data carrying seasonal effect the Seasonal Kendall Test is being used.In this study the trend of air pollutants for Istanbul is tested via the monthly data gathered through 2005-2014 from different monitoring stations established by the Istanbul Metropolitan Municipality,. Among the pollutants especially in SO2 emission, in all monitoring stations, statistically significant negative seasonal trend is seen. CO emission is also determined to be in decrease. However PM10 and NO2 emissions are determined to be increasing in some stations. Besides, the homogeneity testing of pollutants between seasons and stations is also performed. According to this test, SO2 has a homogeneous trend between stations and seasons.

Characterizing and explaining spatio-temporal variation of water quality in a highly disturbed river by multi-statistical techniques.

Assessing the spatio-temporal variations of surface water quality is important for water environment management. In this study, surface water samples are collected from 2008 to 2015 at 17 stations in the Ying River basin in China. The two pollutants i.e. chemical oxygen demand (COD) and ammonia nitrogen (NH3-N) are analyzed to characterize the river water quality. Cluster analysis and the seasonal Kendall test are used to detect the seasonal and inter-annual variations in the dataset, while the Moran’s index is utilized to understand the spatial autocorrelation of the variables. The influence of natural factors such as hydrological regime, water temperature and etc., and anthropogenic activities with respect to land use and pollutant load are considered as driving factors to understand the water quality evolution. The results of cluster analysis present three groups according to the similarity in seasonal pattern of water quality. The trend analysis indicates an improvement in water quality during the dry seasons at most of the stations. Further, the spatial autocorrelation of water quality shows great difference between the dry and wet seasons due to sluices and dams regulation and local nonpoint source pollution. The seasonal variation in water quality is found associated with the climatic factors (hydrological and biochemical processes) and flow regulation. The analysis of land use indicates a good explanation for spatial distribution and seasonality of COD at the sub-catchment scale. Our results suggest that an integrated water quality measures including city sewage treatment, agricultural diffuse pollution control as well as joint scientific operations of river projects is needed for an effective water quality management in the Ying River basin.

Surface water pH variations and trends in China from 2004 to 2014.

With economic development and the increase of energy consumption, surface water acidification has been a potential environmental concern in China. Here, we analyzed variations and trends in surface water pH of 73 sites from ten river basins in China from 2004 to 2014 with nonparametric Seasonal Kendall test method. Our analysis showed that the variations of surface water pH in China ranged from 6.5 to 9.0 in the past decade (2004-2014), which satisfied the water quality criteria in pH for protection of aquatic ecosystems in China (6.0-9.0) and USA (6.5-9.0). However, significant decreasing trends in surface water pH were found in 31 monitoring sites, which were mainly located in Haihe River, Taihu Lake and Yangtze River, while the pH value showed significant increasing trends in 22 sites, which mainly were located in Songhua River and Pearl River. Our results suggested the increased potential acidification of susceptible water bodies in China. Besides the control policy of sulfur dioxide (SO2) emissions, the emissions of nitrous oxides (NOx) should also be reduced to protect the aquatic systems in China.

Changing Regional Emissions of Airborne Pollutants Reflected in the Chemistry of Snowpacks and Wetfall in the Rocky Mountain Region, USA, 1993–2012

Wintertime precipitation sample data from 55 Snowpack sites and 17 National Atmospheric Deposition Program (NADP)/National Trends Network Wetfall sites in the Rocky Mountain region were examined to identify long-term trends in chemical concentration, deposition, and precipitation using Regional and Seasonal Kendall tests. The Natural Resources Conservation Service snow-telemetry (SNOTEL) network provided snow-water-equivalent data from 33 sites located near Snowpack- and NADP Wetfall-sampling sites for further comparisons. Concentration and deposition of ammonium, calcium, nitrate, and sulfate were tested for trends for the period 1993–2012. Precipitation trends were compared between the three monitoring networks for the winter seasons and downward trends were observed for both Snowpack and SNOTEL networks, but not for the NADP Wetfall network. The dry-deposition fraction of total atmospheric deposition, relative to wet deposition, was shown to be considerable in the region. Potential sources of regional airborne pollutant emissions were identified from the U.S. Environmental Protection Agency 2011 National Emissions Inventory, and from long-term emissions data for the period 1996–2013. Changes in the emissions of ammonia, nitrogen oxides, and sulfur dioxide were reflected in significant trends in snowpack and wetfall chemistry. In general, ammonia emissions in the western USA showed a gradual increase over the past decade, while ammonium concentrations and deposition in snowpacks and wetfall showed upward trends. Emissions of nitrogen oxides and sulfur dioxide declined while regional trends in snowpack and wetfall concentrations and deposition of nitrate and sulfate were downward.

Assessment of environmental changes induced by internally displaced person (IDP) camps in the Darfur region, Sudan, based on multitemporal MODIS data

Darfur’s complex conflict situation led to large-scale internal displacement of people with significant implications for the environment as well as for the conflict situation itself. Time series analyses of medium-resolution satellite data for monitoring large regions were carried out over a longer period to detect the impact of camps for internally displaced persons (IDPs) on their surrounding environment. Four regions of interest were defined in the Darfur region, Sudan, which cover the main and most dynamic IDP camps of the region and are characterized by different environmental conditions. Hotspots of anthropogenic impacts on the vegetation are revealed based on the Seasonal Kendall test applied to quality-enhanced enhanced vegetation index and normalized difference vegetation index Moderate Resolution Imaging Spectroradiometer time series. Overlaying the resulting trend pattern with the locations of IDP camps suggests significant impact on the vegetation, especially – but not exclusively – in those areas with very high population densities. A comparison of the temporal development of the detected hotspots with precipitation and population figures over the investigated period help differentiate between natural and human-induced impacts. Subsequent to the analysis of the medium resolution data, the resulting trends in vegetation cover were correlated with changes detected with very-high-resolution satellite imagery for the two areas around Zalingei and Zam Zam. Areas of decreased vegetation cover in the resulting trend pattern can be correlated with logging of trees as well as removal of shrubs and grass, while positive changes in vegetation cover are related to agricultural land expansion.

An Automatic Framework for Detecting and Characterizing Performance Degradation of Software Systems

Software systems that run continuously over a long time have been frequently reported encountering gradual degradation issues. That is, as time progresses, software tends to exhibit degraded performance, deflated service capacity, or deteriorated QoS. Currently, the state-of-the-art approach of Mann-Kendall Test & Seasonal Kendall Test & Sen's Slope Estimator & Seasonal Sen's Slope Estimator (MKSK) detects and characterizes degradation via a combination of techniques in statistical trend analysis. Nevertheless, we pinpoint some drawbacks of MKSK in this paper: 1) MKSK cannot be automated for large scale software degradation analysis, 2) MKSK estimates the degradation trend of software in an oversimplified linear way, 3) MKSK is sensitive to noise, and 4) MKSK suffers from high computational complexity. To overcome all these limitations, we propose a more advanced approach called Modified Cox-Stuart Test & Iterative Hodrick-Prescott Filter (CSHP). The superiority of our CSHP approach over MKSK is validated through extensive Monte Carlo simulations, as well as a real performance dataset measured from 99 real-world web servers.