Monitoring of water quality from roof runoff: Interpretation using multivariate analysis

Evolution of water quality in rainwater harvesting systems during long-term storage in non-rainy seasons

The development of rainwater utilization strategies has relied on rainwater harvesting (RWH) systems for centuries to alleviate the pressure on water resources. However, there are still significant knowledge gaps regarding the changes in water quality in RWH systems during long-term storage in non-rainy seasons. This study evaluated the water quality processes in RWH systems through static rainwater storage experiments for approximately 60 days. The results revealed that nutrients in rainwater accumulated in sediment during storage. Disturbance and redox conditions at the rainwater-sediment interface contribute to the release of sedimentary facies materials. The rainwater showed distinct DO stratification, with the biochemical reactions of sedimentary facies being the primary factor driving oxygen consumption. ORP and turbidity showed positive correlations with COD (r = 0.582; 0.572), TOC (r = 0.678; 0.681), TN (r = 0.452; 0.439), and NH4+-N (r = 0.502; 0.553) (P < 0.05). The regulation of water quality and extension of the usage cycle were identified as critical factors influenced by DO. In addition, bacteria share similar ecological niche preferences. These findings provide scientific evidence for the high-quality reuse of rainwater in decentralized RWH systems during long-term storage in non-rainy seasons.

Water quality and microecosystem of water tanks in karst mountainous area, Southwest China

Karst mountainous areas in Southwest China, the world's largest bare karst area, are faced with growing water shortages. Rainwater harvesting plays an important role in alleviating water shortage. However, there remains a substantial gap in the research regarding the water quality of tanks. Water samples were seasonally collected from ten tanks to investigate the physicochemical properties, microbial communities, and their key influencing factors. The result showed that pH, turbidity, chroma, DOC, and CODMn exceeded drinking water guidelines. The alkaline pH value and the deterioration of sensory properties was the main feature of tank water, from which the over-standard rate of the uncleaned water tanks was higher. Moreover, principal component analyses suggested that tank water quality was influenced by human activities, catchment areas, and material cycling processes within the tanks, of which in-tank microbial activities were the most important driving factors in water quality variation. Proteobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria, Firmicutes, and Verrucomicrobia were the predominant bacterial phyla in water tanks. Acinetobacter, Cyanobium-PCC-6307, CL500-29-marine-group, Candidatus-Aquiluna, and Exiguobacterium were the most abundant genera. The bacterial communities were significantly affected by the management practices. Higher relative abundance of Cyanobacteria and lower relative abundance of Proteobacteria was detected in the uncleaned tanks, which was a sign of tank water quality deterioration. The microbial community structure was closely related to the environmental factors. There was evidence that the water quality was affected by the existence of a microecosystem dominated by photosynthetic microorganisms in the water tanks. In addition, Acinetobacter, Enterobacter, Pseudomonas, and Legionella identified as the potential opportunistic pathogenic genera were frequently detected but the relative abundances except Acinetobacter were low in the tanks. Overall, our findings indicated that management style influences water quality and bacterial communities of tank water.

Assessment of the water quality of Bartın Kışla (Kozcağız) Dam by using geographical information system (GIS) and water quality indices (WQI)

This study was conducted to evaluate the water quality of the Kışla (Kozcagiz) Dam located in the province of Bartın in the Western Black Sea Region of Turkey. Water samples were collected monthly from 5 stations for a year and analyses were conducted using 27 water quality parameters. The quality of the dam and the water quality parameters were evaluated using different indices in comparison to the limits determined according to the standards set by the World Health Organization (WHO) and Turkey Surface Water Quality Regulation (SWQR). Water quality index (WQI), organic pollution index (OPI), sodium adsorption ratio (SAR), magnesium adsorption ratio (MAR), permeability index (PI), and metal pollution index (MPI) were calculated and spatial assessment of pollution was made seasonally by making use of the geographic information system (GIS). A piper diagram was used in determining the facies of the water. The types of Ca²⁺-Mg²⁺-HCO₃^- predominated in the dam water. Moreover, statistical analyses were used in order to determine if there was a significant difference between the parameters. WQI results generally indicate that the water quality was good in all seasons; however, only in the autumn, sampling points S1 (101.58), S2 (100.59), S4 (102.31), and S5 (102.12) showed poor water characteristics. According to the OPI results, while winter and spring yielded good water quality, summer samples were lightly polluted and autumn samples were moderately polluted. Given SAR results, it can be stated that the water of Kışla Dam could be used as irrigation water. Considering the standards specified by WHO and SWQR, the parameters generally exceeded the threshold values, but the water hardness value was much higher than 100 mg L^-1 specified in SWQR as very hard water. The principal component analysis (PCA) results showed that the pollution sources were anthropogenic. Thus, for the dam water to not be affected by the increasing pollutant factors, it should be continuously monitored, and attention should be paid to the irrigation methods used in agricultural activities.

Rotifers of Inter-Forest Springs

Springs are often considered as “hotspots” of aquatic biodiversity. However, small organisms, such as rotifers, substantially contribute to secondary production, but they are rarely investigated in springs. We surveyed the rotifer fauna of 47 springs in the Knyszyn Forest (north-eastern Poland) in summer and autumn 2014–2015. We hypothesized that stream communities of Rotifera may be specific to this habitat. Rotifer samples were taken using a Plexiglas tube in the spring current. Concurrently, water temperature, pH, conductivity, water redox potential and phosphorus and nitrogen concentrations were determined. The springs did not differ statistically in water quality and were stable regarding their temperature and conductivity. Rotifer densities and mean number of monogonont species were very low both in summer and autumn. Nevertheless, the total number of species recorded in all springs was relatively high and accounted for 101 in total. Although strongly differentiated, the rotifer fauna contained a set of several species common to most of the springs. Most of the recorded species are eurytopic and widely spread in water ecosystems. Only the concentration of magnesium and chloride ions had an impact on Monogononta numbers.

Self-organizing map improves understanding on the hydrochemical processes in aquifer systems

The holistic understanding of hydrochemical features is a crucial task for management and protection of water resources. However, it is challenging for a complex region, where multiple factors can cause hydrochemical changes in studied catchment. We collected 208 groundwater samples from such region in Kumamoto, southern Japan to explicitly characterize these processes by applying machine learning technique. The analyzed groundwater chemistry data like major cations and anions were fed to the self-organizing map (SOM) and the results were compared with classical classification approaches like Stiff diagram, standalone cluster analysis and score plots of principal component analysis (PCA). The SOM with integrated application of clustering divided the data into 11 clusters in this complex region. We confirmed that the results provide much greater details for the associated hydrochemical and contamination processes than the traditional approaches, which show quite good correspondence with the recent high resolution hydrological simulation model and aspects from geochemical modeling. However, the careful application of the SOM is necessary for obtaining accurate results. This study tested different normalization approaches for selecting the best SOM map and found that the topographic error (TE) was more important over the quantization error (QE). For instance, the lower QE obtained from min-max and log normalizations showed problems after clustering the SOM map, since the QE did not confirm the topological preservation. In contrast, the lowest TE obtained from Z-transformation data showed better spatial matching of the clusters with relevant hydrochemical characteristics. The results from this study clearly demonstrated that the SOM is a helpful approach for explicit understanding of the hydrochemical processes on reginal scale that may capably facilitate better groundwater resource management.

Dynamic multivariate analysis for pollution assessment and river habitat conservation in the Vietnamese La Buong watershed

Analysis of temporal patterns of high-dimensional time-series water quality data is essential for pollution management worldwide. This study has applied dynamic factor analysis (DFA) and cluster analysis (CA) to analyze time-series water quality data monitored at the five stations installed along the La Buong river in Southern Vietnam. Application of the DFA identified two types of temporal patterns, one of the run-off driven parameters (total suspended solid (TSS), turbidity, and iron) and the other of diffuse source pollution. The association of the variables like BOD₅ and COD at most stations to the run-off-driven parameters revealed their sharing of drivers. On the contrary, separating variables like phosphate (PO₄³) at the three upstream stations from the run-off patterns suggested their local point-source origin. The DFA-derived factors were later used in the time-point CA to explore the seasonality of water quality parameters and their pollution intensities compared to regulatory levels. The result suggested intensification in wet season of Fe, TSS, BOD₅, and COD concentrations at most sites, which are unobservable in run-off detached parameters like reactive nitrogen, phosphate (PO₄^3-), and E. coli. These findings generated robust insights to support water quality management for river habitat conservation.

Characterization of roof runoff microbial quality in four U.S. cities with varying climate and land use characteristics

Roof runoff has the potential to serve as an important local water source in regions with growing populations and limited water supply. Given the scarcity of guidance regulating the use of roof runoff, a need exists to characterize the microbial quality of roof runoff. The objective of this 2-year research effort was to examine roof runoff microbial quality in four U.S. cities: Fort Collins, CO; Tucson, AZ; Baltimore, MD; and Miami, FL. Seven participants, i.e., homeowners and schools, were recruited in each city to collect roof runoff samples across 13 precipitation events. Sample collection was done as part of a citizen science approach. The presence and concentrations of indicator organisms and potentially human-infectious pathogens in roof runoff were determined using culture methods and digital droplet polymerase chain reaction (ddPCR), respectively. The analyzed pathogens included Salmonella spp., Campylobacter spp., Giardia duodenalis, and Cryptosporidium parvum. Several factors were evaluated to study their influence on the presence of potentially human-infectious pathogens including the physicochemical characteristics (total suspended solids, volatile suspended solids, total dissolved solids, chemical oxygen demand, and turbidity) of roof runoff, concentrations of indicator organisms, presence/absence of trees, storm properties (rainfall depth and antecedent dry period), percent of impervious cover surrounding each sampling location, seasonality, and geographical location. E. coli and enterococci were detected in 73.4% and 96.2% of the analyzed samples, respectively. Concentrations of both E. coli and enterococci ranged from <0 log10 to >3.38 log10 MPN/100 mL. Salmonella spp. invA, Campylobacter spp. ceuE, and G. duodenalis β - giardin gene targets were detected in 8.9%, 2.5%, and 5.1% of the analyzed samples, respectively. Campylobacter spp. mapA and C. parvum 18S rRNA gene targets were not detected in any of the analyzed samples. The detection of Salmonella spp. invA was influenced by the geographical location of the sampling site (Chi-square p-value < 0.001) as well as the number of antecedent dry days prior to a rain event (p-value = 0.002, negative correlation). The antecedent dry period was negatively correlated with the occurrence of Campylobacter spp. ceuE as well (p-value = 0.07). On the other hand, the presence of G. duodenalis β-giardin in roof runoff was positively correlated with rainfall depth (p-value = 0.05). While physicochemical parameters and impervious area were not found to be correlated with the presence/absence of potentially human-infectious pathogens, significant correlations were found between meteorological parameters and the presence/absence of potentially human-infectious pathogens. Additionally, a weak, yet significant positive correlation, was found only between the concentrations of E. coli and those of Giardia duodenalis β-giardin. This dataset represents the largest-scale study to date of enteric pathogens in U.S. roof runoff collections and will inform treatment targets for different non-potable end uses for roof runoff. However, the dataset is limited by the low percent detection of bacterial and protozoan pathogens, an issue that is likely to persist challenging the characterization of roof runoff microbial quality given sampling limitations related to the volume and number of samples.

Temporal and spatial variation in water quality in the Yangtze Estuary from 2012 to 2018

Water quality plays an important role in estuarine habitats and affects aquatic organisms. The focus of this study was to understand the temporal-spatial variation of water quality and reveal the natural and anthropogenic drivers by using multiple analysis approaches. Herein, during 2012-2018, six water quality constituents (pH, electrical conductivity (EC), dissolved oxygen (DO), ammonia nitrogen (NH₃N), total nitrogen (TN), and total phosphorus (TP) were examined for eight sites in the Yangtze Estuary, and the hydro-sediment data, i.e., discharge (Q) and sediment transport rate (STR), was collected from the upstream hydrological station Datong. The cluster analysis (CA), principal component analysis (PCA)/factor analysis (FA), Canadian Council of Ministers of the Environment Water Quality Index (CCME-WQI), and the Mann-Kendall (MK) test were applied. The eight sampling sites were geographically grouped into cluster I, cluster II, and cluster III based on the characteristics of water quality changes, which are under the influence of the upstream runoff, the anthropogenic activities, and seawater. The results are as follows: (1) NH₃N, TN, and DO were key constituents representing the water quality of cluster I and cluster III, and those were EC, TN, and DO for cluster II; (2) The monthly-average Q and STR of Datong were negatively correlated to water quality constituents with seasonal variation except for pH; (3) The impact of anthropogenic activities on water quality was especially reflected in cluster III which is close to the Huangpu River Estuary; upstream runoff was the natural driver of water quality changes for cluster I while that was seawater for cluster II. Seawater acts a key role in affecting the water quality of cluster II situated at the North Branch. Revealing the key drivers of water quality change in the Yangtze Estuary provides a reference for water quality management.

Seasonal atmospheric water harvesting yield and water quality using electric-powered desiccant and compressor dehumidifiers

Atmospheric water harvesting (AWH) is an emerging technology for decentralized water supply and is proving to be viable for use in emergencies, military deployment, and sustainable industries. The atmosphere is a freshwater reservoir that contains 12,900 km³ of water, 6-fold more than the volume of global rivers. Dehumidification water harvesting technologies can be powered by solar, wind, or electric sources. Compressor/refrigerant-based dehumidifiers operate via dew point condensation and provide a cold surface upon which water vapor can condense. Conversely, desiccant-based technologies saturate water vapor using a sorbent that is then heated, and the supersaturated water vapor condenses on a surface when interacting with cooler ambient process air. This work compares productivity, energy consumption, efficiency, cost and quality of water produced of two water-harvesting mechanisms. Electric-powered compressor and desiccant dehumidifiers were operated outdoors for more than one year in the arid southwestern USA, where temperatures ranged from 3.1 to 43.7 °C and relative humidity (RH) ranged from 6 to 85%. The compressor system harvested >2-fold more water than the desiccant system when average RH during the run cycle was >30%, average temperature was >20 °C, and average dew point temperature was >5 °C. Desiccant systems performed more favorably when average RH during the run cycle was <30%, average temperature was <20 °C, and average dew point temperature was <5 °C. Water collected by compressor-based technologies had conductivity up to 180 μS/cm, turbidity up to 190 NTU, and aluminum, iron and manganese near or above the US EPA secondary drinking water standard. Dissolved organic carbon (DOC) averaged <2 mg C/L but ranged up to 12 mg C/L. Water collected by desiccant-based technologies had significantly lower conductivity, metals, and turbidity, and DOC was always <6 mg/L. Aldehydes such as formaldehyde and acetaldehyde and carboxylic acids such as formic acid and acetic acid were primary contributors to DOC. The differences in harvested water quality were attributed to differences in the condensation method between compressor and desiccant AWH technologies. Multiple strategies could be employed to prevent these volatile organic compounds (VOCs) from contributing to DOC in harvested water, such as pretreating air to remove VOCs or post-treating DOC in harvested liquid water.

Water Quality Improvement through Rainwater Tanks: A Review and Simulation Study

First, this paper presents a thorough review of water quality data using a rainwater tank, categorizing the data as with and without sedimentation. Data are presented showing minimum, maximum, and mean values for the different parameters. The data measured from several sources reveal that water collected from the tank is much better than the water directly collected from the roof. In addition, to analyse the phenomena through a mathematical model, a hypothetical 5 kL rainwater tank with a 200 m2 roof was modelled with the MUSIC model. The simulations were compared with the measured water quality data from a rainwater tank in Melbourne. In general, we found that MUSIC’s simulations on the mean daily concentrations of total suspended solids (TSS) and total phosphorus (TP) are slight underestimations compared to the measured data from Melbourne. Further MUSIC simulations reveal that significant reductions in the daily maximum concentrations of TSS, TP, and total nitrogen (TN) are expected through a rainwater tank.

Physicochemical and microbiological quality of rainwater harvested in underground retention tanks

A study was made of the physicochemical properties (among others: pH, temperature, conductivity, hardness, chlorides, dissolved oxygen, ammonia, nitrites, nitrates, manganese, iron) and microbiological quality (coliform, psychrophilic and mesophilic microorganisms) of rainwater harvested from the roofs of three large buildings and from a parking lot, stored in three large underground tanks (with storage volume from 60 m³ to ca. 200 m³), including the variability of the quality. The underground tanks were located in the city of Poznań, and were characterized by different parameters, rainwater sources, rainwater treatment processes, and types of rainwater use. Samples of rainwater harvested in these tanks were collected from March 2019 to February 2020. Physicochemical and microbiological laboratory analyses were performed to determine selected parameters which have an impact on potential treatment and disinfection methods. The results obtained underwent statistical analysis. The laboratory tests showed that the physicochemical quality of rainwater collected in the three underground tanks met the Polish and EU requirements for drinking water standards. The main problem concerns microbiological quality: the number of coliform bacteria reached a value of 19,300 CFU/100 mL, the number of psychrophilic bacteria was over 264,000 CFU/1 mL, and the number of mesophilic bacteria was over 100,000 CFU/1 mL. Also the variability of microbiological quality was very high for all tanks. Analysis of the calcium carbonate equilibrium showed that the harvested water had corrosive properties. The treatment of the investigated rainwater for potable purposes should focus mainly on biological and chemical stability.

Interaction of heavy metals and biocide/herbicide from stormwater runoff of buildings with dissolved organic matter

Stormwater runoff from roofs and façades can be contaminated by heavy metals and biocides/herbicides. High efficiency on-site treatment methods are now urgently needed to safeguard the ecosystem. The basis for developing such treatment facilities is an in-depth understanding of their interactions with dissolved organic matter (DOM), as this affects their migration in the environment. Hence, the interactions between copper (Cu), zinc (Zn), benzyl-dimethyl-tetradecylammonium chloride dihydrate (BAC), mecoprop-P (MCPP) and DOM at pH 5 to 9 were investigated separately in this study. The evaluation of the interaction processes was achieved by applying excitation emission matrix and parallel factor analysis (EEM-PARAFAC) to titration samples; obtained data were fitted by two different models. Mechanisms involved in BAC/MCPP-DOM interactions were revealed by Fourier-transform infrared spectroscopy (FTIR) and two-dimensional correlation spectrum (2D-COS) analysis. Results showed that the applied DOM was composed of the two different fluorescent components C1 and C2. More interaction with C1 than with C2 was observed for both Cu/Zn and BAC/MCPP. Increasing the pH enhanced the interactions between Cu/Zn and DOM. At pH 5 with a maximum quencher addition, the remaining fluorescence of CuC1 and ZnC1 were 15.7% and 87.1%, respectively. Corresponding data at pH 9 decreased to 3% and 69.5%. Contrarily, interactions between BAC/MCPP and DOM were impaired by high pH conditions. The increase of pH from 5 to 9 with maximum BAC and MCPP added raised the remaining fluorescence of BAC-C1 and MCPP-C1 by 15.9% and 21.3% separately. The fitting outcomes from the Ryan-Weber equation (Cu/Zn titration) and the Stern-Volmer equation (BAC/MCPP titration) corresponded well with the titration studies. FTIR coupled with 2D-COS analysis revealed that mechanisms involved in BAC/MCPP titration include hydrogen bonding, π-π interaction, and electrostatic effect. The order of mechanisms taking effect during the interaction with DOM is affected by the molecular structure of BAC and MCPP.

Producing and storing self-sustaining drinking water from rainwater for emergency response on isolated island

Drinking water on isolated islands includes treated rainwater, water shipped from the mainland, and desalinated seawater. However, marine transportation and desalination plants are vulnerable to emergencies, such as extreme weather, making self-sustaining stand-by water for emergency response essential. Rainwater is ideal for producing the stand-by water, and rainwater harvesting is sustainable and clean, and prolonged biostability can be ensured by managing biological and chemical parameters. The present study applied a stand-by drinking water purification system (primarily including nanofiltration and low-dose chlorination) to explore the feasibility of producing and storing cleaner drinking water from rainwater and the following conclusions were drawn. First, treatment of rainwaters ensures biosafety for seven days, which is longer than that for untreated rainwater; the proportion of opportunistic pathogens decreased from 23.40-7.77% after nanofiltration, and it was proposed that the microbial community converges after advanced water treatment. Second, chemical qualities were improved. Local resource coral sand prevents pH in rainwater from decreasing below 6.5, and treated rainwater had lower disinfection by-product potential and higher disinfection efficiency, allowing periodical rainwater recycling. Third, harvesting rainwater was extremely cost-effective, with an operation cost of 1.5-2.5 RMB/m³. From biosafety, chemical safety, and economic cost perspectives, self-sustaining water from rainwater can contributes to the development of sustainable and cost-effective water supply systems on isolated islands. Mixing treated rainwater and desalinated seawater reasonably guarantees sufficiency and safety.

Strategies for identifying pollution sources in a headwater catchment based on multi-scale water quality monitoring

Rural headwater catchments are important to describe the connectivity of pollution sources to water bodies. Strategies to optimize water quality monitoring networks, as parameter definition, sampling, and statistical approach, have been widely discussed. The objectives of this study were to describe the spatial and temporal dynamics (intra- and inter-events) of water quality and to establish its implications for environmental monitoring programs. The monitoring was carried out in a rural headwater catchment (1.2 km²) with shallow soils, high slopes, and intense agricultural activity in Southern Brazil. To better describe the impact of agriculture on water resources, the monitoring strategy was based on definition of the best set of parameters and different sampling frequency to incorporate intra- and inter-event variability and statistical analysis approach. We also analyzed parameters in different sub-basins with physiographic traits. Three hydrological compartments were analyzed: surface flow, groundwater, and base flow. Physico-chemical parameters, the concentration of elements associated with agricultural activity, and biological parameters were evaluated. Total phosphorus and turbidity were the parameters most affected by agricultural activity. They reflected on the inter- and intra-events, the impacts of soil and water degradation by agricultural activity, and the precarious rural sanitation conditions. Spatiotemporal variability of the parameters characterizes the different mechanisms for transferring pollutants from diffuse sources to water bodies. Spatial and temporal patterns in water quality changes were used to discuss environmental monitoring strategies, such as parameter and sampling frequency definition, to improve soil and water conservation programs at the catchment scale.

A Review of Roof and Pond Rainwater Harvesting Systems for Water Security: The Design, Performance and Way Forward

Rapid urbanization, population explosion and climate change have threatened water security globally, regionally and locally. While there are many ways of addressing these problems, one of the innovative techniques is the recent employment of Sustainable Urban Drainage Systems (SUDS) which include rainwater harvesting systems (RWHS). Therefore, this paper reviews the design and component of two types of RWHS, the namely roof harvesting system (RHS) and the pond harvesting system (PHS). The performance in terms of quantity and quality of collected rainwater and energy consumption for RWHS with different capacities were evaluated, as well as the benefits and challenges particularly in environmental, economic and social aspects. Presently, the RHS is more commonly applied but its effectiveness is limited by its small scale. The PHS is of larger scale and has greater potentials and effectiveness as an alternative water supply system. Results also indicate the many advantages of the PHS especially in terms of economics, environmental aspects and volume of water harvested. While the RHS may be suited to individual or existing buildings, the PHS has greater potentials and should be applied in newly developed urban areas with wet equatorial climate.

Assessing nutrient salts and trace metals distributions in the coastal water of Jeddah, Red Sea

In this study, eighteen sites at Jeddah coastal area, Red Sea, have been assessed for water quality status, depending on nutrients, metals, Chlorophyll-a (Chl-a) and physical variables during 2018 and 2019. The investigated parameters of the Water Quality Index (WQI) are temperature, pH, salinity, dissolved oxygen (DO), DO saturation, oxidizable organic matter (OOM), suspended particulate matter (SPM), Chl-a, ammonium, nitrite, nitrate, total nitrogen, reactive phosphate, total phosphorus, silicate, Zn, Fe, Mn Cu, Cd, Pb, and Ni. The results revealed that the pH values were slightly alkaline with a range of 7.85–8.20. The results of other parameters were as follow: salinity (36.95–42.61PSU), DO (5.22–6.67 mg/L), OOM (0.40–1.23 mg/L), SPM (12.39–21.5 mg/L), Chl-a (0.10–0.83 µg/L). The range of nutrients (μM) were 0.07–0.22, 0.45–1.47, 9.62–18.64, 23.31–57.65, 0.05–0.15, 0.55–2.78 and 2.54–5.51 for NH₄/N, NO₂/N, NO₃/N, TN, PO₄/P, TP and SiO₄/Si, respectively. Cluster analysis was used to classify the stations studied. From the current study, five clusters were found, indicating the need to perform cluster analysis in the water quality assessment process to confirm the durability and consistency of the data discovered in the current application.

Extreme Hydro-Meteorological Events Influence to Water Quality of Small Rivers in Urban Area: A Case Study in Northeast Poland

This paper presents an impact of hydro-meteorological extreme events and urban catchment to water quality in small rivers in Białystok (Poland). The results from a five-year study have taken into account droughts, continuous precipitation, and storm precipitation causing flash floods. Extreme hydro-meteorological events has a different impact on the physical and chemical parameters of water. It was found that the largest change in water quality occurs on the 2nd day after the rainfall and changed concentration of some chemical parameters persists for a long time. The majority but, what’s important, not all of them are diluted after floods and concentrated after droughts. Flash flooding results in a large increase concentrations of DOC and selected forms of phosphorus. Higher values of EC, Eh, Mg²⁺, HCO₃^-, Cl^-, SiO₃^2-, NO₃^-N, TN were observed during drought compared to the average values from 2014–2018. A high degree of naturalness of the river valley and increased water retention results in a decreased concentration of NH₄⁺-N, DOC and phosphorus forms. The buffer zone plays an important role in limiting the inflow of pollutants and nutrients from the catchment area. That is why it is worth undertaking restoration of river valleys in urban areas.

Analysis of urban land cover influence to organic carbon and nutrients in surface water via impacted groundwater

This paper presents an object-oriented approach for analysing and characterising the urban landscape structure and its influence on the quality of surface waters and shallow groundwater. We investigated springs, streams and ponds from an urban area. The land cover classification was adopted with the conceptual framework of urban land cover (HERCULES model). This study has demonstrated that water quality in the urban area is strongly related to land cover, and the degree of its transformation is not the same in all types of waters. The land with forests and shrubs does not have many extreme values in water chemical characteristics. Statistical analyses indicated that the main environmental factors influencing water chemistry are impermeable surfaces such as buildings. They are an essential element which deteriorates water quality. The patches with buildings and pavements were characterised by a wide gradient of nutrient concentration in rivers and ponds. Shallow groundwater had a limited effect on surface water quality.

Analysis of Potential Risks Associated with Urban Stormwater Quality for Managed Aquifer Recharge

Managed aquifer recharge (MAR) can be used to increase storage and availability of groundwater resources, but water resources available for recharge are constrained due to a surface water shortage. Alternative resources, like stormwater, are receiving increasing attention as sustainable resources for reuse in MAR. However, pollutants in stormwater can impact groundwater quality, and cause clogging of the infiltration system. Based on the stormwater data in the literature, the physicochemical stormwater properties of data were analyzed. The results showed that concentrations of pollutants from different underlying surfaces varied widely. The main pollutants of stormwater were as follows: Total suspended particles (TSSs), organic matter represented by the chemical oxygen demand (COD), nutrients (total nitrogen, TN; total phosphorus, TP; and NH₃-N), and metals (Zn, Pb, Cu, Cd, Fe, and Mn). Based on the simulation of TOUGHREACT, the contamination risk of pollutants for each type of stormwater was assessed. The risk of contamination was divided into four categories due to the different migration times of ions through the sand column. The iron ion has the highest risk of contamination, followed by Zn and Mn, and the contamination risk of nutrients and other metals (Pb, Cu, and Cd) are relatively low. Besides, the physical, biological, and chemical clogging risk were evaluated. The physical clogging potential of all types of stormwater is very high because of the high concentration of TSS. According to the concentration of TN that can spur the growth of bacteria and algae, the relative risk of biological clogging for stormwater is greenbelt stormwater < road stormwater < roof stormwater. However, only road stormwater has high chemical clogging due to the existence of iron, which can generate precipitation that blocks the pore volume.

An Analysis of the Effectiveness of Two Rainwater Harvesting Systems Located in Central Eastern Europe

Decentralized water systems are perceived as solutions that not only save water, but also as a way to partially or completely become independent from centralized suppliers. Taking this into account, an analysis of the effectiveness of rainwater harvesting systems (RWHS) for toilet flushing in existing academic facilities located in Poland and in Slovakia was carried out. The tests took into account the different volumes of storage tanks collecting rainwater. On the basis of two financial ratios, namely Net Present Value and Discounted Payback Period, the profitability of these systems was also assessed. The research was extended by the sensitivity analysis, which allowed determination of the impact of changes in individual cost components on the financial effectiveness of the investments considered. The results obtained clearly showed that the implementation of RWHS in the dormitory in Rzeszów was unprofitable for all tank capacities tested, and the payback period significantly exceeded the period of 30 years accepted for the analysis. Completely different results were obtained for RWHS in a dormitory located in the city of Košice, for which the financial ratios NPV (Net Present Value) and DPP (Discounted Payback Period) were very favorable. It was also confirmed by the results of the sensitivity analysis. The use of rainwater for toilet flushing caused that it was possible to achieve water savings of an average of 29% and 18%, respectively, for facilities located in Slovakia and Poland. The results of the research have a practical aspect and can provide an indication for potential investors and managers of academic facilities, similar to those analyzed in the article. Taking into account that in many countries water and sewage rates are significantly higher than in Poland and Slovakia, the cost-effectiveness of using the analyzed installation options in these countries could be even higher.

Searching variables to assess recreational water quality: the presence of infectious human enterovirus and its correlation with the main variables of water pollution by multivariate statistical approach in Córdoba, Argentina

Surface waters are used by local populations for different purposes, such as recreational activities, water source for human and animal consumption, and irrigation among others, which lead to the need for management strategies on water health and associated risks. During this study, we investigated physicochemical parameters, fecal coliform bacteria, and infectious human enterovirus detection to determine the water quality in different beaches (categorized as an urban area, non-urban areas, and an intermediate position) from San Roque Dam, in Argentina. Multivariate techniques were applied. Principal component analysis allowed identification of subgroup of variables responsible for the water quality. A cluster analysis and multivariate analysis of variance showed the urban beach as the highest pollution area. The following variables (measured at the urban beach) would be enough to describe the quality of the aquatic body: nitrites, fecal coliforms, total phosphorous, and infectious human enterovirus. The infectious human enterovirus was an independent variable detected in 69.1% of the samples showing a steady frequency of detection during the whole period studied and could identify human fecal contaminations as a source of water pollution. The selected variables would contribute to water quality regarding the risk for human health using San Roque dam waters for recreational propose.

Health Risk Assessment of Household Drinking Water in a District in the UAE

The quality of household drinking water in a community of 30 houses in a district in Abu Dhabi, United Arab Emirates (UAE) was assessed over a period of one year (January to November 2015). Standard analytical techniques were used to screen for water quality parameters and contaminants of concern. Water quality was evaluated in the 30 households at four sampling points: kitchen faucet, bathroom faucet, household water tank, and main water pipe. The sampling points were chosen to help identify the source when an elevated level of a particular contaminant is observed. Water quality data was interpreted by utilizing two main techniques: spatial variation analysis and multivariate statistical techniques. Initial analysis showed that many households had As, Cd, and Pb concentrations that were higher than the maximum allowable level set by UAE drinking water standards. In addition, the water main samples had the highest concentration of the heavy metals compared to other sampling points. Health risk assessment results indicated that approximately 30%, 55%, and 15% of the houses studied had a high, moderate, and low risk from the prolonged exposure to heavy metals, respectively. The analysis can help with planning a spatially focused sampling plan to confirm the study findings and set an appropriate course of action.

Microbiological quality of spinach irrigated with reclaimed wastewater and roof-harvest water

AIMS

The effect of reclaimed wastewater (RCW) and roof-harvest rainwater (RHW) on the microbiological quality of irrigated spinach was investigated.

METHODS AND RESULTS

Spinach grown in the controlled environment chamber was irrigated by RCW, RHW or creek water (CW; control water) for 4 weeks, and then six replicate spinach samples from each treatment were collected weekly at 0 h and 24 h postirrigation. Spinach samples were analysed for populations of faecal bacterial indicators and pathogens. Bacterial populations in alternative irrigation water samples were determined by the membrane filtration technique. The RCW samples contained the highest faecal bacterial indicator populations, followed by the CW and RHW throughout the entire study. Irrigation waters containing higher populations of total and faecal coliforms did not necessarily result in higher populations of these bacteria on the irrigated spinach. Higher numbers of E. coli-positive spinach samples were reported from RCW-irrigated spinach, especially with repeated irrigation. Pathogens were not detected from any water or spinach samples.

CONCLUSIONS

Spinach irrigated with RHW did not significantly affect the populations of faecal indicator bacteria when compared with CW-irrigated spinach. Repeat irrigation with RCW is not recommended due to the increased contamination of E. coli on spinach leaves.

SIGNIFICANCE AND IMPACT OF THE STUDY

RHW may potentially be used as alternative irrigation water without deleteriously affecting the microbiological safety of the spinach.

Effect of first-flush device, roofing material, and antecedent dry days on water quality of harvested rainwater

Two rainwater harvesting systems, which included first-flush diversion devices, connected to the roofs of two adjacent buildings, were monitored for water quality. The roofs were constructed from different materials, i.e., one roof was covered with ceramic tiles and the other was made of concrete. Water quality samples from the two storage tanks and the first-flush devices were collected and analyzed, showing satisfactory water quality in the tanks for residential non-potable use, while the water in the first-flush device was of poorer quality. Between the two collection surfaces, statistically significant differences were found only in the concentrations of NH₄-N, orthophosphate, and Ca²⁺. Total coliforms were detected in both the storage tanks and the first-flush devices, indicating that disinfection of harvested rainwater may be necessary if it is collected for potable uses. Finally, first-flush water quality was related to antecedent dry days, showing that when the number of dry days increased, the accumulation of materials on the concrete roof was reduced while it was increased on the ceramic tile roof. This is attributed to the fact that the concrete roof is nearly horizontal (very slightly sloped), and the wind action easily removes various materials which accumulate on it.

Assessment of water quality using multivariate techniques in River Sosiani, Kenya

Multivariate techniques can infer intrinsic characteristics of complex data by generating correlation, similarity, dissimilarity, and covariance vector matrix to ascertain their relationships. The study evaluated the effect of anthropogenic activities by analyzing selected physicochemical water quality parameters (WQP) as indicators of pollution in River Sosiani, located in western Kenya, at six stations from August 2012 to February 2013 (Aug-Oct ≡ wet season, Nov-Feb ≡ Dry season). Temperature, pH, Total Dissolved Solids (TDS), conductivity, and Dissolved Oxygen (DO) were measured in situ while Total Phosphorus (TP), Total Organic Nitrogen (TON), and Biologial Oxygen Demand (BOD) were measured in vitro using standard methods. Except for DO and pH, the other variables were increasing in concentration downstream. Cluster analysis grouped stations with municipal discharge, to be the most distant linked to other stations in both seasons. Multidimensional scaling had four categories of stations with similar WQP: before, after, and wet and dry seasons. Principal component analysis with (60.5 and 26.1% for components 1 and 2) evaluated TON and TP as key pollutants in both seasons. Factor analysis with varifactor two at 35.3 and 27.1% variance in wet and dry seasons, respectively, had strong absolute factor loading of BOD (wet 0.878, dry 0.915) and TP (wet 0.839, dry 0.709) inferring sites with organic pollution also had nutrient pollution. Assessment of pollution with the selected WQP identified two major effects: nutrient and organic. Additional variables may identify other pollutants along the river. Multiple pollution effects, changing environment, and intrinsic characteristics of aquatic ecosystems generate complex data which are better assessed with multivariate techniques.

Urban rainwater harvesting systems: Research, implementation and future perspectives

While the practice of rainwater harvesting (RWH) can be traced back millennia, the degree of its modern implementation varies greatly across the world, often with systems that do not maximize potential benefits. With a global focus, the pertinent practical, theoretical and social aspects of RWH are reviewed in order to ascertain the state of the art. Avenues for future research are also identified. A major finding is that the degree of RWH systems implementation and the technology selection are strongly influenced by economic constraints and local regulations. Moreover, despite design protocols having been set up in many countries, recommendations are still often organized only with the objective of conserving water without considering other potential benefits associated with the multiple-purpose nature of RWH. It is suggested that future work on RWH addresses three priority challenges. Firstly, more empirical data on system operation is needed to allow improved modelling by taking into account multiple objectives of RWH systems. Secondly, maintenance aspects and how they may impact the quality of collected rainwater should be explored in the future as a way to increase confidence on rainwater use. Finally, research should be devoted to the understanding of how institutional and socio-political support can be best targeted to improve system efficacy and community acceptance.

Anthropogenic Influences of Paved Runoff and Sanitary Sewage on the Dissolved Organic Matter Quality of Wet Weather Overflows: An Excitation-Emission Matrix Parallel Factor Analysis Assessment

The quality of dissolved organic matter (DOM) in a wet weather overflow (WWF) can be broadly influenced by anthropogenic factors, such as nonpoint sources of paved runoff and point sources of sanitary sewage within the drainage networks. This study focused on the anthropogenic influences of the paved runoff and sanitary sewage on the DOM quality of WWF using excitation-emission matrix parallel factor analysis (EEM-PARAFAC). Results show that (1) EEM-PARAFAC fitted terrestrial humic-like, anthropogenic humic-like, tryptophan-like, and tyrosine-like components can be regarded as indicators to identify the types of sewage overflows and the illicit connection status of drainage systems. (2) A short emission wavelength (em: 302-313 nm) peak of the tyrosine-like component occurred in the reserved sanitary sewage, while a type of longer emission wavelength (em: 321-325 nm) peak came from the sump deposit. These tyrosine-like components were gradually evacuated in the initial phase of the overflow process with the fading of their EEM signals. Fluorescence signal transformations of all the components confirmed the potential ability of EEM-PARAFAC to monitor the dynamic changes of the primary pollutant sources. (3) The input of the newly increased sanitary sewage had a dominant influence on the quality and yield of the WWF DOM.

Seasonal Assessment of Opportunistic Premise Plumbing Pathogens in Roof-Harvested Rainwater Tanks

A seasonal study on the occurrence of six opportunistic premise plumbing pathogens (OPPPs) in 24 roof-harvested rainwater (RHRW) tanks repeatedly sampled over six monthly sampling events (n = 144) from August 2015 to March 2016 was conducted using quantitative qPCR. Fecal indicator bacteria (FIB) Escherichia coli (E. coli) and Enterococcus spp. were enumerated using culture-based methods. All tank water samples over the six events were positive for at least one OPPP (Legionella spp., Legionella pneumophila, Mycobacterium avium, Mycobacterium intracellulare, Pseudmonas aeruginosa, or Acanthamoeba spp.) during the entire course of the study. FIB were positively but weakly correlated with P. aeruginosa (E. coli vs P. aeruginosa τ = 0.090, p = 0.027; Enterococcus spp. vs P. aeruginosa τ = 0.126, p = 0.002), but not the other OPPPs. FIBs were more prevalent during the wet season than the dry season, and L. pneumophila was only observed during the wet season. However, concentrations of Legionella spp., M. intracellulare, Acanthamoeba spp., and M. avium peaked during the dry season. Correlations were assessed between FIB and OPPPs with meteorological variables, and it was determined that P. aeruginosa was the only OPPP positively associated with an increased antecedent dry period, suggesting stagnation time may play a role for the occurrence of this OPPP in tank water. Infection risks may exceed commonly cited benchmarks for uses reported in the rainwater usage survey such as pool top-up, and warrant further exploration through quantitative microbial risk assessment (QMRA).

Principal factor and hierarchical cluster analyses for the performance assessment of an urban wastewater treatment plant in the Southeast of Spain

Process performance and operation of wastewater treatment plants (WWTP) are carried out to ensure their compliance with legislative requirements imposed by European Union. Because a high amount of variables are daily measured, a coherent and structured approach of such a system is required to understand its inherent behavior and performance efficiency. In this sense, both principal factor analysis (PFA) and hierarchical cluster analysis (HCA) are multivariate techniques that have been widely applied to extract and structure information for different purposes. In this paper, both statistical tools are applied in an urban WWTP situated in the Southeast of Spain, a zone with special characteristics related to the geochemical background composition of water and an important use of fertilizers. Four main factors were extracted in association with nutrients, the ionic component, the organic load to the WWTP, and the efficiency of the whole process. HCA allowed distinguish between influent and effluent parameters, although a deeper examination resulted in a dendrogram with groupings similar to those previously reported for PFA.

Mobilization and distribution of lead originating from roof dust and wet deposition in a roof runoff system

In this research, the mobilization and distribution of lead originating in roof dust and wet deposition were investigated within a roof dust-rooftop-runoff system. The results indicated that lead from roof dust and wet deposition showed different transport dynamics in runoff system and that this process was significantly influenced by the rainfall intensity. Lead present in the roof dust could be easily washed off into the runoff, and nearly 60 % of the total lead content was present in particulate form. Most of the lead from the roof dust was transported during the late period of rainfall; however, the lead concentration was higher for several minutes at the rainfall beginning. Even though some of the lead from wet deposition, simulated with a standard isotope substance, was adsorbed onto adhered roof dust and/or retained on rooftop in runoff system, most of it (50-82 %) remained as dissolved lead in the runoff for rainfall events of varying intensity. Regarding the distribution of lead in the runoff system, the results indicated that it could be carried in the runoff in dissolved and particulate form, be adsorbed to adhered roof dust, or remain on the rooftop because of adsorption to the roof material. Lead from the different sources showed different distribution patterns that were also related to the rainfall intensity. Higher rainfall intensity resulted in a higher proportion of lead in the runoff and a lower proportion of lead remaining on the rooftop.

Storm loads of culturable and molecular fecal indicators in an inland urban stream

Elevated concentrations of fecal indicator bacteria in receiving waters during wet-weather flows are a considerable public health concern that is likely to be exacerbated by future climate change and urbanization. Knowledge of factors driving the fate and transport of fecal indicator bacteria in stormwater is limited, and even less is known about molecular fecal indicators, which may eventually supplant traditional culturable indicators. In this study, concentrations and loading rates of both culturable and molecular fecal indicators were quantified throughout six storm events in an instrumented inland urban stream. While both concentrations and loading rates of each fecal indicator increased rapidly during the rising limb of the storm hydrographs, it is the loading rates rather than instantaneous concentrations that provide a better estimate of transport through the stream during the entire storm. Concentrations of general fecal indicators (both culturable and molecular) correlated most highly with each other during storm events but not with the human-associated HF183 Bacteroides marker. Event loads of general fecal indicators most strongly correlated with total runoff volume, maximum discharge, and maximum turbidity, while event loads of HF183 most strongly correlated with the time to peak flow in a hydrograph. These observations suggest that collection of multiple samples during a storm event is critical for accurate predictions of fecal indicator loading rates and total loads during wet-weather flows, which are required for effective watershed management. In addition, existing predictive models based on general fecal indicators may not be sufficient to predict source-specific genetic markers of fecal contamination.

Assessment of water quality parameters using multivariate analysis for Klang River basin, Malaysia

This case study uses several univariate and multivariate statistical techniques to evaluate and interpret a water quality data set obtained from the Klang River basin located within the state of Selangor and the Federal Territory of Kuala Lumpur, Malaysia. The river drains an area of 1,288 km(2), from the steep mountain rainforests of the main Central Range along Peninsular Malaysia to the river mouth in Port Klang, into the Straits of Malacca. Water quality was monitored at 20 stations, nine of which are situated along the main river and 11 along six tributaries. Data was collected from 1997 to 2007 for seven parameters used to evaluate the status of the water quality, namely dissolved oxygen, biochemical oxygen demand, chemical oxygen demand, suspended solids, ammoniacal nitrogen, pH, and temperature. The data were first investigated using descriptive statistical tools, followed by two practical multivariate analyses that reduced the data dimensions for better interpretation. The analyses employed were factor analysis and principal component analysis, which explain 60 and 81.6% of the total variation in the data, respectively. We found that the resulting latent variables from the factor analysis are interpretable and beneficial for describing the water quality in the Klang River. This study presents the usefulness of several statistical methods in evaluating and interpreting water quality data for the purpose of monitoring the effectiveness of water resource management. The results should provide more straightforward data interpretation as well as valuable insight for managers to conceive optimum action plans for controlling pollution in river water.

Potential source apportionment of polycyclic aromatic hydrocarbons in surface sediments from the middle and lower reaches of the Yellow River, China

In this work, principal component analysis/multiple linear regression (PCA/MLR), positive matrix factorization (PMF), and UNMIX model were employed to apportion potential sources of polycyclic aromatic hydrocarbons (PAHs) in surface sediments from middle and lower reaches of the Yellow River, based on the measured PAHs concentrations in sediments collected from 22 sites in November 2005. The results suggested that pyrogenic sources were major sources of PAHs. Further analysis indicated that source contributions of PAHs compared well among PCA/MLR, PMF, and UNMIX. Vehicles contributed 25.1-36.7 %, coal 34.0-41.6 %, and biomass burning and coke oven 29.2-33.2 % of the total PAHs, respectively. Coal combustion and traffic-related pollution contributed approximately 70 % of anthropogenic PAHs to sediments, which demonstrated that energy consumption was a predominant factor of PAH pollution in middle and lower reaches of the Yellow River. In addition, the distributions of contribution for each identified source category were studied, which showed similar distributed patterns for each source category among the sampling sites.

Reducing monitoring costs in industrially contaminated rivers: cluster and regression analysis approach

Monitoring contamination in river water is an expensive procedure, particularly for developing countries where pollution is a significant problem. This study was conducted to provide a pollution monitoring strategy that reduces the cost of laboratory analysis. The new monitoring strategy was designed as a result of cluster and regression analysis on field data collected from an industrially influenced river. Pollution sources in the study site were coal mining, metallurgy, chemical industry, and metropolitan sewage. This river resembles those in other areas of the world, including developing countries where environmental monitoring is financially constrained. Data were collected on variability of contaminant concentrations during four seasons at the same points on tributaries of the river. The variables described in the study are pH, electrical conductivity, inorganic ions, trace elements, and selected organic pollutants. These variables were divided into groups using cluster analysis. These groups were then tested using regression models to identify how the behavior of one variable changes in relation to another. It was found that up to 86.8% of variability of one parameter could be determined by another in the dataset. We adopted 60, 65, and 70% determination levels () for accepting a regression model. As a result, monitoring could be reduced by 15 (60% level) and 10 variables (65 and 70%) out of 43, which comprises 35 and 23% of the monitored variable total. Cost reduction would be most effective if trace elements or organic pollutants were excluded from monitoring because these are the constituents most expensive to analyze.

Sustainability of rainwater harvesting system in terms of water quality

Water is considered an everlasting free source that can be acquired naturally. Demand for processed supply water is growing higher due to an increasing population. Sustainable use of water could maintain a balance between its demand and supply. Rainwater harvesting (RWH) is the most traditional and sustainable method, which could be easily used for potable and nonpotable purposes both in residential and commercial buildings. This could reduce the pressure on processed supply water which enhances the green living. This paper ensures the sustainability of this system through assessing several water-quality parameters of collected rainwater with respect to allowable limits. A number of parameters were included in the analysis: pH, fecal coliform, total coliform, total dissolved solids, turbidity, NH3-N, lead, BOD5, and so forth. The study reveals that the overall quality of water is quite satisfactory as per Bangladesh standards. RWH system offers sufficient amount of water and energy savings through lower consumption. Moreover, considering the cost for installation and maintenance expenses, the system is effective and economical.

Financial and environmental modelling of water hardness--implications for utilising harvested rainwater in washing machines

A study was conducted to determine the financial and environmental effects of water quality on rainwater harvesting systems. The potential for replacing tap water used in washing machines with rainwater was studied, and then analysis presented in this paper is valid for applications that include washing machines where tap water hardness may be important. A wide range of weather conditions, such as rainfall (284-1,794 mm/year); water hardness (14-315 mg/L CaCO3); tap water prices (0.85-2.65 Euros/m(3)) in different Spanish urban areas (from individual buildings to whole neighbourhoods); and other scenarios (including materials and water storage capacity) were analysed. Rainfall was essential for rainwater harvesting, but the tap water prices and the water hardness were the main factors for consideration in the financial and the environmental analyses, respectively. The local tap water hardness and prices can cause greater financial and environmental impacts than the type of material used for the water storage tank or the volume of the tank. The use of rainwater as a substitute for hard water in washing machines favours financial analysis. Although tap water hardness significantly affects the financial analysis, the greatest effect was found in the environmental analysis. When hard tap water needed to be replaced, it was found that a water price of 1 Euro/m(3) could render the use of rainwater financially feasible when using large-scale rainwater harvesting systems. When the water hardness was greater than 300 mg/L CaCO3, a financial analysis revealed that an net present value greater than 270 Euros/dwelling could be obtained at the neighbourhood scale, and there could be a reduction in the Global Warming Potential (100 years) ranging between 35 and 101 kg CO2 eq./dwelling/year.

Temporal aspects of surface water quality variation using robust statistical tools

Robust statistical tools were applied on the water quality datasets with the aim of determining the most significance parameters and their contribution towards temporal water quality variation. Surface water samples were collected from four different sampling points during dry and wet seasons and analyzed for their physicochemical constituents. Discriminant analysis (DA) provided better results with great discriminatory ability by using five parameters with (P < 0.05) for dry season affording more than 96% correct assignation and used five and six parameters for forward and backward stepwise in wet season data with P-value (P < 0.05) affording 68.20% and 82%, respectively. Partial correlation results revealed that there are strong (r(p) = 0.829) and moderate (r(p) = 0.614) relationships between five-day biochemical oxygen demand (BOD(5)) and chemical oxygen demand (COD), total solids (TS) and dissolved solids (DS) controlling for the linear effect of nitrogen in the form of ammonia (NH(3)) and conductivity for dry and wet seasons, respectively. Multiple linear regression identified the contribution of each variable with significant values r = 0.988, R(2) = 0.976 and r = 0.970, R(2) = 0.942 (P < 0.05) for dry and wet seasons, respectively. Repeated measure t-test confirmed that the surface water quality varies significantly between the seasons with significant value P < 0.05.

Potential source contributions and risk assessment of PAHs in sediments from Taihu Lake, China: comparison of three receptor models

In this work, three receptor models (Principal Component Analysis-Multiple Linear Regression (PCA-MLR) model, Unmix model and Positive Matrix Factorization (PMF) model) were employed to investigate potential source apportionment of PAHs in sediments from Taihu Lake, China. A total of 15 priority PAHs in 29 sediments from Taihu Lake were measured, with ∑PAHs (sum of 15 PAHs) concentrations ranging from 209 to 1003 ng g(-1) dw. Source apportionment results derived from three different models were similar, indicating that the highest contribution to ∑PAHs was from vehicular emission (53.6-54.3%), followed by coal combustion (23.8-28.8%) and wood combustion (11.9-16.0%). The contribution of mixed wood and coal combustion source identified by PCA-MLR was 41.3%. For the first time the risk assessment for each identified source category was quantitatively calculated by combining the BaP equivalents (BaPE) values with estimated source contributions. The results showed that vehicular emission posed the highest toxic risk, with BaPE values of 26.9-31.5 ng g(-1) dw, and the BaPE values for coal combustion and wood combustion were 6.56-15.6 ng g(-1) dw and 2.94-6.11 ng g(-1) dw, respectively. The distributions of contribution and BaPE for each identified source category were studied as well, and showed similar trends among the sampling sites, for each source category.