Disinfection Byproducts and Their Precursors in Drinking Water Sources:Origins,Influencing Factors,and Environmental Insights

Tracing the contamination origins in water sources and identifying the impacts of natural and human processes are essential for ecological safety and public health.However,current analysis approaches are not ideal,as they tend to be laborious,time-consuming,or technically difficult.Disinfection byproducts(DBPs)are a family of well-known secondary pollutants formed by the reactions of chemical disinfectants with DBP precursors during water disinfection treatment.Since DBP precursors have various origins(e.g.,natural,domestic,industrial,and agricultural sources),and since the formation of DBPs from different precursors in the presence of specific disinfectants is distinctive,we argue that DBPs and DBP precursors can serve as alternative indicators to assess the contamination in water sources and identify pollution origins.After providing a retrospective of the origins of DBPs and DBP precursors,as well as the specific formation patterns of DBPs from different precursors,this article presents an overview of the impacts of various natural and anthropogenic factors on DBPs and DBP precursors in drinking water sources.In practice,the DBPs(i.e.,their concentration and speciation)originally present in source water and the DBP precursors determined using DBP formation potential tests—in which water samples are dosed with a stoichiometric excess of specific disinfectants in order to maximize DBP formation under certain reaction conditions—can be considered as alternative metrics.When jointly used with other water quality parameters(e.g.,dissolved organic carbon,dissolved organic nitrogen,fluorescence,and molecular weight distribution)and specific contaminants of emerging concern(e.g.,certain pharmaceuticals and personal care products),DBPs and DBP precursors in drinking water sources can provide a more comprehensive picture of water pollution for better managing water resources and ensuring human health.

Genotoxicity evaluation and a primary risk assessment of organic pollutants in the drinking water sources of Nanjing, China

An increasing number of industrial, agricultural, and commercial chemicals in the aquatic environment leads to various deleterious effects on organisms, which is becoming an increasingly serious problem in China. In this study, the comet assay was conducted to investigate the genotoxicity to human body caused by organic concentrates in the drinking water sources of Nanjing City from Yangtze River of China, and health and ecology risk due to expose to these organic pollutants were evaluated with the multimedia environmental assessment system （MEAS）. For all the water samples, they were collected from four different locations in the drinking water sourcr samples, es of Nanjing City. The results of the comet assay showed that all the organic concentrates from the water samples could induce different levels DNA damages on human peripheral blood lymphocytes, and a statistically significant difference （p〈0.01） was observed compared with the solvent control, which demonstrated the genotoxicity was in existence. According to the ambient severity （AS） of individual compound, we had sorted out the main organic pollutants in the drinking water source of the four waterworks, and the results showed that there was some potential hazard to human body for all the source water, namely the total ambient severity （TAS） of health for each water source was more than 1. However, the TAS of ecology for each water source was less than 1, which indicated that it was safe to ecology. The results of this investigation demonstrate the application of the comet assay and the MEAS in aquatic environmental monitoring studies, and the comet assay found to be fast, sensitive, and suitable for genotoxicity monitoring programs of drinking water source.

Genotoxicity evaluation of drinking water sources in human peripheral blood lymphocytes using the comet assay

The potential harm of organic pollutants in drinking water to human health is widely focused on in the wodd; more and more pollutants with genotoxic substances are released into the aquatic environment. Water source samples were collected from 7 different localities of Nanjing City. The potential genotoxicity of organic extracts from drinking water sources were investigated by means of the comet assay in human peripheral lymphocytes. The results showed that all the organic extracts from all the water source samples could induce DNA damages of human peripheral blood lymphocytes at different levels. A significant difference （P 〈 0.01） was observed when compared with the solvent control, The DNA damage increased with the increase of the dosage of the original water source. Significant differences of DNA damage were observed in different drinking water sources, as shown by the multiple comparisons analysis at the dosage of 100x; the degree of DNA damage treated by Hushu waterworks （at town level） was the most serious, the arbitrary units （AU） was 141.62±6.96, however, that of Shangyuanmen waterworks （at city level） was only 109.64±2.97. The analysis also revealed that the genotoxicity of town＇s water sources was higher than that of the city. The results demonstrated that the comet assay can be successfully applied to the genotoxicity monitoring programs of drinking water sources.

Stable isotope techniques in plant water sources:a review

The stable hydrogen and oxygen isotopes widely exist in various kinds of natural water.Plants have to cope with various water sources:rainwater,soil water,groundwater,sea water,and mixtures.These are usually characterized by different isotopic signatures (18O/16O and D/H ratios).Because there are relative abundance variations in water,and plant roots do not discriminate against specific water isotopes during water uptake,hydrogen and oxygen stable isotope ratios of water within plants provide new information on water sources,interactions between plant species and water use patterns under natural conditions.At present,the measurement of δD,δ18O composition of various potential water sources and stem water has become significant means to identify plant water sources.Based on previous studies,this review highlights recent advances such as theory basis,methodology,as well as different spatial and temporal scales,and existed questions and prospects.Stable isotope techniques for estimating plant water sources have provided valuable tools for conducting basic and applied research.Future studies emphasize the modification of preparing methods,isotope technique combined with other measurements,and aerial organs of plant water source should be en-couraged.

Characteristics of groundwater and urban emergency water sources optimazation in Luoyang,China

The construction of emergency water sources is the material basis for ensuring urban water safety,and it is also an inherent requirement for maintaining social stability and development.The hydrogeological characteristics of groundwater in Luoyang City from the aspects of the division of groundwater aquifer groups,water yield property and groundwater dynamics were described in this paper.Two emergency water sources were selected on basis of comprehensively considering groundwater resources and ecological environmental effects,groundwater quality and exploitation technology,etc.Then it further analysed the aquifer types,water yield properties and groundwater recharge,runoff and discharge conditions of the two emergency water sources,and evaluate the groundwater resources quantity of the water sources.The results are that the shallow underground aquifer in Luoyang City is thick,coarse,and stable in lithology and thickness.The two water sources enjoy good exploitation potential and can be used as backup water sources to supply water in the event of a water source crisis.

Stable isotopes reveal varying water sources of Caragana microphylla in a desert-oasis ecotone near the Badain Jaran Desert

Understanding the variation in a plant’s water sources is critical to understanding hydrological processes in water-limited environments. Here, we measured the stable-isotope ratios(δ18 O) of xylem water of Caragana microphylla, precipitation,soil water from different depths, and groundwater to quantitatively analyze the proportion of water sources for the shrub.We found that the water sources of C. microphylla differed with the plant’s ages and the seasons. The main water source for young shrubs was upper-soil water, and it showed significant changes with seasonal precipitation inputs. In summer,the proportion contributed by shallow water was significantly increased with increased precipitation inputs. Then, the contribution from shallow-soil water decreased with the decline in precipitation input in spring and autumn. However, the adult shrubs resorted to deep-soil layers and groundwater as the main water sources during the whole growing season and showed much less seasonal variation. We conclude that the main water source of the young shrubs was upper-soil water and was controlled by precipitation inputs. However, once the shrub gradually grew up and the roots reached sufficient depth, the main water sources change from the upper-soil layer recharged by precipitation to deep-soil water and groundwater, which were relatively stable and abundant in the desert ecosystem. These results also suggest that desert shrubs may be able to switch their main water sources to deep and reliable water sources as their age increases, and this adjustment to water availability carries significant importance for their acclimation to the desert habitat.

Isolation,identification,characterization and antibiotic sensitivity profile of pathogenic Legionella pneumophila isolates from different water sources

Objective:To investigate the prevalence,isolation,identification,characterization,antibiotic profile and pathogenicity of Legionellae isolated from various set of waters.Methods:A total of 400 water samples were collected from different water sources.Water samples were pretreated using acid treatment followed by concentration and culture on buffered charcoal yeast extract agar.Parameters like ability of Legionella isolates to grow in various p H range,effect of different concentrations of chlorine and effect of different temperature optima were set up.Biochemical tests were performed to separate Legionellae into species.Antibiotic sensitivity tests and test for pathogenicity were also conducted on isolated strains.Results:The rates of isolation of Legionella pneumophila(L.pneumophila) in different water sources were found to be 20%(lakes),10%(ponds),8%(water-tanks) and 1%(rivers).Most of the isolates could grow in variable p H 6–8 and it could also survive the normal level of chlorination and even at temperature of 42 C.Isolated species of Legionellae resulted in identification of 5 different species,L.pneumophila being the dominant one.Strains of L.pneumophila were resistant to many antibiotics.Inoculation of Legionellae into intracerebral route of suckling mice revealed that L.pneumophila was the most virulent.Conclusions:Serious and fatal L.pneumophila infections may be transmitted through water.Legionella can survive under various conditions in various water sources.L.pneumophila is the important pathogen causing human disease.Great challenge prevails to health care professionals because these Legionellae acquired antibiotic resistance to many routinely prescribed antibiotics.

A retrospective survey on the effect of Kaschin-Beck disease prophylaxis by a change of water sources

In order to provide further references for studing on the causes of Kaschin-Beck discase (KBD) and measuring for its prevention and treatment from a macroscopic view, we analyzed the natural growth and declineof KBD and the effects of selenium and humic acid on its occurrence from an epidemiologic angle. In this article through a retrospective survey on the spots of disease areas by comparison between a change in water sources and that without. It was proved that a change in water sources was an effective measure for the prevention of KBD occurrence, and the pathogenic factor of KBD was one (or several kinds) of organic compounds or active radicals related to water.

Water sources of plants and groundwater in typical ecosystems in the lower reaches of the Heihe River Basin

Stable oxygen and hydrogen isotopic compositions （δ18O and δD） of soil water and shallow groundwater of a riparian forest, an artificial shrub forest, and Gobi of the lower reaches of the Heihe River Basin are used to study the recharge water sources of those ecosystems. IsoSource software is used to determine the δ180 values for root water of Populous euphratica and Tamarix ramosissima in the riparian forest ecosystem, Haloxylon ammodendron in the artificial shrub forest, and Reaumuria soongorica in the Gobi, as well as for local soil water and groundwater, and precipitation in the upper reaches of the Heihe River Basin. Our results showed that soil water and shallow groundwater of the riparian forest and the artificial shrub forest were recharged by river water which originated from precipitation in the upper reaches, and strong evaporation occurred in the artificial shrub forest. Soil water of the Gobi was not affected by Heihe River water due to this area being far away from the river channel. The main water sources of Populous euphratica were from 40-60-cm soil water and groundwater, and of Tamarix ramosissima were from 40-80-cm soil water in the riparian forest ecosystem. In the artificial forest, Haloxylon ammodendron used 200-cm saturated-layer soil water and shallow groundwater. The Reaumuria soongorica mainly used soil water from the 175-200-cm depth in the Gobi. Therefore, soil water and groundwater are the main water sources which maintain survival and growth of the plants in the extremely arid regions of the lower reaches of the Heihe River Basin.

Toxicity Screening of Water Sources in Flooded Agricultural Areas of Nen-Shkodra Lowland Using Allium cepa L. Assay

The reaction ofAllium cepa root tips to the presence of potential toxic chemicals was used to evaluate the cyto/genotoxic effects of some water sources of Nen-Shkodra lowland agricultural area after massive 2010-2011 flooding. MRL （Mean root length）, MI （mitotic index）, PI （phase index） and CA （chromosome abnormalities） endpoints of onion roots, grown in four water samples, were measured and compared with tap water and Cu solution 0.5 mg/L （negative and positive controls）. Inhibition of root growth, cell division and induction of mitotic and chromosomal aberrations were detected. The most polluted water sample caused MRL inhibition of 36%, MI decrease of 38%, and a considerable increase in chromosomal aberrations （7.8%） compared to the negative control. Most frequent CA types were： bridges and fragments, stickiness and C-metaphase. The results indicated a slight toxic tendency of analyzed natural waters, serving as an alert of environmental impact that chemical pollution had after flooding.

Stable isotope analysis of water sources for Tamarix laxa in the mega-dunes of the Badain Jaran Desert, China

The complex interactions in desert ecosystems between functional types and environmental conditions could be reflected by plant water use patterns. However, the mechanisms underlying the water use patterns as well as the water sources of Tamarix laxa in the mega-dunes of the Badain Jaran Desert, China, remain unclear. This study investigated the water sources and water use patterns of T. laxa using the stable oxygen isotope method. The δ18O values of xylem water, soil water in different layers(0–200 cm), rainwater, snow water, lake water, atmospheric water vapor, condensate water, and groundwater were measured. The sources of water used by T. laxa were determined using the IsoSource model. The results indicate that T. laxa mainly relies on soil water. At the beginning of the growing season(in May), the species is primarily dependent on water from the middle soil layer(60–120 cm) and deep soil layer(120–200 cm). However, it mainly absorbs water from the shallow soil layer(0–60 cm) as the rainy season commences. In September, water use of T. laxa reverts to the deep soil layer(120–200 cm). The water use patterns of T. laxa are closely linked with heavy precipitation events and soil water content. These findings reveal the drought resistance mechanisms of T. laxa and are of significance for screening species for ecological restoration.

Legislation on protection of drinking water sources and local management practices in the Pearl River Delta region of China

The protection of drinking water sources is vital to urban development and public health.In this study,the current situation of the mandatory protection area for drinking water source in the Pearl River Delta region was investigated using a method combining Google Earth with the field survey.The gaps between management practices and legislation requirements were analyzed.Finally,several countermeasures for water resource protection were proposed as follows:to promote delineation in a more scientific way,to safeguard the sanctity of the law,to make better plan on water saving,and to encourage public participation in supervision and management.

Discussion on possibilities of taking ground ice in permafrost as water sources on the Qinghai-Tibet Plateau during climate warming

Large amounts of ground ice are born with permafrost on the Qinghai-Tibet Plateau.Degradation of permafrost resulted from the climate warming will inevitably lead to melting of ground ice.The water released from the melting ground ice enters hydrologic cycles at various levels,and changes regional hydrologic regimes to various degrees.Due to difficulties in monitoring the perma-frost-degradation-release-water process,direct and reliable evidence is few.The accumulative effect of releasing water,however,is remarkable in the macro-scale hydrologic process.On the basis of the monitoring results of water-levels changes in some lakes on the Qinghai-Tibet Plateau,and combined with the previous results of the hydrologic changing trends at the regional scale,the authors preliminarily discussed the possibilities of the degrading permafrost on the Qinghai-Tibet Plateau as a potential water source during climate warming.

Agriculture and Water Sources Protection Zones in the Czech Republic

The area of interest is located in the South Moravia Region at the confluence of the Jihlava, Oslava and Rokytn^i rivers. Ivan^ice spring area comprises a series of hydrologic boreholes, it is the main water source for water supply of Ivan^ice and Rosice towns and provides water for 30,000 inhabitants. The risk analysis was created on the basis of water quality monitoring, hydrogeological assessment and terrain exploration and a revision of protection zones was proposed. The spring area is situated in nitrate vulnerable zones and recently nitrate concentrations have been decreasing. Water quality evaluation results： high concentration of manganese and iron, sometimes higher concentration of ammonium and COD. This area is intensively used for agriculture and it is necessary to make a compromise solution during protection zones proposal, The regime in protection zones can not affect manganese and iron concentration （their origin is in the natural geological environment）. Therefore, water treatment plant is in operation and its modernization is proposed. Furthermore, the paper deals with spring area intensification construction of a new hydrologic borehole, and managed and unmanaged infiltration of surface water. The proposal of protection zones revision consists of reduction to a 2nd level protection zone.

Isotopic evidence for soil water sources and reciprocal movement in a semi-arid degraded wetland:Implications for wetland restoration

Understanding water dynamics is a prerequisite for the restoration of degraded ecosystems in arid and semiarid regions.In this study,we carried out δD and δ^(18)O analyses of precipitation,unsaturated soil water,overland flow,surface runoff,and groundwater samples from a seasonally flooded wetland in the Momoge National Nature Reserve of the Songnen Plain,Northeast China,to identify the water sources and understand the mechanisms of unsaturated soil water movement.Unsaturated soil water content(W/W%)at every 20 cm along with a soil profile(0–100 cm)was collected during the growing season,and the HYDRUS-1D model was used to simulate temporal-spatial variations.The results showed that the local meteoric water line(δD=5.90δ18O-7.34,R2=0.95)had a smaller slope and intercept than the global meteoric water line because of strong evaporation at our study site under semi-arid climate.The groundwater was partly recharged by local precipitation via overland flow and unsaturated soil water infiltration.Unsaturated soil water was sourced from both precipitation and groundwater with variations at different depths.The upper soil layer at 0–15 cm was mainly sourced from limited precipitation,while the groundwater could move up to a 25 cm layer during the dry period.The unsaturated soil water content increased with soil depth in the top 40 cm,decreased at depths of 40 to 80 cm,and increased again at depths of 80 to 100 cm.The HYDRUS-1D model could simulate the unsaturated soil water dynamics well in the upper(0–40 cm)and lower(80–100 cm)sections,but poorly for depths of 40–80 cm due to the upward and downward flow.The bidirectional unsaturated soil water movement highlights the importance of capillary groundwater for wetland plants with similar climatic or hydrogeological conditions.

Riparian habitat quality as an indicator of land use/land cover effects on riverine water quality

Riparian land use/land cover(LULC)plays a crucial role in maintaining riverine water quality by altering the transport of pollutants and nutrients.Nevertheless,establishing a direct relationship between water quality and LULC is challenging due to the multi-indicator nature of both factors.Water quality encompasses a multitude of physical,chemical,and biological parameters,while LULC represents a diverse array of land use types.Riparian habitat quality(RHQ)serves as an indicator of LULC.Yet,it remains to be seen whether RHQ can act as a proxy of LULC for assessing the impact of LULC on riverine water quality.This study examines the interplay between RHQ,LULC and water quality,and develops a comprehensive indicator to predict water quality.We measured several water quality parameters,including pH(potential of hydrogen),TN(total nitrogen),TP(total phosphorus),T_(water)(water temperature),DO(dissolved oxygen),and EC(electrical conductivity)of the Yue and Jinshui Rivers draining to the Han River during 2016,2017 and 2018.The water quality index(WQI)was further calculated.RHQ is assessed by the InVEST(Integrated Valuation of Ecosystem Services and Tradeoffs)model.Our study found noticeable seasonal differences in water quality,with a higher WQI observed in the dry season.The RHQ was strongly correlated with LULC compositions.RHQ positively correlated with WQI,and DO concentration and vegetation land were negatively correlated with T_(water),TN,TP,EC,cropland,and construction land.These correlations were stronger in the rainy season.Human-dominated land,such as construction land and cropland,significantly contributed to water quality degradation,whereas vegetation promoted water quality.Regression models showed that the RHQ explained variations in WQI better than LULC types.Our study concludes that RHQ is a new and comprehensive indicator for predicting the dynamics of riverine water quality.

Ammonia pollution characteristics of centralized drinking water sources in China

The characteristics of ammonia in drinking water sources in China were evaluated during 2005-2009. The spatial distribution and seasonal changes of ammonia in different types of drinking water sources of 22 provinces, 5 autonomous regions and 4 municipalities were investigated. The levels of ammonia in drinking water sources follow the order of fiver 〉 lake/reservoir 〉 groundwater. The levels of ammonia concentration in river sources gradually decreased from 2005 to 2008, while no obvious change was observed in the lakes/reservoirs and groundwater drinking water sources. The proportion of the type of drinking water sources is different in different regions. In river drinking water sources, the ammonia level was varied in different regions and changed seasonally. The highest value and wide range of annual ammonia was found in South East region, while the lowest value was found in Southwest region. In lake/reservoir drinking water sources, the ammonia levels were not varied obviously in different regions. In underground drinking water sources, the ammonia levels were varied obviously in different regions due to the geological permeability and the natural features of regions. In the drinking water sources with higher ammonia levels, there are enterprises and wastewater drainages in the protected areas of the drinking water sources.

Advances in Microbial Remediation on the Application of Heavy Metal Pollution in Agricultural Water Resources

Heavy metal pollution in agricultural water resources is very serious in re- cent years, resulting in large losses of the agricultural economy and endangering human life and health. Due to the advantages of low cost, high efficiency and less secondary pollution, microbial ramediation technology is widely used in the treatment of heavy metal pollution in agricultural water resources. At present, with the progress of modern biotechnology, microbial remediation of heavy metals in agricul- tural water resources has grown rapidly. The sources and status quo of heavy met- al pollution in agricultural water resources at home and aboard, and the principles of microbial remediation of heavy metals pollution in agricultural water resources were reviewed in this paper, as well as the several common microbial remediation technology of heavy metals in agricultural water resources. Additionally, the further research work of heavy metal contaminated agricultural water resources by microbial ramediation were prospected.

Assessment of Nitrogen Pollutant Sources in Surface Waters of Taihu Lake Region

The nitrogen （N） pollution status of the 12 most important rivers in Changshu, Taihu Lake region was investigated. Water samples were collected from depths of 0.5-1.0 m with the aid of the global positioning system （GPS）. The seasonal variations in the concentrations of different N components in the rivers were measured. Using tension-free monolith lysimeters and ^15N-labeled fertilizer, field experiments were carried out in this region to determine variations of iSN abundance of NO3^- in the leachate during the rice and wheat growing seasons, respectively. Results showed that the main source of N pollution of surface waters in the Taihu Lake region was not the N fertilizer applied in the farmland but the urban domestic sewage and rural human and animal excreta directly discharged into the water bodies without treatment. Atmospheric dry and wet N deposition was another evident source of N pollutant of the surface waters. In conclusion, it would not be correct to attribute the N applied to farmlands as the source of N pollution of the surface waters in this region.

Exploitation of groundwater resources and protection of wetland in the Yuqia Basin

In Yuqia Basin, the climate is arid and the ecologic environment is fragile, and shortage of water resources has seriously restricted the sustainable development of local economy. In order to meet the needs of industrial and domestic water in the Yuqia Basin, numerical simulation was used to evaluate the groundwater resources and potential for exploitation. The results showed that the mathematical model and calculation parameters used were mainly in accordance with practical situation. The calculated value of the underground water level is consistent with measured value during the period of identification and validation. The total recharge of groundwater resources was 22.02×10~4 m^3/d, and the total drainage was 21.95×10~4 m^3/d at present. The Yuqia River leakage is the main supply source of groundwater. There is no significant effect on area of wetland when water source place exploited by 2.5×10~4 m^3/d at alluvial-diluvial fan of Yuqia River. After long-term exploitation, the spring flow reduces from 1.42×10~4 m^3/d to 1.01×10~4 m^3/d and wetland area reduces by 32.7% of original area. The calculation of water balance shows that it is safe to the Yuqia Basin, Da Qiadam Lake, the Mahai Basin at downstream of Yuqia River and wetland under the condition of water source place exploited by 2.5×10~4 m^3/d.