Analysis of Ammonia Nitrogen Content in Water Based on Weighted Least Squares Support Vector Machine (WLSSVM) Algorithm

Determination of ammonia nitrogen content in water is the basic item of the environmental water pollution, and is the key index to evaluate the water quality. This article designs a water quality monitoring system based on the on-line automatic ammonia nitrogen monitoring system, and establishes a forecasting model based on the weighted least squares support vector machine algorithm. The weighted least squares support vector machine algorithm increases the weight parameter setting, improves the speed and accuracy of prediction learning, and improves the robustness. In this article, a comparison between neural network model and weighted least square support vector machine model is made, which shows that the weighted least squares support vector machine model has better prediction accuracy.

Effect of Water Ammonia Nitrogen Concentration on Survival of Mosquitofish Gambusia affinis

In this study, the relationship of the growth of invasion fish with water eutrophication processes was explored in Yangtze estuary, China. High water ammonia nitrogen concentration produced high effects on the growth and survival of mosquitofish Gambusia affinis. When the ammonia nitrogen was higher than 51.75 mg/l, the fish death rate obviously increased with days, and at the 4th day fish presented the highest mortality, while 23.72 mg/l ammonia nitrogen conditions have been able to ensure fish survival for two days in experiment treatment. Therefore, ammonia nitrogen of Grade V polluted water (national water quality criteria) is just 3 mg/l, and the water can be enough to support fish normal survival. Our results suggest mosquitofish was a suitable pioneer species for restoring polluted water ecology and purify water.

Assessment of Point and Nonpoint Sources Pollution in Songhua River Basin,Northeast China by Using Revised Water Quality Model

Individual participation of pollutants in the pollution load should be estimated even if roughly for the appropriate environmental management of a river basin.It is difficult to identify the sources and to quantify the load, especially in modeling nonpoint source.In this study a revised model was established by integrating point and nonpoint sources into one-dimensional Streeter-Phelps(S-P) model on the basis of real-time hydrologic data and surface water quality monitoring data in the Jilin Reach of the Songhua River Basin.Chemical oxygen demand(COD) and ammonia nitrogen(NH 3-N) loads were estimated.Results showed that COD loads of point source and nonpoint source were 134 958 t/yr and 86 209 t/yr, accounting for 61.02% and 38.98% of total loads, respectively.NH 3-N loads of point source and nonpoint source were 16 739 t/yr and 14 272 t/yr, accounting for 53.98% and 46.02%, respectively.Point source pollution was stronger than nonpoint source pollution in the study area at present.The water quality of upstream was better than that of downstream of the rivers and cities.It is indispensable to treat industrial wastewater and municipal sewage out of point sources, to adopt the best management practices to control diffuse pollutants from agricultural land and urban surface runoff in improving water quality of the Songhua River Basin.The revised S-P model can be successfully used to identify pollution source and quantify point source and nonpoint source loads by calibrating and validating.

Discharge Water Quality Models of Storm Runoff in a Catchment

The relationships between the water qualities of nitrogen and phosphorous contents in the discharge water and the discharge of storm runoff of an experimental catchment including terraced paddy field are analyzed based on experiment results of the catchment. By summarizing the currently related research on water quality models, the water quality models of different components of storm runoff of the catchment are presented and verified with the experiment data of water quality analyses and the corresponding discharge of the storm runoffs during 3 storms. Through estimating the specific discharge of storm runoff, the specific load of different components of nitrogen and phosphorus in the discharge water of the catchment can be forecasted by the models. It is found that the mathematical methods of linear regression are very useful for analysis of the relationship between the concentrations of nitrogen and phosphorus and the water discharge of storm runoff. It is also found that the most content of the nitrogen (75%) in the discharge water is organic, while half of the content (49%) of phosphorus in the discharge water is inorganic.

Water quality characteristics of rivers and ponds in Japan

In Japan, various countermeasures have been taken to improve the water quality of public waters such as rivers and lakes. Though water quality has improved, it is still insufficient. In summer, eutrophication is seen in lakes and inner bays, as well as rivers. As a countermeasure to prevent eutrophication, the removal treatment of nutrient salts such as nitrogen and phosphorus is done, in addition to organic substance elimination in the domestic sewerage system. This report will show the water quality characteristics of rivers and ponds in Japan. It is considered that these investigative results are effective when the water quality improvement of the stabilization ponds where eutrophication occurs are examined in China.

PARAMETER ESTIMATION OF MULTI-CONSTITUENT WATER QUALITY MODEL FOR THE LIANGXI RIVER BY MARQUARDT METHOD

A multi-constituent water quality model is presented,Which relates carbonaceous biochemical oxygen demand (CBOD),amonia (NH3-N), nitrite(NO2-N), nitrate(NO3-N) and dissolvedoxygen(DO). The parameters are solved by Marquardt Method (i. e.,Dampled Least Square Method) while initial values inoptimization are produced by Monte-Carlo Method. The Potential ofthe method as a parameter estimation aid is demonstrated for theapplication to the Liangyi Rver, JiangSu Province of China and by aspecial comparison with Gauss Method.

Analysis of Water Quality Variation and Trend in the Ji'an Section of the Ganjiang River

Based on the monitoring data of water quality in the Ji'an section of the Ganjiang River from 2008 to 2018 by the Water Resources Monitoring Center of Ji'an City,single factor evaluation method,comprehensive pollution index method and seasonal Kendall test method were adopted to study and analyze the characteristics of surface water resources and the changing trend of water quality in the river section.The results show that the water quality in the Ji'an section of the Ganjiang River was generally good,and the water quality of each function zone reached the target requirement.The comprehensive pollution index was controlled between 0.21 and 0.40 over the years,and there was no significant change in time and space,and the water quality was relatively stable.The dissolved oxygen and permanganate index tended to improve,and there was no change in five-day biochemical oxygen demand,while ammonia nitrogen and total phosphorus showed an upward trend.The water quality as a whole showed a trend of deterioration.By discussing the influencing factors of the characteristic pollutants,the causes of water quality in the Ji'an section of the Ganjiang River were further analyzed.It is suggested to strengthen the supervision and control of non-point source and point source pollution.

The mediatory role of water quality on the association between extreme precipitation events and infectious diarrhea in the Yangtze River Basin,China

Extreme precipitation is exacerbating the burden of infectious diarrhea in the context of climate change,it is necessary to identify the critical and easy-to-intervene intermediate factors for public health strategies.Water quality may be the most important mediator,while relevant empirical evidence is limited.This study aimed to examine the role of water quality in the process of infectious diarrhea caused by extreme precipitation.Weekly infectious diarrhea cases,meteorological factors and water quality data in Yangtze River Basin in China between October 29,2007 to February 19,2017 were obtained.Two-stage statistical models were used to estimate city-specific extreme precipitation,water quality and infectious diarrhea relationships that were pooled to derive regional estimates.A causal mediation analysis was used to assess the mediation effect of water quality.In Yangtze River Basin,extreme precipitation events had a significant impact on infectious diarrhea(Incidence Rate Ratios[IRR]:1.027,95%Confidence Interval[CI]:1.013~1.041).After extreme precipitation events,the dissolved oxygen(DO)in surface water decreased(-0.123 mg/L,95%CI:-0.159 mg/L~-0.086 mg/L),while the un-ionized ammonia(NH(3)-N)increased(0.004 mg/L,95%CI:0.001 mg/L~0.006 mg/L).The combined overall effect of DO and NH(3)-N on infectious diarrhea showed that both low and high concentrations were associated with an increased risk of infectious diarrhea.The causal mediation analysis showed that the mediation proportion of the two water quality indexes(DO and NH(3)-N)is 70.54%(P<0.001).To reduce the health effects of extreme precipitation,in contrast to current population-oriented health strategies,those that take into account more direct and easy-to-intervene water quality indicators should be encouraged by future policies.

Sensitivity analysis for the total nitrogen pollution of the Danjiangkou Reservoir based on a 3-D water quality model

Inter-basin water deal of nitrogen are great transfers containing a great threats to human health, biodiversity, and air and water quality in the recipient area. Danjiangkou Reservoir, the source reservoir for China＇s South-to-North Water Diversion Middle Route Project, suffers from total nitrogen pollution and threatens the water transfer to a number of metropolises including the capital, Beijing. To locate the main source of nitrogen pollution into the reservoir, especially near the Taocha canal head, where the intake of water transfer begins, we constructed a 3-D water quality model. We then used an inflow sensitivity analysis method to analyze the sig- nificance of inflows from each tributary that may contribute to the total nitrogen pollution and affect water quality. The results indicated that the Han River was the most significant river with a sensitivity index of 0.340, followed by the Dan River with a sensitivity index of 0.089, while the Guanshan River and the Lang River were not significant, with the sensitivity indices of 0.002 and 0.001, respectively. This result implies that the concentration and amount of nitrogen inflow outweighs the geographical position of the tributary for sources of total nitrogen pollution to the Taocha canal head of the Danjiangkou Reservoir.

Effects of flow velocity on water quality and ammonia excretion in recirculating aquaculture system culturing juvenile largemouth bass(Micropterus salmoides)

Flow velocity plays an important role in recirculating aquaculture systems(RAS)and the growing practice of culturing juvenile largemouth bass(Micropterus salmoides).In this study,the effects of flow velocity on the water quality as well as the ammonia excretion were discussed from the perspective of actual production,and a polynomial model of ammonia nitrogen excretion was established,using the juvenile largemouth bass.Results showed that the range of ammonia nitrogen and nitrite nitrogen decreased with flow velocity increasing,while the number and volume share of large particles increased.According to the polynomial model,compared with the medium flow velocity(11 cm/s,2.45 body length(bl)/s),the ammonia excretion of juvenile largemouth bass at high(18 cm/s,4.00 bl/s),and low(4 cm/s,0.90 bl/s)flow velocity changed faster with time,and the excretion rate peaked at the 6th hour after feeding,earlier than that under medium flow velocity.Therefore,it is suggested to increase the flow velocity at the 5th hour after feeding and then decreased it at the 10th hour,to ensure better water quality in RAS culturing juvenile largemouth bass.

The Method of Fast on-site Detection and Real-time Release of Ammonia Nitrogen in Water

Objective:This paper aims to establish a simple and practical method for the rapid detection of ammonia nitrogen in water on the spot,and to transmit the detection results to the Internet via GSM network,and to publish and update them in real time.Methods:Phenol salt colorimetry was used to measure the absorbance value of indigo phenol blue,the product of the reaction between ammonia nitrogen and phenol salt in water samples,using sodium nitrosoferricyanide sodium hydroxide as catalyst and a microphotoelectric colorimetric instrument developed by ourselves,or a simple visual colorimetric semi-quantitative method was used to measure the ammonia nitrogen content in water samples.Then,the general GSM wireless communication module built in the microphotoelectric colorimeter was used to realize the remote transmission of the test result data and the real-time update and release on the Internet.Results:The results of this method showed that the correlation of the method was significant,and the precision and accuracy were similar to the national standard Nessler's reagent spectrophotometry.The relative standard deviation is 4.4%,and the relative error is 2.7%.In 5-10 min,the detection of ammonia and nitrogen in single water sample can be completed on site,and the results can be released.For quantitative and semi-quantitative detection,the lowest detection concentrations are 0.05 mg/L and 0.2 mg/L,respectively,which are basically free from the interference of pH and common ions.In the coverage area of GSM network,the wireless transmission of data results was unobstructed and delayed,and the effect was satisfactory.Conclusion:The method is simple,rapid,practical and reliable,which is suitable for the field rapid determination of ammonia nitrogen in water,and the real-time remote transmission of the detection results.It provides a high-efficiency,low-cost and simple technical means for the field water quality monitoring and the rapid acquisition of water quality data.

Effects of Combined Organic-inorganic Fertilization on Quality and Water Use Efficiency of Spring Maize under Equal Nitrogen Fertilization

The experiment was conducted in the abandoned land of Liangjia Village,Huayin City,Shaanxi Province from April to September 2019.The experimental crop was spring maize.A total of six treatments were set up in a randomized block design.The moisture content of the top 0-60 cm soil was determined regularly,and the yield and quality indices of maize at maturity were checked.The results show that:(i)combined organic-inorganic fertilization increased the yield of spring maize by 3%-8%.(ii)Compared with CK,fertilization treatments significantly improved the water use efficiency of spring maize,with an increase of 59.2%.The average water use efficiency of three combined organic-inorganic fertilization treatments was 27.81 kg/(ha·mm).Compared with CON,combined application of organic and inorganic fertilizers significantly improved the water use efficiency of spring maize,with an increase of 12.5%.(iii)The combined application of organic and inorganic fertilizers increased the moisture,total starch,crude protein and crude fat contents,and reduced crude fiber content of maize kernels.However,with the increase of the proportion of organic fertilizer,the crude protein content of maize kernels decreased.(iv)Yield of spring maize showed a significant parabolic relationship with soil water consumption.In summary,70%inorganic fertilizer+30%organic fertilizer is a scientific and reasonable way of fertilization.

Mechanism of nitrogen loss driven by soil and water erosion in water source areas

Nitrogen(N)present in drinking water as dissolved nitrates can directly affect people’s health,making it important to control N pollution in water source areas.N pollution caused by agricultural fertilizers can be controlled by reducing the amount of fertilizer applied,but pollution caused by soil and water erosion in hilly areas can only be controlled by conservation forests.The catchment area around Fushi Reservoir was selected as a test site and mechanisms of N loss from a vertical spatial perspective through field observations were determined.The main N losses occurred from June to September,accounting for 85.9-95.9%of the annual loss,with the losses in June and July accounting for 46.0%of the total,and in August and September for 41.9%.The N leakage from the water source area was effectively reduced by 38.2%through the optimization of the stand structure of the conservation forests.Establishing well-structured forests for water conservation is crucial to ensure the security of drinking water.This preliminary research lays the foundation for revealing then loss mechanisms in water source areas and improving the control of non-point source pollution in these areas.

Influence on shallow ground water by nitrogen in polluted river

The main purpose of the research is to discuss the influence on ground water by NH4-N in polluted river and river bed.In the lab-scale experiment three kinds of natural sand were chosen as infiltration medium,and polluted rivers were simulated by domestic sewage,after 10-month sand column test it was found that NH_4-N came to adsorption sa- turation on the 17th day in coarse sand and on the 130～140th day in medium sand,then had a higher effluent concentration because of desorption.It is concluded that NH_4-N eas- ily moved to ground water.When the concentration of NH_4-N in Liangshui River were 46.86,26.95 mg/L,that in groundwater are less than 1.10 mg/L.It is found that Liangshui River have a little influence on groundwater because of bottom mud,thickness and char- acter of the infiltration medium under the river bed and seepage quantity of river water. Clean water leaching test states that after the silt is cleared away and clean water is poured,NH_4-N in the penetration media under the polluted river is obviously carried into ground water,and ground water is polluted secondly.

Yield and Quality Response of Cucumber to Irrigation and Nitrogen Fertilization Under Subsurface Drip Irrigation in Solar Greenhouse

The aims of this research were to compare subsurface drip irrigation scheduling and nitrogen fertilization rates in cucumber, and evaluate yield and quality of cucumber fruit, water （WUE）, irrigation water （IWUE）, and nitrogen use （NUE） efficiencies in the solar greenhouse in Southwest China. The irrigation water amounts were determined based on the 20 cm diameter pan （Ep） placed over the crop canopy, and cucumber plant was subjected to three irrigation water levels （I1, 0.6 Ep; I2, 0.8 Ep; and I3, 1.0 Ep） in interaction with three nitrogen fertilization levels （N1, 300 kg ha-1; N2, 450 kg ha-1; and N3, 600 kg ha-1）. The results showed that the cucumber fruit yield increased with the improvement of irrigation water. Irrigation water increased yields by increasing the mean weight of the fruits, and also by increasing fruit number. But the highest values of IWUE and WUE were obtained from I2 treatment. NUE significantly decreased with the improvement of N application, but increased by irrigating more water. The quality of cucumber fruit decreased with the improvement irrigation water and nitrogen fertilization. In conclusion, the optimum irrigation level and nitrogen fertilizer application level for cucunber under subsurface drip irrigation in the solar greenhouse in Southwest China were 0.8 Ep and 450 and 600 kg ha-1, respectively.

Nitrogen Budget in Recirculating Aquaculture and Water Exchange Systems for Culturing Litopenaeus vannamei

In order to investigate the culture characteristics of two indoor intensive Litopenaeus vannamei farming modes, recirculating aquaculture system(RAS) and water exchange system(WES), this study was carried out to analyze the water quality and nitrogen budget including various forms of nitrogen, microorganism and chlorophyll-a. Nitrogen budget was calculated based on feed input, shrimp harvest, water quality and renewal rate, and collection of bottom mud. Input nitrogen retained in shrimp was 23.58% and 19.10% respectively for WES and RAS, and most of nitrogen waste retained in water and bottom mud. In addition, most of nitrogen in the water of WES was TAN(21.32%) and nitrite(15.30%), while in RAS was nitrate(25.97%), which means that more than 76% of ammonia and nitrite were removed. The effect of microalgae in RAS and WES was negligible. However, bacteria played a great role in the culture system considering the highest cultivable cultivable bacterial populations in RAS and WES were 1.03×10^(10) cfu mL^(-1) and 2.92×10~9 cfu mL^(-1), respectively. Meanwhile the proportion of bacteria in nitrogen budget was 29.61% and 24.61% in RAS and WES, respectively. RAS and WES could realize shrimp high stocking culture with water consuming rate of 1.25 m^3 per kg shrimp and 3.89 m^3 per kg shrimp, and power consuming rates of 3.60 kwh per kg shrimp and 2.51 kwh per kg shrimp, respectively. This study revealed the aquatic environment and nitrogen budget of intensive shrimp farming in detail, which provided the scientific basis for improving the industrial shrimp farming.

Irrigation water salinity and N fertilization:Effects on ammonia oxidizer abundance, enzyme activity and cotton growth in a drip irrigated cotton field

Use of saline water in irrigated agriculture has become an important means for alleviating water scarcity in arid and semi-arid regions. The objective of this field experiment was to evaluate the effects of irrigation water salinity and N fertilization on soil physicochemical and biological properties related to nitrification and denitrification. A 3×2 factorial design was used with three levels of irrigation water salinity（0.35, 4.61 and 8.04 d S m-1） and two N rates（0 and 360 kg N ha^（-1））. The results indicated that irrigation water salinity and N fertilization had significant effects on many soil physicochemical properties including water content, salinity, p H, NH_4-N concentration, and NO_3-N concentration. The abundance（i.e., gene copy number） of ammonia-oxidizing archaea（AOA） was greater than that of ammonia-oxidizing bacteria（AOB） in all treatments. Irrigation water salinity had no significant effect on the abundance of AOA or AOB in unfertilized plots. However, saline irrigation water（i.e., the 4.61 and 8.04 d S m-1 treatments） reduced AOA abundance, AOB abundance and potential nitrification rate in N fertilized plots. Regardless of N application rate, saline irrigation water increased urease activity but reduced the activities of both nitrate reductase and nitrite reductase. Irrigation with saline irrigation water significantly reduced cotton biomass, N uptake and yield. Nitrogen application exacerbated the negative effect of saline water. These results suggest that brackish water and saline water irrigation could significantly reduce both the abundance of ammonia oxidizers and potential nitrification rates. The AOA may play a more important role than AOB in nitrification in desert soil.

Effect of Rural Sewage Irrigation Regime on Water-Nitrogen Utilization and Crop Growth of Paddy Rice in Southern China

Reclaimed water irrigation has become an effective mean to alleviate the contradiction between water availability and its consumption worldwide.In this study,three types of irrigation water sources(rural sewage’s primary treated water R1 and secondary treated water R2,and river water R3)meeting the requirements of water quality for farmland irrigation were selected,and three types of irrigation water levels(low water levelW1 of 0–80 mm,medium water level W2 of 0–100 mm,and high water level W3 of 0–150 mm)were adopted to carry out research on the influence mechanismS of different irrigation water sources and water levels on water and nitrogen use and crop growth in paddy field.The water quantity indicators(irrigation times and irrigation volume),soil ammonium nitrogen(NH4+-N)and nitrate nitrogen(NO3−-N),rice yield indicators(thousand-grain weight,the number of grains per spike,and the number of effective spikes),and quality indicators(the amount of protein,amylose,vitamin C,nitrate and nitrite content)of rice were measured.The results showed that,the average irrigation volume under W3 was 2.4 and 1.9 times of that under W1 and W2,respectively.Compared with R3,the peak consumption of rice was lagged behind under R1 and R2,and the nitrogen form in 0–40 cm soil layers under rural sewage irrigation was mainly NH4+-N.The changes of NO3−-N and NH4+-N in the 0–40 cm soil layer showed the trend of declining and then increasing.The water level control only had a significant effect on the change of NO3−-N in the 60–80 cm soil layer.Both irrigation water use efficiency and crop water use efficiency were gradually reduced with the increase of field water level control.The nitrogen utilization efficiency under rural sewage irrigation was significantly higher than that under R3.Compared with the R3,rural sewage irrigation could significantly increase the yield of rice,and as the field water level rose,the effect of yield promotion was more obvious.It was noteworthy that the grain of rice under R1 monitored the low nitrate and nitrite content,but no nitrate and nitrite was discovered under R2 and R3.Therefore,reasonable rural sewage irrigation(R2)and medium water level(W2)were beneficial to improve nitrogen utilization efficiency,crop yield and crop quality promotion.

Spatiotemporal Variation of Riverine Nutrients in a Typical Hilly Watershed in Southeast China Using Multivariate Statistics Tools

The water quality of lakes can be degraded by excessive riverine nutrients.Riverine water quality generally varies depending on region and season because of the spatiotemporal variations in natural factors and anthropogenic activities.Monthly water quality measurements of eight water quality variables were analyzed for two years at 16 sites of the Tianmuhu watershed.The variables were examined using hierarchical cluster analysis(HCA) and factor analysis/principal component analysis(FA/PCA) to reveal the spatiotemporal variations in riverine nutrients and to identify their potential sources.HCA revealed three geographical groups and three periods.Two drainages comprising towns and large villages were the most polluted, six drainages comprising widely distributed tea plantations and orchards were moderately polluted, and eight drainages without the factors were the least polluted.The river was most polluted in June when the first heavy rain(daily rainfall > 50 mm) occurs after fertilization and the number of rainy days is most(monthly number of rainy days > 20 days).Moderate pollution was observed from October to May, during which morethan 60% of the total nitrogen fertilizer and all of the phosphorus fertilizer are applied to the cropland, the total manure is applied to tea plantations and orchards, and a monthly rainfall ranging from 0 mm to 164 mm occurs.The remaining months were characterized by frequent raining(i.e., number of rainy days per month ranged from 5 to 24) and little use of fertilizers, and were thus least polluted.FA/PCA identified that the greatest pollution sources were the runoff from tea plantations and orchards,domestic pollution and the surface runoff from towns and villages, and rural sewage, which had extremely high contributions of riverine nitrogen, phosphorus,and chemical oxygen demand, respectively.The tea plantations and orchards promoted by the agricultural comprehensive development(ACD) were not environmentally friendly.Riverine nitrogen is a major water pollution parameter in hilly watersheds affected by ACD, and this parameter would not be reduced unless its loss load through the runoff from tea plantations and orchards is effectively controlled.

Employing Constructed Wetlands to Sustainably Manage Nutrient-Bearing Water: A Review with an Emphasis on Soil Behavior and Effluent Nutrient Reduction

Constructed wetlands are engineered structures designed to simulate processes of natural wetlands to mitigate anthropogenic organic and inorganic materials to shelter soil and water resources. This review focuses on the global interest in constructed wetland application to sustain soil health and water quality and water abundance. Engineering criterion remains a function of nutrient chemistry and load with suitability factors including the local soil and hydrogeology constraints, climate, vegetation selection, the degree of required influent improvement, and reactor types and sizes. Future research needs to focus on: 1) reactor designs criteria, 2) the biology of the microbial community, 3) selection criteria for native vegetation, and 4) criteria to reapply treated water to foster land productivity, especially for region’s experiencing water deficiencies.