Effects of organic substrates on sulfate-reducing microcosms treating acid mine drainage: Performance dynamics and microbial community comparison.

Bioremediation techniques utilizing sulfate-reducing bacteria (SRB) for acid mine drainage (AMD) treatment have attracted growing attention in recent years, yet substrate bioavailability for SRB is a key factor influencing treatment effectiveness and long-term stability. This study investigated the effects of external organic substrates, including four complex organic wastes (i.e., sugarcane bagasse, straw compost, shrimp shell (SS), and crab shell (CS)) and a small-molecule organic acid (i.e., propionate), on AMD removal performance and associated microbial communities during the 30-day operation of sulfate-reducing microcosms. The results showed that the pH values increased in all five microcosms, while CS exhibited the highest neutralization ability and a maximum alkalinity generation of 1507 mg/L (as CaCO3). Sulfate reduction was more effective in SS and CS microcosms, with sulfate removal efficiencies of 95.6% and 86.0%, respectively. All sulfate-reducing microcosms could remove heavy metals to different degrees, with the highest removal rate of >99.0% observed for aluminum. The removal efficiency of manganese, the most recalcitrant metal, was the highest (96%) in the CS microcosm. Correspondingly, SRB was more abundant in the CS and SS microcosms as revealed by sequencing analysis, while Desulfotomaculum was the dominant SRB in the CS microcosm, accounting for 10.8% of total effective bacterial sequences. Higher abundances of functional genes involved in fermentation and sulfur cycle were identified in CS and SS microcosms. This study suggests that complex organic wastes such as CS and SS could create and maintain preferable micro-environments for active growth and metabolism of functional microorganisms, thus offering a cost-efficient, stable, and environmental-friendly solution for AMD treatment and management.

Benefit of Sponge City monetization based on "water footprint theory": cases of Xi'an and Guyuan.

China has proposed to build "Sponge City" to alleviate the problems of urban waterlogging, water shortage, ecological degradation, and water pollution. The benefits of Sponge City construction have become a focus of attention because of the considerable investment and the extensive participation of all sectors of society. This paper develops a model for monetizing urban, river, and regional benefits, by taking city and river areas as the research objects. This model is based on the regional water balance, water footprint theory, and the shadow price of water. This model monetizes the potential benefits of a Sponge City before construction. Our case study is Xi'an and Guyuan. Applying the benefits calculated at the 7% discount rate, the benefit/cost (B/C) ratios of the two locations are 3.86 and 0.93 times, respectively. Also, applying the benefits calculated at the 5% discount rate, the B/C ratios of the two locations are 5.41 and 1.31 times, respectively. In terms of urban benefits, the static payback periods of Xi'an and Guyuan are about 3.7 years and 15.3 years, respectively. In terms of regional benefits, they are about 4.0 years and 16.2 years, respectively. According to the results, the return of Sponge City construction in Xi'an and Guyuan is much higher than the investment but with some risks in the investment for social investors in Guyuan. In this paper, the model and the research results can provide some references for the research on the monetization of Sponge City benefits.

Accumulation of high-molecular-weight polycyclic aromatic hydrocarbon impacted the performance and microbial ecology of bioretention systems.

Bioretention has been considered as an effective management practice for urban stormwater in the removal of pollutants including polycyclic aromatic hydrocarbons (PAHs). However, the accumulation of high-molecular-weight (HMW) PAHs in bioretention systems and their potential impact on the pollutants removal performance and microbial ecology are still not fully understood. In this study, comparisons of treatment effectiveness, enzyme activity and microbial community in bioretention systems with different types of media amendments were carried out at different spiking levels of pyrene (PYR). The results showed that the removal efficiencies of chemical oxygen demand (COD) and total nitrogen in the bioretention systems were negatively impacted by the PYR levels. The relative activities of soil dehydrogenase and urease were increasingly inhibited by the elevated PYR level, indicating the declining microbial activity regarding organic matter decomposition. The spiking of PYR negatively affected microbial diversity, and distinct time- and influent-dependent changes in microbial communities were observed. The relative abundance of PAH-degrading microorganisms increased in PYR-spiked systems, while the abundance of nitrifiers decreased. The addition of media amendments was beneficial for the enrichment of microorganisms that are more resistant to PYR-related stress, therefore elevating the COD concentration removal rate by ∼50%. This study gives new insight into the multifaceted impacts of HMW PAH accumulation on microbial fingerprinting and enzyme activities, which may provide guidance on better stormwater management practices via bioretention in terms of improved system longevity and performance.

Research on optimal control of non-point source pollution: a case study from the Danjiang River basin in China.

The impact and optimal control of non-point source (NPS) pollution on water environment have become the hot issues of current research. This paper simulates the characteristics of NPS pollution of Danjiang River Basin in 2013, 2014, 2016, and 2018 based on SWAT (Soil and Water Assessment Tool) model. The spatial and temporal distribution is analyzed, and the critical source areas (CSA) according to the intensity of pollution loss are identified. Then, we set up nine single best management practices (BMPs) and three combined BMPs in the CSA, and the reduction effects of NPS pollution load of BMPs at the HRU scale and sub-basin scale are evaluated. The main research conclusions are as follows: (1) Based on the measured water quality and quantity data of Danfeng section from 2011 to 2019, the mean concentration method and the runoff division method are used to estimate the NPS pollution load at the Danfeng section, the NPS pollution loads of the total phosphorus (TP), ammonia nitrogen (NH3-N) and COD account for a large proportion in the total loads, which are 60.95-75.91%, 39.43-56.40%, and 59.37-74.37%, respectively. (2) In terms of temporal distribution, the impact to NPS pollution load is ranked as runoff > sediment > rainfall. In terms of spatial distribution, sediment has a great impact on nitrogen and phosphorus NPS pollution load. (3) The unit area load index method and the natural crack point classification method are used to identify the CSA in the basin. The information-entropy-basedmulti-attribute decision-making method to evaluate the cost-benefit value of management measures shows that control measures preferentially use combined BMPs, and the comprehensive cost-benefit attribute value reaches above 0.8. When using a single BMP, the comprehensive attribute value of returning the grain plots to forestry is high, reaching 0.62, which is suitable for NPS pollution control in a small area; for large-scale NPS pollution control, terrace project, supplemented by residue cover and grassed waterways is the more effective way in the river basin.

Biodegradation performance and diversity of enriched bacterial consortia capable of degrading high-molecular-weight polycyclic aromatic hydrocarbons.

Polycyclic aromatic hydrocarbons (PAHs) are key organic pollutants in the environment that pose threats to the ecosystem and human health. The degradation of high molecular weight (HMW) PAHs by enriched bacterial consortia has been previously studied, while the involved metabolisms and microbial communities are still unclear and warrant further investigations. In this study, five bacterial consortia capable of utilizing different PAHs (naphthalene, anthracene, and pyrene) as the sole carbon and energy sources were enriched from PAH-contaminated soil samples. Among the five consortia, consortium TC exhibited the highest pyrene degradation efficiency (91%) after 19 d of incubation. The degradation efficiency was further enhanced up to 99% by supplementing yeast extract. Besides, consortium TC showed tolerances to high concentrations of pyrene (up to 1000 mg/L) and different heavy metal stresses (including Zn2+, Cd2+, and Pb2+). The dominant genus in consortium TC, GS, and PL showing relatively higher degradation efficiency for anthracene and pyrene was Pseudomonas, whereas consortium PG and GD were predominated by genus Achromobacter and class Enterobacteriaceae, respectively. Consortium TC, as a highly efficient HMW PAH-degrading consortium, could be applied for synergistic biodegradation of HMW PAHs and in situ bioremediation of the sites contaminated with both PAHs and heavy metals.

A Bayesian network approach for determining optimal ecological base flow of rivers in water shortage areas of Northwest China.

How to balance natural river base flow with water loss from agricultural activities such as irrigation has become an important global challenge in areas of water shortage. Using a Bayesian network model, we constructed a decision-making framework for river ecological base flow in the water shortage areas. This framework can be divided into three components: (1) calculation of economic losses caused when priority is given to protect river ecological base flow, (2) construction of a decision-making Bayesian network, and (3) determination of an optimum ecological base flow of rivers based on an acceptable probability of acceptable economic losses the decision-makers selected. We used the Baoji section of the Weihe River as a typical water shortage area case study. The results show that the optimum ecological base flows in the Baoji section of Weihe River in wet, normal, and dry years were 32.35%, 20.59%, and 14.71% of natural inflow in rivers, respectively. From an economic benefit perspective, the beneficiaries should provide more financial support to protect the ecological base flow of rivers. Our approach could be used in other water shortage areas where decisions need to be made between protection of river ecological base flows of rivers and agricultural use.

Quantitative assessment of non-point source pollution load of PN/PP based on RUSLE model: a case study in Beiluo River Basin in China.

The runoff-sediment relationship in the Yellow River Basin of China is still grim. People pay more and more attention to non-point source (NPS) pollution caused by surface pollutants migrating into the receiving water body with rainfall runoff. The particulate load of pollutants adsorbed in the soil and sediment by erosion and denudation and migration into water is also quite serious. It is necessary to deeply analyze the quantitative relationship between particulate nitrogen and phosphorus (PN/PP) load and soil loss. The soil erosion estimation of different administrative units in the study basin is obtained by the revised universal soil loss equation (RUSLE). The spatial distribution and the variation characteristics at different slopes and different land use of PN/PP load are discussed. An empirical equation of particulate organic load is used to calculate the PN/PP load. The results show that the multi-annual average erosion modulus of the basin is 358.33 t/(km2∙a); the multi-annual average soil erosion reaches 9.62 million tons. The PN/PP load caused by soil loss reaches 11,107.1 t and 7909.3 t, and the export coefficients are 4.13 kg/hm2 and 2.94 kg/hm2, respectively. Spatial distribution of the PN/PP load is in step with the soil erosion distribution. Soil erosion is prone to occur in the region under the slope of 8 ~ 25°, the NPS load of PN/PP are relatively large, and the average export coefficients of PN/PP are 7.17 kg/hm2 and 5.06 kg/hm2. With the increase of the slope, the PN/PP load export coefficient increases first and then decreases. Agricultural land (AGRL), forest land (FRST), and pasture (PAST) are the land use types that contribute the most to the PN/PP load and soil erosion, and the average export coefficients of PN/PP are 4.54 kg/hm2 and 3.23 kg/hm2, respectively. The variability of natural elements, the unevenness and heterogeneity of spatial distribution, and the heavy involvement of human activities will have a conspicuous impact on the soil erosion and NPS pollution processes in the basin. The research on the influence of single factor and combined factors on NPS pollution process can be strengthen and provides scientific theoretical basis for formulating reasonable and efficient water and soil conservation measures and NPS pollution control scheme, so as to achieve effective control and scientific management of environment pollution.

Influences of stormwater concentration infiltration on the heavy metal contents of soil in rain gardens.

Many studies have been conducted on water volume reduction and pollutants purification of rain gardens. However, the pollutant variations in rain gardens are rarely explored. Seven soil sampling events were conducted from April 2017 to February 2019 to investigate the influences of stormwater concentration infiltration on soil heavy metals in two rain gardens. The results show that: (1) Cu, Zn, and Cd contents in rain garden soil are greater than those of the control soil. They vary with seasons and are trapped in the top layer of 0-30 cm; (2) Cu, Zn, and Pb exist as iron-manganese oxide combined form (S3), organic bound (S4) and residual forms (S5). However, Cd exists in exchangeable (S1) and carbonate bound (S2) forms, whereas Cr is in the S2, S3, and S4 forms. (3) According to the Soil Environmental Quality Standard in China, rain gardens, running for 8-9 years, are relatively clean and, within level II. However, compared with the background content of Shaanxi Province and the world, they are moderately or even heavily polluted by Cd and Zn and slightly polluted by Cu. It indicates that rain gardens have the risk of heavy metal pollution from stormwater concentration infiltration.

Impact of climate change and human activities on economic values produced by ecosystem service functions of rivers in water shortage area of Northwest China.

Climate change and human activities are affecting the ecological health of rivers and the economic value of its ecosystem services. Taking water quantity as the intermediate variable, we proposed a quantitative calculation method for the impact of climate change and human activities on the economic value produced by the ecosystem service functions of rivers. The framework mainly consists of three steps: firstly, we quantitatively determined the changes in the amount of water coming from rivers due to climate change and human activities; secondly, combining the theory of resource and environmental economics to calculate the economic value generated by ecological service functions of rivers; finally, we quantitatively identified and analyzed the impact of climate change and human activities on the economic value produced by the ecosystem service functions of rivers. Taking Baoji section of Weihe River (BSWR) as an example, we quantitatively analyzed and calculated the impact of climate change and human activities on the economic value produced by ecosystem service functions of rivers. The main conclusions of this paper are as follows: in recent 52 years, the economic value produced by the ecosystem service functions of rivers decreased by 3.57 billion yuan due to the climate change and human activities; the total economic value has been reduced by an average of 68 million yuan per year. This useful work can not only reveal the impact of climate change and human activities on the economic value of ecosystem services of rivers but also can provide an important basis for the reasonable management model of water resource of ecosystem of rivers watershed.

Improvement and application research of the SRM in alpine regions.

The simulation of snowmelt runoff in alpine mountainous areas is of great significance not only for the risk assessment of snowmelt flood in spring and summer, but also for the development and management of water resources in the basin. An improved snowmelt runoff model (SRM) is constructed based on the analysis of change characteristics of climate, runoff, and snow and ice cover in the middle and upper reaches of the Taxkorgan River in Xinjiang Province, China. Because of the large evaporation in the study basin, the evaporation loss is added to the model. The SRM and the improved SRM are calibrated and verified by using data such as temperature, precipitation, water vapor pressure, and snow-covered area (SCA) ratio in the study basin from 2002 to 2012. The results show that, compared with the SRM, the average Nash-Sutcliffe coefficient (NSE) of annual runoff simulation increases from 0.80 to 0.86 in the calibration and increases from 0.74 to 0.83 in the validation through the improved model, and the average runoff error reduces from - 12.8 to 1.32% in the calibration and reduces from - 20.0 to - 11.51% in the validation. After adding the measured flow rate for real-time correction, the average NSE of annual runoff simulation increases from 0.91 to 0.93 and the average annual runoff error reduces from - 7.76 to - 3.91% in the calibration. The average NSE increases from 0.85 to 0.89 and the average runoff error reduces from - 12.35 to - 2.76% in the validation. It indicates that the SRM structure with increased evaporation loss is more in line with the actual situation. The short-term simulation effect of the model is greatly improved by adding the measured flow rate for real-time correction. At the same time, the improved SRM and the hypothetical climate change scenario are used to analyze the impact analysis of the snowmelt runoff simulation in the partial wet year. The results show that in the case of rising temperature, the ice and snow ablation period is prolonged, and the annual runoff also changes significantly in time distribution. It is of guiding significance for the influence of climate change on the runoff of recharged rivers with ice-snow meltwater in the other alpine regions.

Filler improvement and purification effects of constructed rapid infiltration facility.

Purification effects of constructed rapid infiltration system with two main fillers (coarse sand or medium coarse sand) and different addition proportion (5%, 10%, or 15%) modifiers (sponge iron, blast furnace slag, or zeolite) on rainwater runoff were studied through filter column tests. A set of constructed rapid infiltration system test device was designed, which included 9 rainwater filter columns. The test results showed that the permeability of artificial fillers blended with modifiers could have the promotion with varying degrees. There were differences in the characteristics of the modifiers, so the artificial fillers blended with different modifiers had a significant difference for the purification effects on each pollutant. In view of the overall situations, the pollutant removal effects of artificial fillers with two or more modifiers had a smaller gap, and the reduction effects were good, ranging from 38.95 to 46.25% when the main filler is coarse sand and from 46.29 to 49.46% while main filler is medium coarse sand. It was worth noting that the artificial fillers blended with sponge iron showed a slight harden after prolonged used; however, it had little influence on the permeability and water purification effects.

Influences of stormwater concentration infiltration on soil nitrogen, phosphorus, TOC and their relations with enzyme activity in rain garden.

Rain garden is a typical facility with many applications in urban low impact development (LID). It plays an important role in regulating runoff water quantity and quality. Two rain gardens with the discharge ratios of 20:1 and 15:1 were used as studied facilities. Seven soil sampling events were conducted from April 2017 to February 2019 to study the influences of stormwater concentration infiltration in rain gardens on soil nitrogen (N), phosphorus (P) and TOC and their relations with enzymes. The results showed that the contents of soil TN and NO2-N + TON in gardens gradually decreased with time, while those of NH3-N and TP increased with time. The content of NO3-N varied greatly with time, and there was no obvious rule. TOC increased first and then decreased. Vertical distributions of N, P and TOC showed that the contents of NH3-N, NO2-N + TON and TN at 0-50 cm were high, so the upper soil was the sensitive area to the influence of stormwater concentration infiltration in rain gardens. The content of NH3-N decreased gradually with the increase of soil depth, but those of NO3-N and TP increased with the soil depth. Therefore, NO3-N and TP migrated down with water infiltration in soil, and preventing NO3-N and P leaching was critical for effective N and P removal though rain gardens. Soil urease (SU), sucrose (SS), protease (SP) and acid phosphatase (SAP) had a good linear relationship with N, P and TOC, and R2were all greater than 0.5.

Remediation and accumulation characteristics of dissolved pollutants for stormwater in improved bioretention basins.

Dissolved pollutants in stormwater are more mobile/bioavailable, and are captured via different mechanisms than particles. Column-scale bioretention basins are constructed by filling different media, which is used to study the remediation and accumulation characteristics of dissolved pollutants by improved bioretention basins (increased infiltration and adsorption capacity of the media). The media factor (ratio of specific surface area to cubic of porosity) is used to characterize the basic properties of different media, while considering the key factors: infiltration capacity, inflow concentration, recurrence interval, discharge ratio, antecedent dry period, and rainfall duration. The results showed that stormwater pollutants load reduction rate decreased with the increase of recurrence interval and discharge ratio, and increased with the increase of inflow concentration. Based on response surface methodology (RSM), a quantitative relationship model between major pollutants and influencing factors were established (R2 > 0.715), which can be used to estimate the design and operation of the media. By detecting changes in media carbon, nitrogen and phosphorus contents, the results showed that partial pollutants leaching were greater than their accumulation in the initial stage of system operation, and their contents in the media reduced during simulated rainfall. After the pollution contents tend to stabilize, the accumulated pollutants were greater than the leaching, and media pollution contents showed the trend of upper > middle > lower (corresponding to the 10, 35, and 60 cm sections of the media from top to bottom). Six enzymes closely related to the accumulation and migration of nitrogen, phosphorus and organic matter in the media were selected. Pearson correlation analysis found that: the significant correlations between the selected enzyme activity and pollutants were not consistent in bioretention system. For example, catalase was significantly correlated with all the pollutants (P < 0.01), whereas acid phosphatase was not significantly correlated with all the pollutants.

Analysis of rainfall infiltration and its influence on groundwater in rain gardens.

The dynamic observation data on groundwater level and water quality were obtained from rain gardens #2 and #3 from May to October 2016. The water balance method and 2D numerical simulation of variable saturation zone were used to calculate rainfall infiltration recharge coefficient, water supply, and evaporative discharge of rain garden. These parameters were used to simulate and explore the impact of rainfall infiltration in rain gardens on groundwater level and water quality. The groundwater depth of rain gardens was mainly affected by the concentrated infiltration of rainfall. The variation range of groundwater depth was approximately 4.298 ± 0.031 mm for J1, 3.9364 ± 0.097 mm for J2, and 4.0958 ± 0.064 mm for J3, and the specific yield was 0.208. Groundwater quality was naturally attenuated and would not threaten the safety of groundwater at a certain scale. Visual MODFLOW was used to simulate groundwater flow and conduct parameter sensitivity analysis to determine the main influencing factors of garden groundwater level change. Results showed that rainfall recharge was crucial to module sensitivity.

Purification effects of amended bioretention columns on phosphorus in urban rainfall runoff.

In order to develop bioretention fillers with better phosphorus removal capacity, we built 12 bioretention columns with six kinds of modified fillers, and analyzed the operation effects of the columns under different conditions through field tests. Results show that adding water treatment residual has optimal removal rates for total phosphorus (TP) (median = 96.80%) and soluble reactive phosphorus (SRP) (median = 97.13%). The water reduction rates of the columns with improved fillers are 1.23-2.04 times that of the bioretention soil media column. The coconut chaff column has the best water storage capacity (median = 40.54%). Among the external factors affecting column operation, influent concentration of pollutants in urban surface runoff is the biggest influence factor on the removal efficiency of TP. However, there are no significant correlations between the removal efficiency of SRP and rainfall, influent concentration, and discharge ratio. The columns modified with medical stone, vermiculite, peat soil, medical stone + peat soil, green zeolite + peat soil all have good removal for phosphorus pollutant. After entering the columns, the contents of TP and SRP in most columns increased. The recommended fillers and the accumulation performance of phosphorus can help to improve purification effects in bioretention systems.

Design parameters and treatment efficiency of a retrofit bioretention system on runoff nitrogen removal.

Mixed media design is key factor that affects the operation of bioretention systems. In this study, four types of modifiers, namely, water treatment residual (WTR), green zeolite, fly ash, and coconut bran, were mixed with traditional bioretention soil (65% sand + 30% soil + 5% sawdust, by mass). Consequently, four kinds of modified media were obtained. Ten pilot-scale bioretention basins were constructed by setting different configurations. The steady infiltration rates of the modified packing bioretention systems were 3.25~62.78 times that of plant soil, which was 2.88~55.75 m/day. Results showed that the average concentration removal (ACR) of both mixed and layered fly ash and WTR were better than those of the other media, and the effects could reach over 61.92%. In the bioretention basins with WTR as the modifier, the treatment efficiency of nitrogen under the submerged zone height of 150 mm was relatively optimal, and ACR could reach 65.46%. Outflow total nitrogen (TN) load was most influenced by inflow load, and the correlation coefficient was above 0.765. Relative to the change of inflow concentration (IC), the change of recurrence interval (RI) and discharge ratio (DR) was more sensitive to TN load reduction. The reduction rate of TN load decreased by approximately 15% when the recurrence interval increased from 0.5 to 3 years. It decreased by approximately 12% when the discharge ratio increased from 10 to 20. This study will provide additional insights into the treatment performance of retrofit bioretention systems, and thus, can guide media and configuration design, effect evaluation, and related processes.

[Study on water quality monitoring scheme based on non-point source pollution].

In order to improve standardization and normalization of non-point source pollution monitoring, this paper summarized the non-point source pollution monitoring scheme that based on conventional technology condition. The scheme firstly emphasized the preparation work before monitoring, including situation investigation and index selection of the monitoring area and so on; In the process of establishing monitoring scheme, the monitoring area was divided into three types: city, agriculture and watershed. Take urban area monitoring scheme for Xi'an as an example, through dividing function zone setting sampling point, summarized sampling time interval, frequency and sampling methods during a rainfall process. An irrigation district was an example for agricultural monitoring scheme, through unit division, setting sampling point at the approach channel and drain channel, introduced sampling times, interval time and so on in the process of irrigation. Watershed monitoring scheme's example was the Weihe GuanZhong section, raised the setting principle of each sample section, and analyzed each section's sampling law in the process of rainfall. Finally the principal character of different non-point source pollution monitoring areas was discussed, and concluded that non-point source pollution monitoring scheme is the base of non-point source pollution study and control.

[Impact analysis of Xi'an to the water quality of Weihe River].

Based on the water quality inspection results of Weihe River in the Xi'an section and the runoff at the watershed in different representative years, it was found through the pollution load calculated from the mean concentration method that Weihe River's main stream was dominated by point source pollution and non-point source pollution was more serious in tributaries. The input amount of pollutant to Weihe River' main stream from Xi'an which is located within the Xianyang and Lintong section was calculated from the material balance algorithm based on the pollutant concentrations measured in 2009 and 2011. The percentage of the pollution load of Xi'an area on Lower reaches' monitoring section of Lintong was analysed and the impact of Xi'an area on the water quality of Weihe River was quantified. The computational results showed that the upstream of the Xianyang section was the main source of the pollution load of the Lintong section in Weihe River, followed by Xi'an area. More than 40% of TN, COD and NH4+ -N of the Lintong section came from the upstream of the Xianyang section and more than 30% came from Xi'an area, in addition, 53% of TP came from Xi'an area. The non-point source pollution in Xi'an was more serious than in its upstream and downstream areas while point source pollution load accounted for 63% of the total.

[Monitoring and analysis on evolution process of rainfall runoff water quality in urban area].

In order to find the water quality evolution law and pollution characteristics of the rainfall runoff from undisturbed to the neighborhood exit, 6 times evolution process of rainfall runoff water quality were monitored and analyzed from July to October in 2011, and contrasted the clarification efficiency of the grassland to the roof runoff rudimentarily at the same time. The research showed: 1. the results of the comparison from "undisturbed, rainfall-roof, rainfall runoff-road, rainfall-runoff the neighborhood exit runoff " showed that the water quality of the undisturbed rain was better than that from the roof and the neighborhood exist, but the road rainfall runoff water quality was the worst; 2. the average concentrations of the parameters such as COD, ammonia nitrogen and total nitrogen all exceeded the Fifth Class of the Surface Water Quality Standard except for the soluble total phosphorus from undisturbed rainfall to the neighborhood exit; 3. the runoff water quality of the short early fine days was better than that of long early fine days, and the last runoff water quality was better than that of the initial runoff in the same rainfall process; 4. the concentration reduction of the grassland was notable, and the reduction rate of the grassland which is 1.0 meter wide of the roof runoff pollutants such as COD and nitrogen reached 30%.

[Simulation and application of the agricultural non-point source pollutants in drainage ditch].

Drainage ditch system is the transitional zone between yield in the field and receiving waters for agricultural non-point source pollutants. Based on the brief analysis of the migration and transformation process of agricultural non-point source pollutants in drainage ditch system, the one-dimensional transport model of agricultural non-point source pollutants in drainage ditch system was constructed on the basis of the equation of continuity of flow and pollutants migration transform. Taking the Di Yi drainage ditch system, in the Qing-Tong-Xia irrigation district at the Yellow River upstream, as an example, combining with actual situation, the drainage discharge and concentration of nitrate nitrogen and total phosphorus were simulated by this model. The results show that the simulated drainage discharge accords with measured data approximately and Nash-Suttcliffe coefficient is 0.82, the simulated concentration of nitrate nitrogen and total phosphorus in farmland drainage was reasonable.