Identifying Nonpoint Sources of Phosphorus and Nitrogen: A Case Study of Pollution That Enters a Freshwater Wetland (Laguna Cartagena, Puerto Rico)

Point and nonpoint sources of phosphorus (P) and nitrogen (N) can cause reductions in water quality, including eutrophication. Nonpoint pollution represents a special challenge because of dispersed not easily identifiable sources such as the runoff from soil, nutrients, and other chemicals from agricultural fields and residential areas. Laguna Cartagena is a tropical freshwater wetland, situated in southwestern Puerto Rico. It is a eutrophic ecosystem, and its eutrophication is caused by both external nutrient loading and internal, mainly by phosphorus. This wetland has been affected by phosphorus loading from inorganic agricultural fertilizer in this historically oligotrophic wetland system until the end of subsidized fertilizer use and sugar cane cultivation in the late 1990s. This study identifies: 1) nonpoint sources of phosphorus (SRP, Soluble Reactive Phosphorus and TP, Total Phosphorus) and nitrogen (nitrate, nitrite, and ammonia) that enter Laguna Cartagena;and 2) the role of precipitation events on the contributions of phosphorus and nitrogen loading to ecosystems. Herein we assess water samples from five channelized external sources of P and N that enter Laguna Cartagena at two-week intervals from October 2013 through November 2014. Rainfall data were obtained weekly from a rain gauge. Standard methods were used for all chemical analyses. Results showed that the channelized waterways that carry water to the lagoon can be classified as hypereutrophic (>100 μg/L) for TP concentrations and oligotrophic (<200 μg/L) for nitrogen concentrations. Currently agriculture (rice and cattle) is the predominant land use at the nearby University of Puerto Rico (UPR) Lajas Agricultural Experiment Substation, the predominant nonpoint source of nutrient pollution (SRP, TP and ammonia) in the principal channelized water sources to the lagoon. Current nutrient loads are likely derived from fertilizers applied to the Substation’s rice fields, and a high density livestock. The second important cause of external surface water degradation (SRP, TP and ammonia) is the discharge from rural households in the drainage basin that discharge greywater directly to the environment, as indicated by the results from Cerro Alto hills immediately to the north of the lagoon. Precipitation also was associated with SRP, TP and ammonia loads.

Inversion of Water Quality TN-TP Values Based on Hyperspectral Features and Model Validation

Using hyperspectral data collected in January and June 2022 from the Sha River,the concentrations of total nitrogen(TN)and total phosphorus(TP)were estimated using the differential method.The results indicate that the optimal bands for estimation vary monthly due to temperature fluctuations.In the TN model,the power function model at 586 nm in January exhibited the strongest fit,yielding a fit coefficient(R2)of 0.95 and F-value of 164.57 at a significance level(p)of less than 0.01.Conversely,the exponential model at 477 nm in June provided the best fit,with R2=0.93 and F=80.95 at p<0.01.In the TP model,the exponential model fit of the differential values at 851 nm with TP in January produced the best results,with R2=0.78 and F=20.61.However,the overall fit in June outperformed that in January.Specifically,the quadratic and linear model fits of the differential values at 824 and 863 nm with TP achieved R2=0.96 and F-values of 34.42 and 203.34,respectively.

土壤有机质和全氮水平与土壤碳排放的相关性及估算模型

【目的】探明土壤有机质和全氮对土壤碳排放的影响及分析估算碳排放模型的可行性,为土壤固碳减排和创建简单易行、普适性高的土壤碳排放评估方法提供参考。【方法】采用田间试验和模型拟合相结合的方法,以土壤有机质9 g/kg、全氮0.4 g/kg(5~6级肥力)为CK,研究不同土壤肥力水平有机质和全氮含量[OL:有机质41.0 g/kg、全氮2.1 g/kg(1级肥力);SL:有机质31.0 g/kg、全氮1.6 g/kg(2级肥力);TL:有机质21.0 g/kg、全氮1.1 g/kg(3级肥力);FOL:有机质11.0 g/kg、全氮0.8 g/kg(4级肥力);FIL:有机质9.0 g/kg、全氮0.6 g/kg(5级肥力)]对土壤碳排放的影响,并分析以有机质和全氮含量为因子拟合模型用于土壤碳排放量估算的准确性和适用性。【结果】土壤肥力水平为1级时,土壤碳排放量与有机质和全氮含量呈负相关关系;土壤肥力水平为2级时,土壤碳排放量达峰值,为4320.22 kg/hm^(2),较CK显著提高88.81%;当土壤肥力水平为3~6级时,土壤碳排放量与有机质和全氮含量呈正相关关系。【结论】土壤碳排放量与有机质和全氮水平有一定的相关性,土壤有机质含量(x)、全氮含量(y)与土壤碳排放量(CE)的拟合公式为CE=2221.37-263.15x+6174.45y,该模型的预测性和准确性良好,可根据土壤肥力水平分级用于区域土壤的碳排放量估算。

Correlation Analysis between Abundance of Trichodina spp. and Water Quality Parameters

To understand the correlations between the abundance of Trichodina spp. and the water quality parameters, the abundance of Trichodina spp. on the gill of yellow catfish in aquaculture water was investigated. Meanwhile, the temperature and total phosphorus, available phosphorus, total nitrogen, nitrite and ammonia nitro- gen contents of the aquaculture water were measured and determined. The results showed that the abundance of Trichodina spp. on the gill of yellow catfish was negatively correlated with the total phosphorus, available phosphorus and total nitro- gen contents in the aquaculture water, and was positively correlated with the nitrite content in the aquaculture water （P〈0.05）; there were no significant correlations between the abundance of Trichodina spp. and the temperature and ammonia nitrogen content of the aquaculture water （P〉0.05）.

Spatiotemporal variations and determinants of stream nitrogen and phosphorus concentrations from a watershed in the Three Gorges Reservoir Area,China

Socioeconomic development induced nonpoint source(NPS)pollution has aroused an increasing concern,however,most of the previous studies were concentrated on the impacts of environmental determinants.Here,total nitrogen(TN)and total phosphorus(TP)concentrations from 13 sampling sites were collected biweekly from January 2018 to October 2021,and 26 potential factors including environmental and socioeconomic were considered in the Wangjiaqiao watershed of the Three Gorges Reservoir Area,China.Impacts of these factors on TN and TP were evaluated by partial least squares regression(PLSR)model.It showed that average TN and TP concentrations in wet seasons(TN,14.68 mg L^(-1):TP,0.113 mg L^(-1))were higher than that in dry seasons(TN,11.73 mg L^(-1);TP,0.087 mg L^(-1)).Additionally,the TN concentrations were greater in downstream than upstream,however,the highest TP concentrations were found in the middle of the watershed.The optimal PLSR model explained 69.6%,73.1%and 66.1%of the variance in TN concentration,as well as 65.7%,79.5%and 67.4%of the variance in TP concentration during the annual,dry and wet seasons,respectively.Moreover,TN was primarily influenced by topographic wetness index,planting structure,interspersion and juxtaposition index,orchard proportion,nitrogen fertilization,per capita income,and catchment area,whereas TP was mainly controlled by slope gradient,topographic wetness index,hypsometric integral,interspersion and juxtaposition index,and population density.Collectively,environmental factors had greater impacts on the TN and TP concentrations than socioeconomic factors.Raising farmers'awareness of the hazards of NPS pollution is beneficial to watershed NPS pollution control.

Soil Organic Carbon and Nutrients along an Alpine Grassland Transect across Northern Tibet

Soil carbon and nutrient contents and their importance in advancing our understanding of biogeochemical cycling in terrestrial ecosystem, has motivated ecologists to find their spatial patterns in various geographical area. Few studies have focused on changes in the physical and chemical properties of soils at high altitudes. Our aim was to identify the spatial distribution of soil physical and chemical properties in cold and arid climatic region. We also tried to explore relationship between soil organic carbon （SOC） and total nitrogen （TN）, total phosphorus （TP）, available nitrogen （AN）, available phosphorus （AP）, soil particle size distribution （PSD）. Samples were collected at 44 sites along a 300 km transect across the alpine grassland of northern Tibet. The study results showed that grassland type was the main factor influencing SOC, TN and TP distribution along the Gangdise Mountain-Shenzha-Shuanghu Transect. SOC, TN and TP contents were significantly higher in alpine meadow than alpine steppe ecosystems. SOC, TN, TP and AN contents in two soil layers （0-15 cm and 15-3o cm） showed no significant differences, while AP content in top soft （0-15 cm） was significantly higher than that in sub-top soil （15-30cm）. SOC content was correlated positively with TN and TP content （r = 0.901and 0.510, respectively）. No correlations were detected for clay content and fractal dimension of particle size distribution （D）. Our study results indicated the effects of vegetation on soil C, N and P seem to be more important than that of rocks itself along latitude gradient on the northern Tibetan Plateau. However, we did not found similar impacts of vegetation on soil properties in depth. Inaddition, this study also provided an interesting contribution to the global data pool on soil carbon stocks.

Variation in Enzymes Activities of Rhizospheric Substrate and Influencing Factors during Nursing of Watermelon Seedlings

[Objective] This study aimed to investigate the effects of substrate en- zymes activities on nursing of watermelon seedlings. [Method] The composted mushroom residue was mixed with garden soil according to a certain proportion to prepare nursing substrate for watermelon seedlings. During the nursing, the activity variation in alkaline phosphatase, acid phosphatase, neutral phosphatase and urease was investigated. In addition, the correlations between pH value, total nitrogen con- tent, total phosphorus content and organic matter content in substrate and enzyme activity were studied. At different young seedling stages, the rhizospheric substrates with different formulas were sampled for determination of enzymes activities. [Result] The enzyme activity differed significantly among different substrates. The correlation analysis results showed that the higher the organic matter content and total nitrogen content in substrate are, the higher the urease activity is; the phosphatase activity was significantly related to the organic matter content, total nitrogen content and to- tal phosphorus content in substrate; the pH value of substrate was significantly relat- ed to rhizospheric alkaline phosphatase activity; the shoot dry weight was positively related to urease activity; there was a significant correlation between phosphatase activity and root dry weight. [Conclusion] Through determining enzymes activities in the rhizospheric substrate for nursing watermelon seedlings, the optimum substrate M3 was screened out. The activities of rhizospheric urease, alkaline phosphatase, acid phosphatase and neutral phosphatase in the substrate M3 were all higher than those in the substrate fertilized with manure.

Effects of recovery time after fire and fire severity on stand structure and soil of larch forest in the Kanas National Nature Reserve, Northwest China

Forest recovery may be influenced by several factors, of which fire is the most critical.However, moderate-and long-term effects of fire on forest recovery are less researched in Northwest China.Thus, the effects of different forest recovery time after fire(1917(served as the control), 1974, 1983 and 1995) and fire severities(low, moderate and high) on larch(Larix sibirica Ledeb.) forest were investigated in the Kanas National Nature Reserve(KNNR), Northwest China in 2017.This paper analyzed post-fire changes in stand density, total basal area(TBA), litter mass, soil organic carbon(SOC) and soil nutrients(total nitrogen, total phosphorus and total potassium) with one-way analyses of variance.Results indicate that litter mass, TBA, SOC and soil nutrients increased with increasing recovery time after fire and decreasing fire severity, while the stand density showed an opposite response.The effects of fire disturbance on SOC and soil nutrients decreased with increasing soil depth.Moreover, we found that the time of more than 43 a is needed to recover the litter mass, TBA, SOC and soil nutrients to the pre-fire level.In conclusion, high-severity fire caused the greatest variations in stand structure and soil of larch forest, and low-severity fire was more advantageous for post-fire forest stand structure and soil recovery in the KNNR.Therefore, low-severity fire can be an efficient management mean through reducing the accumulation of forest floor fuel of post-fire forests in the KNNR, Northwest China.

Effects of Wetland Reclamation on Soil Nutrient Losses and Reserves in Sanjiang Plain,Northeast China

The carbon （C）, nitrogen （N） and phosphorus （P） variations of a temperate wetland soil under continuous cultivation for 40 yr were determined and evaluated in the Sanjiang Plain, Northeast China. The results showed that the soil organic carbon （SOC） and total nitrogen （TN） contents in each soil layer decreased sharply after cultivation for 2-3 yr, and exhibited minor differences after cultivation for 11 yr, which showed an exponential decline curve with the increase of cultivation years. The reduction rates of carbon and nitrogen reserves were 14.79% and 28.53% yr^-1 at the initial reclamation stages of 2-3 yr and then decreased to 2.02-3.08% yr^-1 and 1.98-2.93% yr^-1 after cultivation for 20 yr, respectively. Soil total phosphorus （TP） reserves decreased within cultivation for 5 yr, and then gradually restored to the initial level after cultivation for 17 yr. Both SOC and TN could be restored slightly when the farmland was left fallow for 8 yr after reclamation for 11 yr, whereas TP had no significant difference. These results demonstrated that wetland cultivation was one of the most important factors influencing on the nutrient fate and reserves in soil, which could lead to the rapid nutrient release and slow restoration through abandon cultivation, therefore protective cultivation techniques preventing nutrients from loss should be immediately established after wetland reclamation.

Improvement of Water and Wastewater Treatment Process Using Various Sound Waves—A Consideration from the Viewpoint of Frequency

Application of sound waves is one of the novel techniques for the improvement of water treatment process. In this study, various sound waves such as 1) ultrasonic wave, 2) music box, and 3) windbell were irradiated to water and wastewater for removing contaminants such as nitrate, phosphorus and BOD/COD. As a result, a possibility of improvement of water and wastewater treatment process using sound waves with various frequencies was proposed.

NIRS Prediction of SOM,TN and TP in a Meadow in the Sanjiang Plain,China

The aim of this study was to establish the applicability of near-infrared reflectance spectroscopy(NIRS)as a rapid method for the accurate estimation of nutrient components in agricultural soils.Focusing on the soil of the Sanjiang Plain,NIRS was used to predict soil organic matter(SOM),the total nitrogen(TN)and the total phosphorus(TP).A total of 540 samples were collected from the three different depths(180 samples from each depth:0-10,10-20 and 20-30 cm),from 2015 to 2017,from the Sanjiang Plain in Heilongjiang Province,China.From every depth,120 samples were used to construct the calibration set.Other 60 samples were used to check the efficiency of the model.Combining the first-order differentiation with the partial least square(PLS)method,a prediction model was obtained to measure SOM,TN and TP.The correlation coefficient of SOM from 0 to 10 cm was R2=0.9567,from 10 to 20 cm was R2=0.9416,and from 20 to 30 cm was R2=0.9402.The corresponding ratio(standard deviation[SD]/root mean square error of prediction[RMSEP])was>2.96.R2 of TN with the three depths was 0.9154,0.9028 and 0.9024,respectively,all with SD/RMSEP>2.89.Meanwhile,R2 of TP with the three depths was 0.8974,0.8624 and 0.7804,respectively,all with SD/RMSEP>2.50.These results demonstrated that NIRS based on the first-order differentiation and PLS could efficiently predict SOM,TN and TP from different soil depths.

Water Environment Improvement of Zhongdong River by Water Diversion and Distribution in Hangzhou

As the development of city economy,Zhongdong River in Hangzhou was seriously polluted,with the worst water quality.In order to obtain the effect of water diversion and distribution from Qiantang River on the water quality of Zhongdong River,7-year continuous monitoring was conducted,which was at the fixed stations before and after the water diversion and distribution.After the water diversion project,the dissolved oxygen concentration of the river water was one to two times higher than before,and the ammonia nitrogen and total phosphorus decreased by 60%and 65%,respectively.When increased the amount of water diversion,the dissolved oxygen concentration of the river water elevated by 13%,and the ammonia nitrogen,total phosphorus and potassium permanganate index decreased by 8%,3%and 14%,respectively.The reason for the river water pollution was contributed to the combined sewer system and riverway sludge,especially during the rainfall,the dissolved oxygen concentration of Zhongdong River sharply declined by 95%,while the ammonia nitrogen and total phosphorus increased by 90%and 87%,respectively.The research results could provide theoretic basis for sustainable improvement of Zhongdong River water quality and river management department making the related regulations and policies.

The Status and Evaluation of Main Soil Nutrients in Xilin Gol Grassland

To reveal the soil nutrient contents of Xilin Gol Prairie,practical data on the main soil nutrient contents from 2006 to 2011 were statistically analyzed and integrated evaluation of soil nutrients was finished on principal component theory. The result showed that the soil nutrients of Xilin Gol Grassland were mainly organic matter,the content of total N,total P and total K were 22. 444 g / kg,1. 047 g / kg,0. 371 g /kg and 23 g / kg respectively,and the degree of variation of each other was moderate except total K's little variability. The contents of soil nutrients were in the moderate level,in which contents of organic matter and total N were in the moderate level( Level 3),content of total P was low level( Level 5),and the content of was much high level( Level 2). The regional integrated evaluation showing that the soil nutrients of Xilinhot was the highest level and Erenhot was the lowest level; the meadow steppe was the highest following by the typical grassland and the grassland as desertification was the lowest,provided a theoretical basis for promoting the restoration of farmland to forest and pasture and the development of animal husbandry and improving the grassland productivity and reasonable utilization of grassland resources.

Activation Effect of Hydrochemical Energy in Regenerative Agriculture on Nutrients of Arsenic Sandstone

[Objectives]To study the activation effect of hydrochemical energy in regenerative agriculture on the nutrients of arsenic sandstone.[Methods]Starting from common environmental factors,moisture,it studied the mechanism of the release and activation of N,P,K nutrient elements in arsenic sandstone under different dry and wet environments.[Results]Water played a positive role in activating soil elements.Under the conditions of long-term dryness and alternating dry and wet conditions,the content of total nitrogen,available phosphorus and available potassium coexisted in the 210 d of culture and the element absorption and release,but the overall trend was increasing;under long-term flooding conditions,the content of total nitrogen and available potassium showed an overall increasing trend during the 210 d of culture,but the content of available phosphorus decreased.[Conclusions]Water plays a positive effect on activating soil elements.The research results are expected to provide a certain reference for the application research of water in regenerative agriculture.

The Effects of Legume Crops （Pea and Faba Bean） on Soil Nutrients Availability and Yield Parameters of Subsequent Cabbage Crops under Organic Production Conditions

Three equal field plots were cultivated with respectively wheat, field pea and faba bean. The common conventional production technology, including the use of chemical fertilizers was applied in wheat, but no fertilizers at all were used in faba bean and field pea plots. Atter legume harvesting, forty day old broccoli and cauliflower seedlings were transplanted to each of them according to three replications randomized block design. The transplanting was conducted at equal planting density, and common organic production practices were applied in entire production cycle. The legume crops improved soil fertility by increasing total soil N （Nitrogen） and improving P （Phosphorus） and K （Potassium） availability to the subsequent crops. As a result, an enhanced vegetative growth, improved curd setting and increased average curd weight was found in broccoli and cauliflower. However, there were significant differences between legume crops themselves regarding the proved benefits to the subsequent crops, confirming a clear advantage of faba bean versus field pea. A significantly higher above ground biomass was recorded in cauliflower plants followed faba bean, compared with field pea and wheat, but no difference was found regarding the biomass production in broccoli. The higher percentage of plants set curds （either broccoli or cauliflower） was obtained in the variants followed faba bean and then field pea. The same was true regarding total curd yield and the average curd weight for both： broccoli and cauliflower.

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.

Spatial distributions of soil nutrients affected by land use,topography and their interactions,in the Loess Plateau of China

Soil nutrient availability and their spatial distributions are strongly related to land use and landscape morphology.This study aims to address the knowledge gap regarding the interaction between these factors and the underlying mechanisms.We selected five land uses(grassland with Artemisia gmelinii,woodland with Robinia pseudoacacia,shrubland with Caragana korshinskii and Hippophae rhamnoides,and apple orchard with Malus pumila)and nine slope positions across hillslopes in the Loess Plateau,China,to investigate their combined effects on the contents and stocks of soil organic carbon(SOC),total nitrogen(TN)and total phosphorus(TP).Parametric and non-parametric statistical tests were conducted to determine the significant differences in the means or the medians of the soil nutrient variables.Results showed that the SOC and TN contents of shrubland with Caragana korshinskii were statistically significantly greater than those of the grassland(p<0.05).SOC and TN contents generally decreased from the upper slope to the middle slope,and to the foot slope for the grassland,woodland and shrublands,and on the contrary,an increasing trend from the upper slope,to the middle slope,and to the foot slope was identified for the apple orchard.This study highlights that land use,slope position and their interaction have significant effects on the spatial distributions of soil nutrients.It provides essential empirical evidence for the identification of the optimal vegetation type and slope positions in land management and vegetation restoration activities.

江苏省太湖流域总氮、总磷排放标准研究

根据太湖流域 (江苏省境内 )不同类型污水中总氮、总磷的浓度和当前废水治理技术及接纳水体的环境质量和经济承受能力等方面的系统分析 ,确定了江苏省太湖流域三级保护区内各类排污单位总氮、总磷允许排放浓度 ,并分析了本标准与其他排放标准之间的关系。最后 ,对实施本标准后的太湖水质影响进行了估算研究。

中国重点污染源总磷、总氮排放状况研究

中国氮、磷污染较为突出,然而氮、磷排放负荷底数不清,尤其是对具有监管优势的工业源和城镇生活源研究不足。利用《中国环境统计公报》数据和污染源监督性监测数据,对中国重点污染源的总磷、总氮排放状况分析得出:农业源是总磷、总氮的主要排放源;污水处理厂、工业企业的总磷、总氮排放浓度基本持平,规模化畜禽养殖企业总磷排放浓度较高;工业源中化工、农副食品加工等大类行业总磷、总氮排放量较大,淀粉制造等小类行业总磷、总氮排放量也较大;中国总磷、总氮排放主要集中在中东部地区。

污水处理厂氮排放特征

为了更好地掌握污水处理厂运行和排放情况,在全国南方、北方分别选取3个省共11个城市122家污水处理厂,于2013年8—10月进行了专项监测。结果表明:75.4%的污水处理厂氨氮出水质量浓度小于2 mg/L,氨氮平均去除率达90.2%,但总氮的平均去除率仅为55.5%,污水处理厂排水中仍存在较多非氨氮形态的氮污染进入环境。氨氮排放达标的污水处理厂中,有约20%的总氮排放未达标。65.5%的污水处理厂出水氨氮占总氮的比例低于10%,而84.4%的污水处理厂进水中氨氮占总氮的比例高于50%。总氮是影响污水处理厂达标排放的主要污染因子。