A Digestion Procedure for the Simultaneous Determination of Total Nitrogen and Total Phosphorus in Pond Water

Abstract— Total phosphorus and total nitrogen often are measured in studies of pond water quality. A laboratory study was conducted to test a digestion procedure for the simultaneous determination of total nitrogen and total phosphorus in pond water. Seventy water samples were collected from channel catfish ponds. Samples were digested in two ways. One digestion followed the standard protocol of persulfate digestion in an acidic environment for total phosphorus analysis, and total phosphorus was then measured with the ascorbic acid procedure. The second digestion was done by the procedure used for determining total nitrogen which involves persulfate digestion in an alkaline environment. The total nitrogen digestion procedure followed by phosphorus determination provided results similar to those obtained in the standard persulfate digestion for phosphorus. The slope of the regression line did not differ from 1.0 ( P < 0.05) and the Y intercept did not differ from 0 ( P < 0.05). Spike recovery averaged 99.1% (range 85–112%) in the total nitrogen digestion procedure; it averaged 98.4% (range 88–113%) in the standard total phosphorus digestion. The results of this investigation indicated that a single digestion can be used to obtain a digest suitable for measurements of total nitrogen and total phosphorus.     

Chemical Characteristics of Bottom Soils from Freshwater and Brackishwater Aquaculture Ponds

Soil chemical analyses were conducted on samples from 358 freshwater fish ponds and 346 brackishwater shrimp ponds. Freshwater ponds were located in Honduras, Rwanda, Bhutan, and the United States. Ponds in the United States were in Alabama, Georgia, Mississippi, Florida, and South Carolina. Brackishwater ponds were in Thailand, Ecuador, Philippines, and Venezuela. Soils of freshwater and brackishwater ponds did not differ greatly in average concentrations and concentration ranges for carbon, nitrogen, calcium, and pH. Concentrations of copper and barium tended to be higher in freshwater soils than in brackishwater ones. All other measured chemical constitutents tended to be more abundant in the soils of brackishwater ponds than in those of freshwater ponds. For the most part, ranges of pond soil chemical properties were similar to those of terrestrial soils, with freshwater pond soils resembling terrestrial soils from humid areas and brackishwater soils being similar in many respects to soils of arid regions. However, some brackishwater pond soils were highly acidic, acid-sulfate soils. Data were arranged into concentration categories (very low, low, medium, high, and very high) to facilitate comparisons of the present data set with other data on soil chemical properties for aquaculture ponds. All ponds included in the present study were used for aquaculture, showing that it is possible to rear fish and shrimp across an extremely wide range of soil chemical properties.     

Liming and Fertilization of Brackishwater Shrimp Ponds

Agricultural limestone and burnt lime are applied either to the water during shrimp production or to pond bottoms between shrimp crops. However, unless the total alkalinity and total hardness of pond water is below 50 mg/L as equivalent CaC0₃ or the pond soils are acidic (pH < 7), liming is of little or no value. The use of burnt lime should be avoided because this material can cause high pH in water and soil. Chemical fertilizers or manures are used to fertilize brackishwater ponds. Fertilization programs for brackishwater ponds usually require more nitrogen (N) than those for freshwater ponds. Phosphorus (P) fertilization is important both in brackishwater and freshwater ponds. Because water is exchanged often in brackishwater ponds, fertilizer should be applied in small doses and at frequent intervals. Most managers of brackishwater ponds prefer a large proportion of diatoms in the phytoplankton community. An N:P application ratio of 20:l in ponds favors diatoms; in fiberglass tanks with water of low silica concentration, fertilization with silica encouraged an abundance of diatoms.     

Evaluation of a Kit for Estimating Organic Matter Concentrations in Bottom Soils of Aquaculture Ponds

Abstract The Hach CEL/700 Organic Matter Laboratory provided estimates of organic carbon concentrations in pond soil samples comparable to those obtained by the commonly-used Walkley-Black method. Dry ashing at 350–400 C tended to overestimate soil organic matter concentrations, and this procedure requires too much equipment and laboratory expertise for use on most aquaculture farms. The Hach kit can provide practical aquaculturists a simple and reliable method for measuring organic matter in pond soils. Samples from brackishwater ponds should be treated with mercuric sulfate to prevent chloride interference and overestimation of organic matter.     

熵权法模糊物元模型在养殖水质评价中的应用

为客观综合评价养殖水体质量,利用熵确定水质指标权重,结合物元分析理论及贴近度的概念,构建养殖水质复合模糊物元模型,对2015—2019年监测的上海地区635批次养殖水样进行地表水环境质量等级分类。水质监测结果显示,池塘水体的pH、总磷、高锰酸盐指数、As(砷)和叶绿素a平均含量显著高于引水河道的(P<0.05),硝酸盐氮、Zn(锌)和石油类的平均分布显著低于后者(P<0.05),其他指标的平均分布差异不显著(P>0.05)。不同养殖品种池塘水体间,淡水鱼塘水体中氮、磷、有机质等相关指标的平均含量最高,蟹塘水体pH均值最高。熵权法模糊物元模型评价结果表明,在养殖水体水质指标中pH的权重最高,其次为高锰酸盐指数、总氮和氨氮,这4项合计权重超过0.5;89.29%的鱼塘、87.91%的虾塘和75.83%的蟹塘水样水质类别属于或优于地表Ⅲ类,相关河道水样水质满足地表Ⅲ类水质标准的样品占比达98.72%。整体上,上海地区的养殖水质满足地表水环境功能要求。     

Carbon and nitrogen budgets in shrimp ponds of extensive mixed shrimp–mangrove forestry farms in the Mekong delta,Vietnam

Mass balance estimates of carbon and nitrogen flux through two extensive shrimp ponds in the Mekong delta, Vietnam, were constructed to identify major sources and sinks of organic matter potentially available for shrimp production. Nutrient transformations in the sediments were measured to further assess rates of decomposition and burial and quality of organic matter. Tidal exchange was the major pathway for inputs and outputs of carbon and nitrogen in both ponds, with net primary production, nitrogen fixation and precipitation being minor inputs. No fertilizers or artificial feeds were added to either pond. The nutrient budgets identified burial and respiration as the next most important outputs after tidal exchange losses of particulate and dissolved carbon and nitrogen. There was no measurable denitrification in either pond, and volatilization was negligible. Mineralization efficiency of carbon in the water column was high (> 100%) in pond 23 reflecting rapid respiration rates; efficiency was lower (36%) in pond 12 waters. Mineralization efficiency of sediment nutrients averaged 34% for C and 41% for N in the pond with a higher annual shrimp yield (pond 12); lower mineralization efficiencies (11% for C, 10% for N) were calculated for the lower yield pond (pond 23). High burial efficiencies for both C (66–89%) and N (59–90%) in the sediments of both ponds suggest that little organic matter was shunted into biological production. Conversion efficiency for shrimp averaged 16% for C and 24% for N from pond 12, and 6% for C and 18% for N from pond 23. The high quantity but low quality of organic matter entering the ponds coupled with other factors, such as poor water quality, limits shrimp productivity. On average, nutrient outputs were greater than inputs in both ponds. This imbalance partly explains why shrimp yields are declining in these ponds.     

三种总氮总磷联合消解液测定效果的比较

在同一试验条件下对三种总氮总磷联合消解液的基本参数(空白值、检出限、精密度和耗药量)、标准物质的回收率和不同自然水样的分析等方面进行了比较。三种联合消解液的标准物质加标回收率均比较高,总氮,总磷标准物质的回收率范围分别为97.2%~101.3%和95.8%~100.8%;利用三种联合消解液消解测定22个自然水样中总氮、总磷的结果均与国家标准方法相近(P>0.05)。三种联合消解方法可以替代国家标准方法测定水体的总氮、总磷浓度,满足单个水样消解一次完成总氮总磷的连续测定,节省药品、简化操作。但在测定氮、磷含量较高的水体时,消解液一和消解液二分别存在总磷、总氮结果偏低的可能。     

Effect of organic nitrogen and carbon mineralization on sediment organic matter accumulation in fish ponds

In aquaculture, ponds with high loads of organic inputs, organic matter accumulates at the bottom over time. Uneaten feed, senescent phytoplankton and faeces are the principal sources of accumulated material, but quantifications are scarce. The sedimented organic matter develops into a flocculent layer in which different processes transform the material into inorganic forms. A better understanding of factors influencing organic matter accumulation/decomposition in the sediment is needed to better understand and manage the dynamics of nitrogen in fish ponds. In this study, the rate of mineralization of organic nitrogen and the nitrogen flux between the sediment and the water column were measured. Organic matter accumulation in fish ponds was quantified, and the data were used to construct, calibrate and validate a dynamic simulation model of organic matter deposition/decomposition in fish ponds. The accumulating material consisted of dead phytoplankton, fish faeces and uneaten feed. Through model calibration, the proportion of these materials in the total accumulated organic matter was determined. In the model, gross photosynthetic rate was estimated from an empirical relationship with feed input. After calibration, the model was validated using independent data. The model simulated well the concentrations of organic carbon and nitrogen in the sediments but it may be developed further, especially by considering the effects of resuspension.     

Anaerobic Treatment of Brackishwater Aquaculture Sludge: An Alternative to Waste Stabilization Ponds

Environmental pressure, land utilization, and economic feasibility have resulted in the development of recirculating aquaculture systems (RAS). For many RAS, sludge is collected and washed from the system to waste stabilization ponds (WSPs). However, disposal of brackishwater aquaculture sludge into WSP is often prohibited because the high salinity can interfere with treatment. Moreover, there are problems associated with WSPs because of elevated salt content, such as the common practice of reusing treated water and land application of stabilized sludge. We tested and compared the treatment of brackishwater aquaculture sludge in an upflow anaerobic sludge blanket (UASB) reactor as an alternative to a WSP. In UASB, wastewater flows upward through a blanket of granular sludge and is treated by anaerobic micro‐organisms. Reduction in organic matter and 5‐d biochemical oxygen demand by 97 and 91%, respectively, was achieved in a UASB as compared to corresponding reductions of 22 and 41% in a WSP. During the UASB digestion process, methane is produced and recovered. Overall, a reduction in potential environmentally harmful factors such as salinization, land requirements, greenhouse gas emissions, as well as transportation costs are achieved, making the UASB reactor an attractive possible alternative for saline aquaculture sludge management.     

A study on the relative efficiency of organic manures and the effect of salinity on its mineralisation in brackishwater fish farm soil

The influence of salinity on the mineralisation of organic nitrogen in the form of mustard oil cake, poultry manure and cow-dung in brackishwater pond soils was studied under laboratory conditions. The concentration of mineralised nitrogen for mustard oil cake and poultry manure showed a marked increase during 7 to 30 days after which it decreased gradually and in 90 days assumed practically the same value as that of the control over the salinity range of 0–40‰. The mineralised nitrogen of cow-dung treatment was lower than that of the control,till 30 days,after which it increased gradually. The loss of nitrogen is minimum in the higher salinity range for all three types of manure used. Mustard oil cake is a better manure for brackishwater soil than poultry droppings and cow-dung.     

Accumulation, organic carbon and dry matter concentration of sediment in commercial channel catfish ponds

Sediment depth and organic carbon (OC) concentration were measured in sediment cores (n=675) collected from 45 commercial channel catfish ponds in northwest Mississippi from April to September in 1998 and 1999. Ponds had been in continuous catfish production from 14 days to 21 years. Sediment depth ranged from 1 to 95 cm and was heterogeneously distributed within ponds: least in the shallow end (26.3 cm) and greatest in deeper areas (33.7 cm). Mean sediment depth increased with pond age, although the rate of sediment accumulation was greatest in the first year (12.5 cm per year). Organic carbon concentration varied slightly within ponds ranging from 0.76 to 3.43% of dry matter (DM). Mean organic carbon concentration in the upper 2 cm of sediment (1.77%) was significantly greater than in the deeper sediment layer (1.55%). Mean dry matter content in the upper 2 cm of sediment averaged 24.2% of total wet weight. Mean dry matter for the lower sediment fraction was 37.8% of total wet weight. Despite large inputs of organic matter from feed and primary production, sediment organic carbon concentrations did not increase with pond age.     

三峡库区水位消涨对杉木溪消落带土壤性质的影响

为了准确揭示杉木溪消落带土壤养分及其空间分布对三峡库区水位消涨及其所带来的环境变化的响应,2014年研究了5个完整水位消涨周期的不同海拔梯度和土层深度土壤。沿海拔梯度分别在150、155、160、165、170、175 m处各设置1个样带,180 m处设置1个对照样带,每样带设置5个样方,在各样方内选取4个角及中心点共5个样点,用土壤采集器分别在0~5、5~10和10~15 cm土层分层采集土样。结果表明,在水位消涨的作用下,消落带土壤养分含量显著下降,有机质、全氮和全磷含量与非消落带土壤相比分别减少了14.55%、20.00%和26.12%,土壤p H值则显著增加。水位消涨还导致消落带土壤养分随海拔梯度呈显著的空间变化。其中,有机质、全氮和全钾含量以中部消落带土壤的含量最高,全磷含量则以中下部消落带土壤的含量最高,而土壤p H值随着海拔梯度的减少而增加。消落带和非消落带土壤养分在不同土层之间有着显著差异,有机质、全氮、全磷含量随土壤的加深而显著减少。在水位消涨的影响下,消落带表层土与下层土有机质和全氮含量的差异显著减少,而全磷和全钾含量的差异则有所增加。     

Bottom soil quality in Tilapia ponds of different age in Thailand

Bottom soil samples were collected from 35 ponds in the vicinity of Samutprakarn, Thailand. Ponds ranged in age from 3 to 39 years and had been used continuously for production of tilapia. Liming materials had been applied in large amounts, and bottom soils of all ponds had pH above 7, low exchange acidity, and free carbonate. Pond soils often contained between 1% and 2% total sulphur, suggesting that they were potential acid–sulphate soils. However, acidity from sulphide oxidation was not expressed because carbonate in the soil neutralized it. Concentrations of total carbon seldom exceeded 4% and the average for organic carbon was 1.90%. The correlations between pond age and both total carbon and organic carbon concentration were weak (r=0.34 and 0.36 respectively). Concentrations of nitrogen in bottom soils did not differ with pond age and ranged from 0.1% to 0.3% with an average of 0.19%. The average ratio of concentrations of carbon and nitrogen was 11. Acid‐extractable phosphorus concentrations averaged 217 mg kg^?1, but the phosphorus adsorption capacity averaged 768 mg kg^?1 suggesting that soils still have considerable reserve capacity to adsorb phosphorus. Ponds can be used annually for semi‐intensive production of tilapia, and presumably other species, for many years without serious deterioration of bottom soil quality.     

Physical and chemical characteristics of sediments in catfish, freshwater prawn and carp ponds in Thailand

Sediment samples were collected from 42 catfish (Clarias hybrid) ponds, 40 freshwater prawn (Macrobrachium rosenbergii) ponds and 18 carp (Puntius spp.) ponds in Thailand. Regression analysis revealed that pond age (1–30 years) was not a major factor influencing the physical and chemical composition of pond sediments. Sediment depth, F+S horizon thickness and bulk density of S horizon were greater (P<0.05) in carp ponds than in catfish and prawn ponds. This occurred because sediment was removed from catfish and prawn ponds more frequently than from carp ponds. Total carbon, organic carbon and total nitrogen concentrations were greater (P<0.05) in carp ponds than prawn and catfish ponds. Few ponds had sediment organic carbon concentrations above 3%, and carbon:nitrogen ratio values did not differ (P>0.05) among ponds for the three species. Total phosphorus and other sediment phosphorus fractions increased in the order prawn ponds, carp ponds and catfish ponds. Sediment sulphur concentrations also increased in the same order. There were no differences in major or minor nutrient concentrations in sediment that would influence aquacultural production. Although there were significant correlations (P<0.05) between various sediment quality variables, no single variable or group of variables would be useful in estimating sediment quality. Pond bottom management practices used by producers in Thailand included drying of pond bottoms between crops, liming, tilling and periodic sediment removal. These practices have maintained relatively good bottom quality. They should be continued in Thailand and adopted in other places.     

Free water productivity measurements in leaky mariculture ponds

The rate of net organic productivity in experimental shrimp mariculture ponds was determined via free water methods for each hour over a two month period in late summer 1985. Automated measurements of pH and temperature served as the basis for development of a mass balance budget for dissolved inorganic carbon. Pond surface area and volume changed with depth in a complex but predictable fashion. The seepage rate, which is a quantitatively important term in the inorganic carbon budget, was determined with the salt mass balance. Seepage rates averaged 136–182 mm day⁻¹ (23–37% of pond volume per day). Close agreement between evaporation rates, independently determined from water budgets for each of the four adiacent ponds, demonstrated that the calculated seepage rates were accurate. All four ponds were net producers of organic matter despite the fact that three of the four received additions of allochthonous organic matter. Net productivity averaged 14–65 mmol C m⁻² day⁻¹.     

Chemical Budgets for Organically Fertilized Fish Ponds in the Dry Tropics

Chemical budgets were determined for nitrogen, phosphorns, dissolved oxygen and chemical oxygen demand for three 0.1-ha earthen ponds stocked with Onwchrornis nilotieus at the El Carao National Fish Culture Research Center, Comayagna, Honduras, for two 150-d culture periods, corresponding to the rainy and dry seasons. Layer chicken litter was added to ponds weekly at 500 kg dry matter/ha. Concentrations of nitrogen (N), phosphorus (P), and chemical oxygen demand (COD) in pond water increased during each season. No significant seasonal differencea in concentrations of water quality variables were observed. Chicken litter added to ponds represented 92–94% of N input, 93–95% of P input, and 43–52% of COD input. Photosynthesis by phytoplnnkton provided 47–56% of COD and 98% of dissolved oxygen (DO) added to ponds. Net inward diffnsion of oxygen added 1.2–1.5% of total DO. Regulated inflow was a minor source of nutrients, and contributed 3–4% of input N, 3–4% of input P, 1% of COD input, and 1% of DO input. Nutrient inputs from rain were ≤1% of total for each nutrient. Fish harvest accounted for 18–21% of total N, 16–18% of total P and 2% of COD added to ponds. Community respiration accounted for 48–57% of COD and 99.5% of DO added to ponds. Nutrient losses in pond effluent at draining were: 7–9% of total N, 29–37% of total P and 2–3% of COD. While measured gains exceeded measrued losses, significpntly greater N, P and organic matter concentrations in pre-drain samples indicated pond mud was a major sink for added nutrients, accumulation in mud represented 70% of total N, 35–40% of total P, and 38–46% of COD.     

上海地区池塘沉积物中氮、磷、有机碳及重金属风险评价

为综合评估上海地区池塘沉积物环境质量状况,2016-2019年对上海地区36个养殖场池塘采集沉积物样品360个,检测和分析沉积物中总氮（TN）、总磷（TP）、总有机碳（TOC）及重金属Cu、Zn、Pb、Cd、Cr、Hg和As含量。研究结果表明,池塘0~10 cm层和10~20 cm层沉积物中TN、TP、TOC及各重金属均值分布无显著差异（P>0.05）,0~20 cm层沉积物（干重）中TN、TP和TOC平均含量分别为（873.37±352.45）mg/kg、（685.66±199.66）mg/kg和（6.62±3.05）mg/g,三者相关性显著。综合污染指数法和有机指数法评价结果表明,池塘沉积物中氮和有机物质的累积量较低,磷累积量相对较高,均低于其他地区高产池塘。池塘沉积物中Cr、Cd、Cu和Hg样品超标率分别为6.42%、3.21%、4.13%和1.38%,Zn、Pb和As无超标现象。地质累积指数、潜在生态危害指数法和一致性沉积物质量基准评价结果表明,上海地区池塘沉积物中重金属整体上处于清洁等级、低潜在生态危害状态,预测不会引发生物毒性效应。     

Effect of organic fertilizer and formulated feed in pond culture of the freshwater prawn, Macrobrachium rosenbergii (de Man): pond productivity

Abstract. The application of different combinations and levels of pellet formulated feed and chicken manure to ponds stocked with Macrobrachium rosenbergii (de Man) did not result in any significant differences in water quality, sediment chemistry, or benthic macroinvertebrate populations. Water chemistry data indicated that all ponds were eutrophic. Chlorophyll was strongly correlated with total nitrogen, but not with total phosphorus, suggesting that nitrogen limited algal biomass. There was evidence that added organic matter was rapidly decomposed and mineralized. The sediments appeared to act alternately as sources and sinks of nutrients, although there was least variation in sediment nutrient levels in the treatment which received manure only. Applied pelleted feed was directly consumed by the prawns. In the absence of pelleted feeds, macrobenthos appeared to limit prawn growth after 1 month of culture. Simple nutrient mass-balance equations indicated that the losses of nitrogen, phosphorus and carbon from the treatments receiving feed were not dissimilar to previously reported values in finfish culture.     

Sediment Quality in Arkansas Bait Minnow Ponds

Sediment cores were collected from 7-yr-old, 20- to 25-yr-old, and 30- to 35-yr-old ponds at a bait minnow farm at Lonoke, Arkansas, USA. Average depths of soft sediment (S and M horizons) were 8 cm in young ponds, 12 em in intermediate-age ponds, and 26 cm in old ponds. Organic carbon concentrations in sediment were low to moderate (1–2%) and carbon to nitrogen ratios were wide (20–50). Phosphorus and sulfur concentrations increased as ponds aged. Most of the phosphorus (78.9%) was in organic form, but sulfur was primarily inorganic in form (presumably iron sulfide). There appears to be two major problems associated with sediment accumulation over time. Deep, soft sediment interferes with pond management and especially with harvest. High phosphorus concentration in old sediment may contribute to dense phytoplankton blooms by supplying phosphorus to the water. Sodium nitrate treatment did not increase the rate of sediment organic matter decomposition in laboratory trials and would not be expected to enhance the degradation of sediment organic matter in ponds. The best method for improving the condition of bottoms in older bait minnow ponds probably is to remove the sediment.     

氢化物发生-原子荧光光谱法测定水产品中有机硒和无机硒

采用硝酸、双氧水将水产样品中的有机硒氧化成无机硒后测定总硒含量;用50%盐酸提取样品中的无机硒并用硝酸、双氧水消解,测定无机硒含量,再通过差减法获得有机硒的含量。研究结果表明,在优化的工作条件下,硒的检出限为7.1 ng/mL,线性范围为0～20μg/L。经回收实验和实际样品检测,总硒加标回收率为93.88%～107.65%,相对标准偏差(RSD)为0.82%～4.97%;无机硒加标回收率为82.88%～90.10%,RSD为2.33%～7.73%。用标准物质对照,其测定数据完全在标准值范围内。实验表明,该方法线性范围宽,相关性好,精密度和准确度高,可操作性强,应用范围广,适合水产品中有机硒和无机硒测定。