Average Concentrations Of Total Nitrogen Research Articles

Study on Spatial Distribution of OM, N, P in Surface Soil around Lake Chaohu

The concentration of total nitrogen (TN), total phosphorus (TP) and organic material (OM) at sixty grid division in Lake Chaohu basin around the lake was studied, in order to investigate their spatial distribution characteristics. The results showed that the average concentrations of TN, TP and OM were 1027 mg/kg, 483 mg/kg, 1.95%, and their concentrations ranged from 253 mg/kg to 2273 mg/kg, 223 mg/kg to 1173 mg/kg and 0.291% to 5.48%, respectively. The high concentration areas were located at the basins of Tuogao river and Zhao river while the low concentration areas were located at basins of Pai river, Nanfei river and Dianpu river. The concentrations of TN and OM were higher in East part than in West part. The spatial distribution of TN, TP and OM concentrations of the surface soil showed inconsistent with those of the water quality of the inflow rivers and the lake and the TN and TP of lake sediment studied.

PURIFICATION OF REFINERY WASTEWATER BY DIFFERENT PERENNIAL GRASSES GROWING IN A FLOATING BED

Four species of perennial grasses [Geophila herbacea O Kumtze (GHK), Lolium perenn CV. Caddieshack (LCC), Lolium perenne Topone (LPT) and Lolium perenne L. (LPL)] were used to remove nutrients and pollutants from refinery wastewater, of which the average concentration of total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (CODMn), total petroleum hydrocarbons (TPH) were 15.6 mg L−1, 0.6 mg L−1, 142.8 mg L−1 and 1720 mg L−1, respectively. These perennial grasses had performed extremely well in removing the nutrients and pollutants and were capable of removing up to 60% of TN and 56% of TP from the refinery wastewater during 35 days treatment period, to which plant uptake contributed only 5%–10% and 10%–20%. The removal rates of CODMn and TPH were fluctuating within 52% to 67% and 40% to 55%, respectively. The nutritional value of these perennial grasses as animal feeds such as crude protein, crude fat, crude fiber, crude ash and nitrogen-free extraction after growing in refinery wastewater for 35 days were analyzed and the results suggested that these indicators were superior to national animal feed thresholds, with its nitrites and several heavy metals including zinc (Zn), arsenic (As), cadmium (Cd), and lead (Pb) concentration far below the thresholds. We concluded that perennial grass floating-bed system was effective for purifying refinery wastewater during its growing season and harvested perennial grass had great value as animal feeds.

Non-linear Responses of a Coastal Aquatic Ecosystem to Large Decreases in Nutrient and Organic Loadings

Between 1991 and 2000, Boston Harbor, a bay–estuary in the northeast USA, experienced a decrease in loadings of total nitrogen (TN), total phosphorus (TP), and particulate organic carbon (PC) of between ∼80% and ∼90%. The average concentrations of TN and TP in the harbor water column were decreased in linear proportion to the loadings. The changes to the chlorophyll-a (chl-a), PC, and bottom water DO concentrations were curvilinear relative to the loadings, with larger changes at low than high loadings. For TN and TP, the starts of the decreases in concentrations coincided with the starts of the decreases in loadings. For the three variables that showed curvilinear responses, the starts of the changes lagged by 2 to 3 years the starts of the decreases in TN loadings. Total suspended solid concentrations and water clarity in the harbor were unchanged. The study shows that for systems such as Boston Harbor, decreases in nutrient loadings will have quite different effects depending on the base loadings to the system.

Removal of nitrogen in constructed wetlands with horizontal sub-sureface flow: a review

The paper describes the removal of nitrogen in horizontal sub-surface flow constructed wetlands (HF CWs) for various types of wastewater. The survey includes more than 900 annual means from more than 300 systems in 36 countries that were categorized into municipal, industrial, agricultural, and landfill leachate. The results revealed that the highest average concentration of total nitrogen (TN) was found in landfill leachate (211 mg l−1), while the highest average loading (3,080 g N m−2 yr−1) was recorded for systems treating wastewater from industrial operations. The average inflow TN concentration and loading for all systems were 63 mg l−1 and 1,158 g N m−2 yr−1, respectively. For ammonia-N the results were similar — the highest average inflow concentration (162 mg 1−1 was recorded for landfill leachate and the highest average loading was recorded for agricultural wastewaters (2,722 g N−2 yr−1). The results also indicated that there is a good relationship between inflow and outflow concentrations and loadings for both TN and NH4-N. Harvesting aboveground biomass of emergent macrophytes in HF CWs removes only limited amount of nitrogen as compared to inflow load (commonly <10%).

Soil bacterial communities in constructed wetlands treated with swine wastewater using PCR-DGGE technique

Marsh-pond-marsh (MPM) constructed wetlands were designed for the treatment of swine wastewater. The goal of this study was to characterize bacterial communities in these wetlands and determine the nutrient removal from influent to effluent. Surface soil samples were collected and analyzed by culture-dependent and culture-independent techniques. The results showed that the bacterial colony forming units (CFU) and the average concentrations of total nitrogen, NH 4 + , total phosphorous (TP) and PO 4 3 - from the influent to the effluent decreased. The NH 4 + and the PO 4 3 - concentrations showed the most dramatic changes, with decreases of 39.97% and 16.92%, respectively. Data of culture-independent samples produced by using PCR-denaturing gradient gel electrophoresis (DGGE) technique showed that the Shannon diversity index and richness decreased significantly ( P < 0.05) from influent to effluent. Bacterium species distributions strongly correlated with the concentrations of TP, NH 4 + and the PO 4 3 - . Sequencing of partial 16S rRNA genes fragments revealed that the total bacterial community composition was dominated by Pseudomonas sp., Arthrobacter sp., Bacillus sp. and other soil bacteria. Anammox (anaerobic ammonium oxidation) stains were detected. Phylogenetic analysis demonstrated that some of the partial 16S rRNA gene sequences had close relationships with unculturable denitrification bacteria. The activities of these bacteria might contribute to the nutrient removal in the wetlands.

Seasonal variation of nitrogen and phosphorus in Xiaojiang River—A tributary of the Three Gorges Reservoir

A yearlong monitoring program in the backwater area of Xiaojiang River (XBA) was launched in order to investigate the eutrophication of backwater areas in tributaries of the Yangtze River in the Three Gorges Reservoir (TGR) in China, starting after the impoundment water level of the TGR reached 156 m. From March 2007 to March 2008, the average concentration of total nitrogen (TN) and total phosphorus (TP) were (1553±484) μg·L−1 and (62±31) μg·L−1, respectively. The mean value of chlorophyll was (9.07±0.91) μg·L−1. The trophic level of XBA was meso-eutrophic, while the general nutrient limitation was phosphorus. The results indicated that XBA has a strong ability to purify itself and has non-point source pollution from terrestrial runoff. The variation of TN/TP ratio was caused by a variation in TN rather than in TP when TN/TP < 22. N-fixation from cyanobacteria occurred and became an important process in overcoming the nitrogen deficit under a low TN/TP ratio. When TN/TP ⩾ 22, the variation of TP affected the TN/TP ratio more significantly than TN. The increase of TP in XBA was caused mainly by particulate phosphorus, which could originate from a non-point source as adsorptive inorganic forms after heavy rainfall and surface runoff. An increase in the river’s flow could also contribute to an unstable environment for the growth of phytoplankton.

Temporal and spatial distribution of different species of nitrogen in Lake Wuliangsuhai,Inner Mongolia

为揭示不同形态氮在乌梁素海空间分布特征及变化规律,运用ArcGIS统计模块分析了2006-2007年乌梁素海不同形态氮浓度的时空变异.研究表明:乌梁素海水体中各监测点总氮浓度夏、冬季高,秋季低,季节性差异较为明显;秋、冬季氨氮平均浓度明显高于夏季;不同季节亚硝态氮平均浓度明显高于硝态氮.在空间分布上,乌梁素海不同形态氮浓度分布呈现出由北向南逐渐降低的趋势.总之,乌梁素海氮素污染问题已十分严重,主要污染源为河套灌区农田排水、沿总干渠区域的工业废水和生活污水,随水体的流动氮污染减少,但某些区域因芦苇、水草密集而使不同形态氮有不同程度的增减.;The temporal and spatial variation characteristics of nitrogen forms are very important for environmental pollution controlof lake. Concentrations of different nitrogen forms were studied using the geostatistical analysis module of ArcGIS in LakeWuliangsuhai. The results indicate that average concentrations of total nitrogen were higher in summer and winter than autumn inseasonal time series, the average concentrations of ammonia nitrogen were lower in summer than autumn and winter, and the averageconcentration of nitrite nitrogen was higher than nitrate nitrogen in different seasons. In space, concentration distribution of differentforms ofnitrogen showed gradually decreasing from north to south. In a word, nitrogen pollution is very serious in LakeWuliangsuhai. The main pollutions were sourced from farm field drainage of the Hetao irrigated areas, industrial waste water anddomestic sewage close to main irrigation canal, which caused different forms of nitrogen contents decreases with the discharge of flowingwater. However, in the region of density reed and aquatic, the contents of nitrogen forms will change with increase or decrease.

Measurements and Characteristics of Nitrogen-Containing Compounds in Atmospheric Particulate Matter in Beijing, China

The total nitrogen (TN) and water-soluble nitrogenous ions were determined by using CHN Elemental Analyzer and ion chromatography method, respectively, from November 24, 1998 to February 12, 1999 in Beijing. The average concentrations of TN, NH(4) (+) and NO(3) (-) were 10.62 microg N m(-3), 6.67 microg m(-3) and 10.01 microg m(-3), respectively. The total inorganic nitrogen (IN) calculated from NH(4) (+) and NO(3) (-) was 7.45 microg N m(-3), accounting for 70% of TN, i.e., 30% of TN existed as organic nitrogen form (ON). The correlation between ON and other pollution tracers showed that, coal combustion, biomass burning, soil humic matter and secondary formation were the important sources of ON in particulate matter in Beijing.

Assessment of biological Nitrogen fixing potentials of &lt;i&gt;Pigeonpea&lt;/i&gt; genotypes intercropped with sorghum for soil fertility improvement in Southern Guinea savanna of Nigeria

In a 2-year field/laboratory study, the biological nitrogen fixing potentials of 14 newly introduced pigeonpea (Cajanus cajan (L.) Millsp.) genotypes from ICRISAT along with a local check were assessed under intercropping with sorghum (Sorghum bicolour (L.) Moench.) in Southern Guinea Savanna of Nigeria. Using sorghum as the non-fixing control and N-difference method, estimates of fixed N in pigeonpea genotypes of different maturity ratings ranged from 37.52kg/ha to 164.82kg/ha under intercropping. The average total nitrogen concentration of shoot in intercropped pigeonpea genotypes at harvest (2.83%) was higher than that for intercropped sorghum (1.83%). There were very little differences between sole cropping and intercropping in total soil N for each of the crops in the intercrop combinations in both years.. Keywords: v > Agro-Science Vol. 6 (1) 2007: pp. 33-45

Long-term fluctuation and regional variation of nutrient loads from the atmosphere to lakes

The atmospheric depositions were collected by ordinary bulk-samplers mounted with a glass or polyethylene funnel of 30 cm orifice. A long-term observation was carried out at a site (35 degrees 01'30"N, 135 degrees 58'07"E) in the urbanized area for 21 years since 1974. The annual volume-weighted average concentrations of total nitrogen (TN) and phosphorus (TP) were 1.02 +/- 0.30 and 0.031 +/- 0.015 mg(-1), respectively, and the loading rates were 14.5 +/- 2.8 and 0.43 +/- 0.16 kg ha(-1) yr(-1). The rates neither had a relationship with the precipitation (1,492 +/- 343 mm yr(-1)) nor showed any diachronic tendencies. In order to obtain the loading rate of TN and TP within 10% uncertainty under the significant level of 0.01, there is no way but to continue the observation for seven and eleven years or more, respectively. In order to clarify the regional variation of the loading amounts of the depositions, the samplers were set at 12 sites distributing throughout the Kinki District for two years. The distance from northernmost (2322 mm yr(-1)) to southernmost (1242 mm yr(-1)) is about 150 km. The average loading rates of the 12 sites were 16.2 +/- 2.5 kg ha(-1) yr(-1) of TN and 0.730 +/- 0.247 kg ha(-1) yr(-1) of TP. The depositions of NO3-N, NH4-N, and TN as well as TP showed tendencies with distances neither from a big city nor from Japan Sea.

Application of USLE for the prediction of nutrient losses in soil erosion processes

Soil erosion in agricultural fields affects not only land productivity but also water environment down stream. Many investigations have been made for the prediction of soil erosion processes. The Universal Soil Loss Equation (USLE) has been applied broadly for the prediction of average annual soil loss from upland fields. However, there are few reports concerning the prediction of nutrient (N, P) losses based on the USLE. Thus, the objective of this study is to propose the prediction equation of nitrogen and phosphorus losses during soil erosion processes on the basis of the USLE. In order to predict total nitrogen and phosphorus losses, the coefficients for total nitrogen or phosphorus transfer are derived on the basis of results from experimental field plots. Three bare-cover USLE plots with different amounts of granular chemical fertilizer were installed in an experimental upland field. There was a tendency for the coefficient of total nitrogen or phosphorus transfer to increase with the average concentration of total nitrogen or phosphorus in the soils. It follows that the more granular chemical fertilizer applied caused a higher coefficient of total nitrogen or phosphorus transfer in the calculations. Moreover, the coefficients in heavily fertilized plots were higher than 1.0. Through this investigation, it became clear that the nutrient losses during soil erosion could be predicted on the basis of the coefficient of total nitrogen or phosphorus transfer along with other soil erosion parameters.

ベトナム北部Ｒｅｄ Ｒｉｖｅｒ Ｄｅｌｔａにおける河川水・井戸水の窒素・リン濃度

Nitrogen and phosphorus concentrations were measured in rivers (15 sites) and domestic wells (10 sites) in the Red River Delta, north of Vietnam in two dry and two rainy seasons between 2002 and 2004. The average concentrations of total nitrogen (TN) including particulate forms in the water samples from the rivers were 2.1 mg N·l-1 in the urban areas and 1.3 mg N·l-1 in the rural areas, with little differences between the dry and rainy seasons. The stable nitrogen isotope ratios (δ15N) of nitrate were from 1.4 to 11.7 ‰ (5.9 ‰ on average) in the river water samples. Markedly high concentrations of TN (4.7 mg N·l-1 in the dry season and 6.7 mg N·l-1 in the rainy season) were observed in water samples from wells in the rural areas. In those water samples, considerably high ammonium N concentrations and high δ15N values (upto 31.6 ‰) were often observed. Particulate forms of P predominated in the river and well water samples. The average concentration of total phosphorus (TP) in the rainy season (0.24 mg P·l-1 ) was twofold higher than that in the dry season (0.12 mg P·l-1) in the river water samples. The average concentrations of TP and dissolved total phosphorus (DTP) in the well water samples were 0.09 and 0.02 mg P·l-1, respectively, with little seasonal and areal differences. The relatively low nitrogen concentrations and intermediate δ15N values of the river water samples suggest that nitrogen pollution is not yet serious in rivers in the Red River Delta, despite the rapid increase in the use of chemical fertilizers and population there. On the other hand, contamination by wastes from human or livestock is suggested in domestic wells in the rural areas.

Controlling nitrogen removal using redox and ammonium sensors

At the Ejby Mølle WWTP (300,000 PE) operated by the Odense Water Ltd. a system of aeration control which combines ammonium concentration and redox potential has proven itself as a method of reducing nitrogen levels in the effluent. The nitrogen removal process at this plant proceeds in parallel aeration tanks that alternate between periods of aeration and denitrification. At the same time influent is redirected from one tank to the other such that influent and effluent is primarily to and from the tank where denitrification is going on. The aeration stops and the tanks open and close when the ammonium concentration reaches its set point. Aeration is restarted again when redox potential drops to its low set point or when ammonium reaches its upper set point. The average total nitrogen concentration in the effluent from the Ejby Mølle WWTP went from 4.7 down to 2.1 mgN/l after this control system was implemented. Not all of this reduction can be explained by better control. However we believe that at least 1 mgN/L of the reduction and probably more was the result of the control system based on the combination of ammonium and redox sensors.

The impact of intensive dairy farming on the leaching losses of nitrogen and phosphorus from a mole and pipe drained soil

While it is widely believed that intensive dairy farming is a major contributor to the increased nutrient loads in surface waters, there is little current research quantifying the magnitude of nutrient loss from dairy farms to waterways, particularly from artificial drainage. An experimental site has been established on a Pallic soil (Tokomaru silt loam) to measure the impacts of intensive dairying on the quality and quantity of drainage water exiting from an artificial drainage system. A key component of this study is the development and evaluation of a land-based treatment system for farm dairy effluent (deferred irrigation). The research site has eight replicated plots, each with an isolated mole and pipe drain network. All the plots are subjected to the farm's standard grazing management. Four of the plots receive fer tiliser according to the farm's fertiliser programme, while the other four plots receive applications of farm dairy effluent. Measurements of drainage flows during year one of this study showed that the average concentrations of total nitrogen (12.9 mg N/L) and total phosphorus (0.15 mg P/L) in drainage water for the winter of 2002 under standard dairy farming practices were all well above the levels necessary to prevent aquatic weed growth in fresh water bodies. Adherence to the scheduling criteria prescribed by the 'deferred irrigation' system prevented the direct loss of nutrients during irrigation of farm dairy effluent in the summer of 2001/2002. Summer applications of farm dairy effluent did not increase N loss in subsequent winter drainage. Effluent irrigation increased P loss during the subsequent winter drainage period by 0.52 kg total-P/ha (0.38 kg P/ha as DIP). However, this increase in total loss corresponds to less than 4% of the P (16 kg/ha) applied as effluent. Deferred irrigation proved to be a very successful tool for minimising nutrient losses from effluent irrigated areas in direct drainage of effluent at the time of irrigation and subsequent winter drainage. Dairy cattle grazing events also increased nutrient concentrations in drainage waters following grazing by approximately 5 mg total-N/L (nearly all in the nitrate form) and 0.1 mg total-P/L (nearly all in the DIP form). The effect of an application of urea in spring on nitrate-N concentrations in drainage water was minimal. Keywords: dairying, effluent irrigation, mole and pipe drainage, nitrogen, nutrient leaching phosphorus, water quality

Brook Water Quality and Background Leaching from Unmanaged Forested Catchments in Finland

The water chemistry of 21 outlet brooks in undisturbed, forested catchments (0.074–38 km2) in Finland was monitored during three years (1997–1999) in order to estimate the background levels and leaching of total organic carbon (TOC), iron, nitrogen and phosphorus, and examine the relationships between catchment characteristics and brook water quality in pristine forested areas. The studied catchments are located throughout Finland except the northernmost parts of the country. The concentrations of TOC were relatively high, on average 20 mg L-1. Annual leaching of TOC ranged from 3000 to 10 000 kg km-2. The average total nitrogen concentration and annual leaching were 430 μg L-1 and 140 kg km-2, respectively. The average total phosphorus concentration and annual leaching were 15 μg L-1 and 5.4 kg km-2, respectively. On a national level temperature and discharge conditions were the most important variables for predicting total phosphorus, total nitrogen and TOC concentrations. Both total nitrogen and total phosphorus concentrationsdisplayed positive correlation with temperature, and thus the concentrations were higher in the south than in the north. Nitrogen was mainly organic and showed strong correlation with TOC. On the catchment level, both TOC and total nitrogen concentrations and export had a strongpositive correlation with the abundance of Norway spruce (Piceaabies Karsten) and a strong negative correlation with the abundance of Scots pine (Pinus sylvestris L.). Nitrate concentrations and leaching were related to average site type. The more fertile the average site type was in the catchment, the higher the nitrate concentrations and export were.

Global patterns of dissolved N, P and Si in large rivers

The concentration of dissolved inorganic nitrogen (DIN), dissolved nitrate-N, Total-N (TN), dissolved inorganic phosphate (DIP), total phosphorus (TP), dissolved silicate-Si (DSi) and their ratios in the world's largest rivers are examined using a global data base that includes 37% of the earth's watershed area and half its population. These data were compared to water quality in 42 subbasins of the relatively well-monitored Mississippi River basin (MRB) and of 82 small watersheds of the United States. The average total nitrogen concentration varies over three orders of magnitude among both world river watersheds and the MRB, and is primarily dependent on variations in dissolved nitrate concentration, rather than particulate or dissolved organic matter or ammonium. There is also a direct relationship between the DIN:DIP ratio and nitrate concentration. When nitrate-N exceeds 100 μg-at l−1, the DIN:DIP ratio is generally above the Redfield ratio (16:1), which implies phosphorus limitation of phytoplankton growth. Compared to nitrate, the among river variation in the DSi concentration is relatively small so that the DSi loading (mass/area/time) is largely controlled by runoff volume. The well-documented influence of human activities on dissolved inorganic nitrogen loading thus exceeds the influences arising from the great variability in soil types, climate and geography among these watersheds. The DSi:nitrate-N ratio is controlled primarily by nitrogen loading and is shown to be inversely correlated with an index of landscape development – the “City Lights” nighttime imagery. Increased nitrogen loading is thus driving the world's largest rivers towards a higher DIN:DIP ratio and a lower DSi:DIN ratio. About 7.3 and 21 % of the world's population lives in watersheds with a DSi:nitrate-N ratio near a 1:1 and 2:1 ratio, respectively. The empirical evidence is that this percentage will increase with further economic development. When the DSi:nitrate-N atomic ratio is near 1:1, aquatic food webs leading from diatoms (which require silicate) to fish may be compromised and the frequency or size of harmful or noxious algal blooms may increase. Used together, the DSi:nitrate-N ratio and nitrate-N concentration are useful and robust comparative indicators of eutrophication in large rivers. Finally, we estimate the riverine loading to the ocean for nitrate-N, TN, DIP, TP and DSi to be 16.2, 21, 2.6, 3.7 to 5.6, and 194 Tg yr−1, respectively.

Distribution of Total, Exchangeable and Fixed Nitrogen in the Sediments of Two Lakes in Guizhou Province

氮是引起湖泊水体富营养化的关键营养元素之一.本次工作从贵州两个重要水库(红枫湖和百花湖)采集了未受扰动的沉积物样品柱,分析了分层沉积物样品中的总氮、无机交换性氮和固定铵的含量及垂直剖面分布.研究表明,红枫湖和百花湖沉积物中具有较高的全氮含量,平均含量约为沉积物干重的0.36%~0.40%,其垂直分布在埋藏过程中受到成岩作用改造;沉积物交换性氮在沉积物中的赋存受到全氮含量和埋藏环境的双重控制;红枫湖和百花湖沉积物具有较强的吸持固定铵的能力,沉积物固定铵的绝对含量的平均值分别为434.05 mg/kg和416.94mg/kg;分别占全氮的13.53%和12.53%.;Nitrogen plays a key role in lake eutrophication.We collected several undisturbed sediment corevS from two lakes, Lake Hongfeng and Lake Baihua in Guizhou Province to analyze the concentration and profile distributions of total, exchangeable inorganic and fixed nitrogen.The result's show that: (1) the nitrogen loctcl in the sediments of the two lakewS is higher in comparison with the average of lakes and reservoirs in China.Their average concentration of total nitrogen ranges from 0.36% to 0.40% Cdry sediment weight).It is obviously due to influence of diagenesis on vertical profile of total nitrogen in the sediment.The sediment of the reservoirs may be one of main nitrogen sources to cause the eutrophication.(2) The concentrations of total nitrogen and the burial environmental conditions are two main factors in distribution of the exchangeable nitrogen on sediment cores.(3) The fixed nitrogen is one of major sinks of nitrogen in the two reservoirs sediments.The concentration of fixed nitrogen in Lake Hongfeng and Lake Baihua, 434.05 mg/kg and 416.94mg/kg respectively, is higher than the data reported for others lakes or reservoirs of China.

Effects of water management practices on discharge of nutrients and organic matter from channel catfish ( Ictalurus punctatus) ponds

A water quality data set generated by sampling commercial ponds for 2 years was used in a hydrological model of pond overflow volume to describe the effects of water management practices on discharge of nutrients and organic matter from channel catfish Ictalurus punctatus ponds in northwest Mississippi, USA. Average concentrations of total nitrogen, total phosphorus, chemical oxygen demand, and biochemical oxygen demand in pond waters were highest in the summer but waste discharge was strongly influenced by pond overflow volume, and the model indicated that greatest quantities of nutrients and organic matter were discharged in the winter when pond overflow volume was greatest. The model also showed that managing pond water levels to maintain a minimum 7.5-cm water storage potential reduced average discharge of nitrogen, phosphorus, and organic matter in pond overflow by about 70% compared with ponds not managed to maintain storage potential. The model further showed that harvesting fish without draining ponds between fish crops could reduce average annual nutrient and organic matter discharge by over 60% relative to annually drained ponds. Maintaining water storage potential and not draining ponds between fish crops therefore appear to be simple and effective methods of reducing waste discharge from aquaculture ponds and have the added benefit of substantially reducing the need for pumped water to maintain pond water levels.

Optimization of a nitrogen‐removing biological wastewater treatment plant using on‐line measurements

ABSTRACT: The installation of continuous on‐line measurements of ammonium and nitrate in the aeration tanks of a nitrogen removing activated sludge plant has reduced the nitrate amount in the effluent by 60%. This corresponds to a drop in the average total nitrogen concentration in the effluent from 7.8 mg/L to 5.1 mg/L. The operation of the nitrogen removal process and thereby the effluent concentrations has become more stable. By combining operational changes in the biosorption with on‐line control of the process, it is possible to maintain full and stable denitrification at a BOD/N ratio of 3 to 4 without the use of any external carbon source, despite great variations in the loading of the plant. Monitoring of the microscopic characteristics of the sludge can be closely correlated with macroscopic characteristics such as sludge volume index.

CHEMISTRY OF PALMAR SWEAT

Previous studies 1 on the chemistry of palmar sweat were carried out on substances (chloride, urea, glucose and uric acid) which were also present in measurable concentration in the blood. In some instances (urea, glucose and uric acid) 2 the studies included observations on the concentration in palmar sweat of a chemical constituent at a time when its level in the blood had been raised artificially above normal. The normal concentration of ammonia in the blood is low (0.1 mg. per hundred cubic centimeters). Studies on renal physiology have shown that the urinary ammonia, known to be normally as high as 40 mg. of ammonia nitrogen per hundred cubic centimeters of urine, is formed by the kidneys. It is thought that by manufacturing ammonia the kidneys act to help conserve the stores of fixed base for the body. 3 Barney 4 showed that the average total nitrogen concentration per hundred