Chemical properties of an acidified humic headwater lake with respect to reducing acidic depositions and expected climate change

During the hydrological years 1989 and 1990, water analyses of the dystrophic mountain cirque Lake Huzenbach and the precipitation within its watershed were performed. Periods of droughts which are supposed to be induced by climate change as well as acidic pulses modify the chemical composition of lake water. Snow melt and heavy rains cause flash floods in lake inflows which are controlled by subsurface-flow. One of the inflows exhibits extremely low pH values [pH_min = 3.66], high concentrations for aluminium [Al_max = 1.10 mg l^-1], dissolved organic carbon [DOC_max = 30.7 mg l^-1], and sulfate [SO_4max = 9.08 mg l^-1]. Organic and inorganic acids are both likely to contribute to the acidity of these surface waters. During baseflow conditions, groundwater springs still show slightly positive alkalinity values as well as increased pH values up to about 6.0. Since 1985 lake surface samples demonstrate an increasing tendency towards pH values higher than 5.0 during dry summer periods. Positive alkalinity values occur in the hypolimnion during anoxic conditions.     

Soil frost enhances stream dissolved organic carbon concentrations during episodic spring snow melt from boreal mires

Changes in winter time conditions at high‐latitude ecosystems could severely affect the carbon exchange processes. Using a 15 year stream record combined with winter field measurements and laboratory experiment, we studied the regulation of dissolved organic carbon (DOC) concentration in stream water draining boreal mire during snow melt. The most unanticipated finding was that cold soils with deep soil frost resulted in increased snow melt DOC concentrations in the stream runoff. Wintertime field measurements of DOC concentrations below the mire soil frost showed that this phenomenon could be explained by freeze‐out of DOC giving higher levels of DOC in the soil water below the ice as the soil frost developed downwards in the mire. Experimental freezing of water with a certain DOC concentration in the laboratory further corroborated the freeze‐out of DOC. In this experiment, as much as 96% of the DOC was excluded from the ice, whereas the freeze‐out in the mire was less effective (60%). The difference between the proportion of DOC retained in pure water relative to the proportion retained in peat water during freezing is probably due to trapped DOC in the solid peat soil matrix. A simple mass‐balance model showed that to explain the higher stream DOC concentrations during a winter with deep soil frost, approximately 0.5% of the mire area needed to be hydrologically connected to the stream discharge. In the stream records, we also found that the DOC concentrations during snow melt episodic runoff were negatively related to increasing intensity of the snow melt episodes (dilution by low DOC snow melt water) and higher previous export of DOC.     

Seasonal and Interannual changes of chemical characteristics and phytoplankton in a mountain lake of the Eastern Italian Alps (Lake Calaita,Trentino)

Measurements at Lake, Calaita, a small mountain lake located at 1605 m. a.s .l. in a metamorphic catchment area in the south of the Trentino Region (Northern Italy), have revealed great seasonal variations in the chemical characteristics and phytoplankton community during the ice free period in 1992 and 1993. The acidity present in wet precipitations (H⁺, NH₄⁺) was neutralised within the drainage basin by mineral dissolution which led to an increase of basic cations and alkalinity in the runoff. The dilution during periods of higher discharge, e.g. in spring and autumn, resulted in low values of alkalinity (up to 60 μeq 1⁻¹), pH (mostly <6.7) and conductivity (<8 μS cm⁻¹, 20°C). In summer, the decrease in runoff caused higher alkalinity (>10 μeq 1⁻¹), pH (6.9–7.4) and conductivity values (up to 30 μS cm⁻¹). The phytoplankton showed a major development in summer (with biovolume values of up to 7000 mm³ m⁻³), two different taxa being dominant in 1992 (Oocystis cf. lacustris) and 1993 (Synedra sp.). Unpredictable climatic conditions have a strong influence on the physical stability of the lake, which makes it more difficult to explain the evolution of the phytoplankton community as opposed to deeper lakes.     

Influence of calcareous soil on Cry3Bb1 expression and efficacy in the field

Greater than expected injury by western corn rootworm (WCR) (Diabrotica virgifera virgifera LeConte) to Cry3Bb1 expressing maize hybrids (Zea mays L.) has been reported in southwestern Nebraska. Affected areas of some fields are often associated with high pH calcareous soils where maize growth is poor and iron chlorosis is common. As part of a comprehensive study to understand potential causes of unexpected injury, experiments were conducted during 2013 and 2014 to ascertain whether the calcareous soil conditions and associated poor maize growth negatively affect the expression of Cry3Bb1. Quantitative determination of Cry3Bb1 protein expression levels in root tissues was carried out on plants at V5–V6 growth stage using the enzyme-linked immunosorbent assay. Cry3Bb1 and non-Bt near isoline maize hybrids were artificially infested with Cry3Bb1-susceptible WCR eggs to measure survival and efficacy of Cry3Bb1 maize in calcareous and non-calcareous soils. Results showed that there was not a significant difference in expression of Cry3Bb1 protein between plants from calcareous and non-calcareous soils (18.9–21.2 µg/g fresh weight). Western corn rootworm survival was about sevenfold greater from the non-Bt isoline than Cry3Bb1 maize indicating that Cry3Bb1 performed as expected when infested with a Cry3Bb1 susceptible rootworm population. When survival from calcareous and non-calcareous soils was compared, no significant differences were observed in each soil. A significant positive correlation between soil pH and expression of Cry3Bb1 protein in roots was detected from samples collected in 2014 but not in 2013. No such correlation was found between soil pH and survival of WCR. Results suggest that Cry3Bb1 expression levels were sufficient to provide adequate root protection against WCR regardless of soil environment, indicating that lowered Cry3Bb1 expression is not a contributing factor to the greater than expected WCR injury observed in some southwestern Nebraska maize fields.     

pH fluctuation of Sawano-ike Pond in Kyoto accompanied by water level changes

The supply and consumption of alkalinity in Sawano-ike Pond was investigated to reveal the mechanisms of pH fluctuation in the pond. Alkalinity in the bottom layer at the deepest point of the pond increased in summer, but in-pond generation of alkalinity was estimated to be very small because of the low depth of water in the pond. According to the calculations of water budget and solute balance, subsurface water, the alkalinity of which is moderately high, accounted for 45% of the total influx during a period of relatively high water level. The predicted concentrations of major ions and alkalinity in the pond calculated from the mass balance coincided well with measured concentrations. The relatively high pH values of the pond water during a period of high water level are considered to be mainly caused by alkalinity supplied by influxes, especially subsurface water. During a period of relatively low water level, predicted alkalinity exceeded measured alkalinity by 29%, indicating the occurrence of in-pond consumption of alkalinity with a resultant decrease in pH.     

岷江上游水文气象因子多尺度周期性分析

采用Dmey小波变换法对岷江上游杂谷脑流域1959年至2006年月径流量、月平均气温和月降水量不同时间尺度下的变化周期进行分析,探讨三者在长时间序列周期性变化中的相互响应,并根据主周期预测未来气温、降水和径流的变化趋势,结果表明:气温、径流和降水存在多尺度周期性变化,在不同的尺度周期中,表现出不同的冷暖、丰枯和干湿的振荡规律,总体表现为由小尺度无明显规律的剧烈振荡向大尺度有明显规律的振荡变化。3个要素同以8—12个月的小尺度为周期剧烈振荡,在较大时间尺度上,具有明显规律振荡变化的周期分别为气温500个月、径流150个月和降水120个月。受森林砍伐的影响,研究区域在1962—1988年期间径流对降水变化的周期性响应迟钝,而在1988—2006年期间基本同步。根据大尺度周期性波动趋势预测,未来十几年研究区域处于偏暖的年代际背景下,未来6—7a为多雨期,但径流量偏少。     

A model for the hydrological cycle of a forested catchment and assessment of the changes caused in water balance by cuttings

A physicomathematical model of the hydrological cycle in a forested catchment was constructed. This model describes the interception of liquid and solid precipitation by tree crowns; snow accumulation and melting; vertical transfer of moisture in soil and its evaporation; and surface, subsurface, and channeled runoffs. The model was calibrated and verified using the observation data for the completely forested Taezhnyi catchment within the area of the Valdai Water Balance Station. Then the model was used to assess possible changes in the hydrological cycle after clear cuttings in this catchment. The values of model parameters were compared to the corresponding soil characteristics in the adjacent treeless (field) Usad’evskii catchment. Modeling results demonstrate that the average water reserve in the snow cover before melting can increase by 15% after forest cutting in the Taezhnyi catchment. The losses for snow sublimation are reduced almost two-fold. The snow melting intensity increases by 30% and its duration decreases by 10 days. The annual runoff after cutting increases by 7–10%; however, the seasonal distribution of the runoff and the constituents of the water balance change to a greater degree. During spring flood, the maximal water discharge in the forested catchment is 50% smaller than after forest cutting. The duration of spring flood after cutting is reduced by 5–7 days. The changes in the hydrological cycle depending on the age-related alteration in leaf area index were also studied.     

控释氮肥对洞庭湖区双季稻田表面水氮素动态及其径流损失的影响

用渗漏池模拟洞庭湖区2种主要稻田土壤(河沙泥和紫潮泥),研究了施用尿素(CF)和控释氮肥(CRNF)对双季稻田表面水pH、电导率(EC)、全氮（TN）、铵态氮（NH₄⁺-N）和硝态氮（NO₃^--N）浓度变化规律及TN径流损失的影响.结果表明,双季稻田施用尿素后,表面水TN、NH₄⁺-N浓度分别在第1、3天达到高峰,然后迅速下降;NO₃^--N浓度普遍很低;早稻表面水pH在施用尿素后15 d内(晚稻3 d)逐渐升高;EC与NH₄⁺动态变化一致.与尿素相比,施用CRNF能显著降低双季稻田表面水pH、EC、TN和NH₄⁺-N浓度,70% N控释氮肥的控制效果最显著;但后期NO₃^--N浓度略有升高.径流监测结果表明,洞庭湖区种植双季稻期间施用尿素的TN径流损失为7.70 kg·hm^-2,占施氮量的2.57%;施肥后20 d内发生的径流事件对双季稻田TN径流损失的贡献极为显著;与施用尿素相比,施用控释氮肥显著降低了施肥后10 d内发生的第1次径流液中的TN浓度,施用CRNF和70%N CRNF的氮素径流损失分别降低24.5%和27.2%.     

The role of geological substrate for horn growth in ungulates: a case study on Alpine chamois

Ecological factors such as environmental and climatic conditions affect the growth of ornaments in ungulates. Studies about their influence can reveal key information on individual life histories and detect the events that can have important evolutionary consequences. Among the ecological factors commonly thought to play a role in such ecological processes, researches have so far neglected the possible influence of the geological feature which may either promote or restrain the early investment in horn growth. This study takes into consideration a broad range of ecological factors that are expected to affect horn growth and analyses how the substrate (calcareous versus siliceous) could modify the horn size in 1,685 yearling Alpine chamois (Rupicapra rupicapra) which were legally shot during 5 consecutive years in Central-Eastern Italian Alps. Interestingly, we found shorter horns in chamois shot on siliceous than on calcareous substrate, irrespective of the sex, showing how the substrate (and related ecological conditions) may affect horn growth. The substrate interacted with two ecological factors in shaping the horn size, i.e. aspect and snow cover. Differences between horn lengths recorded for chamois shot on these two substrates were less pronounced where South-facing slopes prevailed. During an average winter (about 100 days with more than 10 cm of snow on the ground) chamois horns were longer in individuals using calcareous areas, although the increase of number of days with more than 10 cm of snow on the ground had a stronger impact in reducing horn length in calcareous environment. We demonstrated that substrate, and related ecological conditions, influence horn growth. In ungulate species where ornament size is related to reproductive success, environmental factors, such as geological feature, can thus cause evolutionary consequences in the expression of ornaments and individual fitness.     

磷高效基因型小麦对缺磷胁迫的根际适应性反应

采用奶箱分隔栽培试验法,进行了磷高效与磷低效小麦基因型根际土壤ＰＨ与有效磷变化的研究,结果表明：小麦根际土壤ＰＨ和有效磷含量皆明显低于外围土壤,表现出明显的根际效应特征;磷高效基因型小麦的根际ＰＨ和有效磷含量明显低于磷低效基因型,ＰＨ变异范围和磷素亏缺区也表现明显较大。为了进一步验证磷高效小麦基因型这的这一根际特征,同时进行了施用水溶性,枸溶性磷肥的试验研究,结果表明,以水溶性磷肥对根际ＰＨ和有效     

Bicarbonate,the most important factor inducing iron chlorosis in vine grapes on calcareous soil

Summary In pot experiments grape vine was grown on a calcareous and on a non calcareous soil with a low and with a high water saturation. During the growing period soil solution samples were collected and analyzed for their pH and for HCO ₃ ⁻ , phosphate, Fe, and Ca. High water saturation resulted in a pH increase and in an increase of the HCO ₃ ⁻ concentration in both soils. The level in pH and HCO ₃ ⁻ , however, was much higher in the calcareous soil than in the non calcareous soil. The Fe concentration varied much throughout the experimental period, but there was no major differences between soils and water saturation treatments. The Ca concentration of the soil solution increased with time in the calcareous soil; for the non calcareous soil rather the reverse was true. The phosphate level in the soil solution of the non calcareous soil was about 10 times higher than in the calcareous soil. After 3 weeks growth all plants of the calcareous soil with the high water saturation showed first symptoms of Fe deficiency. These became more intense from day to day. Plants of the other treatments did not show any chlorotic symptoms. In the treatment with the chlorotic plants the HCO ₃ ⁻ concentration of the soil solution was the highest, the phosphate concentration the lowest from all treatments. It is therefore concluded that HCO ₃ ⁻ and not phosphate is the primary cause for lime induced Fe chlorosis. Despite the low phosphate concentration in the soil solution, the P concentration in the chlorotic leaves was more than twice as high as the P concentration in green leaves grown on the same soil. It is thus assumed that the high P content frequently found in chlorotic leaves is the result and not the cause for Fe chlorosis.     

A comparison of some populations of Eucalyptus viminalis Labill. growing on calcareous and acid soils in Victoria,Australia

A study of populations of Eucalyptus viminalis found on both acid and alkaline soils showed that seedlings differ in their tolerance of calcareous soils and their susceptibility to lime chlorosis. Seedlings from an open-forest population on calcareous dunes in the Otway Ranges, Victoria, averaged a significantly greater yield than seedlings of three other populations found on acid soils when all were grown on calcareous soil of pH 6.8. A tall ribbon gum form of E. viminalis, from Paradise gully in the Otways, was the least tolerant of alkaline conditions and showed severe signs of chlorosis and reddening of leaf margins. The latter appeared to be related to high uptake of phosphorus. This population showed rapid growth on a fertile acid loam. The data presented also emphasize the need to consider the variation in soils which can occur at any one site. Population differences were most marked when seedlings were grown on soils of pH near 7.0. Yield was reduced in the Otways calcareous population when seedlings were grown on the more leached soil from swales (pH 6.5) between dunes and on the highly calcareous soil from the dune crests (pH 7.8–8.0). The failure of any of the populations of E. viminalis studied to grow well on soils of high pH suggest that this species is not tolerant of highly calcareous soils. This may in part explain the absence of this species from the drier calcareous areas on the Mornington Peninsula and the Yanakie Isthmus, Victoria. Since seedlings had reduced root development on the soil collected from the Peninsula, E. viminalis may be restricted, in effect because of drought stress, to non-calcareous sites in the eastern part of Victoria.     

豫南黏板土壤分层酸化和耕层速效磷分布特征

黄淮海平原南部以黄褐土和砂姜黑土等为代表的耕地土壤酸化趋势明显.为深入认识该类型黏板土壤垂直剖面上pH值和耕层养分的空间变异情况,以豫南西平县为例,对县域范围内63个耕地样点进行pH值和速效磷测定,运用地统计学方法和ArcGIS技术分析不同深度土壤pH值和耕层土壤(0～20 cm)速效磷的空间分布状况,并分析了pH值与...     

Microbial load of drinking water reservoir tributaries during extreme rainfall and runoff

Hygienic and microbiological examinations of watercourses are usually not carried out during heavy rainfall and runoff events. After rainfall or snowmelt, there are often massive increases in turbidity in flooding creeks in mountain ranges, which are frequently interpreted as an indication of microbial contamination. The aim of this study was to quantify the microbial loads of watercourses during such runoff events and to compare these loads with loads occurring during regular conditions. In a 14-month monitoring period we investigated the microbial loads of three tributaries of different drinking water reservoirs. A total of 99 water samples were taken under different runoff conditions and analyzed to determine physical, chemical, bacterial, and parasitic parameters. Thirty-two water samples were considered event samples during nine measuring series. The criteria for events, based on duration and intensity of precipitation, water depth gauge measurements, and dynamics, had been fixed before the investigation for each creek individually. Of the physical and chemical parameters examined, only the turbidity, pH, and nitrate values differed clearly from the values obtained for regular samples. Most of the bacteriological parameters investigated (colony, Escherichia coli, coliform, fecal streptococcal, and Clostridium perfringens counts) increased considerably during extreme runoff events. If relevant sources of parasitic contamination occurred in catchment areas, the concentrations of Giardia and Cryptosporidium rose significantly during events. The results show that substantial shares of the total microbial loads in watercourses and in drinking water reservoirs result from rainfall and extreme runoff events. Consequently, regular samples are considered inadequate for representing the microbial contamination of watercourse systems. The procedures for raw water surveillance in the context of multiple-barrier protection and risk assessment ought to include sampling during extreme runoff situations.     

Microbial Load of Drinking Water Reservoir Tributaries during Extreme Rainfall and Runoff

Hygienic and microbiological examinations of watercourses are usually not carried out during heavy rainfall and runoff events. After rainfall or snowmelt, there are often massive increases in turbidity in flooding creeks in mountain ranges, which are frequently interpreted as an indication of microbial contamination. The aim of this study was to quantify the microbial loads of watercourses during such runoff events and to compare these loads with loads occurring during regular conditions. In a 14-month monitoring period we investigated the microbial loads of three tributaries of different drinking water reservoirs. A total of 99 water samples were taken under different runoff conditions and analyzed to determine physical, chemical, bacterial, and parasitic parameters. Thirty-two water samples were considered event samples during nine measuring series. The criteria for events, based on duration and intensity of precipitation, water depth gauge measurements, and dynamics, had been fixed before the investigation for each creek individually. Of the physical and chemical parameters examined, only the turbidity, pH, and nitrate values differed clearly from the values obtained for regular samples. Most of the bacteriological parameters investigated (colony, Escherichia coli, coliform, fecal streptococcal, and Clostridium perfringens counts) increased considerably during extreme runoff events. If relevant sources of parasitic contamination occurred in catchment areas, the concentrations of Giardia and Cryptosporidium rose significantly during events. The results show that substantial shares of the total microbial loads in watercourses and in drinking water reservoirs result from rainfall and extreme runoff events. Consequently, regular samples are considered inadequate for representing the microbial contamination of watercourse systems. The procedures for raw water surveillance in the context of multiple-barrier protection and risk assessment ought to include sampling during extreme runoff situations.     

Copper uptake and phytotoxicity as assessed in situ for durum wheat (Triticum turgidum durum L.) cultivated in Cu-contaminated, former vineyard soils

This work assessed in situ, copper (Cu) uptake and phytotoxicity for durum wheat (Triticum turgidum durum L.) cropped in a range of Cu-contaminated, former vineyard soils (pH 4.2–7.8 and total Cu concentration 32–1,030 mg Cu kg⁻¹) and identified the underlying soil chemical properties and related root-induced chemical changes in the rhizosphere. Copper concentrations in plants were significantly and positively correlated to soil Cu concentration (total and EDTA). In addition, Cu concentration in roots which was positively correlated to soil pH tended to be larger in calcareous soils than in non-calcareous soils. Symptoms of Cu phytotoxicity (interveinal chlorosis) were observed in some calcareous soils. Iron (Fe)–Cu antagonism was found in calcareous soils. Rhizosphere alkalisation in the most acidic soils was related to decreased CaCl₂-extractable Cu. Conversely, water-extractable Cu increased in the rhizosphere of both non-calcareous and calcareous soils. This work suggests that plant Cu uptake and risks of Cu phytotoxicity in situ might be greater in calcareous soils due to interaction with Fe nutrition. Larger water extractability of Cu in the rhizosphere might relate to greater Cu uptake in plants exhibiting Cu phytotoxic symptoms.     

Effects on water chemistry after drainage of a bog for forestry

Drainage for forestry has received increasing interest during recent decades. Generally, drainage concerns wet mineral soils while the utilization of peatlands is a matter of controversy. The peatlands mainly involved are fens, while forestry on bogs is an insignificant activity. Consequently, hydrology of bogs and effects of drainage on their hydrochemistry are little known.The investigation performed aimed at elucidating the parent conditions and the drainage impact on the hydrology and hydrochemistry of an ombrotrophic bog. Two bogs were first compared during a calibration period of two years and then, after drainage of one of them, during a period of three years. The second bog was kept virgin as a control.Considerable influences on runoff and stream water quality were found from the surrounding mineral soil uplands of the bog. Significant differences occurred between the chemical composition of the groundwater in the mineral soil and in the bog peat.Effects on runoff water from drainage of the bog deviate from drainage of minerotrophic peatlands with respect to decreased concentrations and losses of organic carbon and nitrogen. From two small bog catchments within the drained bog, there generally were greater losses of nutrients than from the catchment as a whole. Furthermore, the runoff from the drained bog decreased in comparison with the undrained condition. However, there were also similarities to drainage of other peatlands as regards increased pH, alkalinity and concentrations of sulphate. Also, concentrations of total-phosphorus increased in spite of a decreased phosphate (MRP) concentration.     

Emergence chronology of brook charr,Salvenus fontinalis,alevins in an acidic stream

Synopsis The emergence chronology of brook charr alevins in the Chikanishing River, Ontario, Canada and the concurrent changes in stream chemistry resulting from acidic snowmelt runoff were examined during the spring, 1986–1988. Emergence patterns were similar among years with the most intense emergence (> 70%) occurring during the declining stream discharge following the spring flood. This period coincided with stream pH depressions (minimum pH 5.2) in 2 of 3 years, suggesting emergence behaviour frequently subjects the earliest free-swimming life interval of brook charr to episodic acidification events.     

Environmental factors affecting the occurrence of mycobacteria in brook sediments

The occurrence of mycobacteria was studied in aerobic brook sediments from 39 drainage areas in Finland. The culturable counts of mycobacteria were related to climatic conditions, characteristics of the drainage area, chemical characteristics of the sediment and water, culturable counts of other heterotrophic bacteria, and microbial respiration rate in the sediment. The counts of mycobacteria varied from 1·1 × 10² to 1·5 × 10⁴ cfu g⁻¹ dry weight of sediment. They correlated positively with the proportion of the drainage area consisting of peatland, total content of C, content of Pb, microbial respiration rate in the sediment, and chemical oxygen demand of the water. The correlations of the mycobacterial counts with pH of sediment and alkalinity of water were negative. The results of the present sediment study and of the forest soil study published earlier strongly suggest that an increase in acidity increases the counts of mycobacteria and decreases the counts and activity of other heterotrophic bacteria. Mycobacterial counts were more than 100 times higher (per dry weight) in forest soils with pH 3·5–4·3 than in sediments with pH 4·5–6·3.     

The drifting of invertebrates and particulate organic matter in an Austrian mountain brook

1. The drift of organisms and particulate organic matter in a calcareous mountain brook near Lunz, Lower Austria, was investigated for 1 year. Five sets of three drift nets (sampling at different water depths) were distributed along a cross-section of the brook. 2. From February to March 1989, samples were taken at intervals of 2–7 days over 24-h periods, at the end of which the drift nets were emptied. From April 1989 to March 1990, sampling was carried out at monthly intervals and the nets emptied every 3h for 1 full day. 3. Of 71 810 organisms caught, the most abundant taxa were Diptera (46.6%; mainly Chironomidae and Simuliidae), Ephemeroptera (24.0%; dominated by Baetis spp.) and Plecoptera (16.1%). 4. The drift density (mean ± 95% CL) was significantly higher (P<0.05) in spring and summer (2.50 ± 0.32 specimens m^?3) than in autumn and winter (2.01 ± 0,22 specimens m^?3). In terms of biomass (wet weight), drift density was also significantly higher (P < 0.001) in spring and summer (2.50 ± 0.48 mgm^?3) than during the rest of the year (1.04±0.12mgm ^?3). 5. Total drift rates through a cross-section of the brook ranged from 17366 organisms per day at low discharge (water depth = 10cm) to 955152 individuals per day at a water depth of 50cm in autumn and winter; in spring and summer the corresponding values were 21600 and 1188000 specimens per day. 6. Ephemeroptera, Plecoptera, Coleoptera and Simuliidae were most abundant in night samples, whereas Hydracarina, Trichoptera and Chironomidae drifted mainly during daylight hours. 7. Drift density (dry weight) of particulate organic matter was positively correlated with discharge and ranged from 2.16mgm^?3 at a water depth of 10cm to 17.39mgm^?3 at 50cm.