Fecal Sterol and Bile Acid Biomarkers: Runoff Concentrations in Animal Waste-Amended Pastures

Nonpoint source pollution is the leading remaining cause of water quality problems. The extent of NPS pollution is often more difficult or expensive to monitor at the point(s) of origin, as compared to monitoring of point sources. This study evaluated the hypothesis that animal manure (chicken, cow, horse, and pig) applied to pasture contribute fecal sterols and bile acids to runoff. The study also assessed the potential benefit of fecal sterols and bile acids as biomarkers in distinguishing fecal pollution and its sources. Fecal sterol and bile acid concentrations were determined in flow-weighted composite runoff samples collected from 2.4?×?6.1 m plots (n?=?3) amended with manure. Runoff was generated from simulated rainfall (152 mm.h^?1). Runoff samples from manure-amended plots showed high concentrations of fecal sterol (ranged from 13?±?1 to 1,287?±?183) and bile acid (ranged from 24?±?1 to 2,251?±?248) biomarkers. The profiles of fecal sterols and bile acids in runoff samples were similar to those of fresh manure for all selected animals. For runoff and fresh manure, chenodeoxycholic acid, deoxycholic acid, epicoprostanol, and hyodeoxycholic acid were consistent biomarkers for chicken, cow, horse, and pig, respectively, suggesting that sterols and bile acids can be used to identify sources and occurrence of fecal matter in water and sediments.     

Discharge of Escherichia Coli from Agricultural Surface and Subsurface Drainage Water: Tillage Effects

Drainage water from agricultural fields with applied manure can degrade the bacterial quality of surface and groundwater. The impact of conventional tillage (CT) and zero tillage (ZT) practices on Escherichia coli (E.coli) discharge through artificially drained soils is not well understood. Consequently, two field trials were conducted during 2002–2004. The first trial involved fall applications of beef manure while the second involved spring applications of dairy manure. Both surface and subsurface drainage water were monitored in the first trial while only subsurface drainage water was monitored in the second. Under fall applied beef manure (trial 1), no differences (p?>?0.05) were observed in E.coli concentrations (cfu/100 ml) in combined drainage water under both tillage systems. However, during 2003–2004, subsurface drainage water under ZT had higher E.coli concentrations and loads than drainage water under CT. When the combined (surface + subsurface) annual E.coli loads were considered, CT loads were greater than ZT during 2002–2003 with an opposite situation during 2003–2004. Overall, annual E.coli loads were similar under ZT (4.7?×?10¹⁰ cfu/ha) and CT (4.8?×?10¹⁰ cfu/ha). Spring dairy manure application (trial 2) produced significant (p?>?0.03) tillage effect on E.coli loads in subsurface drainage water only during the second year. During the study period, ZT plots (1.55?×?10¹⁰ cfu/ha) discharged 5× more E.coli than CT (0.23?×?10¹⁰ cfu/ha). A longer duration of ZT practices resulted in higher subsurface flow volumes and subsequently greater loads of E.coli discharge in both trials.     

Relationship Between Fecal Indicators in Sediment and Recreational Waters in a Danish Estuary

The European Union has introduced a new bathing water directive where future classification of recreational waters will be based on the microbial parameters Escherichia coli, and intestinal enterococci. Introduction of enterococci as a new quality parameter may pose a challenge in some areas because relatively less is known about these organisms compared to E. coli. In the present study, the relative abundance of intestinal enterococci, E. coli, and ten fecal sterol and stanol biomarkers were investigated in water and sediment at two estuarine beach sites affected by fecal pollution. In the bathing water, enterococci were relatively more abundant at low E. coli concentrations. In the sediment, enterococci were generally more abundant than E. coli with surface concentrations between 1.0?×?10² and 4.5?×?10³ CFU cm^?3. Enterococci populations were relatively similar in water and sediment, and were phenotypically different from that of nearby pollution sources. The putative human specific genetic marker esp in Enterococcus faecium was not detected in water or sediment samples despite occasional inputs of human waste from storm water overflows. Sterol and stanol profiles suggested a direct link between water and sediment pollution profiles on days with wind conditions that facilitated resuspension. Sediment resuspension may occur at wind speeds exceeding 6–8 m s^?1, and could contribute significantly to enterococci concentrations in the overlying water. The study emphasized that recontamination of the water column due to wind induced resuspension should be considered when evaluating indicator levels and microbial hazards in estuarine recreational waters.     

Manure as a Source of Antibiotic-Resistant Escherichia coli and Enterococci: a Case Study of a Wisconsin, USA Family Dairy Farm

The spread of antibiotic-resistant bacteria in the environment is raising serious public health concerns, and manure is being increasingly recognized as a major source of antibiotic-resistant bacteria. In this research, we isolated Escherichia coli and enterococci from manure produced in a Wisconsin, USA family dairy farm to determine their resistance to six representative antibiotics. The average densities for E. coli and enterococci were 6.37(±4.38)?×?10⁷ colony formation units (CFU)?g^?1 and 1.60(±1.57)?×?10⁴ CFU g^?1, respectively. The E. coli isolates were found to be resistant to cephalothin, ampicillin, tetracycline, and erythromycin. In addition to these four antibiotics, the Enterococcus isolates were also resistant to gentamicin and ciprofloxacin. Additionally, we examined the survival and growth of E. coli and enterococci in dairy manure over a period of ~3 days. While the densities of enterococci remained stable over the study period, the concentrations of E. coli on average increased by 1.5 log10 units. Further tests of the bacterial antibiotic resistance over time showed no significant changes in the prevalence of antibiotic resistance. This result indicated that slightly aged manure could represent a larger source of antibiotic-resistant E. coli than fresh manure and the accumulation of antibiotic-resistant E. coli and enterococci in the agricultural fields must be accounted for in the modeling of the spread of antibiotic-resistant bacteria in the environment.     

Bacterial Transport from Agricultural Lands Fertilized with Animal Manure

A plot scale study was conducted to determine bacterial transport in runoff from cropland treated with poultry litter and dairy manure applied at phosphorus (P) agronomic rates. Treatments included surface application of dairy manure, surface application of poultry litter, incorporation of dairy manure and control. A rainfall simulator was used to induce runoff 1 and 2 days after manure application. Runoff was analyzed to determine the concentration of indicator bacteria-fecal coliform, Escherichia coli, and Enterococcus. Observed edge-of-field bacterial concentrations were 10² to 10⁵ times higher than Virginia’s in-stream bacteria criteria for primary contact recreation waters. No significant treatment effects were observed on edge-of-field bacteria concentration or yield. Results suggest that the manure application based on agronomic P rates may yield significant bacterial loading to downstream waterbodies if rainfall occurs soon after manure application. This research underscores the need for BMPs that reduce runoff volumes and filter pollutants associated with animal manures.     

Escherichia coli and Enterococci Attachment to Particles in Runoff from Highly and Sparsely Vegetated Grassland

Limited data on microbial partitioning between the freely suspended and particulate attached phases during transport along overland flow pathways have resulted in high uncertainty in bacterial fate and transport models and the application of these models to watershed management plans. The objectives of this study were to examine differences in attachment between E. coli and enterococci in runoff from plots with highly and sparsely vegetated grassland; investigate relations between flow regime, total suspended solids, and E. coli and enterococci attachment; and identify the particle size categories to which the attached cells were associated. Two rainfall simulations were conducted on large field plots 3 m wide by 18.3 m long with highly and both highly and sparsely vegetated covers and treated with standard cowpats. Results from the first experiment representing pasture with highly vegetated cover indicate that the majority of E. coli and enterococci are transported from the fresh manure source in the unattached state with only 4.8% of E. coli and 13% of enterococci associated with particles. The second experiment which compared partitioning in runoff from both highly and sparsely vegetated covers found lower bacterial attachment rates: the average E. coli percent attached was 0.06% from plots with highly vegetated cover and 2.8% from plots with sparsely vegetated cover while the corresponding values for enterococci were 0.98% and 1.23%, respectively. The findings from this study provide the first set of data on bacterial partitioning in overland flow from large field plots, and results may be helpful for parameterizing water quality models and designing conservation practices.     

Effect of heavy metals on growth population of a fecal coliform bacterium Escherichia coli in aquatic environment

The data on the effects of the concentrations (0.5, l, 2, 5 mg L^?1) of the heavy metals, Hg, As, Pb, Cu, Cd, and Cr on changes in growth population of a fecal coliform bacterium Escherichia coli (in term of number of E. coli per 100 mL water) showed a gradual decline in growth population of the fecal coliform bacterium with the increase of exposure time, as well as concentrations of the metals over control data. The effects were markedly recorded with the treatment of 5 mg L^?1. In general, the harmful effects of the metals on growth population of E. coli were found by the treatments in the order: Cd>Ph>Cu>As>Hg>Cr.     

Influence of Freshwater Sediment Characteristics on Persistence of Fecal Indicator Bacteria

Extended persistence of enteric bacteria in coastal sediments and potential remobilization of pathogens during natural turbulence or human activities may induce an increased risk of human infections. In this study, the effect of sediment characteristics such as particle grain size and nutrient and organic matter contents on the survival of fecal indicator bacteria (FIB) including total coliforms, Escherichia coli, and Enterococcus was investigated. The experimentation was carried out for 50 days in microcosms containing lake water and different contaminated freshwater sediments in continuous-flow and batch conditions. Results of this study revealed: (1) extended FIB survival in sediments up to 50 days, (2) higher growth and lower decay rates of FIB in sediments with high levels of organic matter and nutrients and small (mainly silt) grain size, and (3) longer survival of Enterococcus sp. compared to E. coli and total coliforms. FIB survival in sediments and possible resuspension are of considerable significance for the understanding of permanent microbial pollution in water column and therefore human risk during recreational activities.     

Influence of pH on the elimination of fecal coliform bacteria in waste stabilization ponds

From the results of in vitro studies carried out on wastewater from a stabilization pond it can be concluded that pH values close to 9, as a single factor, do not play any essential role in the die-off of fecal coliform bacteria. The percentage of elmination that occurs in pond water inoculated with 1.1×10¹⁰ cells of E. coli mL^?1 where the pH is maintained at 8.2 (original pH) is 99.997%, a much greater reduction than that observed (94.1%) in distilled water inoculated with the same concentration of E. coli and where pH is increased up to 9.     

Thirteen-year survival study of an environmentalEscherichia coli in field mini-plots

A multiple-antibiotic resistantE. coli was applied to rye-grass covered field mini-plots to simulate point-source contamination. Using three mini-plots for testing and a fourth as a control, the ability of the tracer bacterium to survive under field conditions was studied. Three test plots each received separately 10⁷, 10⁸, or 10¹⁰ cfu mL^?1 E. coli grown for 24 h. in 5 L one-third strength Tryptic soy broth. In Phase I of the study, it was determined that the tracer disappeared from leaf surfaces of rye-grass covering the plots after 41 days. In Phase II, determination of the presence of the tracer in the top 2″ (5 cm) of soil after two months elapsed time indicated that tracer cfu/g dry wt. of soil had declined five, three, and three-logs for test plots 1,2, and 3. In Phase III, subsurface soil sampling using a soil auger on the three test minei-plots indicated the tracer had penetrated through the top-soil and into the underlying B horizon (20 to 50 cm down). In Phase IV, detailed sampling by excavation of the subsurface soil Horizons of the third test mini-plot showed that the tracer had also penetrated through the hardpan (C Horizon) located 0.6 m below the surface to enter the groundwater (1.06 m deep) (Phase V).E. coli counts fell precipitously to 10³ cfu g^?1 in soil and then, in the groundwater at the groundwater-soil interface, persisted at a concentration of 10³ cfu 100 mL^?1 for 2 yr. As time past, tracer counts fell to 145 cfu/100 mL in 6 yr. rose to 820 cfu 100 mL^?1 in 1986 (8 yr elapsed time), and then fell to 25 cfu 100 mL^?1 in 1991 after 13 yr. Serotyping of 1986E. coli isolates indicated that 62% were of the original tracer serotype (0.128:B12) while only 43% of the 1991 isolates were of the same serotype. The penetration rate of the tracer down through the mini-plot soil into the groundwater was 0.02 m day^?1 while downslope dispersion occurred at an estimated rate of 1.0 m day^?1. The implications of the above findings are discussed.     

Sediment and phosphorus transfer in overland flow from a maize field receiving manure

Abstract. The transfer of suspended sediment (SS) and phosphorus (P) in overland flow from 30 m² field plots receiving either nil, surface‐applied or incorporated manure (slurry) were monitored to determine the vulnerability of land cropped to continuous forage maize to diffuse pollutant transfer in winter runoff. In the absence of slurry, P export was dominated by particulate forms, with up to 1 t SS ha^?1 and 0.75 kg total P ha^?1 collected from an individual storm event. Background concentrations of P in soluble (<0.45 μm) form were large (c. 0.5 mg L^?1) by eutrophication standards due to the previous build‐up of soil P, and largely independent of SS concentrations. Largest P exports (representing up to 23% of the slurry P applied) were measured when dairy slurry (3–13% dry solids) was surface‐applied. The P mobilized from the slurry accounted for up to 60% of total plot P export, with the majority occurring in a soluble bioavailable form during the first storm event. Initial P concentrations in runoff were in proportion to the amount of slurry P applied and significantly lower where rainfall was delayed after application. In one year, splitting the slurry application (3 × 10 kg ha^?1) reduced total P export by 25% compared to a single surface application (30 kg P ha^?1). In two years, incorporation of slurry, either by ploughing, or by tine cultivation, reduced the amount of overland flow by 50%, and the amount of P export by up to 60%, compared to the surface‐applied slurry treatments. Timeliness of slurry spreading to avoid periods of wet weather and simple cultivation of maize fields after harvest are practical and effective options to minimize SS and P transfer in land runoff from maize fields. The results also draw attention to the need to grow maize, and apply slurry to fields with a low P loss risk.     

Concentrations of Free and Conjugated Estrogens at Different Landscape Positions in an Agricultural Watershed Receiving Poultry Litter

Animal hormones can enter the aquatic environment along with runoff as a result of manure or litter application on agricultural landscapes. Our understanding of the transport of these hormones and their concentrations at various points along the watershed drainage is however limited. We investigated the transport of naturally produced poultry hormones in an agricultural watershed located on coastal plain soils of Delaware receiving land application of raw poultry manure. The objective of this study was to determine the concentrations of free and conjugated forms of estrogens in agricultural runoff at selected landscape positions in the agricultural watershed. Estrogen concentrations were determined for surface water, soil water, and runoff sediment. Estrogen forms that were analyzed were: Estrone (E1), Estradiol (E2?? and E2??), Estriol (E3), and their sulfate and glucuronide conjugates. Poultry litter application occurred at a rate of 9 Mg ha^?1 in early spring (April 2010). Sampling was performed for surface runoff, subsurface drainage, and sediment for nine storm events extending over 187 days before and after manure application (March?COctober 2010). Runoff was collected from the field edge, upland and lowland riparian positions and from the stream. Samples were analyzed by for liquid chromatography with tandem mass spectrometry (LC-MS/MS). Concentrations of estrogens were low (<20 ng l^?1) for most of the samples and decreased from the field edge into the riparian zone. Estrogens were not detected in soil water and runoff sediments. Overall, this study suggests that manure application practices at our sites in Delaware such as incorporation of litter into the soil likely reduced the concentrations of estrogens in runoff and reduced the threat posed to aquatic ecosystems.     

Applying MAR Analysis to Identify Human and Non-Human Fecal Sources in Small Kentucky Watersheds

The recurrence of reports citing water quality impairments in watersheds is evidence that tools are needed to identify pollution sources and facilitate restoration efforts such as implementing total maximum daily limits (TMDLs) or best management practices (BMPs). Fecal bacteria in surface waters are one of the most commonly cited impairments to water quality. This study evaluated microbial source tracking (MST), specifically multiple antibiotic resistance (MAR) analysis, as a management tool to differentiate nonpoint source pollution into source groups. A library containing Escherichia coli (E. coli, EC) and fecal streptococci (FS) isolates from poultry (EC n?=?282, FS n?=?650), human (EC n?=?152, FS n?=?240), wildlife (EC n?=?17, FS n?=?43), horse (EC n?=?79, FS n?=?82), dairy cattle (EC n?=?38, FS n?=?42), and beef cattle (EC n?=?49, FS n?=?46) sources was created. The MAR analysis was conducted on the isolates using a profile of seven antibiotics. The antibiotic signatures of unknown source isolates from Elkhorn and Hickman Creek watersheds were evaluated against the library to determine the contributions of potential fecal inputs from the respective sources. Correct classification was >60% when analyzed at the human and non-human-level of classification. On a watershed basis, both watersheds produced similar results; inputs from non-human sources were the greatest contributors to nonpoint source pollution. The results from the multiple antibiotic resistance (MAR) analysis revealed that the information produced, coupled with knowledge of the watershed and its associated land uses, would be helpful in allocating resources to remediate impaired water quality in such watersheds.     

Influence of Soil Properties and Manure Sources on Phosphorus in Runoff during Simulated Rainfall

Runoff from agricultural fields amended with animal manure or fertilizer is a source of phosphorus (P) pollution to surface waters, which can have harmful effects such as eutrophication. The objectives of this study were to evaluate the impact of soil P status and the P composition of manure sources on P in runoff and characterize the effects of manure sources on mass loss of dissolved reactive P, total dissolved P, and total P in runoff. Soil boxes set at 5% slopes received 7.5 cm h^?1 of simulated rainfall for 30 min. Study soils included a Kenansville loamy sand (loamy siliceous subactive thermic Arenic Hapludults, a Coastal Plain soil) and a Davidson silt loam (kaolinitic thermic Rhodic Kandiudults, a Piedmont soil). Soil test P concentrations ranged from 16 to 283 mg P kg^?1. Sources of P included broiler litter, breeder manure, and breeder manure treated with three rates of aluminum sulfate (Al₂(SO₄)₃) 0, 3.9, and 7.8 kg m^?2, di-ammonium phosphate (DAP), and an un-amended control. All manure sources were surface applied at 66 kg P ha^?1 without incorporation. Water extractable P represented an average of 10 ± 6% total P in manure. Runoff samples were taken over a 30-min period. Piedmont soil contained greater amounts of clay, aluminum (Al), and iron (Fe) concentrations, and higher P sorption capacities that produced significantly lower dissolved reactive P, total dissolved P, and total P losses than the Coastal Plain soil. Runoff P loss did not differ significantly for low and high STP Coastal Plain soils. Water extractable P in manures accounted for all dissolved reactive P lost in runoff with dissolved reactive P correlating strongly with water extractable P concentration (r² = 0.9961). Overall, manures containing the highest water extractable P concentrations contributed to the largest amounts of dissolved reactive P in runoff. Manure treated with 3.9 and 7.8 kg m^?2 of Al₂(SO₄)₃ (alum) decreased dissolved reactive P in runoff by 29%. While this soil box runoff study represents a worst-case scenario for P loss, highly significant effects of soil properties and manure sources were obtained. Management based on these results should help ameliorate harmful effects of P in runoff.     

多菌灵降解菌djl-6和啶虫脒降解菌D-2固体菌剂的研发

以蚯蚓粪肥、猪粪肥、鸡粪肥、秸秆肥、米糠、泥炭以及花生壳粉作为载体,以多菌灵降解菌Rhodococcus qingshengii djl-6和啶虫脒降解菌Pigmentiphaga sp. D-2为材料,开展了固体菌剂的研发。接种菌株djl-6及D-2后,各载体均能够促进供试菌株的生长。以蚯蚓粪肥作为载体时,菌株djl-6、D-2有效菌数释放率最高,分别为100.40%和82.03%。在保存120 d时,除花生壳粉外,其余各载体中的活菌数均高于10~7 cfu/g;以蚯蚓粪为载体的djl-6菌剂活菌数达到了7.00×10~8 cfu/g,以猪粪为载体的D-2菌剂活菌数达到了4.29×10~8 cfu/g。固体菌剂保存30 d后进行土壤农药残留降解试验,以蚯蚓粪为载体的djl-6菌剂对5 mg/kg的多菌灵降解率为94.30%,以蚯蚓粪为载体的D-2菌剂对10 mg/kg的啶虫脒降解率为81.87%。研究结果表明,以蚯蚓粪为载体的固体农残降解菌剂活菌数高、保存期长,具有较好的应用前景。     

Effects of shelter belts on fence-line pacing of deer and associated impacts on water and soil quality

Sustainable land use for deer farming requires the maintenance of good soil and water quality, which can be adversely affected by fence‐line pacing. This study tested the hypothesis that the absence or presence of shelter belts (one or two) in paddocks decreases fence‐line pacing and associated soil and water quality impacts. Soils near the fence line and in the rest of the paddock, in paddocks containing zero, one or two shelter belts, were sampled for bulk density and macroporosity (pores >30 μm diameter). Large intact samples (1 × 0.2 × 0.1 m³) were used to generate overland flow via rainfall simulation. The flow was tested for nutrients [phosphorus (P) and nitrogen (N) fractions], suspended sediment (SS), and the faecal indicator bacteria, Escherichia coli. Results showed that bulk density, void volume, SS, particulate P and total P were affected by location (fence line or rest of paddock) but, along with all other measurements except E. coli, were not affected by the number of shelter belts. Thus, the inclusion of shelter had no effect on the concentration of contaminant lost in overland flow or any soil physical or hydrological parameter, but decreased the run‐off of E. coli. The lack of contrast between the location of soils can be partly attributed to the soil type (Brown, NZ soil classification, USDA Taxonomy: Typic Fragiudalf), which when compared with past studies was less erosive and lost less P into solution. Other factors may have been different management or the lesser impact of weaners compared with older hinds and stags on soil properties. Although only E. coli concentrations were decreased by the inclusion of shelter, factors such as improved production and animal welfare weigh heavily in favour of installing and maintaining shelter on deer farms. However, the environmental benefit of shelter should be tested in other farms where factors such as slope, soil, climate and farm management may increase the contrast with no shelter.     

Inactivation of Escherichia coli O157:H7 and Salmonella Typhimurium in manure-amended soils studied in outdoor lysimeters

The inactivation of Escherichia coli O157:H7 (CCUG 44857) and Salmonella enterica serovar Typhimurium was investigated in two agricultural soils (sandy loam and silty clay) amended with poultry manure, cattle manure slurry or human urine. The study was performed in soil lysimeters placed outdoors, and was repeated over two consecutive years. The amendments, inoculated with E. coli O157:H7 and Salmonella Typhimurium, were mixed with soil on the top of the lysimeters. Samples were collected from the top 5-cm layer of each lysimeter at regular intervals, and the inactivation was monitored over 6 months, by the plate spread method and by enrichment. The inactivation was modelled by fitting a non-linear model to the data, and pathogen reduction times were calculated (90 and 99% reduction). The results showed that the inactivation of E. coli O157:H7 and Salmonella Typhimurium varied depending on the manure type used and its carbon content. The longest inactivation time occurred in samples amended with poultry manure, in which both E. coli O157:H7 and Salmonella Typhimurium were detected up to day 90 with the spread plate method. The most rapid inactivation for both pathogens occurred in soil amended with urine. However, low amounts of culturable E. coli O157:H7 and Salmonella Typhimurium were detected by enrichment throughout the study period (180 days), regardless of manure type.     

Die‐off of Escherichia coli in intact and disrupted cowpats

Diffuse pollution from grazed pastures is recognised as an important source of faecal microbial contamination of surface waters, and farmers urgently require mitigation options to reduce this impact of their farming activities. An obvious mitigation strategy is to reduce the size of the reservoir of faecal material in pastures during critical periods when overland flow is most likely. This work tested the hypothesis that smearing fresh cowpats to increase their surface area would increase exposure to solar radiation and increase desiccation, which in turn would accelerate the die‐off of Escherichia coli in the faecal material. The total solids content and E. coli concentration in intact and disrupted cowpats were monitored during the four seasons. The total solids content was significantly (P < 0.001) higher in the disrupted cowpats compared to the intact cowpats. This indicates that increased desiccation of the faecal material was successful. However, there was no significant difference (P > 0.05) in E. coli concentrations in the disrupted and intact cowpats. The physical disruption of cowpats did not therefore accelerate the die‐off of E. coli in the faecal material. The disrupted cowpats did appear to decompose faster than the intact cowpats. Mitigation options to reduce faecal micro‐organism losses in overland flow from grazed pastures will now need to focus on other methods to reduce the build up of reservoirs of faecal material on farm.     

湖南洞庭湖区农地畜禽粪便承载量估算及其风险评价

根据洞庭湖区畜禽养殖现状,采用排泄系数估算法测算了洞庭湖区畜禽粪便产生量,并对不同农地畜禽粪便承载量和畜禽粪便污染风险进行了评估.结果表明:2006年,洞庭湖区年产畜禽粪1 616.93万t,尿液1 248.30万t,BOD5 72.41万t,COD 79.33万t,NH3-N 7.48万t,农地畜禽粪便承载量平均为19.25 t·hm-2,风险预警值平均为0.47,仍未造成环境污染,畜禽养殖业还有较大发展空间.但个别地区的畜禽粪便已对农地造成污染,必须引起注意.