陕北某化工企业周围污灌区土壤-作物系统重金属积累特征及评价

对陕西北部某化工企业污灌区土壤-作物系统的重金属积累状况及空间分布进行了深入研究.结果表明,污水排放导致了周围农田土壤中Cd和Cu的聚集,其中Cd的积累量超过国家土壤环境二级标准;土壤Cu、Zn和Pb的单因子污染指数均小于1,Cd的单因子污染指数为1.21,属轻度污染,4种重金属综合污染指数为0.74,属警戒线等级.在剖面上,所有重金属元素均表现出明显的表聚现象,主要聚集在土壤表层0~10 cm范围内,在空间分布上,污水排放企业污灌区土壤和作物重金属Cu、Zn和Cd的强烈聚集区出现在企业排污口附近100 m范围内,而Pb集中在200 m范围内,并随着距企业距离的增加重金属含量呈降低趋势.在企业污水灌溉的影响下,玉米籽粒中Cu、Pb和Cd的平均含量分别为4.74、0.129和0.036 mg·kg-1,明显高于对照区,其中Pb达到5.7%的超标率.玉米籽粒中重金属单因子污染指数均小于1,大小为PbCuZnCd,综合污染指数为0.53,属安全清洁等级;4种重金属元素中,除Cd在作物中与土壤中有效态和全量之间均呈现极显著的正相关关系外,其余元素作物中和土壤中含量相关性均未达到显著水平.因此,该化工企业周围,尽管由于污灌引起重金属在土壤中的累积,但由于在农作物中的积累有限,暂时未对人体健康造成威胁,但由于交通及烟尘引起的Pb的超标应引起重视.     

Spatial and Seasonal Response of Municipal Water Use to Weather across the Contiguous U.S.

Weather variability has the potential to influence municipal water use, particularly in dry regions such as the western United States (U.S.). Outdoor water use can account for more than half of annual household water use and may be particularly responsive to weather, but little is known about how the expected magnitude of these responses varies across the U.S. This nationwide study identified the response of municipal water use to monthly weather (i.e., temperature, precipitation, evapotranspiration [ET]) using monthly water deliveries for 229 cities in the contiguous U.S. Using city‐specific multiple regression and region‐specific models with city fixed effects, we investigated what portion of the variability in municipal water use was explained by weather across cities, and also estimated responses to weather across seasons and climate regions. Our findings indicated municipal water use was generally well‐explained by weather, with median adjusted R² ranging from 63% to 95% across climate regions. Weather was more predictive of water use in dry climates compared to wet, and temperature had more explanatory power than precipitation or ET. In response to a 1°C increase in monthly maximum temperature, municipal water use was shown to increase by 3.2% and 3.9% in dry cities in winter and summer, respectively, with smaller changes in wet cities. Quantifying these responses allows urban water managers to plan for weather‐driven variability in water use.     

Use of Predictive Weather Uncertainties in an Irrigation Scheduling Tool Part II: An Application of Metrics and Adjoints

We apply predictive weather metrics and land model sensitivities to improve the Colorado State University Water Irrigation Scheduler for Efficient Application (WISE). WISE is an irrigation decision aid that integrates environmental and user information for optimizing water use. Rainfall forecasts and verification performance metrics are used to estimate predictive rainfall probabilities that are used as input data within the irrigation decision aid. These input data errors are also used within a land model sensitivity study to diagnose important prognostic water movement behaviors for irrigation tool development purposes simultaneously performing the analysis in space and time. Thus, important questions such as “how long can a crop water application be delayed while maintaining crop yield production?” are addressed by evaluating crop growth stage interactions as a function of soil depth (i.e., space), rainfall events (i.e., time), and their probabilistic uncertainties. Editor’s note : This paper is part of the featured series on Optimizing Ogallala Aquifer Water Use to Sustain Food Systems. See the February 2019 issue for the introduction and background to the series.     

Integrated Risk Framework for Onsite Wastewater Treatment Systems

Onsite wastewater treatment systems (OWTS) are becoming increasingly important for the treatment and dispersal of effluent in new urbanised developments that are not serviced by centralised wastewater collection and treatment systems. However, the current standards and guidelines adopted by many local authorities for assessing suitable site and soil conditions for OWTS are increasingly coming under scrutiny due to the public health and environmental impacts caused by poorly performing systems, in particular septic tank-soil adsorption systems. In order to achieve sustainable onsite wastewater treatment with minimal impacts on the environment and public health, more appropriate means of assessment are required. This paper highlights an integrated risk based approach for assessing the inherent hazards associated with OWTS in order to manage and mitigate the environmental and public health risks inherent with onsite wastewater treatment. In developing a sound and cohesive integrated risk framework for OWTS, several key issues must be recognised. These include the inclusion of relevant stakeholders throughout framework development, the integration of scientific knowledge, data and analysis with risk assessment and management ideals, and identification of the appropriate performance goals for successful management and mitigation of associated risks. These issues were addressed in the development of the risk framework to provide a generic approach to assessing risk from OWTS. The utilisation of the developed risk framework for achieving more appropriate assessment and management techniques for OWTS is presented in a case study for the Gold Coast region, Queensland State, Australia.     

污水直接膜过滤用于农灌可行性试验

本试验尝试用膜直接截留污水中对人体健康有害的细菌病毒,而保留水中对作物有益的氮、磷等营养元素,以期实现水、肥双成分资源化。试验结果表明,无论是微滤膜还是超滤膜均对细菌及粪大肠菌有很高的截留率(99.9%～99.999%),污水中有机物、氮与磷的保留率分别为32%～67%、72%～78%和60%～62%。用渗滤液灌溉的小麦较之清水灌溉和常规灌溉的小麦,麦穗单重分别提高13%和7.5%。     

桂林市某蔬菜种植基地重金属污染调查及分析

通过对桂林市某蔬菜种植基地灌溉水、土壤与蔬菜中重金属的测定,结合国家农灌水、土壤和食品卫生标准,分析了该区Cu、Pb、Zn、Cd污染状况。经测定分析,该区灌溉水质达到了国家三类水质标准;土壤中重金属含量普遍超过背景值,但达到了国家土壤环境质量标准;蔬菜中的重金属含量符合国家无公害蔬菜的标准。结果表明,该区尚未受到重金属污染,符合无公害食品种植基地要求。     

Spatial distribution of aerosol pollution based on MODIS data over Beijing, China

With the help of regression analysis,the relationships were detected between aerosol's contribution to apparent reflectance(ACR) derived from Moderate Resolution Imaging Spectroradiometer(MODIS)on board Terra and hourly PM_(10)mass concentration measured at 30 ground-based locations in Beijing for the August of 2003 and 2004.It was shown that there was a good correlation between the ACR and PM_(10)(linear correlation coefficient,R=0.56).On the basis of this relationship,spatial distribution and possible sources of PM_(10)derived from MODIS were analyzed and two frequently heavily-polluted regions were found,namely downtown of the city and the district near Xishan Mountain.These two regions coincidently are also urban heat island centers.The foundings of this paper will be greatly useful for environmental monitoring and urban planning for Beijing,especially for the 2008 Olympic game to be held in Beijing.     

Treated wastewater irrigation effect on soil, crop and environment： Wastewater recycling in the loess area of China

A study was carried out at the Loess Plateau in Dongzhi,China,to test the feasibility of using secondary treatment sewage effluent and to determine whether the water quality would then meet the recommended irrigation norm.Seven crops,including celery,wheat, maize,millet,apples,rapeseed and yellow beans,were tested in the study.Physical and chemical properties of the soil,crop yield and quality and leachate at different soil depths were measured.In most cases,the quality of the crops that made use of treated sewage was not distinctively different from those that did not use treated sewage.However,yields for the former were much higher than they were for the latter.Leachates at different soil depths were analyzed and the results did not show alarming levels of constituents.For a period of approximately 14 months,the treated sewage irrigation had no significant effect on the loess soil and no cases of illness resulting from contact with the treated sewage were reported.With treated sewage irrigation,a slight increase in the organic content of the soil was observed.     

Characterizing Drought in Irrigated Agricultural Systems: The Surface Water Delivery Index (SWDI)

Quantifying surface water shortages in arid and semiarid agricultural regions is challenging because limited water supplies are distributed over long distances based on complex water management systems constrained by legal, economic, and social frameworks that evolve with time. In such regions, the water supply is often derived in a climate dramatically different from where the water is diverted to meet agricultural demand. The existing drought indices which rely on local climate do not portray the complexities of the economic and legal constraints on water delivery. Nor do these indices quantify the shortages that occur in drought. Therefore, this research proposes a methodological approach to define surface water shortages in irrigated agricultural systems using a newly developed index termed the Surface Water Delivery Index (SWDI). The SWDI can be used to uniformly quantify surface water deficits/shortages at the end of the irrigation season. Results from the SWDI clearly illustrate how water shortages in droughts identified by the existing indices (e.g., SPI and PDSI) vary strongly both within and between basins. Some surface water entities are much more prone to water shortages than other entities based both on their source of water supply and water right portfolios.     

Irrigation Water Allocation Using an Inexact Two‐Stage Quadratic Programming with Fuzzy Input under Climate Change

Agricultural irrigation accounts for nearly 70% of the total water use around the world. Uncertainties and climate change together exacerbate the complexity of optimal allocation of water resources for irrigation. An interval‐fuzzy two‐stage stochastic quadratic programming model is developed for determining the plans for water allocation for irrigation with maximum benefits. The model is shown to be applicable when inputs are expressed as discrete, fuzzy or random. In order to reflect the effect of marginal utility on benefit and cost, the model can also deal with nonlinearities in the objective function. Results from applying the model to a case study in the middle reaches of the Heihe River basin, China, show schemes for water allocation for irrigation of different crops in every month of the crop growth period under various flow levels are effective for achieving high economic benefits. Different climate change scenarios are used to analyze the impact of changing water requirement and water availability on irrigation water allocation. The proposed model can aid the decision maker in formulating desired irrigation water management policies in the wake of uncertainties and changing environment.