海外耕地保护的社会化扶持对策及其启示

由于耕地为公众提供了大量的、具有强烈外部性的非生产性功能,很多国家都把耕地保护作为一个公共目标,并通过社会化扶持手段来得到实施.中国作为一个人多地少,人均耕地占有量低的国家,耕地保护任务更加突出,虽然"切实保护耕地"成为我国的一个基本国策,提出要执行"世界上最严格的耕地保护",并制定了耕地总量动态平衡、土地用途管制等一系列耕地保护政策,但耕地保护整体效果却不窖乐观,其中一个原因就是没有形成全社会共同保护耕地的氛围.本文对当今世界耕地保护社会化扶持的政策依据及实践手段进行综合与分析,并结合我国耕地保护的形势,提出了我国耕地保护社会化扶持的一系列对策措施,包括加快耕地产权制度建设,明确耕地保护的责任主体;重视耕地的非生产功能,提高全社会的耕地保护意识;采用综合优惠措施,激励农户的耕地保护行为;完善城镇发展规划,严格控制城镇对耕地的侵占;延长农产晶产业链,增加农业产业的经济收入.     

The occurrence of glyphosate, atrazine, and other pesticides in vernal pools and adjacent streams in Washington, DC, Maryland, Iowa, and Wyoming, 2005–2006

Vernal pools are sensitive environments that provide critical habitat for many species, including amphibians. These small water bodies are not always protected by pesticide label requirements for no-spray buffer zones, and the occurrence of pesticides in them is poorly documented. In this study, we investigated the occurrence of glyphosate, its primary degradation product aminomethylphosphonic acid, and additional pesticides in vernal pools and adjacent flowing waters. Most sampling sites were chosen to be in areas where glyphosate was being used either in production agriculture or for nonindigenous plant control. The four site locations were in otherwise protected areas (e.g., in a National Park). When possible, water samples were collected both before and after glyphosate application in 2005 and 2006. Twenty-eight pesticides or pesticide degradation products were detected in the study, and as many as 11 were identified in individual samples. Atrazine was detected most frequently and concentrations exceeded the freshwater aquatic life standard of 1.8 micrograms per liter (microg/l) in samples from Rands Ditch and Browns Ditch in DeSoto National Wildlife Refuge. Glyphosate was measured at the highest concentration (328 microg/l) in a sample from Riley Spring Pond in Rock Creek National Park. This concentration exceeded the freshwater aquatic life standard for glyphosate of 65 microg/l. Aminomethylphosphonic acid, triclopyr, and nicosulfuron also were detected at concentrations greater than 3.0 microg/l.     

Role of Riparian Areas in Atmospheric Pesticide Deposition and Its Potential Effect on Water Quality

Riparian buffers are known to mitigate hydrologic losses of nutrients and other contaminants as they exit agricultural fields. The vegetation of riparian buffers can also trap atmospheric contaminants, and these pollutants can subsequently be delivered via rain to the riparian buffer floor. These processes, however, are poorly understood especially for pesticide residues. Therefore, we conducted a four‐year study examining stemflow and throughfall to a riparian buffer which was adjacent a cultured Zea mays field treated with atrazine and metolachlor. Stemflow is rain contacting the tree canopy traveling down smaller to larger branches and down the tree trunk, whereas throughfall is rain that may or may not contact leaves and branches and reaches the earth. Stemflow concentrations of the herbicides were larger than throughfall concentrations and accounted for 5‐15% of the atrazine and 6‐66% of the metolachlor depositional fluxes under the canopy. Larger depositional fluxes were measured when leaves were more fully emerged and temperatures and humidity were elevated. Rain collected outside the riparian buffer on the field side and on the back side revealed the trees trapped the herbicide residues. Herbicide loading to the riparian buffer stream was found to be linked to tree canopy deposition and subsequent washoff during rain events. These results indicate that in agricultural areas canopy washoff can be an important source of pesticides to surface waters.     

Fate of Triclosan and Methyltriclosan in soil from biosolids application

This study investigates the persistence of Triclosan (TCS), and its degradation product, Methyltriclosan (MeTCS), after land application of biosolids to an experimental agricultural plot under both till and no till. Surface soil samples (n = 40) were collected several times over a three years period and sieved to remove biosolids. Concentration of TCS in the soil gradually increased with maximum levels of 63.7 ± 14.1 ng g(-1) dry wt., far below the predicted maximum concentration of 307.5 ng g(-1) dry wt. TCS disappearance corresponded with MeTCS appearance, suggesting in situ formation. Our results suggest that soil incorporation and degradation processes are taking place simultaneously and that TCS background levels are achieved within two years. TCS half-life (t(0.5)) was determined as 104 d and MeTCS t(0.5), which was more persistent than TCS, was estimated at 443 d.     

Effects of organic contaminants on reproduction of the starry flounder Platichthys stellatus in San Francisco Bay

Gonadally mature Platichthys stellatus (Pallas) were captured at two localities in San Francisco Bay in 1983–1985 and were induced to spawn in the laboratory; they were evaluated for relationships between several measures of survival through successive early life-history stages, chlorinated hydrocarbon concentrations in maternal liver and spawned eggs, and maternal hepatic mixed-function oxidase (MFO) activity. The effect of laboratory holding on hepatic aryl hydrocarbon hydroxylase (AHH), a particular MFO activity, and concentrations of chlorinated hydrocarbons were also evaluated. Significant negative correlations were found between maternal hepatic AHH activity at the time of spawning and percent viable (floating) eggs, fertilization success, and embryological success. Embryological success was also negatively correlated with concentrations of polychlorinated biphenyls (PCBs) in eggs. Laboratory holding for 45d, about twice the mean time to spawning, resulted in no significant changes in chlorinated hydrocarbon concentrations, but significant decreases in liver concentrations of phthalate esters and hepatic AHH activity. Females captured at the more urbanized central bay site, Berkeley (Bk), had a lesser proportion of floating eggs, poorer fertilization success, and higher hepatic AHH activities than those captured at a site in northern San Pablo Bay (SP). These results indicate the potential for a serious effect of lipophilic neutral organic contaminants on reproduction of an important estuarine flatfish species. Several mechanisms of toxic action are suggested to account for the observed effects, including the binding of toxic metabolites of contaminants to macromolecules and the alteration of sex steroids in females with contaminant-induced P-450 isozyme(s).Some preliminary findings included in this study were presented at the Third International Symposium on Responses of Marine Organisms to Pollutants (Spies et al. 1985 a)     

ESTIMATING EROSION RISKS ASSOCIATED WITH LOGGING AND FOREST ROADS IN NORTHWESTERN CALIFORNIA1

ABSTRACT: Erosion resulting from logging and road building has long been a concern to forest managers and the general public. An objective methodology was developed to estimate erosion risk on forest roads and in harvest areas on private land in northwestern California. It was based on 260 plots sampled from the area harvested under 415 Timber Harvest Plans completed between November 1978 and October 1979. Results confirmed previous findings that most erosion related to forest management occurs on a small fraction of the managed area. Erosion features larger than the minimum size inventories in this study (> 13 yd³) occupied only 0.2 percent of the area investigated. Linear discriminant analysis was used to develop two equations for identifying critical sites (sites with erosion >100 yd³ac^?1). The equations were based on slope, horizontal curvature (an expression of local topography), and soil color (on road sites) or the strength of the underlying rocks (on harvest sites). The equations can be used in planning to estimate the erosion risk of proposed activities. They can also be used to estimate acceptable risk thresholds based on the value of competing resources.     

The influence of lipids on the energetics of uptake of polycyclic aromatic hydrocarbons by natural organic matter

Although most of the organic carbon in soils and sediments may be composed of humic substances, their interaction with other compounds, especially their sorption interactions, may be significantly affected by the presence of small amounts of the other components of natural organic matter (NOM). In this investigation, the influence of the lipid fraction of NOM on the sorption thermodynamics of fluorene, phenanthrene, and pyrene to several geosorbent samples was examined before and after extraction of lipids. Batch experiments were performed at the same concentration for all polycyclic aromatic hydrocarbons (PAHs) (0.025 x their solubility in water) at different temperatures (10, 20, 30, and 40 degrees C), and the thermodynamic parameters were calculated. Removal of the lipids increases the sorption capacity of the samples as well as the exothermicity of the process. The free energy change was negative for all the samples and no significant differences were noticed on lipid removal. The entropy changes were small and positive for the whole geosorbent samples, but even smaller or more negative when the lipids were removed. This indicates that the interaction of PAHs with soils and sediments in the absence of extractable lipids is stronger and the mechanisms involved may be different, changing from a partitioning-like mechanism to specific adsorption. Because of the competition between lipids and PAHs for the same sorption sites, the lipids can be viewed as an "implicit sorbate."     

汕头红树林湿地表层沉积物环境因子对PAHs分布的影响

为了探明红树林湿地表层沉积物环境因子对多环芳烃分布的影响,野外采集了汕头红树林湿地表层沉积物样品,实验室内有机溶剂提取、氧化铝硅胶柱净化和气质联用分析了沉积物多环芳烃的质量分数、CHN元素仪分析了沉积物有机碳和黑碳的质量分数、激光粒度仪分析了沉积物的粒级组成,研究了沉积物有机碳、黑碳和粒度等各环境因子与多环芳烃的相关性.结果表明:有机碳与2～3环、4环和总多环芳烃的质量分数显著相关(P<0.05),表明表层沉积物有机碳的质量分数对PAHs的分布产生了显著的影响;黑碳与2～3环、4环、5～6环和总多环芳烃的质量分数显著相关(P<0.01),表明表层沉积物黑碳的质量分数对PAHs的分布产生了显著的影响;粘粒与2～3环多环芳烃的质量分数显著相关(P<0.05),与4环、5～6环和总多环芳烃的质量分数显著相关(P<0.01),表明表层沉积物粘粒的质量分数对PAHs的分布也产生了显著的影响;多元线性逐步回归分析显示,各回归方程黑碳的偏回归系数值都是最大,沉积物黑碳的质量分数对多环芳烃的质量分数贡献最大,表明黑碳是多环芳烃分布的主要影响因素.     

Observations on the burrows and burrowing behaviour of two mud-dwelling decapod crustaceans,Nephrops norvegicus and Goneplax rhomboides

The burrows of the Norway lobster Nephrops norvegicus (L.) and of the crab Goneplax rhomboides (L.) were studied in Loch Torridon, Scotland. Polyester resin casts of burrows in the sea were made by divers to reveal their subsurface form. Tunnels made by N. norvegicus were usually simple, with two or more openings on the mud surface, and penetrated to a depth of about 30 cm. G. rhomboides burrows did not descend more than about 15 cm beneath the surface, but were usually more complex than the lobster burrows and had several openings. The methods of burrow construction used by the two crustaceans are described from aquarium observations. Neither N. norvegicus nor G. rhomboides show obvious morphological adaptations for burrowing, and it is suggested that the fossorial habit was adopted very early by decapods. The burrows of N. norvegicus do not seem to have assumed any functions in addition to the original one of providing refuge from predators. There is not sufficient known of the biology of the crab to indicate whether the same is true in its case.