共查询到20条相似文献，搜索用时 31 毫秒
1.
Bioavailability of dissolved organic phosphorus compounds to typical harmful dinoflagellate Prorocentrum donghaiense Lu 总被引：1，自引：0，他引：1
Bangqin Huang Linjian Ou Huasheng Hong Haiwei Luo Dazhi Wang 《Marine pollution bulletin》2005,51(8-12):838
The bioavailability of dissolved organic phosphorus (DOP) compounds to harmful alga Prorocentrum donghaiense Lu and its alkaline phosphatase activity (APA) were studied. Results showed that P. donghaiense could utilize the test DOP compounds such as glucose-6-phosphate (G-6-P), adenosine triphosphate (ATP) and ribonucleic acid (RNA) to sustain its growth. Nutrition between the test DOP compounds and orthophosphate was comparable. P. donghaiense could utilize intracellular phosphorus to sustain growth under depletion of dissolved phosphorus. Variation of APA in different test DOP compounds was addressed; the controlling mechanism of APA in different DOP media was discussed. 相似文献
2.
本研究探索了铜绿微囊藻(Microcystis aeruginosa)和蛋白核小球藻(Chlorella pyrenoidosa)在单藻批式培养条件下对三种不同形态的可溶性有机磷化合物:1-磷酸-葡萄糖,环磷酸腺苷(c-AMP)和三磷酸腺苷(ATP)的利用及其生长.结果表明铜绿微囊藻和蛋白核小球藻能够利用这三种有机磷源进行生长.铜绿微囊藻对三种不同形态有机磷源的利用效率由高到低依次是:1-磷酸-葡萄糖,ATP和c-AMP,尤其是对磷酸单酯类磷源——1-磷酸-葡萄糖有极高的利用效率,在该磷源培养条件下微囊藻最大藻浓度能达到正磷酸盐培养条件下的最大藻浓度.小球藻对1-磷酸-葡萄糖和ATP的利用率略高于c-AMP.总体上铜绿微囊藻对这三种有机磷源的利用能力要高于小球藻.碱性磷酸酶与藻利用有机磷的能力有重要的关系,藻对有机磷的利用能力随着胞内酶活的增加而增强.随着富营养化程度的加剧,水体中可溶性有机磷在总磷中的比例也不断升高,铜绿微囊藻对可溶性有机磷的较强利用能力,可能促使其成为富营养化水体中优势种的原因之一. 相似文献
3.
Alkaline Phosphatase Activity and Utilization of Dissolved Organic Phosphorus by Algae in Subtropical Coastal Waters 总被引：7，自引：0，他引：7
Alkaline phosphatase activity (APA) and the availability of dissolved organic phosphorus (DOP) to marine algae were determined in Xiamen Bay and in algal batch culture systems. Results showed that APA changed with seasons, increasing to the highest value in summer and decreasing to the lowest in autumn and spring in Xiamen Bay. Tests on natural populations of planktonic algae and bacteria community showed that algae were mostly responsible for DOP utilization, while bacteria could not take up DOP compounds. Results from algal batch cultures also supported the above conclusion. Relationships between APA and environmental factors indicated that APA was negatively correlated with phosphorus level such as phosphate and small molecular DOP, and APA played an important role in utilization of DOP by algae. All the results emphasized the ecological significance of DOP in subtropical coastal waters. 相似文献
4.
The phosphorus fractions, the alkaline phosphatase activity (APA) and other water chemical parameters were concomitantly monitored from April 2003 to October 2004 in different eco-type sites of Lake Taihu. During the stages of algae growth, the phosphorus fractions and their relationships with APA in different ecotype sites were discussed and the phosphorus mineralization rate was calculated. In the water of Lake Taihu, most of the phosphorus (70.2%) could be attributed to the suspended particulate phosphorus, while the dissolved reactive phosphorus (DRP) seems to contribute less than 7%. About 58% of the total phosphorus, however, can be hydrolyzed as inorganic phosphate to compensate for phosphorus deficiency of algae and bacteria growth. During the different algae growth stages, the APA and its Kinetic parameters were varied significantly between different ecotype sites of Lake Taihu. This trend is also visible by comparing the phosphorus mineralization rate, and the most rapidly phosphorus turnover time is only several minutes. The fast recycle of phosphorus can, to some extent, be explained that the phosphorus source of algal blooms. The phytoplankton seems to compensate for phosphorus deficiency by using the alkaline phosphatase to hydrolyze phosphomonoesters. 相似文献
5.
滇池入湖河流磷负荷时空变化及形态组成贡献 总被引：5，自引：2，他引：3
研究了2013年滇池主要入湖河流总磷(TP)及各形态磷浓度的时空变化与入湖负荷特征,并探讨了不同形态磷的入湖负荷贡献.结果表明:(1)滇池河流入湖TP浓度在0.11~1.93 mg/L之间,以溶解性无机磷(DIP)和颗粒态磷(PP)为主,溶解性有机磷(DOP)浓度较低;(2)滇池河流入湖磷负荷总量为280.51 t/a,绝大多数河流主要以DIP形态入湖,平均贡献率为43.48%;PP形态入湖负荷次之,平均贡献率为31.64%;DOP入湖负荷较低,平均贡献率为24.88%;(3)DIP入湖负荷贡献率较高值出现在3、4和11月的枯水期,平均入湖负荷贡献率达到55.30%;PP入湖负荷贡献率较高值出现在1和7月,平均入湖负荷贡献率为56.14%;DOP入湖负荷贡献率月变化差异较小,最高值出现在12月,贡献率为21.85%;(4)研究滇池入湖河流污染负荷不仅要考虑溶解态无机磷的贡献,而且需要重视PP和DOP负荷,控制滇池入湖河流污染负荷需要考虑不同河流不同形态磷负荷组成及月变化差异特征,有针对性地采取相应措施. 相似文献
6.
滇池沉水植物生长过程对间隙水氮、磷时空变化的影响 总被引：4，自引：0，他引：4
2015年6-10月通过原位采集滇池沉水植物分布区和无植物对照区柱状沉积物间隙水,分析其溶解性总氮(DTN)和溶解性总磷(DTP)、溶解性无机氮(DIN)和溶解性无机磷(DIP)及溶解性有机氮(DON)和溶解性有机磷(DOP)浓度的时空变化,探讨沉水植物分布对间隙水氮、磷浓度、形态贡献及氮磷比的影响.结果表明:滇池沉水植物生长过程显著影响间隙水氮、磷浓度.与无植物对照区相比,沉水植物生长过程对间隙水氮浓度的削减主要发生在6、8月,而对间隙水磷浓度的削减主要发生在7月,反映了沉水植物对氮、磷两种元素的生物地球化学循环作用机制不同;间隙水氮形态贡献受季节性影响较大,6-7月以DON贡献为主,沉水植物分布区和无植物对照区分别达到61%和84%;而8-10月以DIN贡献为主,沉水植物分布区和无植物对照区分别为76%和75%;沉水植物分布区磷形态贡献随季节波动变化,沉水植物分布区以DOP贡献为主(63%),无植物对照区以DIP贡献为主(62%);沉水植物生长对沉积物间隙水各形态氮磷比影响显著.沉水植物生长显著增加间隙水DTN/DTP比,尤其是DIN/DIP比,相反降低DON/DOP比.沉水植物对间隙水氮、磷吸收及转化过程改变了沉积物氮、磷释放机制,从而影响上覆水氮、磷组成及氮磷比,很可能会影响到浮游植物生长及藻类水华过程,这对于湖泊水质管理具有重要意义. 相似文献
7.
8.
三峡水库香溪河库湾拟多甲藻(Peridiniopsis)的昼夜垂直迁移行为对碳磷分布的响应 总被引：1，自引：0，他引：1
于2015年2月26-27日在香溪河库湾高岚河段拟多甲藻(Peridiniopsis)水华发生地昼夜监测其在水体中的垂直迁移,分别在6个时间段(8:00、12:00、16:00、20:00、0:00、4:00)分层取样分析拟多甲藻在水中的叶绿素a浓度、细胞密度、碳酸酐酶(CA)与碱性磷酸酶(AP)活性;分析总磷(TP)、溶解性总磷(DTP)、溶解性反应磷(SRP)与溶解性有机磷(DOP)浓度在水中的垂直分布.结果显示,水华发生期拟多甲藻为绝对优势种,监测的6个时段中,拟多甲藻呈显著的昼夜垂直迁移规律,正午12:00,表层细胞密度最大,可达5.2×10~6cells/L,凌晨0:00表层细胞密度最低,仅为0.4×10~6cells/L;TP与DTP浓度无垂直分布规律,但SRP与DOP浓度呈现显著的垂直分布规律,SRP浓度随水深增加而减小,DOP浓度随水深增加而增加;CA活性日间高于夜间,日间CA活性呈垂直分布规律,随水深增加而减小,但夜间无垂直分布规律;AP活性在水中昼夜呈极其显著的垂直分布规律,随着水深增加逐渐增加.相关性分析结果表明,拟多甲藻细胞密度与水深、DOP浓度呈极显著负相关,水深与CA和AP活性分别呈极其显著负相关与正相关,拟多甲藻细胞密度与CA和AP浓度分别呈极其显著正相关与负相关.因此,拟多甲藻的垂直迁移行为可能是对日间迁移至表层获取光能和无机碳来源、夜间迁移至水下获取磷源的一种适应. 相似文献
9.
The phosphorus fractions, the alkaline phosphatase activity (APA) and other water chemical parameters were concomitantly monitored from April 2003 to October 2004 in different ecotype sites of Lake Taihu. During the stages of algae growth, the phosphorus fractions and their relationships with APA in different ecotype sites were discussed and the phosphorus mineralization rate was calculated. In the water of Lake Taihu, most of the phosphorus (70.2%) could be attributed to the suspended particulate phosphorus, while the dissolved reactive phosphorus (DRP) seems to contribute less than 7%. About 58% of the total phosphorus, however, can be hydrolyzed as inorganic phosphate to compensate for phosphorus deficiency of algae and bacteria growth. During the different algae growth stages, the APA and its Kinetic parameters were varied significantly between different ecotype sites of Lake Taihu. This trend is also visible by comparing the phosphorus mineralization rate, and the most rapidly phosphorus turnover time is only several minutes. The fast recycle of phosphorus can, to some extent, be explained that the phosphorus source of algal blooms. The phytoplankton seems to compensate for phosphorus deficiency by using the alkaline phosphatase to hydrolyze phosphomonoesters. 相似文献
10.
The cardiac activity of three limpets (Patella rustica, P. caerulea and P. aspera), having a different vertical zonation on the Mediterranean rocky shores, was monitored using a non-invasive technique, during 6 h exposure to copper solutions (0.1 and 0.5 ppm), and after return to copper-free conditions. At 0.1 ppm no significant variation of heart rate was observed in the three species with respect to control conditions, while after 3 h at 0.5 ppm a consistent bradycardia was evident in P. caerulea and P. aspera, but not in P. rustica. After 6 h at 0.5 ppm most of the specimens of the three species were acardic but still reactive to mechanical stimulation. Tests on the resumption of cardiac activity after 6 h exposure to 0.5 ppm showed that even after a prolonged cessation of cardiac activity, limpets quickly resumed heartbeating once returned to clean seawater. However, recovery of heartbeating was faster in the mid- and high-shore species (P. caerulea and P. rustica, respectively) than in the lower-shore P. aspera. Moreover, the cardiac pattern upon recovery was definitely bradycardic in P. aspera, while the other two species showed a significant overshooting in heartbeating rate. Measurement of body burdens of copper showed that P. rustica and P. caerulea were faster in removing the excess of copper than the lower-shore P. aspera. In conclusion, this study showed that taxonomically close and syntopic species having a different zonal distribution exhibit different cardiac responses to waterborne copper and stresses the importance of comparative studies on physiological responses of organisms to metal pollution. 相似文献
11.
Ecological significance of alkaline phosphatase activity and phosphatase-hydrolyzed phosphorus in the northern part of Gamak Bay, Korea 总被引：1，自引：0，他引：1
We investigated the ecological significance of alkaline phsophatase (APase) and alkaline phosphatase-hydrolyzable phosphorus (APHP) in the northern part of Gamak Bay, Korea. APase activity was detectable throughout the year, and dissolved inorganic phosphorus (DIP) concentration and APase activity are highly correlated and can be regarded as an indicator of DIP-limiting conditions. Also, a strong linear positive correlation between APase activity and Chl a concentration indicated that the major part of APase activity may have been induced by phytoplanktons. The APHP proportion in dissolved organic phosphorus (DOP) was above ca. 30% from winter to spring and below ca. 15% from summer to autumn due to freshwater discharge and uptake by phytoplankton. APHP may play an important role in species competition in coastal area such as northern part of Gamak Bay where DIP is limiting. Thus, APase induction by phytoplanktons may be ecologically significant, allowing dominance by these organisms under DIP-limiting conditions. 相似文献
12.
Variations in phosphorus (P) speciation were compared for two types of pilot scale wetlands: a blast furnace slag‐based constructed wetland (SCW), and a gravel‐based constructed wetland (GCW). Synthetic secondary effluent was used as the influent of the wetlands, which contained 1.1 mg/L P with more than 95% present as soluble reactive P (SRP). However, dissolved organic phosphorus (DOP) and particulate phosphorus (PP) emerged in the water along both wetlands. The levels of these three P species varied between the two wetlands. The GCW was more efficient than SCW at removing SRP, but showed a different trend. SRP decreased continually in the SCW, while it increased at the end of the GCW due to biological release. DOP was constant in SCW and GCW, and the mean value was 0.023 and 0.020 mg/L, respectively. The mean values of PP in the GCW ranged between 0.093 and 0.216 mg/L; much higher than the 0.05 ± 0.01 mg/L measured in the SCW. Sequential extractions showed that iron bound PP (Fe‐PP), aluminum bound PP (Al‐PP), organic PP (Org‐PP) and occluded PP (Oc‐PP) were the major components of PP at most locations of the GCW. Fe‐PP decreased from 0.53 to 0.14 mg/L in the upper layer, with DO steady at about 0.15 mg/L at the bottom. Oc‐PP increased at each layer. Al‐PP and Org‐PP were steady in the first 140 cm of the GCW, but decreased sharply at the end. Considering the variation of SRP, DOP and PP fractionations, it can be seen that PP exchanged intensively with SRP in the GCW, and might act as an intermediate in the P removal process. Part of the SRP was first transformed into PP, and then absorbed by substrates or deposited in the wetlands. P removal was mainly via Ca precipitation in the SCW, but involved multiple mechanisms in the GCW, such as precipitation, adsorption and biological interactions. The multiple P removal mechanisms might be the reason for the low proportion of SRP, and the better P removal efficiency observed in the GCW. 相似文献
13.
phoD基因编码的碱性磷酸酶驱动沉积物有机磷矿化并释放生物可利用磷,促进了富营养化湖泊蓝藻的生长与暴发,但对富营养化湖泊蓝藻生消周期phoD基因细菌群落动态变化的认识依然有限.本文研究了中国典型富营养化湖泊巢湖蓝藻生消过程沉积物碱性磷酸酶活性（APA）、phoD基因细菌多样性和群落结构的动态变化及其与环境的关系.结果显示：巢湖沉积物APA活性在蓝藻生长与暴发阶段显著升高,且与水温、pH、溶解氧（DO）等环境因子显著相关.蓝藻生消各阶段沉积物phoD基因细菌群落的优势菌属均由Pseudonocardia和Friedmanniella构成;与蓝藻潜伏期和衰亡期相比,生长初期与暴发期大多数样点沉积物Pseudonocardia的丰度显著降低而Friedmanniella显著升高.携带phoD基因的菌属丰度呈显著的时空变化,其中菌属丰度的空间异质性较高.蓝藻生长初期与暴发期的phoD基因细菌群落的Ace指数与Shannon多样性指数显著大于潜伏期与衰亡期.研究表明,携带phoD基因细菌群落结构的变化主要受APA、DO、叶绿素a、水温、总磷以及无机磷的驱动;春季蓝藻的生长消耗大量上覆水溶解性无机磷,激发了沉积物APA活性并诱发Friedmanniella生长从而缓解水体磷限制. 相似文献
14.
滇池水体不同形态磷负荷时空分布特征 总被引：1，自引：1，他引：0
利用Arc GIS空间插值的方法,通过2013年逐月监测(12个月)36个站点水量及不同形态磷浓度,揭示滇池水体磷浓度和磷负荷的时空变化,并探讨不同形态磷负荷的组成贡献,旨在为进一步实施滇池水污染治理及污染负荷控制提供依据.结果表明:滇池水体总磷(TP)浓度在0.13~0.46 mg/L之间,其中颗粒态磷(PP)浓度占TP浓度的72.6%,溶解性活性磷(SRP)浓度占TP浓度的12.8%,溶解性有机磷(DOP)浓度占TP浓度的14%;2013年水体TP负荷为251 t/a,其中PP负荷为190 t/a,SRP负荷为26 t/a,DOP负荷为34 t/a;滇池水体PP负荷对TP负荷的贡献最大,为76%,其次为DOP和SRP,贡献分别为13%和10%;TP及不同形态磷浓度与其负荷在季节分布上差异显著,负荷随季节变化呈现秋、冬季较高,春、夏季较低,而浓度呈现夏、秋季较高,冬、春季相对较低的趋势.定量评估滇池水体不同形态磷负荷及其组成贡献,对进一步揭示滇池藻源和泥源内负荷对水污染的贡献具有重要意义. 相似文献
15.
16.
太湖梅梁湾中碱性磷酸酶的活性及其与藻类生长的关系 总被引：34，自引：12，他引：22
通过对1998年5月-1999年5月的太湖梅梁湾水体中碱性磷酸酶活性及其它水化学因子的同步实地监测,初步探讨了富营养化较严重的太湖梅梁湾湖区的碱性磷酸酶活性的时空变化规律及其与藻类水华的相关性.研究表明,水体中各种形态磷之间的转化非常快.在磷的循环、转化过程中,碱性磷酸酶的作用至关重要.太湖梅梁湾各采样点水体中碱性磷酸酶的最大反应速率(Vmax)的年际变化有着显著的规律性,各点位在春季(3-4月)及夏季(7-8月)均分别出现峰值,与水体中水华出现的峰值相吻合.尤其在水体中水华暴发前的4月份,各采样点中的碱性磷酸酶的活性急剧增加,其Vmax均为年内的最大值或接近最大值,预示着水体中其它形态磷的转化速率加快,为水华的形成提供了充足的活性磷.水体中特异性碱性磷酸酶活性(总碱性磷酸酶活性/Chl.a)与水体中的PO43-存在着较好的负相关.尤其是在春季相关性更加显著,可达-0.9以上;夏季太湖梅梁湾水华暴发时,水体中的磷酸盐浓度远低于碱性磷酸酶的激发阈值,藻类体中的酶被诱导大量产生,从而使得水体中碱性磷酸酶的数量、活性急剧增加,达到较高的水平.这种短时间的有机质快速降解以及由此导致的营养盐释放,维持了水体中藻类的生长. 相似文献
17.
The activities of particulate and soluble phosphatase were analyzed monthly for 1 year in the coastal ecosystems of the NW Mediterranean Sea. The mean contribution of the particulate activity increased from 56% at an MUF-P concentration of 30 μM to 77% at 0.04 μM. This particulate activity was negatively correlated with the DIP, DOP and TDP concentrations when the activities were related to the seawater volume, chlorophyll a or the protein concentration. The TDP correlations were highly significant (p: 0.001). The DOP correlations were significant (p: 0.04) and became highly significant (p: 0.009) at low DIP concentrations (<0.13 μM). The DIP correlations were significant (p: 0.04) only at low DOP concentrations (<0.18 μM). Thus, the effects of seawater DIP and DOP were found to be linked. The soluble activity exhibited distinct phosphatase fractions with high (0.5–29.5 μM) and low (0.02–2 μM) Km values, but none exhibited significant correlations with phosphorus compounds. 相似文献
18.
太湖3种优势微囊藻对不同形态磷的吸收利用 总被引：1，自引：0，他引：1
微囊藻(Microcystis)是最常见的淡水水华蓝藻,它们对磷营养盐的竞争力是其成为优势种的最主要影响因素.本文以太湖水华中的3种优势微囊藻(Microcystis flos-aquae,Microcystis wesenbergii和Microcystis aeruginosa)为材料,比较研究了它们对正磷酸盐(K2HPO4)、三聚磷酸盐(Na5P3O10)、小分子溶解态有机磷(葡萄糖-6-磷酸,G-6-P)和大分子溶解态有机磷(卵磷脂)的吸收和利用能力.结果发现,3种微囊藻对4种磷形态有明显的嗜好.当磷浓度为0.2 mg/L时,M. flosaquae只在正磷酸盐下生长最快,M. wesenbergii在三聚磷酸盐和大、小分子有机磷下生长最快,M. aeruginosa在所有磷形态下生长都最慢.而当磷浓度为2.0 mg/L时,M. flos-aquae在所有形态磷下生长都最快.在2种磷浓度下M. wesenbergii都表现出最高的溶解态无机磷比例和光合活性Fv/Fm.以上结果说明,3种藻在磷形态利用方面存在明显的互补性差异,即低磷浓度下M. wesenbergii适宜利用的磷形态更多,高磷浓度下M. flos-aquae适宜利用的磷形态更多,而不论磷浓度高低,M. aeruginosa对4种形态磷的适应性最差.由此可知,可利用磷形态的丰富性只是部分优势微囊藻的竞争策略. 相似文献
19.
水体浮游植物具有捕获利用磷的能力以及沉水植物能够显著抑制水体中藻类生长已得到国内外广泛共识,但相应的潜在机制尚缺乏深入了解.本研究选取金鱼藻(Ceratophyllum demersum)为研究对象,基于室内模拟实验,探讨了沉水植物调控浮游植物捕获磷与过度生长的机制.结果显示,尽管未种植金鱼藻的对照组上覆水中总磷、总溶解态磷和可溶性活性磷的平均浓度均显著高于种植金鱼藻的实验组(约4倍),但是两个系统中这3种磷浓度随时间的变化趋势均符合S形的对数曲线.实验组藻类密度、有效光量子产量、总碱性磷酸酶活性(TAPA)以及细颗粒碱性磷酸酶活性(细颗粒APA)也远低于对照组.此外,对照组中粗颗粒碱性磷酸酶活性(粗颗粒APA)占TAPA的44.7%,显著高于细颗粒APA.结构方程模型结果表明,对照组水体藻类密度对TAPA具有直接的正向作用,而金鱼藻的生长显著弱化了不同形态磷与APA、藻类密度、细菌动力以及光量子产量之间的相互作用.这说明沉水植物对水体浮游植物生长的调控具有多种策略. 相似文献
20.
Biomonitoring of heavy metals and trace organics using the intertidal mussel Perna viridis in Hong Kong coastal waters 总被引：2，自引：0，他引：2
This paper presents the results of a 6-year (1998–2003) survey of trace toxics in the intertidal mussel Perna viridis conducted by the Hong Kong Environmental Protection Department. Concentrations of heavy metals and trace organics were measured in the soft bodies of P. viridis collected from five sites in Hong Kong waters, i.e. Wu Kai Sha (Tolo Harbour), Ma Wan (Northwest), Tsim Sha Tsui (Victoria Harbour), Tai Tam (Hong Kong South) and Lamma Island (Southern Waters) in order to establish the spatial patterns of contaminants in mussels. Among the metals analysed, Cd showed a significant concentration gradient in Hong Kong waters. The levels of Cd in P. viridis were significantly higher at Ma Wan as compared to the other sites studied. Ma Wan also had relatively higher concentrations of Pb. Mn concentrations were particularly prominent at Wu Kai Sha. Significantly higher concentrations of Hg and Cu were recorded at Tai Tam and Tsim Sha Tsui. Tai Tam and Wu Kai Sha had higher levels of V; whereas higher Ni concentrations were recorded at Lamma Island and Tai Tam. No clear spatial patterns for Al, As, Cr, Fe and Zn were observed.
Higher concentrations of PAHs in P. viridis were observed around urban centres impacted by sewage discharges (e.g. Tsim Sha Tsui); whereas higher PCB levels were found not only in Tsim Sha Tsui but also in less urbanised areas such as Lamma Island and Tai Tam, suggesting that these may be due to non-sewage related inputs. The study also shows that Northwest and Southern waters are subject to a higher degree of DDT pollution compared with other sites. Of the 17 dioxin compounds analysed, positive data were mostly recorded for two compounds which are of low toxicity (i.e. OCDD and 1,2,3,4,6,7,8-HpCDD) whereas the most toxic congeners (i.e. 2,3,7,8-TCDD and 1,2,3,7,8-PeCDD) were not detected in the 6 years of monitoring. In general, the levels of OCDD in P. viridis were found to be higher in Tai Tam and Lamma Island in Southern Waters of Hong Kong.
This study found that the levels of some highly toxic heavy metals (i.e. Cd, Hg and Pb) in the mussel P. viridis did not exceed the recommended limits for shellfish as food in Hong Kong (i.e. Cd: 2.0 ppm; Hg: 0.5 ppm; Pb: 6.0 ppm wet weight). The levels of As and Ni in P. viridis were also well below the action limits set by the US FDA (i.e. As: 86 ppm; Ni: 80 ppm wet weight). DDT and PCB contaminations in P. viridis were below the concentrations of concern. Compared with data obtained in the 1980s, the current levels of DDTs in P. viridis were 4–16 times lower; whereas Pb concentrations recorded in Tsim Sha Tsui have also been lowered significantly. This is mainly related to reduction in local and regional pollution sources in the past 20 years. 相似文献