Uptake of arsenic species by turnip (Brassica rapa L.) and lettuce (Lactuca sativa L.) treated with roxarsone and its metabolites in chicken manure.

Roxarsone is an organoarsenic feed additive that can be metabolised to other higher toxic arsenic (As) species in animal manure such as arsenate, arsenite, monomethylarsonic acid, dimethylarsinic acid, 3-amino-4-hydroxyphenylarsonic acid and other unknown As species. The accumulation, transport and distribution of As species in turnip (Brassica rapa L.) and lettuce (Lactuca sativa L.) amended with roxarsone and its metabolites in chicken manure were investigated. Results showed arsenite was the predominant As form, followed by arsenate in turnip and lettuce plants, and a low content of dimethylarsinic acid was detected only in lettuce roots. Compared with the control plants treated with chicken manure without roxarsone and its metabolites, the treatments containing roxarsone and its metabolites increased arsenite content by 2.0-3.2% in turnip shoots, by 6.6-6.7% in lettuce shoots, by 11-44% in turnip tubers and by 18-20% in lettuce roots at two growth stages. The enhanced proportion of arsenate content in turnip shoots, turnip tubers and lettuce roots was 4.3-14%, 20-35% and 70%, respectively, while dimethylarsinic acid content in lettuce roots increased 2.4 times. Results showed that the occurrence of dimethylarsinic acid in lettuce roots might be converted from the inorganic As species and the uptake of both inorganic and organic As compounds in turnip and lettuce plants would be enhanced by roxarsone and its metabolites in chicken manure. The pathway of roxarsone metabolites introduced into the human body via roxarsone → animal → manure → soil → crop was indicated.

[Investigation of As, Cu and Zn species and concentrations in animal feeds].

Seventy chicken and seventy-six pig feeds were collected from the feed stores in Guangdong province, and the species and concentrations of As, Cu and Zn were determined. We also examined the stability of roxarsone (ROX), one of the most widely used organoarsenical additives, either in the additive or in the feed at room temperature. The results showed that, averagely, the chicken and pig feeds contained 3.6 and 6.5 mg.kg-1 (As), 18.2 and 119.4 mg.kg-1 (Cu),and 124.6 and 486.2 mg.kg-1 (Zn), respectively. The excessive dosages of As, Cu and As in animal feeds will lead to higher residue of As, Cu and Zn in animal manures. Based on the national limit criteria for feed or feed additive, it was supposed that organoarsenicals had been used, only few feed samples exceeded the As limit, however, the excessive Cu and Zn in pig feeds were much more common. Organoarsenicals were found in 25.4% of the total feed samples, and As(Ill) and As(V) were the two most commonly detected As impurities in feeds bearing organoarsenicals. The mean detectable ROX and arsenilic acid were 7.0 and 21.2 mg.kg-1, respectively. Organoarsenicals were detectable in 24. 3% of the chicken feed samples and 26. 3% of the pig feed samples. Moreover, ROX was commonly used in chicken feeds, while p-ASA in pig feeds. ROX and the inorganic As impurities, either in the commercial additive or in the feed, remained stable for at least 30 days at room temperature, indicating the higher As impurities in feeds probably originated from the As impurities in organoarsenical additives. This is a new As exposure pathway for the producer and user of organoarsenicals and feeds amending organoarsenicals.

[Pesticide residual status in litchi orchard soils in Guangdong, China].

Litchi is a famous tropical and subtropical fruit originated in South China. Guangdong is one of the most important litchi production areas in China. Two hundred and eight soil samples were collected in litchi orchards after harvesting the fruit, in which nine often-used pesticides including metalaxyl, mancozeb, carbendazim, deltamethrin, cypermethrin, cyhalothrin, dipterex, dimethoate and dichlorvos were detected. The results showed that the detectable rates of various pesticides were ranked cypermethrin (59.1%) > carbendazim (51.0%) > mancozeb (11.1%) > metalaxyl (6.7%) > cyhalothrin (3.4%). Dimethoate and dichlorvos were detectable in few soil samples, and deltamethrin and dipterex were undetectable in all samples. The percentages of soil samples where different pesticides could be detected in one sample followed the order: one pesticide detectable (40.4%) > two pesticides simultaneously detectable (31.3%) > pesticide undetectable (18.8%) > three pesticides simultaneously detectable (8.2%) > four pesticides simultaneously detectable (1.4%). The concentrations of mancozeb in detectable samples averaged 39.05 microg x kg(-1), and that of cypermethrin was 7.83 microg x kg(-1). The mean concentrations of the other five pesticides ranged from 0.19 microg x kg(-1) to 1.65 microg x kg(-1). Totally, the pesticide residue status in litchi orchards in Guangdong was venial.