Isu keselamatan makanan dan air telah diutarakan secara konvensional dan bebas, dan kini, perhubungan tersebut telah muncul sebagai agenda global yang rumit. Hari ini, pengairan air sisa telah muncul sebagai satu strategi meluas untuk memenuhi keperluan mendesak terhadap sumber air bukan-konvensional. Sumber buangan tersebut mengandungi unsur toksik, melebihi had maksimum yang dibenarkan, dan merupakan penanda risiko terhadap tanaman makanan dan rantaian makanan. Logam berat merupakan juzuk karsinogenik, teratogenik dan mutagenik, yang terkumpul dalam air pengairan. Kromium trivalen [Cr (III)], plumbum [Pb (II)] dan nikel [Ni (II)] merupakan bahan pencemar yang paling berbahaya, berasaskan sifat kimia elektronik yang kompleks, ketakterbiodegradan, kelarutan dan mobiliti. Kajian ini bertujuan untuk menyiasat salinghubungan kompleks antara pengairan air yang diperkayakan dengan logam terhadap Vigna radiata, Ipomoea aquatica dan Brassica chinensis, dalam perhubungannya dengan pertumbuhan fizikal; ciri-ciri fisiologi: pigmen fotosintesis, proline, tindak balas anti-oksidatif [guaiacol peroxidase (POD), catalase (CAT) dan ascorbate peroxidase (APX)], dan keupayaan antioksidan; serta ciri morfologi. Implikasi toksik telah dinilai dengan pengujian in vitro. Pengairan air yang diperkayakan dengan logam berat menginduksikan perencatan permanjangan akar dan pucuk secara ketara berasaskan kepekatan dan tempoh pengairan. Perawatan Cr (III) mencatatkan kadar perencatan tertinggi dalam Vigna radiata dan Brassica chinensis, sebanyak 68.04% untuk akar dan 75.69% untuk pucuk. Ipomoea aquatica adalah amat sensitif terhadap perawatan Ni (II), dengan catatan perencatan pertumbuhan sebanyak 83.78% dan 87.33% masing-masing pada akar dan pucuk. Kandungan klorofil-a, klorofil-b, dan karotenoid berkurangan pada 83.92%, 75.86%, dan 63%. Lipid peroxidasi yang ketara (170.30%) dan peningkatan proline (201.08%), dikesan selaras dengan perubahan aktiviti POD, APX dan CAT yang nyata. Penindasan aktiviti antioksidan yang ketara melebihi paras ambang kepekatan 0.50 mM Pb (II), 0.20 mM Cr (III) dan 0.05 mM Ni (II) dalam ketiga-tiga model tumbuhan, menunjukkan bahawa mekanisme pertahanan antioksidan tidak dapat melindungi sistem tumbuhan daripada kerosakan oksidatif. Gangguan ini disokong dengan herotan xilem dan floem, serta gangguan ke atas stomata. Kesan sitotoksik yang ketara dengan penurunan 50% dalam keupayaan sel HepG2 dapat diperhatikan, pada kepekatan 0.20 mM Pb (II), 0.40 mM Ni (II) dan 1.20 mM Cr (III). Kesan genotoksik pada momen ekor dan kerosakan ekor DNA dicatatkan pada kepekatan terendah, iaitu 0.04 μg/mL dalam ketiga-tiga ion logam berat. Kesimpulannya, ancaman kesihatan yang berkait rapat dengan tekanan oksidatif dan kemerosotan terhadap tanaman makanan akan berleluasa, dengan pengamalan pengairan air sisa tercemar dengan logam berat secara tidak terkawal, yang memberikan tamparan hebat terhadap kelestarian hubungan nexus makanan-air.
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The issues of food and water security have conventionally been addressed independently, and to date, their nexus has emerged to be the most intricate global agenda. Today, wastewater irrigation has emerged to be a widespread strategy to fulfil the pressing need of non-conventional water resources. These discharges carry toxic elements, exceeding the maximum allowable limits, suggesting the possible risks to food crops and food chain. Heavy metals are the most carcinogenic, teratogenic and mutagenic constituents, accumulating in the irrigation water. Trivalent chromium [Cr (III)], lead [Pb (II)] and nickel [Ni (II)] are the most insidious pollutants, ascribed to their complex electronic chemistry, non-biodegradability, solubility and mobility. This study aimed to investigate the complex interconnection of metals-enriched water irrigation on Vigna radiata, Ipomoea aquatica and Brassica chinensis in relation to the physical growth; physiological characteristics: photosynthetic pigments, proline, antioxidative response [guaiacol peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX)], antioxidant capacities and morphological characteristics. The toxicity implications were evaluated using in vitro bioassays. Metals-enriched water irrigation adversely induced significant concentration- and duration-dependent reductions in the elongation of roots and shoots; with Cr (III) exerted the highest inhibition in Vigna radiata and Brassica chinensis, denoted the reduction of 68.04% and 75.69% for root and shoot. Ipomoea aquatica was specifically sensitive to Ni (II), with the highest root and shoot inhibition of 83.78% and 87.33%. Chlorophyll-a, chlorophyll-b, and carotenoid contents were significantly reduced, up to 83.92%, 75.86%, and 63%. Profound lipid peroxidation (170.30%) and rising proline content (201.08%) were complementary with the pronounced alterations for POD, APX and CAT activities. The marked suppressions of antioxidant activities above the threshold levels of 0.50 mM Pb (II), 0.20 mM Cr (III) and 0.05 mM Ni (II) in the plant models indicated that the antioxidant defense machinery could no longer protect the plant systems against the oxidative damages. These disturbances corroborated with the xylem and phloem distortion, and stomata disruption. Significant cytotoxic effect with 50% reduction in HepG2 cell viability was noted at 0.20 mM Pb (II), 0.40 mM Ni (II) and 1.20 mM Cr (III). Genotoxic effects on DNA tail moment and tail damage were observed at the lowest concentration of 0.04 μg/mL. Conclusively, the oxidative stress-related health threats associated with the deteriorating effects on the food crops could be exacerbated by a wide scale unregulated metals-polluted wastewater irrigation practice, and place alarming threats to the sustainability of water-food nexus.
Phytotoxic effects of heavy metals-enriched water irrigation on food crops using a closed hydroponic system_Chow Yuh Nien_REDAC_2019_MYMY